Weight, pseudocholinesterase activity, and succinylcholine requirement

Abstract

The duration of action of succinylcholine appears to be determined primarily by the level of pseudocholinesterase activity in the blood and the volume of the extracellular fluid space. Compared to nonobese patients, obese patients have both increased pseudocholinesterase levels and an increased extracellular fluid space. These factors should increase the succinylcholine dosage requirement of obese patients which is consistent with our clinical observations. To investigate this observation, body weight was correlated with the activity of serum pseudocholinesterase in subjects of varying weight. Subsequently, an additional group of patients were given succinylcholine on the basis of total body weight and the duration of neuromuscular blockade was measured. When succinylcholine was administered on the basis of mg/kg (total body weight) a similar duration of action was found in all patients regardless of weight. Succinylcholine should be administered on the basis of total rather than lean body weight in adult patients.