Background. Studies regarding the pharmacokinetics of muscle relaxants for cardiopulmonary bypass (CPB) abound but are conflicting. The available dose regimen does not guarantee adequate muscle relaxation. This study aims to determine the optimum rocuronium dose and mode of administration to maintain an adequate degree of muscular relaxation during CPB among adult patients.
Methods. This is a randomized controlled open label trial involving patients undergoing cardiac surgery. Eighty (80) subjects were randomly assigned to four treatment groups. For Group A, intubating dose was given at 0.6 mg/kg and maintenance by infusion. For Group B, intubating dose was given at 0.6 mg/kg andmaintenance by bolus. For Group C, intubating dose was given at 0.9 mg/kg and maintenance by infusion. For Group D, intubating dose was given at 0.9 mg/kg and maintenance by bolus. Maintenance dose was started when TOF count was >2. Onset and duration of action of the intubating dose and the total maintenance dose requirement were noted. All other aspects of anesthesia care followed the standard protocol.
Results. Subjects were homogenously distributed according to age (p-value =0.134), gender (p-value = 0.415), body mass index (p-value =0.636), type of surgery (p-value =0.191), and presence or absence of diabetes (pvalue 0.131) and hypertension (0.07). Rocuronium at 0.9mg/kg had faster onset (3.74 ± 2.99 min) compared to that given at 0.6mg/kg (6.28 ± 2.58 min). The two dosages did not differ in duration of action. Maintenance dose by bolus decreases the requirement to 2.64±0.821 mcg/kg/min compared to that by infusion given at 3.09 ± 1.12 mcg/kg/min.
Conclusion. For cardiac surgery under cardiopulmonary bypass, rocuronium at 0.9 mg/kg had a faster onset on action and maintenance dose by bolus decreases the requirements compared to that by infusion.