Combined vs. Isoflurane/Fentanyl anesthesia for major abdominal surgery: Effects on hormones and hemodynamics

Combination of epidural and general anesthesia (combined anesthesia) avoids the intraoperative use of intravenous analgesics and may reduce the surgical stress response during major abdominal surgery. This study examines the differences in intraoperative hemodynamic stability, cortisol levels and activity of cardiovascular hormones between combined anesthesia and isoflurane/fentanyl anesthesia. Sixty ASA I-II patients were prospectively randomized to receive either combined anesthesia, i.e, isoflurane anesthesia combined with thoracic epidural analgesia (bolus of 12 ml 0.2% ropivacaine containing 1 microg/ml sufentanil 30 min before incision, followed by continuous infusion at 6 ml/h) or isoflurane/fentanyl anesthesia (IV fentanyl as required) for major abdominal surgery. Depth of anesthesia was monitored using Bispectral Index. Administration of fluids and of vasopressors was directed by a standardized protocol. Blood samples for angiotensin II, vasopressin, catecholamines, and cortisol were drawn before anesthesia, after induction (but before using the epidural catheter), and 40 min after skin incision. After induction of anesthesia, mean arterial pressure decreased by 12-20 mmHg in both groups and angiotensin-II concentrations increased. Vasopressin increased predominantly after opening the abdomen in both groups. Under combined anesthesia, intraoperative epinephrine and cortisol concentrations were considerably lower. Intraoperative crystalloid fluid substitution, blood loss and urine output did not differ between groups. There were more hypotensive periods and the demand for colloids and low-dose continuous norepinephrine was greater under combined anesthesia. Combined anesthesia reduces the intraoperative stress response, but moderate hemodynamic instability is relatively common and has to be compensated for by adequate volume replacement and vasopressor support.