Pancuronium Does Not Decrease Oxygen Consumption During Hypothermic or Normothermic Cardiopulmonary Bypass

Muscle relaxation reportedly reduces systemic oxygen consumption 30% during hypothermic cardiopulmonary bypass.A potential mechanism is inhibition of hypothermia-induced subclinical muscle tone ("microshivering"). Accordingly, we tested the hypothesis that pancuronium administration would decrease systemic oxygen consumption during hypothermic cardiopulmonary bypass, but not during normothermic bypass. We studied 20 patients undergoing normothermic cardiopulmonary bypass at a nasopharyngeal temperature of 37.6 +/- 0.8 degrees C (mean +/- SD) and 15 patients undergoing hypothermic bypass at a nasopharyngeal temperature of 28.2 +/- 1.2 degrees C. Oxygen consumption during bypass was determined, using the Fick principle, before and after administration of pancuronium 0.15 mg/kg. Morphometric characteristics and anesthetic management were similar in the two groups. Oxygen consumption averaged 93 +/- 28 mL centered dot min-1 centered dot m-2 in the normothermic patients and 43 +/- 10 mL centered dot min-1 centered dot m-2 in the hypothermic group. Administration of pancuronium decreased oxygen consumption only 2% in the normothermic patients. However, muscle relaxation also decreased oxygen consumption only 2% in the hypothermic patients. We were thus unable to confirm our hypothesis because muscle relaxation induced by administration of pancuronium did not significantly reduce oxygen consumption in either group. (Anesth Analg 1995;81:465-8)