Plasma epinephrine and norepinephrine levels during anesthesia: enflurane-N2O-O2 compared with fentanyl-N2O-O2.

During intra-abdominal surgery, plasma levels of norepinephrine in peripheral venous blood were higher in 11 patients who received fentanyl-nitrous oxide-oxygen than in 10 patients who received enflurane-nitrous oxide-oxygen [703 +/- 95 vs 463 +/- 38 (SEM) pg/ml]. At the same time, systolic blood pressure (143 +/- 6 vs 121 +/- 4 torr), mean blood pressure (108 +/- 4 vs 98 +/- 3 torr), and pulse rate (87 +/- 3 vs 98 +/- 4 beats per minute) also differed significantly (p less than 0.05); plasma levels of epinephrine (235 +/- 61 vs 113 +/- 21) did not. These values did not differ significantly between the two groups before induction of anesthesia, after induction but before skin incision, or in the recovery room. These data support the concept that enflurane anesthesia blocks the sympathetic response to surgical stress more effectively than low dose fentanyl anesthesia.