The cardiovascular effects of naloxone administration after fentanyl anesthesia in hypercapnic patients.

Hemodynamic changes and plasma catecholamine levels after naloxone administration were studied in seventeen postoperative patients who received nitrous oxide, oxygen, and fentanyl anesthesia combined with epidural block. Group I consisted of ten postoperative hypercapnic (PaCO2 = 55.2 +/- 2.4 torr) and group II seven postoperative normocapnic patients (PaCO2 = 38.4 +/- 2.1 torr), respectively. In group I, naloxone reversal resulted in significant increases in heart rate (13.5%), mean arterial pressure (46.6%), systemic vascular resistance (32.1%), and rate pressure product (68.8%), whereas mean pulmonary artery pressure and pulmonary vascular resistance were significantly decreased. No significant hemodynamic changes after naloxone administration were observed in group II. There were no significant differences in arterial norepinephrine and epinephrine levels either before or after naloxone administration in the both groups. This study indicates that the postoperative hypercapnia elicits the cardiovascular stimulation after fentanyl reversal by naloxone.