Chapter 12. Evaluation of the Patient with Neuromuscular, Skeletal, or Motion Disorders
Loren A. Bauman; Joseph R. Tobin
Bauman LA, Tobin JR. Bauman L.A., & Tobin J.R. Bauman, Loren A., and Joseph R. Tobin.Chapter 12. Evaluation of the Patient with Neuromuscular, Skeletal, or Motion Disorders. In: Longnecker DE, Brown DL, Newman MF, Zapol WM. Longnecker D.E., & Brown D.L., & Newman M.F., & Zapol W.M.(Eds.),Eds. David E. Longnecker, et al.eds. Anesthesiology, 2e. McGraw Hill; 2012. Accessed February 02, 2023. https://accessanesthesiology.mhmedical.com/content.aspx?bookid=490&sectionid=40114694
Bauman LA, Tobin JR. Bauman L.A., & Tobin J.R. Bauman, Loren A., and Joseph R. Tobin. (2012). Chapter 12. evaluation of the patient with neuromuscular, skeletal, or motion disorders. Longnecker DE, Brown DL, Newman MF, Zapol WM. Longnecker D.E., & Brown D.L., & Newman M.F., & Zapol W.M.(Eds.),Eds. David E. Longnecker, et al. Anesthesiology, 2e. McGraw Hill. https://accessanesthesiology.mhmedical.com/content.aspx?bookid=490&sectionid=40114694
Bauman LA, Tobin JR. Bauman L.A., & Tobin J.R. Bauman, Loren A., and Joseph R. Tobin. "Chapter 12. Evaluation of the Patient with Neuromuscular, Skeletal, or Motion Disorders." Anesthesiology, 2e Longnecker DE, Brown DL, Newman MF, Zapol WM. Longnecker D.E., & Brown D.L., & Newman M.F., & Zapol W.M.(Eds.),Eds. David E. Longnecker, et al. McGraw Hill, 2012, https://accessanesthesiology.mhmedical.com/content.aspx?bookid=490&sectionid=40114694.
Evaluation of the Patient with Neuromuscular, Skeletal, or Motion Disorders: Introduction
Preoperative Assessment
Perioperative Assessment of Specific Neuromuscular Diseases
Perioperative Assessment of Musculoskeletal Conditions
The major cause of death in patients with neuromuscular disorders is respiratory insufficiency. Respiratory involvement varies considerably among the various neuromuscular disorders, and the extent of general muscle weakness does not necessarily correlate with the severity of respiratory muscle involvement.
Cardiovascular involvement may manifest as myocardial failure in patients with myopathic disorders and as autonomic dysfunction in patients with neuropathic disorders. Clinical signs of autonomic dysfunction include orthostatic hypotension, resting tachycardia, paralytic ileus, anhidrosis, and constricted pupils. The presence of these clinical signs may indicate profound hemodynamic instability that may manifest during the perioperative period, requiring invasive monitoring to manage intravascular volume status and myocardial contractility.
In patients with neuromuscular disorders, the severity of skeletal muscle involvement does not necessarily correlate with the severity of cardiac involvement.
Children with asymptomatic, undiagnosed muscular dystrophy are at significant risk for serious, life-threatening anesthetic complications. Specifically, these patients may develop intractable hyperkalemic cardiac arrest after receiving succinylcholine intravenously.
Spinal anesthesia has been associated with exacerbation of multiple sclerosis, although the mechanism is unclear. Speculation is that demyelinated areas of the spinal cord are more sensitive to the effects of the local anesthetic, resulting in a relative neurotoxicity.
Numerous anesthetics may exacerbate an acute attack of porphyria and should be avoided. Propofol, ketamine, local anesthetics, muscle relaxants, nitrous oxide, isoflurane, and opioids are considered safe.
Myasthenic crisis is a rapid deterioration of neuromuscular and respiratory function that may occur at any time perioperatively as a result of infection, stress, or an overdose with anticholinesterase drugs (cholinergic crisis).
Patients with myasthenia gravis and myasthenic syndrome are exquisitely sensitive to the effects of nondepolarizing muscle relaxants.
Succinylcholine should be avoided in patients with muscular dystrophies; it may further damage the already abnormal muscle membrane and cause the release of intracellular contents.
Succinylcholine produces an exaggerated contracture, and its use should be avoided in patients with myotonias. The myotonic response produced by succinylcholine may be so severe that ventilation and tracheal intubation are difficult and may be impossible.
Rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis all are associated with possible cervical spine disease and may make airway management difficult.
Some musculoskeletal disorders are associated with an abnormal heat dissipation mechanism; central temperature monitoring is essential in these patients.
Many etiologies of high creatine kinase concentrations or rhabdomyolysis may be associated with malignant hyperthermia susceptibility.
Perioperative management of patients with neuromuscular disorders is challenging because of the low incidence, diverse etiology, coexisting diseases, and variable responses to anesthetics that often are present. A safe anesthetic plan demands that the anesthesia provider assess the extent of disease and its progression. Despite distinct etiologies, all neuromuscular disorders may adversely affect the respiratory and cardiovascular systems. Unfortunately, the extent of peripheral muscle involvement does not always correlate with the extent of cardiovascular and respiratory system involvement. Indeed, during stressful intervals such as acute illness, anesthesia, or surgery, the patient with a neuromuscular disorder may have his or her reserve easily overwhelmed, resulting in unanticipated complications such as respiratory failure requiring postoperative assisted ventilation, especially when the extent of the underlying neuromuscular disorder is underestimated.
This chapter focuses on the perioperative evaluation of patients with neuromuscular and skeletal diseases, emphasizing the respiratory and cardiovascular systems while highlighting important anesthetic issues. Individual neuromuscular disorders are grouped anatomically in an attempt to delineate specific anesthetic issues and to help predict possible anesthetic complications.
The major cause of death in patients with neuromuscular disorders is respiratory insufficiency.1 Respiratory involvement often varies considerably among various neuromuscular disorders, and the extent of general muscle weakness does not necessarily correlate with the severity of respiratory muscle involvement.2 In fact, patients with peripheral neuropathy tend to experience less frequent and less severe respiratory involvement as compared with individuals with myopathy, myelopathy, and neuromuscular junction disease.3 Significant respiratory muscle involvement may occur early (eg, Guillain-Barré syndrome) in the course of the disease or late (eg, myasthenia gravis), and it may be progressive, reversible, or intermittent. Impaired upper airway function and cranial nerve involvement often result in airflow obstruction and recurrent aspiration. Symptoms of airway involvement may be present preoperatively or after administration of sedation or induction agents, or symptoms may develop early after anesthetic administration, requiring persistent airway control.
Inspiratory muscle disease is frequently observed as a change in respiratory pattern, alternating work between fatiguing muscles and accessory muscles and increasing the respiratory rate to allow more efficient use of weakened muscles early in the course of the disease.4 In addition, inspiratory time and the ratio of dead space to tidal volume are increased, resulting in decreased ventilatory efficiency, increasing the risk of respiratory embarrassment. More advanced inspiratory muscle disease is characterized by hypoventilation, atelectasis, and hypoxemia. When muscle strength is less than 30% of normal, hypercapnia develops.5 Ventilatory responses to hypercapnia and hypoxia usually are impaired, especially in the presence of motor neuron and demyelinating disorders.6 Although central ventilatory drive usually remains intact, it may be diminished in some patients with certain neuromuscular disorders (eg, myotonic dystrophy). Indeed, respiratory drive may reflexively diminish in order to protect against respiratory muscle fatigue, injury, and failure. Chronic hypoventilation or hypoxemia may result in pulmonary hypertension and right ventricular failure, further complicating cardiopulmonary function.
The ability to cough and clear secretions is impaired in patients who have expiratory muscle dysfunction and bulbar palsies, and reductions in forced expiratory capacity after abdominal and thoracic procedures may be exacerbated. When cough is impaired, atelectasis may develop and secretions are retained, predisposing patients to bacterial contamination and pneumonia.
Preoperative evaluation should focus on history, physical examination, and diagnostic studies. Breathlessness on exertion is common; however, many patients who have advanced disease cannot generate sufficient exertion to offer this complaint. Orthopnea is a prominent symptom of diaphragmatic weakness because the abdominal contents limit diaphragmatic movement when a patient is in the supine position. Snoring, morning headaches, and daytime somnolence are indicative of sleep-related breathing disorders that are commonly present in patients with neuromuscular disease. In addition, liquids tend to be harder to swallow than solids in patients who have pharyngeal muscle weakness, and patients often report a perioperative history of aspiration or chest infection after procedures even with minimal sedation. A history of use of nocturnal respiratory assist devices (continuous positive airway pressure [CPAP] or bi-level positive airway pressure [BiPAP]) predicts an increased propensity to postanesthesia airway or respiratory problems and may require advanced monitoring (intensive care unit [ICU] or similar site) for postoperative respiratory/airway complications. Even with a peripheral surgical site not involving the torso, the residual effects of anesthetics may worsen the patient's respiratory status.
Important findings indicative of ventilatory muscle weakness, such as frequent changes in respiratory pattern, tachypnea, use of accessory muscles, and ventilatory muscle incoordination, may be observed during relaxed breathing and auscultation.7 In addition, paradoxical motion of the abdomen during inspiratory efforts suggests profound weakness of the diaphragm; this is best observed when a patient is supine.
Preoperative laboratory evaluation should focus on the patient's oxygenation and ventilation. Radiographic examination of the chest is useful to exclude pulmonary abnormalities but is not very helpful for diagnosing muscle weakness. Arterial blood gas analysis helps identify patients with hypercapnia and hypoxia. Newer noninvasive technology permits evaluation of preoperative oxygen saturation and hemoglobin estimation; however, these devices do not estimate respiratory reserve. Restrictive patterns typically are demonstrated by classic pulmonary function testing. However, vital capacity is not significantly affected until respiratory muscle strength is 50% below normal. Diaphragmatic weakness is suggested when greater than 25% decrease in vital capacity is observed between upright and supine positions.8 Total lung capacity decreases in patients with inspiratory muscle weakness, whereas residual volume increases. Flow-volume loop studies commonly reveal truncation of peak inspiratory and expiratory flow rates, a delay in reaching peak expiratory flow rate, and an abrupt decrease in end-expiratory flow rate. Upper airway muscle weakness results in oscillations of forced inspiratory or expiratory flow, as well as plateauing of the inspiratory flow curve.9 Inspiratory pressure generated by maximal effort against a closed airway can be used to measure the strength of respiratory muscles. Clinically significant ventilatory failure becomes more likely when maximum inspiratory pressure generated is less than 30 cm H2O.10
Cardiovascular involvement in patients with neuromuscular disorders may manifest as myocardial failure in patients with myopathies or as autonomic dysfunction in patients with neuropathic disorders. Patients are at risk for left ventricular thrombi, systemic emboli, pulmonary hypertension, and right ventricular failure. Also, because most patients with neuromuscular disorders are relatively immobile, deep venous thromboses and pulmonary emboli are a concern. With clinically significant symptoms from neuromuscular diseases, patients often cannot demonstrate their cardiorespiratory responses to exercise; therefore, further preoperative testing with echocardiography may be necessary.
Paradoxically, cardiomyopathy can range from subclinical in individuals with advanced neuromuscular disease to severe in patients with mild neuromuscular disorders, such as mildly affected female carriers of Duchenne muscular dystrophy11 or patients with Friedreich ataxia. Factors influencing the severity of Duchenne muscular dystrophy cardiomyopathy are multifactorial and may not be predicted by the extent of Xp21 (dystrophin) gene deletion.12
Heart rate, inotropic state, venous tone, and systemic vascular resistance are regulated by the autonomic nervous system. The most sensitive indicator of autonomic cardiac involvement is loss of beat-to-beat variability.13 Resting tachycardia and postural hypotension often are observed when autonomic dysfunction is present and has been associated with intraoperative hemodynamic instability. Clinical signs of autonomic dysfunction include orthostatic hypotension, resting tachycardia, paralytic ileus, anhidrosis, and constricted pupils.
The presence of these clinical signs suggests profound hemodynamic instability that may manifest in the perioperative period and require invasive monitoring to manage volume status. Recently, transesophageal echocardiography has been used more commonly to monitor cardiovascular performance and end-diastolic ventricular volume.
Cardiomyopathy is difficult to assess by auscultation in the early stages. Persistent tachycardia usually is the earliest manifestation of cardiomyopathy. Although determination of creatine phosphokinase level is used to detect active systemic myopathy, it may not detect myocardial dystrophy. Both atrial natriuretic peptide and norepinephrine concentrations are useful for detecting and monitoring heart failure. Atrial natriuretic peptide concentrations typically increase in patients with muscular dystrophy when left ventricular ejection fraction is greater than 25%.14 Preoperative troponin measurement has not been routinely recommended due to chronicity of the cardiomyopathies. Troponin levels are correlated with myocardial damage during acute myocardial injury.
The electrocardiogram (ECG) is a very reliable test for evaluating suspected cardiac involvement in patients with neuromuscular disorders. Characteristics include tall right precordial R and Q waves in leads I, aVL, V5, and V6.15 Fibrous replacement of the myocardium is thought to be responsible for the Q wave often observed on the ECG. Unfortunately, the prognostic value of the ECG is not very good because of very little correlation among the clinical course, ECG alterations, and the level of cardiac enzymes.16 Chest radiograph may be helpful to determine heart size; however, echocardiography is preferred to determine the size of the cardiac chambers, valvular involvement, and regional wall-motion abnormalities. In addition, serial measurements of fractional shortening and left ventricular ejection fraction are useful to monitor progression of cardiomyopathy and response to therapy.17
In patients with neuromuscular disorders, the severity of disease tends to correlate well with the incidence of perioperative complications. Postoperative respiratory failure can occur, especially in patients with severe restrictive lung disease. The presence of cardiomyopathy can lead to arrhythmias, blood pressure lability, and increased sensitivity to the depressant effects of anesthetics. The risk of aspiration is increased in patients who have a diminished, or absent, gag reflex. Positioning injuries may occur as a result of contractures, skeletal deformity, and lack of subcutaneous adipose tissue. Also, adverse reactions with anesthetics, particularly succinylcholine-induced hyperkalemia, are well documented in patients with neuromuscular disorders.18–20 The anesthetic concerns for patients with neuromuscular disease are summarized in Table 12-1.
Table 12-1 Anesthetic Considerations in Patients with Neuromuscular Disorders
Response to Succinylcholine
Response to Nondepolarizing Muscle Relaxants
Other Anesthetic Considerations
Amyotrophic lateral sclerosis (ALS) Hyperkalemia, contracture Increased sensitivity Impaired ventilation
Aspiration risk
Epidural anesthetics have been used successfully
Multiple sclerosis Hyperkalemia in severe disease Decreased sensitivity Avoid stress and hyperthermia
Spinal anesthesia may exacerbate disease and cause neurotoxicity
Guillain-Barré syndrome Hyperkalemia Increased/decreased sensitivity depending on phase of disease Autonomic instability
Postoperative respiratory failure
Porphyrias Normal response Normal response Avoid barbiturates, etomidate
Propofol, ketamine, local anesthetics, opioids, nitrous oxide, isoflurane are considered safe
Neuromuscular Junction Disease
Myasthenia gravis Decreased sensitivity Increased sensitivity Avoid muscle relaxants
Myasthenic syndrome Increased sensitivity Increased sensitivity Avoid muscle relaxants
Myopathy
Dystrophinopathies Increased sensitivity, hyperkalemic response Increased sensitivity Succinylcholine contraindicated
Regional anesthesia safe
Avoid inhalational agents if possible (membrane destablizers)
Delayed recovery of muscle strength
Myotonias Induced myotonia Increased sensitivity if major muscle wasting is present Avoid factors known to induce perioperative myotonia (cold, succinylcholine, hypothermia, anticholinesterase drugs)
Monitor for cardiac dysrhythmias
Periodic Paralyses
Hyperkalemic Hyperkalemic response Increased sensitivity Avoid factors known to induce myotonia
Avoid potassium supplementation
Avoid carbohydrate depletion
Monitor for dysrhythmias
Monitor serum potassium levels
Regional anesthetics best avoided
Hypokalemic Alters serum potassium level Increased sensitivity Avoid hypothermia
Avoid carbohydrate loading
Of concern are reports of children with asymptomatic, undiagnosed muscular dystrophy who are at significant risk for serious, life-threatening, anesthetic complications. Specifically, these patients may develop intractable cardiac arrest after receiving succinylcholine intravenously (IV) or after intramuscular injection, with or without the use of halogenated agents.21,22 In this situation, hyperkalemia, acidosis, and myoglobinuria are common clinical findings. A number of these patients have been found to have abnormal or absent dystrophin, usually indicating myopathy, more specifically Duchenne muscular dystrophy. As a result, the US Food and Drug Administration has determined that succinylcholine should be used in children and adolescent patients only for emergency tracheal intubation or in cases in which immediate securing of the airway is necessary (black box warning).
Amyotrophic lateral sclerosis (ALS) is a degenerative disease involving the corticospinal tract and anterior horn cells. Loss of motor function is progressive, with development of asymmetric weakness of the limbs (lower motor neurons are affected first), spasticity, and muscle atrophy. Death usually occurs within 3 to 5 years of diagnosis, although approximately 10% of patients may live more than 10 years.23 The etiology of ALS is unknown, but possible causes include viral or prion infection, glutamate excitotoxicity, free radical stress, autoimmune response, and heavy metal exposures and other undefined mechanisms.24
Involvement of the bulbar region typically manifests as respiratory and pharyngeal muscular insufficiency. Pulmonary function tests reveal a decrease in vital capacity, maximal voluntary ventilation, and diminished expiratory muscle function.25 Ventilatory support will be necessary as the disease progresses because respiratory failure eventually develops in all patients. Indeed, the cause of death in most patients with ALS, as in most patients with neuromuscular disorders, is respiratory failure. Autonomic dysfunction may be present in patients with ALS, as evidenced by resting tachycardia, orthostatic hypotension, and increased concentrations of catecholamines.
The antiglutamate drug riluzole is approved specifically for treatment of ALS. Riluzole has been demonstrated to prolong survival and delay the need for tracheostomy.26 Anticholinergic agents usually are administered to decrease secretions and facilitate swallowing, whereas dantrolene sodium and benzodiazepines are commonly administered to relieve muscle cramps and spasticity. However, these agents may exacerbate respiratory and skeletal muscle weakness. Anticholinesterase therapy may transiently improve muscle function and therefore is sometimes administered to these patients.
Ventilatory and upper airway muscle impairment significantly affects anesthetic management. Aspiration is an ongoing risk, and the need for postoperative ventilatory support is high because the already decreased respiratory reserve is reduced even further postoperatively. In ALS patients, the response to muscle relaxants, either depolarizing or nondepolarizing, is altered and may be compounded by perioperative administration of anticholinesterase medication. As with other patients with muscle denervation and muscle wasting, ALS patients are susceptible to succinylcholine-induced hyperkalemia and cardiovascular arrest.27 Therefore, whenever possible, depolarizing and long-acting nondepolarizing muscle relaxants should be avoided. Autonomic dysfunction may produce exaggerated decreases in cardiovascular function in response to anesthesia. No evidence indicates that any one specific anesthetic drug or anesthetic technique is best for patients with ALS. Neuraxial anesthesia has been safely used in patients and can be considered.28 Concern has been raised regarding neuraxial anesthesia and acute or subacute worsening of symptoms postoperatively, but no scientific evidence has been forthcoming. Multiple novel avenues of investigation are developing new treatments as mechanistic targets are being identified.29
Multiple sclerosis is a chronic disease of the central nervous system (CNS) that is characterized by a demyelinating process of the brain and spinal cord with unpredictable intervals of exacerbations and remissions. The cause of the disease is multifactorial, involving immunologic-mediated events occurring in susceptible individuals. Initially, a virus or other agent triggers an inflammatory response that initiates an autoimmune response to myelin. Plaques in the white matter of the CNS are the fundamental lesions. The ability of the CNS to repair itself during the early phases of the disease accounts for the relapsing nature of the disease. Unfortunately, there is no curative treatment.
The symptoms of multiple sclerosis depend on the site(s) of demyelination. The most common presenting symptoms are sensory losses and ocular disturbances. Limb weakness and paresthesias may occur as a result of demyelination of motor neurons and sensory pathways. The lower extremities are affected more than the upper extremities. Brainstem involvement may produce cranial nerve deficits and abnormal ventilatory drive. Hypotension may reflect the presence of autonomic nervous system involvement. Bowel and bladder irregularities are frequent complaints. The course of multiple sclerosis is characterized by exacerbation of symptoms at unpredictable intervals over a prolonged period. Eventually, residual symptoms persist and lead to progressive disability. However, 10% to 20% of patients have a relatively benign course and trivial disability.30 Interestingly, pregnancy is associated with an improvement in symptoms, but relapse occurs postpartum.31
The diagnosis is based primarily on clinical signs and symptoms. Laboratory confirmation of the diagnosis may be made by analysis of the cerebrospinal fluid (CSF) and magnetic resonance imaging (MRI). The CSF typically reveals increased concentrations of albumin and immunoglobulin G. MRI can detect CNS and spinal cord involvement and can be used as a measure to determine the effectiveness of various treatment modalities.32,33
Therapeutic modalities are directed at modulating the immunologic and inflammatory responses that damage myelin. Corticosteroids and interferon are used most commonly. Glatiramer is a polypeptide mixture that mimics the structure of myelin and serves as a distraction for autoantibodies. Mitoxantrone can be used to treat aggressive disease; however, it is cardiotoxic. Dantrolene, baclofen, and benzodiazepines can be used to treat spasticity. Carbamazepine can be used to treat painful dysesthesias, seizures, and paroxysmal symptoms. Antidepressants and anticholinergic drugs can be given for depression and urinary incontinence, respectively. Other promising new therapies are currently under investigation but are not currently approved for routine clinical use.34 Avoidance of emotional stress, fatigue, and hyperthermia is essential. Indeed, a 0.5°C increase in temperature can block impulse conduction in demyelinated fibers, resulting in an exacerbation or relapse.35
Surgery may be required more frequently in patients with multiple sclerosis because of orthopedic, urologic, and neurologic issues. Unfortunately, the effects of surgery and anesthesia on the course of this disease are controversial. Both regional and general anesthesias have been reported to exacerbate multiple sclerosis.36 However, factors other than anesthesia, such as emotional stress and hyperpyrexia, may increase the risk of an exacerbation as well. The patient should be adequately informed that, despite a well-managed anesthetic, a relapse might occur perioperatively. Patients with multiple sclerosis should undergo a comprehensive, well-documented neurologic examination aimed at identifying any existing deficits before anesthetic management. After surgery, the neurologic examination should be repeated in order to correlate preoperative and postoperative findings. Although patients may reveal no new symptomatology immediately after anesthesia, new symptoms may become present subacutely in the postoperative period.
Spinal anesthesia has been associated with exacerbation of multiple sclerosis, although the mechanism is unclear.36 Speculation is that lesions may cause the breakdown of the blood–brain barrier, and, in demyelinated areas of the spinal cord, the CNS is more sensitive to the effects of the local anesthetic, causing a relative neurotoxicity. Indeed, higher concentrations of local anesthetics are more likely to cause a relapse than are lower concentrations of local anesthetics. Interestingly, epidural analgesia has been used safely and does not appear to increase the incidence of disease relapse.31,36 General anesthetics do not appear to have any significant intrinsic adverse effect.
Consideration must be given to the potential interactions of anesthetics with medications patients may be taking for their disease. Patients receiving corticosteroids may require stress doses in the perioperative period. Immunosuppressants may produce subclinical cardiac dysfunction. Anticonvulsants produce resistance to nondepolarizing muscle relaxants,37-39 whereas baclofen may increase the sensitivity to nondepolarizing agents. Patients with significant muscle denervation or atrophy theoretically have an increased risk of a hyperkalemic response to succinylcholine, so it should be avoided. The hypotensive effects of volatile anesthetics may be exaggerated by autonomic dysfunction, so patients with severe disease may require invasive monitoring, possibly including transesophageal echocardiography. Respiratory dysfunction, when present, increases the likelihood of the need for postoperative mechanical ventilation.
Guillain-Barré syndrome, the most common cause of acute flaccid paralysis, is an autoimmune inflammatory polyneuropathy of motor, sensory, autonomic, and cranial nerves. The syndrome is triggered by an immune response to either a viral or bacterial infection that produces antibodies to an antigen of the infectious agent. The antigen mimics an epitope of the Schwann cell, and affected axons undergo lymphocytic infiltration and demyelination. A respiratory or gastrointestinal infection 3 to 4 weeks earlier usually precedes the onset of this disorder. Usually, the disease evolves over the course of 3 to 4 weeks, with complete recovery eventually occurring in fewer than 80% of patients. Unfortunately, 3% to 10% of patients die, and up to 20% may be permanently disabled.40
The clinical course is characterized by an ascending, usually symmetric muscle weakness of the lower extremities that develops over several days, followed by gradual recovery. Paresthesias often precede weakness and paralysis. Difficulty swallowing and impaired ventilation may occur if bulbar and respiratory muscles are involved. Respiratory insufficiency often is characterized by decreased forced exhalation and impaired cough.41 Rapid shallow breathing indicates inspiratory muscle weakness and usually develops later in the disease. Vital capacity should be measured frequently. When vital capacity is less than 15 to 20 mL/kg, mechanical ventilation often is required.42 In addition, tracheostomy may be required for management of ventilatory failure and for bulbar muscle weakness even after ventilatory function returns to normal. Autonomic dysfunction may be severe, especially in patients experiencing respiratory failure and quadriparesis. Blood pressure lability, tachycardia, and cardiac conduction abnormalities may be present. Physical stimulation may precipitate hypertension, tachycardia, and cardiac dysrhythmias.43
Management is primarily supportive and directed at intensive respiratory care and treatment of autonomic dysfunction. Plasmapheresis and IV immunoglobulin may hasten recovery and may alleviate the harmful effects of the immune response. Corticosteroids and immunosuppressive therapy have not been demonstrated to be effective.19
Anesthetic management of the patient with Guillain-Barré syndrome often is dictated by the severity of respiratory and autonomic nervous system dysfunction. Compensatory cardiovascular responses may be absent. Hypotension secondary to hypovolemia, positional changes, and positive-pressure ventilation is possible. Severe autonomic dysfunction may produce exaggerated responses in heart rate and blood pressure; thus invasive monitors may be necessary, and direct-acting vasopressors and antihypertensives must be readily available.
Succinylcholine should be avoided because it can precipitate hyperkalemic arrest.44 Interestingly, this risk may persist for some time after recovery from the disease. Depending on the phase of the disease, the sensitivity of patients to nondepolarizing muscle relaxants may vary from extreme sensitivity to resistance.45 Mechanical ventilation should be anticipated postoperatively. Profound sensory disturbance may be present, and patients will need adequate pain control. Although the use of regional anesthesia is limited, the use of epidural opioids has been reported and appears beneficial to patients experiencing intense sensory disturbance.46 Systemic opioid use must be judicious and closely monitored because these patients may be more sensitive to respiratory weakness or depression secondary to their underlying disease.
Familial Dysautonomia (Riley-Day Syndrome)
Familial dysautonomia is an inherited disease thought to be caused by a deficiency of dopamine-hydroxylase with a subsequent decrease in the level of norepinephrine. Patients with this disorder exhibit impaired temperature regulation, denervation supersensitivity, insensitivity to pain, vasomotor instability, and copious pulmonary secretions.
Riley-Day syndrome has numerous anesthetic implications, including excess secretions, pneumonia, decreased responsiveness to hypoxia and hypercarbia, labile blood pressure, intravascular volume depletion, postural hypotension, decreased gag reflex, corneal abrasions, and emetic crisis.47 Preparation of the patient for surgery includes achieving adequate pulmonary function and correcting fluid and electrolyte imbalance. Opioids should be used sparingly because pain, hypercapnic, and hypoxic responses are blunted. Because of a risk for aspiration, a nonparticulate antacid can be given. Invasive monitoring may be necessary, and vasopressors should be titrated carefully using direct-acting agents as needed.47 Profound bradycardia and hemodynamic collapse may occur, and the anesthesiologist should be prepared for hemodynamic support and resuscitation.
Porphyrias
Porphyrias are a group of inherited disorders of heme synthesis that result in overproduction and accumulation of porphyrin compounds because of a specific enzyme deficiency in the production of heme. Porphyrias are classified as acute (inducible) or nonacute (noninducible) on the basis of clinical presentation. Several reviews contain more detailed discussions of porphyrias.48,49
Acute porphyria may affect the CNS and peripheral nervous system via direct neuronal damage, axonal degeneration, and demyelination. Generally, clinical manifestations of acute attacks occur after puberty. Severe abdominal pain, nausea and vomiting, autonomic dysfunction, mental status changes, electrolyte abnormalities, and peripheral neuropathy ranging from paresis to flaccid quadriplegia characterize acute attacks. Death may occur from respiratory muscle paralysis. The cause of neurologic involvement is unknown but may be related to metabolites of heme intermediates or result from deficiency of the heme pigment in the nerve cell. Factors known to precipitate acute porphyric crisis include fasting, dehydration, infection, emotional stress, excessive ethanol intake, and administration of certain drugs.50 Nonacute porphyrias are not associated with neurologic disorders or acute crisis.
Because the porphyrias are rare disorders, experience with the clinical use of many drugs, particularly anesthetics, is limited. Pharmacologic therapy of acute attacks is aimed at decreasing the activity of aminolevulinic acid synthetase, the rate-limiting step in heme production. Hematin and heme arginate are potent suppressors of aminolevulinic acid synthetase and markedly decrease the pain associated with acute crisis within 48 hours.51,52 Hydration and correction of electrolyte imbalance, glucose infusion to prevent starvation, and propranolol to control autonomic dysfunction and aminolevulinic acid suppression are several mainstays of treatment. Avoidance of precipitating factors is the foundation of therapy in the latent period.
Commonly used anesthetics rarely precipitate an acute attack during latent porphyria.53 Numerous anesthetics have been implicated to exacerbate an acute attack of porphyria and should be avoided. Propofol, ketamine, local anesthetics, muscle relaxants, nitrous oxide, isoflurane, and opioids are considered safe (Table 12-2). Drugs that induce cytochrome enzyme production may trigger a crisis and should be avoided (eg, barbiturates, ethyl alcohol, etomidate, nonbarbiturate sedatives, hydantoin anticonvulsants, hydralazine, and glucocorticoids).50 Although regional anesthetic techniques have been described in porphyria, most experts advise against them because of a risk for exacerbating preexisting neuropathy, which could create confusion if neurologic signs develop postoperatively.54 Perioperative glucose infusion should be administered. Careful positioning is necessary to protect fragile blisters and skin during surgery.
Table 12-2 Safe Anesthetic Drugs in the Presence of Acute Porphyria
Inhaled Anesthetics
Nitrous oxide: safe
Isoflurane: probably safe
Desflurane: probably safe
Sevoflurane: probably safe
Intravenous Anesthetics
Propofol: safe
Ketamine: probably safe
Morphine: safe
Fentanyl: safe
Sufentanil: safe
Acetaminophen: safe
Neuromuscular Blocking Agents
Succinylcholine: safe
Pancuronium: safe
Cisatracurium: probably safe
Vecuronium: probably safe
Rocuronium: probably safe
Mivacurium: probably safe
Anticholinesterases and Anticholinergics
Neostigmine: safe
Atropine: safe
Glycopyrrolate: safe
Local Anesthetics
Lidocaine: safe
Bupivacaine: safe
Tetracaine: safe
Mepivacaine: safe
Ropivacaine: probably safe
Midazolam: probably safe
Droperidol: safe
Metoclopramide: probably safe
Ondansetron: probably safe
Charcot-Marie-Tooth Disease
Charcot-Marie-Tooth disease is the most frequent inherited peripheral neuropathy. Typically, the defect is restricted to the lower third of the legs, causing foot deformities and peroneal muscle atrophy; however, the disease may slowly progress and affect other areas. Patients typically have stocking-glove sensory loss. Sensory deficits usually are milder than are the motor disturbances.55 Pregnancy has been associated with exacerbations.56 Despite long-term disability, life expectancy is not decreased, and treatment usually is supportive.
The effects of nondepolarizing neuromuscular blocking agents appear to be predictable. Although succinylcholine has been used without untoward consequences, it seems prudent to avoid using this neuromuscular blocker given theoretical concerns about hyperkalemia and cardiac arrest.57 Respiratory insufficiency, vocal cord paresis, and cardiac conduction disturbances have been described.58-60
Myasthenia gravis is an autoimmune disorder involving the neuromuscular junction. Antibodies develop and are directed against postsynaptic acetylcholine receptors and other muscle membrane proteins.61,62 The thymus is abnormal in 90% of patients with this disorder (ie, thymic hyperplasia, thymoma, or thymic atrophy).63,64 Autoimmune disorders such as thyroiditis, pernicious anemia, and systemic lupus erythematosus are common in patients with myasthenia gravis.
The hallmark of this disorder is skeletal muscle weakness that is aggravated by exercise and improves with rest. Exacerbations and remissions are common. Any skeletal muscle may be affected, but the most common clinical presentation is ocular muscle weakness. Bulbar involvement may cause difficulty swallowing and respiratory insufficiency. When peripheral muscle groups are involved, ambulation may be difficult. Interestingly, the first manifestation of myasthenia gravis may occur when a patient is administered drugs that stabilize the muscle membrane, such as magnesium sulfate or local anesthetics. Myasthenic crisis occurs in approximately 20% of patients during the course of the disease and usually is precipitated by pulmonary infections.64
The diagnosis of myasthenia gravis is suggested by complaints of muscle weakness, particularly ocular and bulbar muscles. In addition to clinical history, the edrophonium tests (or challenge), electromyography, and detection of circulating antiacetylcholine receptor antibodies may confirm the diagnosis. Surprisingly, the extent of the disease is not proportional to the receptor antibody titer.
Treatment aims to improve function by increasing the amount of acetylcholine available at the neuromuscular junction. Cholinesterase inhibitors effectively increase the concentration of acetylcholine available at the neuromuscular junction. Because of its long duration of action, pyridostigmine is the drug of choice. Consistent control of myasthenia gravis with cholinesterase inhibitors may be a challenge. Underdosing results in worsening of the disease, and overdosing may cause cholinergic crisis. Circulating acetylcholine receptor antibodies are reduced by plasmapheresis, immunosuppressants, and corticosteroids. Thymectomy is controversial, but improvement occurs in the majority of patients with myasthenia gravis, especially if performed early in the course of the disease.65
Myasthenic crisis is a rapid deterioration of neuromuscular and respiratory function that may occur at any time perioperatively as a result of infection, stress, or an overdose with anticholinesterase drugs (cholinergic crisis). Cholinergic crisis typically presents with respiratory and bulbar muscle weakness, excessive salivation, miosis, bradycardia, and abdominal cramps. The diagnosis usually is made after a small dose of edrophonium is administered and worsening of these symptoms is observed. Control of a cholinergic crisis is achieved with supportive measures and administration of atropine or glycopyrrolate.
Preoperative preparation includes assessment of pulmonary function and optimization of medical therapy. Preoperative plasmapheresis has been shown to decrease ICU stay and the need for mechanical ventilation after thymectomy.66 Risk factors that have been identified to predict postoperative respiratory failure after transsternal thymectomy are disease duration greater than 6 years, history of chronic respiratory disease, pyridostigmine dose greater than 750 mg/d, and preoperative vital capacity less than 2.9 L.66 Transcervical thymectomy carries a lower incidence of prolonged postoperative mechanical ventilation than does transsternal thymectomy.67 Whether anticholinesterase medication should be continued up to and including the day of surgery is controversial.68
Volatile anesthetics can be used as the sole anesthetic to provide analgesia, amnesia, and muscle relaxation.69 Muscle relaxants should generally be avoided in most patients with myasthenia gravis. Anticholinesterase therapy should antagonize nondepolarizing muscle relaxants in theory, but in practice, patients with myasthenia gravis may be up to 100 times more sensitive to nondepolarizing relaxants than are unaffected patients.70 Increased sensitivity remains in patients who are asymptomatic. The need for careful titration of nondepolarizing neuromuscular blockers via monitoring with a peripheral nerve stimulator in all patients with a history of myasthenia gravis is confirmed by these findings. Also, anticholinesterase therapy prolongs the response to succinylcholine by impairing plasma cholinesterase activity. Phase II block may be seen after administration of low doses of succinylcholine.71 The decrease in the number of acetylcholine receptors also resists the action of succinylcholine.
Adjuvant drugs such as aminoglycoside antibiotics, magnesium, corticosteroids, loop diuretics, lithium salts, quinidine, and procainamide may exacerbate muscle weakness in myasthenic patients. Central respiratory depression is common in myasthenic patients, and the respiratory depressant effects of opioids and benzodiazepines may be enhanced.72
Epidural analgesia and anesthesia have been used in myasthenic patients.73,74 However, caution is necessary because the muscle relaxation induced by regional anesthesia may accentuate the inherent weakness of myasthenia. Amide local anesthetics are theoretically a better choice than are the ester local anesthetics because cholinesterase activity does not affect amide anesthetic metabolism (see Chapter 45 for a discussion of the local anesthetic structures). Pregnancy has an unpredictable affect on myasthenia, and exacerbations should be anticipated.
Myasthenic Syndrome (Eaton-Lambert Syndrome)
Myasthenic syndrome (Eaton-Lambert syndrome) is an acquired autoimmune disorder of the neuromuscular junction, often associated with carcinomas, in which release of acetylcholine from the nerve terminal is impaired despite normal production and processing of acetylcholine by the nerve cell. Onset of this disorder, when present, often precedes discovery of the malignancy by several years. Antibodies are produced against calcium channels, specific to tumor cells, but unfortunately cross-reactivity with calcium channels at the neuromuscular junction results in a decreased release of acetylcholine. Proximal extremity weakness is common, with the bulbar musculature less likely to be involved. In contrast to myasthenia gravis, muscle weakness is not consistently reversed by anticholinesterase administration, and exercise tends to improve muscle function (Table 12-3). Diagnosis may be made with electromyography or antibody assay. 3,4-Diaminopyridine is commonly administered and increases the presynaptic release of acetylcholine. Treatment of an underlying neoplasm, if present, usually improves symptoms. Immunosuppression, plasmapheresis, and immunoglobulin may be effective.75
Table 12-3 Myasthenia Gravis and Myasthenic Syndrome
Myasthenic Syndrome
Extraocular, bulbar, facial muscle weakness Proximal limb (arms > legs) weakness
Fatigue with exercise Improved strength with exercise
Female > male Male > female
Thymoma Carcinoma (small cell of the lung)
Resistant to succinylcholine Sensitive to succinylcholine
Sensitive to nondepolarizing muscle relaxants Sensitive to nondepolarizing muscle relaxants
Good response to anticholinesterases Poor response to anticholinesterases
Adapted from Stoelting RK, Dierdorf SF, eds. Anesthesia and Co-existing Disease. 4th ed. New York, NY: Churchill Livingstone; 2002. Copyright Elsevier.
Anesthetic management should focus on interactions with muscle relaxants. Patients with myasthenic syndrome are hypersensitive to the effect of depolarizing and nondepolarizing muscle relaxants. Doses should be reduced and titrated to effect with a peripheral nerve stimulator. Administration of 3,4-diaminopyridine should be continued perioperatively.76
Myopathies and Channelopathies
Muscular Dystrophies
Muscular dystrophies are disorders associated with abnormalities of the muscle membrane, resulting in variable, and progressive, loss of skeletal muscle function (Table 12-4). Dystrophin is a major component of the muscle cell cytoskeleton, which provides structural support to the muscle membrane in normal muscle. Lack of dystrophin results in membrane instability and permeability, eventually leading to intracellular calcium accumulation, cell necrosis, and replacement of degenerated muscle by fibrous and adipose tissue.77 In addition to skeletal muscle dysfunction, cardiac and smooth muscles are affected. Indeed, in many types of muscular dystrophy, cardiac muscle involvement may be more significant than skeletal muscle involvement.
Table 12-4 Types of Muscular Dystrophies and Myotonias
Emery-Dreifuss
Fascioscapulohumeral
Limb-girdle
Oculopharyngeal
Myotonias
Hyperkalemic periodic paralysis
Hypokalemic periodic paralysis
Paramyotonia congenita
Proximal myotonic dystrophy
Recessive myotonia
Duchenne muscular dystrophy is the most common muscular dystrophy (1:3500 male births) and has the most severe clinical course.78 This disorder is a recessive, sex-linked genetic abnormality that is clinically evident in males, although female carriers may manifest subclinical abnormalities. Duchenne muscular dystrophy is characterized by painless skeletal muscle degeneration and atrophy. Muscle degeneration and weakness usually manifest in early childhood (age 2-5 years). Severe limitation in movement with development of contractures and kyphoscoliosis confine the child to a wheelchair by early adolescence. Marked increases in serum creatine kinase levels are present. Death commonly results from congestive heart failure or pneumonia. Although aggressive therapy for cardiopulmonary dysfunction has improved survival, afflicted individuals rarely survive beyond the third decade of life.79,80
As the patient ages and the disease progresses, cardiac muscle involvement typically is reflected by a progressive loss of R-wave amplitude in the lateral precordial leads of the ECG. Cardiomyopathy, ventricular dysrhythmias, and mitral regurgitation may develop as cardiac muscle is progressively lost and fibrous tissue replaces myocardial and conducting tissue. Treatment options include administration of angiotensin-converting enzyme inhibitors and β-adrenergic blockers to slow the deterioration of cardiac function.80 Pulmonary function testing reveals a restrictive pulmonary disease pattern. Ineffective cough, resulting from diminished respiratory muscle strength, causes retention of secretions, pneumonia, and oftentimes death.81 Many patients and families choose a tracheostomy and assisted ventilation, which may add years of life, but repetitive pulmonary infection contributes to a shortened life span.82 Intestinal tract hypomotility develops as a result of smooth muscle involvement. Supplemental feedings may slow the process of cachexia, but the disease continues.
Although the cause of Duchenne muscular dystrophy is known, specific genetic therapy is elusive. Therapy is supportive and focuses on improving cardiopulmonary function and better nutrition.
Becker muscular dystrophy is similar to Duchenne muscular dystrophy; however, it has a later onset in life and slower clinical progression. Typically, patients remain ambulatory past the age of 16 years, and cardiac failure caused by occult cardiomyopathy may be the presenting symptom.83 Any male with a persistent elevation in serum creatine kinase concentration should be evaluated for Becker muscular dystrophy.
Emery-Dreifuss X-linked muscular dystrophy is characterized by humeropectoral muscle weakness and contractures of the spine, elbows, and ankles. The autosomal-dominant type of this disorder is caused by a defect in the protein lamin, whereas the recessive form is caused by a defect in the protein emerin. Clinical manifestations of skeletal muscle weakness usually are mild, but cardiac conduction defects may manifest as sudden death. Patients with this disorder are candidates for implantable defibrillating pacemakers.84
Limb-girdle muscular dystrophy patients have weakness of the muscles of the shoulder and pelvic girdles. Most forms of this disorder are inherited in an autosomal-recessive fashion, although autosomal-dominant defects have been discovered. A defect in the sarcoglycan protein is the usual etiology of this abnormality.85 Cardiomyopathy and cardiac conduction defects may occur.
Fascioscapulohumeral muscular dystrophy is a disease with diverse clinical manifestations that is inherited in an autosomal-dominant fashion. Facial, scapulohumeral, anterior tibial, and pelvic-girdle muscle weakness are common. Cardiac conduction defects as well as deafness and retinal vascular disease may occur.
Oculopharyngeal muscular dystrophy primarily manifests with ptosis and dysphagia late in adulthood. Commonly, weakness of the head and neck develop in addition to dysphagia that is present from pharyngeal muscle weakness and esophageal dysmotility.
Merosin-deficient muscular dystrophy, Fukuyama muscular dystrophy, Walker-Warburg syndrome, Ulrich disease, muscle–eye–brain disease, nemaline myopathy, myotubular myopathy, and rigid spine muscular dystrophy are a group of muscular dystrophies that comprise congenital muscular dystrophy.85,86 Congenital muscular dystrophies are characterized by early onset of muscle weakness, feeding difficulties, and respiratory dysfunction, frequently with accompanying mental retardation.
Perioperative complications from anesthesia in patients with muscular dystrophies usually result from the effects of anesthetic drugs on myocardial and skeletal muscle. Preexisting myocardial dysfunction makes the patient with muscular dystrophy susceptible to the myocardial depressant effects of anesthetics. The abnormal muscle cell membrane predisposes patients with muscular dystrophy to hyperkalemia and rhabdomyolysis when subjected to volatile anesthetics alone or in combination with succinylcholine, as numerous case reports support. In light of the abnormal muscle membrane, succinylcholine administration may further damage the muscle membrane and cause the release of intracellular contents. Therefore, succinylcholine should be avoided in patients with muscular dystrophies. It has been speculated that volatile anesthetics cause the release of calcium from the sarcoplasmic reticulum and may elicit damage to the muscle cell membrane and cause rhabdomyolysis. Interestingly, sevoflurane appears to be a less potent stimulus for release of calcium from the sarcoplasmic reticulum than are other volatile agents.87
Nondepolarizing muscle relaxants may have a prolonged duration of action in patients with muscular dystrophy, although the response to mivacurium appears to be normal.88 Therefore, close monitoring of neuromuscular function is indicated. Although unpredictable, some patients with muscular dystrophies may be susceptible to developing malignant hyperthermia (MH). Without regard to specific etiology, patients who have chronically increased creatine phosphokinase levels may have a 40% to 45% risk of being MH susceptible.89 Therefore, careful consideration of anesthetic plan may be to avoid all MH-triggering agents until a patient has been evaluated by the caffeine–halothane contracture test on a muscle biopsy specimen. (A detailed discussion of malignant hyperthermia is provided in Chapter 87.)
Delayed gastric emptying and impaired swallowing increase the risk of perioperative aspiration. Postoperatively, patients with muscular dystrophies must be closely monitored for evidence of pulmonary dysfunction and retained secretions. Vigorous pulmonary toilet and mechanical ventilation are frequently required. Regardless of the need for postoperative mechanical ventilation, these patients should be placed in an advanced monitoring unit (ICU) for appropriate analgesic therapy and respiratory monitoring.
The myotonias are a diverse group of hereditary skeletal muscle disorders with a common clinical sign: myotonia (Table 12-1). Myotonia is the persistent contracture and delayed relaxation of skeletal muscle after cessation of voluntary contraction or stimulation of the muscle. One of the typical signs of myotonic dystrophy is the inability to relax the handgrip. Progressive muscle wasting, ptosis, and facial muscle weakness also are common in patients with myotonic dystrophy. Interestingly, in other myotonic syndromes, the most common finding is stiffness that improves with exercise. However, paramyotonia (cold-induced myotonia) is an exception, wherein exercise exacerbates symptoms. Recently, genetic defects in sodium, chloride, and calcium ion channels in the muscle membrane have been identified as the abnormalities responsible for myotonia. Therefore, drugs such as mexiletine, procainamide, tocainide, and quinine may relax myotonic contractures by altering ion channel activity and skeletal muscle membrane excitability.
The most common of the myotonic disorders is myotonic dystrophy (Steinert disease), although proximal myotonic myopathy, myotonic dystrophy type II, and proximal myotonic dystrophy are other myotonic diseases. Myotonic dystrophy is inherited in an autosomal-dominant pattern, and symptoms typically appear in the second or third decade of life. A defect on chromosome 19 produces a decrease in protein kinase that causes degeneration of the sarcoplasmic reticulum.90 This myotonic dystrophy is the only myotonic disorder to exhibit extramuscular manifestations. Cataracts, premature balding, diabetes mellitus, thyroid dysfunction, adrenal insufficiency, gonadal dysfunction, and cardiac conduction defects are common. Cardiac involvement does not correlate with the severity of skeletal muscle involvement.91 There is a progressive deterioration of the conduction system resulting in atrioventricular conduction delay. First-degree atrioventricular block, bundle-branch block, and widening of the QRS complex are common. Cardiomyopathy, cardiac failure, and sudden death may occur, and the incidences of septal defects, mitral valve prolapse, and valvular disease are increased.
Recurrent pulmonary infections and aspiration may result when bulbar musculature is affected. Pulmonary function testing demonstrates a restrictive lung disease pattern, mild arterial hypoxemia, and diminished ventilatory responses to hypercapnia and hypoxia. Gastric atony may develop as a result of alterations in smooth muscle function. Exacerbations of myotonic dystrophy often occur during pregnancy as a result of increased concentrations of progesterone. Congestive heart failure is common during pregnancy, and cesarean delivery is indicated because of uterine smooth muscle involvement. Labor typically is prolonged, and the incidence of postpartum hemorrhage is increased. Infants may have congenital myotonic dystrophy, which typically is characterized by hypotonia, respiratory insufficiency, and feeding difficulties.
Therapy for myotonic dystrophy is focused on treating coexisting diseases and cardiac dysrhythmias. Drugs that alter sodium channel function have been the most effective for managing myotonia (eg, mexiletine). Avoiding factors known to precipitate myotonia is important.
Anesthetic considerations for patients with myotonic dystrophy include the presence of coexisting diseases, abnormal responses to drugs, and avoiding factors that are associated with the development of perioperative myotonia. Perioperative myotonia has been precipitated by drugs (propofol and succinylcholine), physical factors (hypothermia), electrocautery, and surgical manipulation. Potassium administration worsens clinical myotonia. Succinylcholine produces an exaggerated contracture, and its use should be avoided. The myotonic response produced by succinylcholine may be so severe that ventilation and tracheal intubation are difficult and may be impossible. The typical presentation of succinylcholine-induced myotonic contracture includes jaw, abdominal, and chest rigidity. Perioperative myotonia may be difficult to differentiate from MH. A recent thorough review of the pathophysiology and clinical experience related to the myotonias concluded that MH is no more common in these patients than in the general population, despite the frequent suggestion of such a relationship (a minor theoretical concern remained for hypokalemic periodic paralysis, but no clinical episodes of MH have been reported in these patients).92 Nondepolarizing muscle relaxants and peripheral nerve blocks do not abolish myotonic contractures. Induction agents, volatile anesthetics, opioids (systemic and neuraxial), and sedatives may cause profound respiratory depression. Increased sensitivity to nondepolarizing muscle relaxants may occur, especially when there is muscle wasting. Prudence dictates the use of short-acting muscle relaxants when necessary, with careful monitoring of the response. Peripheral nerve stimulation may cause myotonia or be misinterpreted as sustained tetanus, even though significant neuromuscular blockade exists. Reversal of neuromuscular blockade may induce myotonia.
Although no specific anesthetic technique has been determined to be superior for patients with myotonic dystrophy, close monitoring of cardiac and pulmonary function is critical to ensure an optimal perioperative outcome. Mechanical ventilation should be used until muscle strength and function return to baseline.93 Regional anesthesia has been successfully performed in patients with myotonic dystrophy.94
Familial Periodic Paralysis
Periodic paralyses are skeletal muscle channelopathies, which include hyperkalemic and hypokalemic periodic paralysis, paramyotonia congenita, and potassium-aggravated myotonia.95-97 Periodic paralyses are characterized by acute reversible episodes of muscle weakness or paralysis of the extremities, with sparing of the respiratory muscles. Although these disorders are classified by changes in serum potassium concentrations during an acute episode, these changes are relative to the baseline potassium concentration and are not always abnormally increased or decreased (Table 12-5).
Table 12-5 Clinical Features of Hypokalemic and Hyperkalemic Familial Periodic Paralysis
Hyperkalemic
Potassium concentration >5.5 mEq/L (or normal) during crisis
Precipitating events
Potassium infusion
Rest after strenuous exercise
Duration of paralysis
Minutes to hours (rarely a few days)
Hypokalemic
Potassium concentration <3 mEq/L during crisis
High glucose intake
Strenuous exercise
Stress (including trauma or surgery)
Glucose-insulin infusion
Hours to days
Hyperkalemic periodic paralysis is inherited in an autosomal-dominant fashion. The dominant trait has been discovered as a mutation in the sodium ion channel on chromosome 17.90 As a consequence of this dysfunction, when the resting membrane potential becomes slightly more positive, the myofiber can more easily reach threshold and the muscle becomes hyperexcitable, which clinically manifests as myotonia.98 When the membrane potential becomes even more positive, the myofiber cannot fire an action potential because of the loss of a sufficient membrane potential, and the result is paralysis.98 Normokalemic periodic paralysis is rare and most likely is a variant of hyperkalemic paralysis in which the potassium concentration does not change during attacks.99
Attacks usually begin during childhood and vary in frequency from several times per week to once in a lifetime. These episodes of myotonia and paralysis may last several hours after exposure to a trigger. Triggering events include eating potassium-rich foods, IV infusion of potassium, fasting, cold exposure, and rest after strenuous exercise. Thiazide diuretics, acetazolamide and a low-potassium diet are the mainstays of preventive treatment. Glucose and insulin infusion, careful catecholamine infusions, and IV calcium administration can be used to manage acute attacks.
Hypokalemic periodic paralysis is usually inherited in an autosomal-dominant pattern. The dominant trait produces a defect in the calcium ion channel on chromosome 1.100 The dihydropyridine receptor is a voltage-gated ion channel that is responsible for attacks, but the mechanism by which this defect results in attacks of paralysis is under investigation.
Attacks usually begin during childhood or early adulthood and vary in frequency. In contrast to the hyperkalemic form, attacks last longer—from hours to days. Also, cardiac arrhythmias are more common, ventricular dilatation may be seen, myotonia is absent, and permanent muscle weakness eventually develops by the fifth decade of life. Paralysis is commonly triggered by ingestion of carbohydrates, strenuous exercise, glucose and insulin infusion, IV calcium, and exposure to cold. Paralysis often is incomplete, affecting the limbs and trunk but sparing the diaphragm. Rarely are respiratory muscles involved, but asphyxia has been reported. Treatment involves the administration of potassium, acetazolamide, and dichlorphenamide.
Maintenance of normal potassium concentrations and avoidance of events that precipitate weakness are the primary goals of the perioperative management of patients with hyperkalemic and hypokalemic periodic paralysis. Electrolyte abnormalities should be addressed and corrected as best as possible before surgery. Patients may be sensitive to nondepolarizing muscle relaxants; therefore, short-acting relaxants should be administered when necessary. The response should be monitored with a peripheral nerve stimulator. Reversal should be avoided because of concern that reversal agents may precipitate myotonia. However, adequate muscle strength must be assured before extubation.101 Succinylcholine should be avoided because it alters serum potassium concentrations and therefore may precipitate an attack. Reductions in serum potassium from metabolic changes or medications should be avoided because this situation may initiate an episode of paralysis. Perioperative potassium values should be monitored serially. The ECG should be continuously monitored for evidence of arrhythmia, and normothermia and normocapnia should be maintained. Volatile anesthetics have been administered without complication. Regional anesthesia has been used successfully, although there is concern that regional techniques can create confusion if neurologic signs develop postoperatively.102 MH has been associated with periodic paralyses.103
Skeletal Muscle Diseases
Central Core Disease
Central core disease is a hereditary, nonprogressive, congenital myopathy that typically is characterized by lower extremity muscle weakness. Increased lumbar lordosis, kyphoscoliosis, and hip dislocations may occur. Histologically, type I muscle fibers display amorphous central areas (cores). The underlying defect is thought to be associated with the ryanodine receptor gene, similar to MH.104 Susceptibility for MH is a great concern when anesthetizing patients with central core disease.105,106 MH precautions should be taken and nontriggering anesthetics used when anesthetizing patients with central core disease (see Chapter 87 for a thorough discussion of malignant hyperthermia).
Glycogen Storage Diseases
Glycogen storage diseases are inherited disorders characterized by a deficiency of enzymes involved in glucose metabolism. An enzyme deficiency results in a lack or excess of precursors and end-products of glycogen formation and breakdown. Type II (Pompe disease) glycogen storage disease is notable for the buildup of glycogen in smooth, skeletal, and cardiac muscle. Cardiac involvement typically leads to congestive heart failure. Anesthetic experience is limited.107,108 Skeletal muscle involvement predisposes patients to upper airway obstruction secondary to glycogen infiltration of the tongue. Aspiration is common secondary to neurologic involvement and subsequent impairment of cough, gag, and swallowing mechanisms. Volatile anesthetics may precipitate cardiovascular embarrassment or collapse. Administration of succinylcholine to these patients may not be prudent because theoretically it could result in myoglobinuria and perhaps hyperkalemia with subsequent cardiac arrest. Hypoglycemia and acidosis may develop perioperatively, and patients should be hydrated and receive exogenous glucose. Hepatic dysfunction usually is present, so judicious administration of drugs hepatically metabolized should be taken into consideration. Regional anesthesia has been performed in patients with glycogen storage disorders.109 Patients with type V (McArdle disease) glycogen storage disease are prone to developing myoglobinuria and rhabdomyolysis. Automated blood pressure readings should be performed cautiously, and tourniquets should be avoided to prevent muscle damage.110
Mitochondrial Myopathies
Mitochondrial myopathies are a group of disorders that affect oxidative phosphorylation, resulting in impaired adenosine triphosphate production. These disorders have many manifestations, including CNS and muscle pathology. Exercise intolerance, fatigue, muscle pain, progressive weakness, and cardiomyopathy may be present. Respiratory depression is common after administration of general anesthesia. There does not appear to be an association with MH with most mitochondrial disorders.111-114 However, avoidance of succinylcholine seems prudent because of the potential for hyperkalemia.
Kearns-Sayre syndrome and mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS syndrome) are distinct mitochondrial disorders. The anesthetic concerns are similar to the general concerns previously stated, but, in addition, Kearns-Sayre syndrome is associated with heart block due to involvement of the cardiac conduction system. General anesthesia should be used with caution because it may increase the risk of myocardial depression and cardiac conduction defects.115 MELAS syndrome is characterized by stroke-like episodes, seizures, dementia, recurrent headaches, vomiting, and lactic acidosis. There is suspicion that MH susceptibility may be increased, and propofol-based anesthesia has been used successfully. Myocardial depression may occur with administration of volatile anesthetics, so they therefore should be used with caution. Additional precautions include maintenance of normothermia, avoidance of lactated solutions or acidosis, and careful attention to blood glucose control. A full discussion of this unusual syndrome is beyond the scope of this chapter, but a recent case report contains a useful review of overall anesthetic considerations.116
Patients with musculoskeletal disease may present varied challenges to the anesthesiologist. A number of more common musculoskeletal conditions are included here for consideration in the evaluation of a patient for anesthesia.
Osteoarthritis (OA) is a prevalent condition with advancing age.117 Multiple joints are affected, most commonly weight-bearing joints. Patients with OA may require joint replacement surgery or other intricate orthopedic procedures. In patients with OA, the cervical spine may have a reduced range of motion, and the lumbar spine may be affected with osteal growths such that performing regional anesthesia may be difficult. Determination of what the surgical approach required for patient positioning is important. Whether regional anesthesia will be used intraoperatively or only for postoperative analgesia must be considered. How soon the patient is expected to become ambulatory and require full sensation and motor capabilities may dictate whether long-acting regional anesthetics or techniques can be used.
A careful list of recent nonsteroidal anti-inflammatory drug (NSAID) use should be obtained. With many of the newer, more powerful, and long-lasting NSAIDs, there is concern for possible hematoma formation after regional or neuraxial anesthesia. Most practitioners are willing to perform peripheral blocks in patients who are receiving moderate doses of NSAIDs, provided there is no history of excessive bleeding; however, high-dose NSAID use or a history of bleeding should trigger a note of caution.
OA results in moderate to severe disability that may be relieved by surgical approaches. Of significant concern to the anesthesiologist is cervical spine disease with reduced range of motion and implications of difficulty in visualizing or securing the airway. Neurologic manifestations may occur from development of spinal stenosis at any spinal level. Chronic, subacute, and acute symptoms may be present, and acute neurologic symptoms may require emergency operation. This may require rapid sequence intubation, which may become complicated if the airway is not easily visualized.
Treatment of OA includes salicylates, NSAIDs, local heat, and surgical procedures to ameliorate painful symptoms. There is no effective therapy for slowing the pathogenesis of the disease. Selective cyclooxygenase-2 inhibitors were found to be effective in patients with OA, and their side-effect profile initially was thought to be advantageous compared with that of other nonselective NSAIDs. However, some of these drugs were withdrawn from the market when cardiovascular events associated with use of cyclooxygenase-2 agents were discovered. A careful history of medication use is necessary before considering neuraxial blockade.
Rheumatoid arthritis (RA) is an autoimmune disease that attacks numerous joints throughout the body and has some special considerations for the anesthesiologist.118 Patients with RA may have complications primarily from their disease or secondarily from treatment of the disease, including use of glucocorticoids, NSAIDs, and immunosuppressive drugs.
Patients with advanced stages of RA may have temporomandibular ankylosis that makes direct laryngoscopy for endotracheal intubation very challenging, if not impossible. Fiberoptic intubation may be required, or tracheostomy may be necessary. The cervical spine may be involved, including laxity of the C1-2 ligament, causing instability of the cervical spine. Subluxation of the atlantoaxial joint and instability can progress to spinal cord compression. Long tract signs, including bowel and bladder dysfunction, may occur, and sudden death has occurred from spinal cord laceration by the odontoid process. Recognizing early signs of serious cervical spine instability is critical in planning the approach to the airway. Cricoarytenoid (CA) joint involvement may occur in RA. This condition may make the glottis more rigid and require insertion of a smaller-diameter endotracheal tube. CA joints that are fixed in adduction may be life-threatening and require tracheostomy in order to establish a stable airway.
Awake or fiberoptic intubation may be necessary to permit neurologic examination immediately after placement of an endotracheal tube (see Chapters 10 and 36 regarding airway evaluation and management). Patients with RA often have involvement of multiple digits and may suffer from compression fractures of the vertebral bodies secondary to glucocorticoid use. These presentations in this illness may make anesthesia particularly challenging.
RA afflicts peripheral joints, most often symmetrically. As the disease advances, patients may have severe limitations in movement because of inflammatory contractions, pain with motion, or bone joint fusions due to long-standing inflammation. These patients may present for multiarticular surgical procedures or other surgical procedures secondary to complications of RA.
RA is a systemic disease with pulmonary and cardiac manifestations. Restrictive lung disease occurs from multiple complications. Pulmonary interstitial fibrosis, pulmonary effusions, and parenchymal rheumatoid nodules may lead to crepitations. With advanced disease, ventilation and oxygenation may require attention to small-volume, positive-pressure ventilation during surgery and supplemental oxygen use preoperatively and postoperatively. Consideration for assisted ventilation postoperatively should be discussed with the patient.
RA can be associated with pericardial effusion and pericarditis. Tamponade is rare but well described. Conduction disturbances and valvular dysfunction occurs in advanced stages of RA. Preoperative echocardiographic evaluation and a 12-lead ECG are indicated on the basis of symptomatology or length of duration of the disease.
Treatment of RA includes use of NSAIDs, glucocorticoids, gold salts, penicillin, and immunosuppressive (cytotoxic) drugs.119 These drugs have multiple serious side effects. Glucocorticoids cause hypertension, cataracts, skin and muscle atrophy, and osteopenia, which may result in vertebral compression fractures. Immunosuppressive therapy may predispose to infections and can be cardiotoxic. NSAIDs and aspirin will result in thrombasthenia or other coagulation disorders, which must be considered before performance of regional neuraxial blockade. Peripheral neural blockade may have less risk of hemorrhagic complications, but the rare complications do not deter some anesthesiologists from careful use of peripheral neural blockade after thorough preoperative assessment of alternatives.
Ankylosing spondylitis is an inflammatory disease of the spine and paraspinal tissue.120 Ankylosing spondylitis typically affects young men and may become disabling due to chronic pain in less than a decade. Back pain with or without peripheral arthritis occurs. Ankylosis of the hip and sacroiliac joints may occur, and the cervical spine may also be involved. Cauda equina syndrome may occur with devastating consequences.
Anesthetic considerations are similar to those for patients with RA. Cervical fusion (ankylosis) or atlantoaxial subluxation may occur. Cardiopulmonary complications include restrictive pulmonary fibrosis, and possibly cardiac conduction abnormalities and aortic insufficiency.
Pharmacologic therapy includes NSAIDs and glucocorticoids. Side-effect profiles of each of these classes are as discussed previously. Neuroaxial blockade may be contraindicated on the basis of coagulation status and recent use of NSAIDs.
Cerebral palsy (CP) is considered a static encephalopathy. It is included in the discussion of musculoskeletal diseases because of the number of symptoms secondary to loss of upper motor neuron control. Patients have imbalances of flexor/extensor muscle activity resulting in significant contractures. These conditions may make the patient's airway difficult to approach, and the neck may have a reduced range of motion or fixed abnormal position. The usual extremity positions may not be obtainable because of contractures, and IV access may be difficult. Because patients with CP live into adulthood, the anesthesiologist must be aware that multiple procedures for CP are meant to reduce the patient's burden of care by allowing him or her to obtain a more neutral or balanced position. Procedures including osteotomies, botulinum toxin and phenol injections, and other major procedures often are necessary. Patients with CP are one of a group of patients presenting for neuromuscular scoliosis repair. Kyphoscoliosis can be a particularly challenging orthopedic problem requiring extensive instrumentation of the spine posteriorly and sometimes release of multiple ligaments anteriorly. The two-phased approach may be performed in one procedure or may be separated by a number of days or weeks (see Chapter 65 for a discussion of spinal surgery).
Anesthesia considerations include providing a stable airway, appropriate invasive monitoring for anticipated major blood loss, IV access for resuscitative fluid administration, and possible postoperative assisted ventilation. Patients may be limited to nonverbal communication skills, thereby making pain management challenging. Patients with CP may have a seizure disorder from brain injury at birth or traumatic or anoxic brain injury later in life. Anesthesia clinicians should be familiar with the many antiepileptic drugs currently prescribed. If therapeutic monitoring methods are available, optimal serum concentrations should be achieved preoperatively.
Osteoporosis is a generic diagnostic term describing loss of bone mass from one of several disease states. Osteoporosis occurs with advancing age and affects women more frequently than men. Decreased bone density may result in pathologic fractures and kyphosis. Although a systemic disorder, axial spine involvement usually is responsible for acute manifestations, and this is the problem that often presents the most difficulty for the anesthesia practitioner.
Osteoporotic fractures and kyphosis may significantly complicate regional anesthetic neuroaxial procedures. Acute fractures may be severely painful and, in rare circumstances, may result in neurologic compromise necessitating urgent operation. Patients may be unable to assume a sitting or supine position comfortably. With increasing kyphosis, a restrictive lung disease pattern appears. Airway management should include plans to ameliorate the patient's pain, use thorough preoxygenation, and institute assisted ventilation for neurodecompressive procedures with prone positioning. Postoperative respiratory insufficiency should be monitored secondary to underlying respiratory concerns and the moderate-to-heavy opioid requirement for postoperative analgesia.
Most patients with osteoporosis may have an idiopathic etiology. These patients have normal laboratory values for calcium, phosphorus, and alkaline phosphatase. Patients with abnormal laboratory values should be evaluated for coexisting diseases such as hyperparathyroidism or malignancy (hypercalcemia). Paget disease usually is accompanied by a high alkaline phosphatase.
Osteogenesis imperfecta (OI) is an inherited disorder of connective tissue that usually manifests in 1 of 2 presentations: osteogenesis imperfecta congenita or osteogenesis imperfecta tarda.121 Newborns and children suffer multiple fractures in the congenital form, whereas the onset of fractures occurs in later childhood, adolescence, and adulthood in the tarda form. In addition to musculoskeletal presentations, these patients may suffer otosclerosis and progressive hearing loss, dental hypoplasia, ligamentous laxity, cardiac valvular insufficiency, and easy bruisability.
Evaluation of a patient with OI includes attention to dental deformities preexisting at the time of anesthesia and echocardiographic evaluation if a murmur is present. Airway management usually is not complicated; however, patient positioning for comfort may be challenging. Regional anesthesia is a reasonable option as in healthy patients, but tourniquet use should be avoided to reduce risk of fracture.
When surgeons may not have the benefit of tourniquet use for a specific procedure, greater than expected blood loss should be anticipated. Although bleeding tendency in patients with OI has been described, this finding does not absolutely contraindicate regional anesthesia.
Patients with OI and many patients with musculoskeletal dysplasias tend to become febrile in the operating room. Ectodermal dysplasia or lack of vasorelaxation may prevent mechanisms of heat loss usually encountered in the operating room or during anesthesia. Special attention should be directed to temperature monitoring and control, even for short procedures. With recent attention to prevention of heat loss during anesthesia, patients often are protected from hypothermia. However, in patients with OI, moderate to severe generalized hyperthermia may occur, and this may be confused with MH. Patients with OI do not have an increased susceptibility for MH.
Scleroderma (progressive systemic sclerosis [PSS]) is a disorder of connective tissue with destruction of small arterioles, leading to fibrosis of the skin and internal organs. It is not specifically a musculoskeletal disease. PSS causes swollen and stiff fingers and Raynaud phenomenon. Pain of the digits and knee joints is common, and a polyarthritis resembling RA may occur. Limited mobility secondary to diffuse fibrosis (scleroderma) becomes a feature that may make patient positioning for surgery difficult.
Visceral involvement in scleroderma includes esophageal (dysphagia and gastroesophageal reflux), gastric atony and dilation, intestinal (abdominal pain), pulmonary fibrosis, and cardiac involvement, including varying degrees of heart block, cardiomyopathy, and pericarditis, which may result in tamponade.122
Preoperative evaluation includes a comprehensive history of symptoms related to the airway, pulmonary, and cardiac systems. Airway management may require a rapid sequence or an awake technique. Cardiopulmonary evaluation depends on duration of the disease and symptoms of disability or signs on physical examination. Cardiac rhythm and performance should be thoroughly evaluated before elective anesthesia and operation.
When a patient with PSS presents for emergent surgery, a 12-lead ECG, and possibly echocardiography, should be considered. Electrolytes should be measured. Causes of death in PSS include cardiovascular etiologies and renal failure. Subclinical renal failure (increased blood urea nitrogen and creatinine, hyperkalemia, and hyperphosphatemia) is a relative contraindication to succinylcholine use. Patients may experience amnesia from lack of absorption of nutrients and microangiopathic hemolytic anemia.
Postoperative care should include cardiovascular monitoring, serial electrolytes evaluation, and supplemental oxygen to address the combined effects of pulmonary involvement and opioid use for postoperative analgesia.
Carpal tunnel syndrome is an entrapment neuropathy that may be idiopathic or secondary to a number of illnesses, including RA, tenosynovitis, and amyloidoses, and may occur secondary to edema during pregnancy. The surgical approach to entrapment is decompression by release of the transverse ligaments or removal of a space-occupying lesion compressing the nerve.
The anesthetic approach may include general anesthesia, upper extremity regional blockade, or local intravenous anesthesia (Bier block). These procedures usually are performed in an ambulatory surgical suite, and the anesthesia plan should anticipate the need for rapid recovery. Some surgeons will want to perform a sensorimotor examination immediately postoperatively to establish that no surgical complication occurred, but most are comfortable with regional anesthetic techniques for this procedure.
Achondroplasia
Achondroplasia is one etiology of dwarfism. A defect in endochondral ossification appears to lead to short tubular bones. Children often are identified at birth by their phenotypic presentation. Relative macrocephaly and hypoplastic midfacial features are common.
The two most concerning issues with achondroplasia are a relative stenotic foramen magnum, which may result in obstructive hydrocephalus, and atlantoaxial instability. These problems may cause acute neurologic presentation of increased intracranial pressure or spinal cord compression, respectively. These problems may present early in infancy and require emergent decompression.
As these children grow, they develop increasing lordosis and require spinal fixation/stabilization.123 Multiple procedures may be necessary.
Anesthetic implications in patients with achondroplasia include anticipating a difficult seal of a face mask because of midfacial hypoplasia. Tracheal intubation is generally not difficult; however, care should be taken not to hyperextend the neck for visualization of the vocal cords to avoid cervical spinal cord injury. No additional side effects are associated with use of succinylcholine, and there is no association of achondroplasia with susceptibility to MH.
Patients with achondroplasia may have an inability to disseminate heat effectively. Special attention to central temperature monitoring and management should be anticipated. These patients may have an excessive thermal response to anticholinergic agents.
Polymyositis/Dermatomyositis
Polymyositis and dermatomyositis are diseases that involve skeletal muscle, connective tissue, and the skin.124 The etiologies are unknown, but autoimmune phenomena are suspected. Usually slow progressive weakness occurring over months to years affects proximal extremity muscle groups, followed by neck involvement. Pharyngeal and laryngeal muscles also may be involved.
Cardiac involvement may include rhythm disturbances, myocardial necrosis, or inflammation. Pulmonary fibrosis or interstitial pneumonitis may be seen. Treatment of the illness consists of corticosteroids and immunosuppressive drugs. The consequences of these treatments should be considered in the preoperative evaluation (eg, stress doses of corticosteroids may be indicated for major invasive procedures, and meticulous attention to sterile technique is required to prevent risk of infection after vascular access).
Anesthetic implications of these diseases are primarily of pharyngeal muscle activity and the risk for aspiration. No known anesthetic-associated exacerbation of cardiac involvement has been reported. Patients do not routinely experience respiratory weakness after anesthesia or use of neuromuscular blocking agents.
Rhabdomyolysis is a condition associated with many inherited disorders,125 toxin and drug exposure,126,127 ischemia, crushing, and burn injury.128 Exercise-induced rhabdomyolysis can occur secondary to inborn errors or secondary to exercise-induced bioenergetic failure at the cellular level. Perioperative rhabdomyolysis has been associated with positioning, cardiopulmonary bypass, an excessive response to succinylcholine, and as a prominent symptom of MH syndrome129 (see Chapter 87 for details regarding malignant hyperthermia).
A preoperative history of rhabdomyolysis should alert the anesthesiologist to the possibility of inborn genetic errors (carnitine palmitoyltransferase deficiency [not related to MH]) and susceptibility to MH. Exercise-induced rhabdomyolysis patients and patients with chronic hypercreatine kinasemia (hyperCKemia) are considered subgroups at high risk for MH susceptibility.89,130,131 When in doubt regarding the possibility of susceptibility to MH, the MH hotline consultants are available 24 hours per day (1-800-MH-HYPER) in the United States and Canada (see Chapter 87).
Malignant Hyperthermia
MH is related to very specific muscle disorders as referred (hyperCKemia and exercise-induced rhabdomyolysis, central core disease, and others). MH is covered extensively in Chapter 87.
Movement Disorders: Parkinson Disease
Parkinson disease is the second most common neurodegenerative disease (after Alzheimer disease) and the most common of the movement disorders. This section focuses specifically on Parkinson disease because it is not uncommon in patients requiring anesthetic care for the primary condition (eg, for deep brain stimulation) or for unrelated conditions that occur in the elderly. More than half of persons aged 85 years or older have Parkinson disease or parkinsonian symptoms. The cause of Parkinson disease is unknown, but it involves neuronal destruction in the substantia nigra, locus ceruleus, and other brain centers. The resulting loss of dopamine production produces extrapyramidal signs and symptoms including bradykinesia, festinating (short, jerky, accelerating) gait, tremor, rigidity, and loss of balance. The mainstay of treatment is oral levodopa (L-dopa), a precursor that is converted to dopamine in the brain. Dopamine agonists or type B monoamine oxidase inhibitors (MAOIs) may also be used. The diagnosis of Parkinson disease is made by clinical observation and response to L-dopa; confirmation requires autopsy showing the characteristic Levy bodies in the substantia nigra.
Anesthesia represents a significant hazard for Parkinson disease patients.132 These patients are susceptible to pulmonary aspiration, laryngospasm, diaphragmatic spasm, and altered function of the ventilatory muscles, resulting in an obstructive breathing pattern.133–135 Respiratory complications (ie, aspiration) represent the most common cause of death in these patients.136 Preoperative evaluation should include careful evaluation of the airway and chest, including a chest radiograph if chronic aspiration is suspected.
Perioperative management of multiple medications requires special attention, often among several medical specialists. Withdrawal of Parkinson disease medications in the perioperative period can cause a clinically significant worsening of the respiratory symptoms.137 Polypharmacy in Parkinson disease patients may also contribute to a greater incidence of orthostatic hypotension.138 This is further exacerbated by the direct vasodilatory effects of dopamine agonists or tricyclic antidepressants, which are used commonly in this population. The addition of systemic opiates for postoperative analgesia may lead to drug interactions in these patients who are often receiving multiple medications. These factors may contribute to the 8-fold increase in postoperative delirium observed in Parkinson disease patients.139
The approach to anesthetic care varies depending on the proposed procedure. Broadly, these patients can be classified as those undergoing deep brain stimulation (ie, primary disease surgery) and those undergoing other procedures (ie, incidental surgery). For the latter, the regularly prescribed medications should be administered immediately preoperatively and resumed as soon as possible postoperatively. Regional anesthesia may offer significant advantages in patients with Parkinson disease by allowing an earlier return to oral intake, eliminating the use of neuromuscular blocking drugs and the risks of general anesthesia.132,140 Those undergoing deep brain stimulation require a uniquely different approach; their anti-Parkinson medications are withheld before the procedure in order to produce maximum effect during deep brain stimulation, which is performed under local anesthesia141 (see Chapter 51 for greater discussion of the anesthetic care of patients undergoing deep brain stimulation).
General anesthesia may be required for some procedures, and there are reported problems associated with the use of numerous anesthetics and related medications. Parkinson symptoms were triggered in a patient by general anesthesia who went on to develop the disease.142 Propofol triggered dyskinetic movements in these patients.143 Muscle relaxants, including succinylcholine, have been used safely in Parkinson disease patients.144 Opioids can produce uncommon reactions. Alfentanil has been linked to an acute dystonic reaction in a Parkinson disease patient.145 Morphine has been reported to reduce dyskinesia at low doses but to induce akinesia at greater doses.146 The concomitant use of meperidine and selegiline, a selective MAO type B inhibitor, has resulted in agitation, muscle rigidity, sweating, and hyperpyrexia, and their use is not recommended.147 Ketorolac has been used safely in patients taking MAOIs.148 Phenothiazines, butyrophenones, and metoclopramide should be used with caution, if at all, in the management of Parkinson disease patients because of their antidopaminergic effects. Finally, the short half-life of oral L-dopa (1-3 hours) can result in symptom exacerbation during long procedures. Although absorption takes place primarily in the duodenum, administration of L-dopa by nasogastric tube has been reported to be effective.149
Patients with neuromuscular or skeletal disease present special problems for anesthetic care. Issues range from physical problems such as airway access or patient positioning to biochemical problems and abnormal thermal regulation. Cardiovascular or respiratory abnormalities accompany several of these diseases and further complicate perioperative anesthetic care. Patients with these differing coexisting comorbidities should be carefully considered for assisted ventilation postoperatively if the effects of residual anesthetics or analgesics remain at the completion of the surgical procedure or if moderate to high doses of opioids will be necessary postoperatively for pain management. Susceptibility to serious anesthetic-related complications, such as rhabdomyolysis or MH, may occur in some patients. Thorough preoperative evaluation, knowledge of the underlying disease, and careful anesthetic planning and management are required to achieve the goals of safe and uneventful anesthetic care.
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