Lean tissue mass is a useful predictor of induction dose requirements for propofol

The effect of age and sex on ED50 values for propofol was studied in 92 patients aged between 16 and 85 years. All doses were based on lean tissue mass (LTM). The end-point for loss of consciousness was loss of the ability to hold a light object. The mean of the ED50 values for males was 1.31 mg.kg LTM-1 and for females 1.28 mg.kg LTM-1. For males the ED50 values ranged from 0.94 to 1.69 mg.kg LTM-1. For females, the range was 1.06-1.57 mg.kg LTM-1. On statistical analysis, these differences were not significant. These data contrast with other studies in which dosage was based on total body mass where a decrease in dose requirement with age was demonstrated. We propose that by using lean tissue mass to calculate dosage, considerable normalisation of patient response can be achieved. There is considerable inter-individual variation in response to propofol. Age is less important than this variation in determining the correct dose for each patient, provided doses are based on LTM.