The Dose of Succinylcholine in Morbid Obesity

Abstract

In Brief The appropriate dose of succinylcholine (SCH) in morbidly obese patients is unknown. We studied 45 morbidly obese (body mass index >40 kg/m2) adults scheduled for gastric bypass surgery. The response to ulnar nerve stimulation of the adductor pollicis muscle at the wrist was recorded using the TOF-Watch SX® acceleromyograph. In a randomized double-blind fashion, patients were assigned to one of three study groups. In Group I, patients received SCH 1 mg/kg ideal body weight, in Group II 1 mg/kg lean body weight, and in Group III 1 mg/kg total body weight. After SCH administration, endotracheal intubating conditions were scored. The recovery from neuromuscular block was recorded for 20 min. There was no difference in the onset time of maximum neuromuscular blockade among groups, but maximum block was significantly less in Group I. The recovery intervals were significantly shorter in Groups I and II. In one third of the patients in Group I, intubating conditions were rated poor, whereas no patient in Group III had poor intubating conditions. Our study demonstrates that for complete neuromuscular paralysis and predictable laryngoscopy conditions, SCH 1 mg/kg total body weight is recommended. IMPLICATIONS: In morbidly obese patients, successful tracheal intubation can be achieved when 1.0 mg/kg succinylcholine is administered based on ideal body weight, lean body weight, or total body weight. None of these dosing regimens will provide both adequate intubating conditions and a safe (short) duration of apnea. Succinylcholine given in a dose of 1.0 mg/kg based on total body weight provides complete neuromuscular paralysis and predictable tracheal intubating conditions in morbidly obese patients. Smaller doses are not as effective.