Anesthetic management of a patient with Bartter's syndrome undergoing bilateral sagittal split osteotomy
Our patient is a 22-year-old Saudi girl, had mandibular prognathism (class III malocclusion with 5 mm discrepancy), and stunted stature, weighing 41 kg, a known case of Bartter's syndrome since childhood and currently complicated by nephrosclerosis. She was scheduled for bilateral sagittal split mandibular osteotomy (BSSO) under general anesthesia. After 2 years of orthodontic preparation, and after discussing all the details of the surgery with its suspected complications with the patient and her family. The patient was insisting for the surgery in spite of her medically challenging condition. In her family the disease is inherited as an autosomal recessive trait (her brother suffers the same condition). She has a previous history of receiving growth hormone at the age of puberty as well as a history of receiving indomethacin; however, discontinued by the nephrologists.\nThe patient was seen in the preanesthesia clinics 2 weeks before the predetermined date of surgery. Her current medications were potassium chloride 600 mg and calcium carbonate 600 mg taken 2 times daily; spironolactone 100 mg, allopurinol 100 mg, and calciterol 0.5 mg taken once daily. The investigations showed a hypokalemic, hypochloremic, metabolic alkalosis Na+135, K+2.3, Cl−92, and a HCO3−35 mmol/L. The patient's oral potassium chloride intake was increased to 600 mg 3 times daily.\nOn admission to the hospital (2 days preoperatively), the patient's physical examination was normal, and blood pressure was 110/75 mmHg. The electrocardiogram demonstrated only nonspecific ST-T changes. Laboratory data indicated that the electrolyte derangement was corrected; serum sodium, potassium, and chloride were 147, 4.4 mmol/L, and 107 mmol/L, respectively []. Calcium (2.67 mmol/L), corrected calcium (2.7 mmol/l mol/L) and magnesium (0.8 mmol/L) levels were all within normal. Urea and creatinine were slightly elevated indicating underlying renal disease (8 mmol/L and 117 μmol/L, respectively). The patient was neither anemic (hemoglobin 124 g/L) nor had high hematocrit (36%). Laboratory results obtained in a day before or immediately before the surgery were within normal ranges; except for blood urea and creatinine that was still increasing and the nephrologist was consulted []. It was decided to proceed to the surgery without any further correction.\nPatient's medications were continued till the day of surgery. Clindamycin 600 mg and dexamethazone 6 mg intravenously were administered at the night before the surgery as well as on the induction of anesthesia as recommended by the surgeons. The patient was premedicated 60 min preoperatively with lorazepam, 1 mg, ranitidine 150 mg, and metoclopramide 10 mg orally.\nBefore induction of anesthesia, percutaneous radial arterial was inserted. The insertion of central venous pressure catheters was discussed and decided not to be inserted. Intravenous fluid replacement for the hours of fasting (D5 I/2N saline) was completed before starting anesthesia.\nThe anesthesia was induced intravenously by high-dose fentanyl 5 μg/kg, propofol increments (total of 40 mg), and cisatracurium 6 mg. After nasal preparation with vasoconstrictor; cuffed endotracheal tube size 6.5 mm was inserted. Mechanical ventilation was initiated bearing in mind to avoid hyperventilation. With tidal volume of 400 mL and respiratory rate of 10, end-tidal CO2 was maintained between 34 and 37 mmHg. Besides the standard monitoring, urine output, neuromuscular assessment, and bispectral index were also included.\nArterial blood pressure before induction of anesthesia was 120/70 mmHg and heart rate 82 beats/min. Systolic blood pressure never exceeded 150 mmHg or decreased below 100 mmHg. However, heart rate increased over 130 beats/min immediately after infiltration of local anesthetic (xylocaine 2% with adrenaline 1/100,000) into the surgical field. IV labetalol 15 mg (increments of 5 mg) was given until the tachycardia was controlled. Two measurements of serum electrolyte and blood gas levels were done intraoperatively and there were no significant changes [].\nSurgical procedure was as follows: BSSO cuts were done intraorally following the technique described by Nooh and Abdullah (2007),[] then a 7 mm straight forward setback of the mandible was done and fixed using one 2 mm titanium plate and 4 screws (2 screws of 5 mm length anterior to the bone cut, and 2 screws of 7 mm length posterior to the bone cut) at each side.\nThe surgical time was 90 min, bleeding was minimal; vasopressors to maintain the blood pressure were not required. Intraoperative fluid balance was as such (Intake = 1000 mL Lactate Ringer solution and 500 mL D5 I/2N saline and the output; urine output (UOP) = 700 mL/3 h). The patient tolerated the procedure very well.\nThe patient was transferred to the surgical intensive care unit (SICU). Intravenous fluid D5 I/2N saline 80 mL/h together with KCl 20 meq/L every 6 h was commenced till the patient resumed oral intake. Magnesium level dropped to 0.6 mmol/L. MgSO4 2 g was given as IV infusion over 2 h twice daily. Ca gluconate 1 g was ordered if serum calcium level fell below 2 mmol/L and only one dose was administered. Electrolytes were measured on an 8-hourly basis. UOP did not surpass 100 mL/kg/day in the postoperative period. However, at the night of surgery the patient showed hypokalemic, hypochloremic, and metabolic alkalosis []. Na+135, K+3.0, Cl−90, HCO3− 28.3 mmol and a pH 7.49. Intravenous fluids were changed to normal saline and intravenous potassium chloride replacement increased to 30 meq/6 h, next day the oral potassium chloride was gradually introduced instead of the intravenous replacement. Eventually, the patient was discharged 3 days postoperatively on the same treatment she had received preoperatively.