Incidence of Residual Neuromuscular Blockade at Tracheal Extubation: Comparison of Atracurium With Vecuronium

Abstract

BACKGROUND:Occurrence of undetected residual neuromuscular blockade is a common event in the post anaesthesia care unit. AIM: To compare the incidence and degree of residual neuromuscular blockade with the use of intermediate acting neuromuscular blocking agents Atracurium and Vecuronium. METHODS: 360 patients satisfying the inclusion and exclusion criteria were enrolled in the study and randomly allocated into one of the two study groups of 180 each to receive either Atracurium or Vecuronium intraoperatively. The anaesthesiologist blinded from the study extubated the patient based on the standard clinical criteria and the corresponding Train of Four(TOF) ratios were noted by a blinded research assistant using a TOF watch (TOF-Watch® SX Organon, Ireland Ltd., Dublin, Ireland). Residual neuromuscular blockade was defined as a TOF ratio of <0.9. TOF measurements thirty minutes after tracheal extubation were noted in the recovery room. RESULTS: 196 out of the 360 patients had TOF ratio <0.9 with an overall incidence of post-operative residual curarization (PORC) of 54.4%. Patients in Vecuronium group had a higher incidence of PORC compared to the Atracurium group (p = 0.003); 9/196 had TOF ratios 0.7-0.79 and all of them received Vecuronium; 187/196 had TOF 0.8-0.89; 103/187 patients with TOF 0.8-0.89 received Vecuronium, while the rest 84 received Atracurium. All the 360 study subjects had TOF ratio >0.9 thirty minutes after tracheal extubation. CONCLUSION: We conclude from our study that significant post-operative residual curarization (TOF < 0.9) exists in majority of patients at the time of tracheal extubation (54.4% incidence) despite the use of intermediate acting neuromuscular blocking drugs. The incidence and degree of post-operative residual curarization is significantly greater with Vecuronium compared to Atracurium. Thus we suggest that quantitative neuromuscular monitoring is required to assure complete neuromuscular recovery.