Residual Curarization in the Recovery Room : the Occurrence and Risk Factors

Lapisatepun W.,M.D.,Punjasawadwong Y.,M.D.,Pongchiewboon A.,M.D.,

Paiboonworachatti S.,M.D.,Piriyakunthorn M.,M.D.

Department of Anesthesiology, Faculty of Medicine, Chiangmai University, Chiangmai 50002

  The train-of-four(TOF) stimulation of the ulnar nerve was assessed to determine residual curarization in 100 adult patients on immediate arrival in the recovery room,after general balanced anesthesia. A peripheral nerve stimulator was not used in any patient intraoperatively. When the criterion of a TOF ratio of 70 percent was used to indicate adequate neuromuscular recovery,there was 34 percent of patients having residual curarization. With respect to pancuronium,which was given in a majority of the studied patients (n=77),42 percent of the patients given this relaxant was found to inadequately recover. In this group,after exclusion of 8 with renal dysfunction (n=69),the incidence of residual curarization was higher in the subgroup of 2 increments or greater as well as the incremental dose of greater than 1 mg (p<0.05). The results also showed that in the non-increment subgroup,a logarithmic relationship was found between dose (mg/kg/hr) and the TOF ratio (r=-0.566,p<0.01) as well as between the time from the first injection of pancuronium to the injection of neostigmine and the TOF ratio (r=0.515,p<0.05). In conclusion,residual curarization in the recovery room is commonly encountered following the use of long-acting non-depolarizing muscle relaxants,particularly when a nerve stimulator has not been used intraoperatively. In case of pancuronium,residual curarization is associated with the number and dose of increments. And,when a single bolus dose of pancuronium is administered without increment,the TOF ratio after reversal is associated with the dose (mg/kg/hr) and the time from injection of the relaxant to the injection of neostigmine.