Muscle relaxation does not influence venous oxygen saturation during cardiopulmonary bypass

Study ObjectiveTo examine whether the omission of neuromuscular blocking drugs during cardiopulmonary bypass (CPB) is associated with increased anesthetic requirements, higher frequency of intraoperative movements, and lower venous oxygen saturation (SvO2).DesignProspective, randomized study.SettingLarge community hospital.Patients30 ASA physical status III and IV patients scheduled for cardiac surgery.InterventionsPatients were randomized to one of two groups: group 1 (n = 15) received a 3× ED95 bolus dose of cisatracurium at induction and thereafter no more neuromuscular blocking drug; group 2 (n = 15) received a continuous infusion of cisatracurium during the entire procedure.InterventionsBoth groups received a standardized anesthetic with bispectral index–guided propofol target-controlled infusion and a remifentanil infusion steered by hemodynamic changes. Venous oxygen saturation was continuously determined during CPB.Measurements and Main ResultsPropofol consumption was 5.4 ± 1.7 and 4.4 ± 1.0 mg/(kg/h) in groups 1 and 2, respectively (P = 0.07). Remifentanil consumption was 0.15 ± 0.05 and 0.17 ± 0.05 μg/(kg/min) in groups 1 and 2, respectively (P = 0.19). In groups 1 and 2, no patient recalled any intraoperative phenomena; none moved or had diaphragmatic contractions. During CPB, SvO2 was 81.3 ± 3.2% (76%-85%) in group 1 and 80.6 ± 3.1% (73%-85%) in group 2 (P = 0.53).ConclusionsOmitting the continuous administration of neuromuscular blocking drugs during CPB did not increase anesthetic requirements. No intraoperative movements occurred, nor was there decreased SvO2.