The Effects Of Hepatic Dysfunction On Neuromuscular Blockade Of Vecuronium

Objective To investigate the effects of hepatic dysfunction on neuromuscular blockade of vecuronium in bolus or continuous infusion in patients with hepatic failure scheduled for orthotopic liver transplantation.Methods This is a randomized, controlled and prospective clinical trial. Forty patients were included in this study. Twenty ASAΙ^II patients with normal hepatic function undergoing gastrointestinal surgery were assigned to control group (group 1); while other twenty Child-Pugh B or C patients with hepatic dysfunction undergoing orthotopic liver transplantation were included in the experimental group(group 2). Excluded criterion : patients with severe heart dysfunction, pulmonary dysfunction and renal dysfunction preoperatively , with neuromuscular disorder preoperatively, with morbid oberity, with psychiatric history, difficult airway, severe hepatic encephalopathy, and patients undergoing the liver retransplantation. Mechanomyography of the adductor pollicis muscle with single twitch (ST;0.1 Hz) stimulation was used to monitor neuromuscular function during anesthesia. After intravenous injection of midazolam 0.03mg/kg and fentanyl 4μg/kg, a continuous 0.1 Hz single stimulus with 0.2 ms square wave and current of 50mA was delivered to the ulnar nerve at the wrist and the evoked response of the the adductor pollicis muscle was recorded. The twitch response was stablized for 3-5 minutes. Then propofol 1^-1.5mg/kg and vecuronium 0.15mg/kg were administered intravenously. After T1 became 0, tracheal intubation and mechanical ventilation were performed. The end-tidal carbon dioxide tension was kept between 30 and 35mmHg . Core temperature was measured with an oesophageal probe. Anesthesia was maintained with a continuous intravenous infusion of propofol and boluses of fentanyl 0.1mg IV as required. The onset of vecuronium,duration of action,the time of T1 recovery to 10% of baseline were observed and recorded. The condition of tracheal intubation was judged. When T1 returned to 10% of baseline, vecuronium was infused continuously at a initial rate of 2μg·kg^-1·min^-1 to maintain T1 at 5%^-10% of baseline by adjusting the infusion rate. The vecuronium consumption in every thirty minutes was recorded and the average infusion rate in ninety minutes was calculated.Results The onset of vecuronium were 104.00±16.04s in group 1,and 134.75±29.01s in group 2 respectively with statistically significant difference(P < 0.01). Duration of action of first dose of vecuronium were 2700.00±516.83s in group 1 and 2515.20±428.02s in group 2(P > 0.05). Times of T1 recovery to 10% were 3076.70±558.95s in group 1,and 2907.30±460.36s in group 2(P > 0.05). The first thirty-minute consumption of vecuronium in group 1 and group 2 were 2.27±0.54mg and 2.90±0.57mg( P<0.01 ); the second were 1.75±0.45mg ,2.02±0.42mg,and the third were 1.73±0.52mg,1.89±0.66mg(P > 0.05).The average infusion rate in ninety minutes were 1.02±0.28μg·kg^-1·min^-1 in group 1and 1.21±0.20μg·kg^-1·min^-1 in group 2(P < 0.05).Conclusion Vecuronium 0.15mg/kg can provide satisfactory condition of tracheal intubaton. Hepatic dysfunction will delay the onset of vecuronium without significant changing its duration of action. The average rate of vecuronium administration should be increased at the beginning of infusion in these patients.