ANTHROPOMETRIC VARIABLES AS PREDICTORS FOR DURATION OF ACTION OF ATRACURIUM-INDUCED NEUROMUSCULAR BLOCK

Reports concerning duration of action of atracurium in obese patients are conflicting. The aim of this study was to evaluate different anthr opometric variables as predictors for duration of action of atracurium -induced block. We studied 127 female patients (total body weight 46-1 19 kg) anesthetized with midazolam, fentanyl, thiopental, nitrous oxid e, and halothane. Twelve different anthropometric variables were evalu ated as predictors for duration of action. Linear, least-square, regre ssion analyses were used. There was a significant correlation between each of the 12 variables and the duration of action. The predictors wi th the greatest correlation coefficients for duration of action of the atracurium induction dose (0.5 mg/kg) were total body weight divided by surface area (r(2) = 0.284, P < 0.0001), body mass index (r(2) = 0. 265, P < 0.0001), and total body weight (r(2) = 0.264, P < 0.0001). Th e most significant predictors for the duration of action of the first supplemental atracurium dose (0.15 mg/kg) were total body weight divid ed by surface area (r(2) = 0.170, P < 0.0001) and total body weight (r (2) = 0.160, P < 0.0001). We propose that the atracurium dose should b e reduced with 0.23 mg for each kilogram of total body weight above 70 kg. We conclude that the duration of action of atracurium block is pr olonged in obese patients, and that atracurium dose in milligrams per kilogram of total body weight should be reduced in these patients. Tot al body weight divided by the surface area and total body weight were the best predictors for duration of action of atracurium-induced neuro muscular block.