Coronary Hemodynamic Effects of General Anesthesia and Surgery: Modification by Epidural Analgesia in Patients with Ischemic Heart Disease

Abstract

The coronary hemodynamic effects of neurolept anesthesia (NLA II) [fentanyl 15 μg/kg, droperidol 200 μg/kg, and 70% N20], 1% end-tidal halothane, 1% end-tidal isoflurane, and 1.4% end-tidal enflurane were investigated in 34 patients with ischemic heart disease. All anesthetics induced reduction in coronary perfusion pressure, most pronounced during enflurane. Oxygen demand was met by supply during NLA II. Combined findings of unchanged or decreasing coronary vascular resistance with decreased myocardial oxygen extraction indicate that halothane, isoflurane, and enflurane induced coronary vasodilatation. Isoflurane and enflurane were approximately equipotent and more powerful than halothane. Ischemic ST-T segment changes were observed in approximately half the isoflurane and enflurane patients likely due to a combination of decreased coronary perfusion pressure and coronary steal effects. The coronary hemodynamic effects of surgical stimulation were studied in 13 patients during NLA II and enflurane anesthesia. Ten minutes of abdominal surgery induced coronary vasoconstriction in both groups, most pronounced with enflurane anesthesia and closely related to increased myocardial extraction of norepinephrine. It is suggested that droperidol may modify the coronary vasoconstrictor response to surgery. Addition of epidural analgesia during surgery in the NLA II group abolished the constrictor response to surgery. Forty-five patients undergoing major vascular surgery within three months of a myocardial infarction were investigated with regards to intraoperative circulatory morbidity and postoperative reinfarction rate. The patients were randomly assigned to NLA II or epidural analgesia combined with light balanced general anesthesia (ED). The ED patients had significantly better intraoperative cardiovascular stability with lower incidence of ischemic events and lower reinfarction rate (4% versus 23%), whereas postoperative mortality rates were equal. It is concluded that the combination of epidural analgesia and light balanced general anesthesia is safe and provides excellent intraoperative cardiovascular stability.