the most important reason for this is the apparent development of a nondepolarizing , relaxant - induced neuropathy , which leads to difficulty in weaning patients from artificial ventilation , among other problems . some frequently used drugs , such as corticosteriods and aminoglycoside antibiotics , contribute to this neuropathy . therefore , nowadays relaxants are only administered in the icu for specific indications , such as when decreased muscle tone is required , for treating patients who fight the ventilator and in order to allow permissive hypercapnia . relaxants are still needed frequently in surgical anaesthesia to facilitate quick procedures such as endotracheal intubation . its ultra - short duration of action renders rapid return of spontaneous breathing possible if intubation fails . the situation in the icu is different , however . during anaesthesia , intubation and artificial ventilation are only indicated to facilitate surgery by ensuring an open airway . in the icu these are absolute indications , and rapid return of spontaneous ventilation is not necessary , given that intubation is mainly indicated to start artificial ventilation . its mechanism of action ( depolarization of muscle cell membrane ) results in the release of intracellular potassium by upregulating acetylcholine receptors , especially outside the motor endplate , and changing their characteristics . potassium release is already massively increased in a number of circumstances and diseases that are frequently present in icu patients , including long - term immobilization , extensive muscle trauma , many neuromuscular diseases , denervation of muscles , burns , sepsis , encephalitis and acute renal failure . potassium release can be further augmented by acid - base balance disturbances and by corticosteroids . when such an arrest occurs it is difficult to resuscitate the patient . in patients with myopathy or those receiving long - term treatment with corticosteroids it is likely that cardiac arrest in such cases has an even higher mortality rate than cardiac arrest in succinylcholine - induced hyperkalaemia alone . in intensive care patients there is large variability in the activity of plasma cholinesterase , an enzyme that metabolizes succinylcholine . for example , many drugs decrease plasma cholinesterase activity , including ecothiopate , bambuterol , corticosteroids , cytotoxics , anticonceptives and oestrogens . heart - lung machines that are used during cardiac surgery induce a decrease in plasma cholinesterase activity , which lasts for approximately 10 days . repeated plasma exchange decreases plasma cholinesterase activity . in pregnancy ( i.e. in patients with hellp syndrome [ haemolysis , elevated liver enzymes , low platelets ] , eclampsia , etc . ) , plasma cholinesterase activity is markedly decreased , resulting in a prolonged succinylcholine effect . the same holds for patients with sepsis , malignancy , burn trauma and liver disease . in such patients there is a wide variability in the neuromuscular blocking effect , onset and duration of paralysis caused by succinylcholine . muscle hypertonia , myalgia , hypersalivation , elevated intraocular and intracranial pressures , and induction of malignant hyperthermia are also side effects of succinylcholine . occasionally , harmful cardiovascular effects also occur following succinylcholine administration , caused by stimulation of nicotinic receptors in the autonomic ganglia ( sympathetic and parasympathetic ) and of cardiac muscarinic receptors . furthermore , succinylcholine increases plasma noradrenaline ( norepinephrine ) concentrations , resulting in cardiovascular effects . finally , the histamine - releasing properties of muscle relaxants are well known , and succinylcholine has the strongest histamine - releasing effect of all such agents . given the profile described above , it is unlikely that many authorities would approve succinylcholine for registration if it were presented today as a new drug . nondepolarizing muscle relaxants do not have the deleterious effects connected with depolarization . in order to be useful for facilitating endotracheal intubation in the icu , they must have an acceptable speed of onset , have a relatively short to intermediate duration of action , be noncumulative , and preferably should not have cardiovascular side effects or induce histamine release . candidates to replace succinylcholine for intubation include vecuronium , rocuronium , atracurium , cisatracurium and mivacurium . the onset of action of atracurium , cisatracurium and vecuronium is rather long , and atracurium and cisatracurium can release histamine . rocuronium has an onset of action similar to that of succinylcholine , and provides similar intubation conditions 1 min after administration . the duration of action of mivacurium is shorter , but it has a slower onset , the intubation conditions are comparable only after 45 min , and it has stronger histamine - releasing properties than does rocuronium . because mivacurium is metabolized by plasma cholinesterase , the interindividual variability in effect is as wide as with succinylcholine . many studies have shown that rocuronium is a highly acceptable replacement for succinylcholine in the icu ; therefore , in my opinion , succinylcholine is obsolete . suitability of relaxants for use in the icu the number of ' + 's or ' - 's indicates the degree to which the drug is favourable or unfavourable with respect to the parameter under question .