Dose-reversal effect relationship of three different doses of neostigmine in obese patients: A randomised clinical trial

Background and Aims Previous studies suggest that administration of vecuronium based on total body weight rather than ideal body weight (IBW) in obesity results in overdosing with prolonged recovery times. We hypothesised that larger doses of neostigmine could result in faster recovery in obese patients administered vecuronium based on total body weight. Methods Forty-five obese American Society of Anesthesiologists' II patients undergoing elective surgery under general anaesthesia were randomised into 3 groups to receive neostigmine 30, 40 and 50 μg/kg. Following induction, patients were paralysed with vecuronium 0.1 mg/kg based on total body weight. Reversal was achieved with neostigmine based on the patient's group, and time to train-of-four (TOF) ratios of 0.5, 0.7 and 0.9 measured. The primary outcome variable was time to achieve TOF ratio >0.9. Results Neostigmine 50 μg/kg achieved faster recovery to TOF 0.7 than neostigmine 30 and 40 μg/kg. There was no significant difference in recovery times to TOF 0.7 in patients receiving either 30 or 40 μg/kg of neostigmine. However, neostigmine 40 μg/kg attained TOF ratio 0.9 faster than 30 μg/kg. We did not note a significant difference between the 40 and 50 μg/kg dose with regard to recovery of TOF to 0.9. Conclusion Facilitated recovery from neuromuscular blockade to TOF of 0.7 was faster with neostigmine 50 μg/kg compared to 40 or 30 μg/kg. Recovery to TOF ratio of 0.9 was not significantly different with 40 or 50 μg/kg doses although such time was faster as compared to 30 μg/kg dose.