In 50 patients scheduled for infrarenal aortic bypass surgery the cardiovascular effects of two anaesthetic regimes were investigated prior to surgery. A Swan-Ganz-catheter was used for haemodynamic measurements. These patients, having been randomized into two groups, were optimally volume loaded (PCWP 10 mmHg) before anaesthesia. In 24 patients a thoracic epidural was induced with 12-15 ml 0.25% plain bupivacaine. When segmental anaesthesia had extended from T4/5 to L1/2 general anaesthesia was additionally applied (flunitrazepam 1.5-2 mg, pancuronium bromide 0.1 mg/kg). In 26 patients neuroleptanaesthesia was induced (droperidol 0.1-0.2 mg/kg, fentanyl 0.01 mg/kg, pancuronium bromide 0.1 mg/kg, and thiopentone 100-150 mg. Haemodynamic measurements were made before injection into the epidural catheter, after complete spread of anaesthesia, before commencing general anaesthesia and 10-15 min thereafter.
Results: Neither of the two procedures were associated with severe haemodynamic alterations. In the epidural group HR fell slightly during latency of complete spread and increased to the same extend following general anaesthesia. The epidural caused MAP (104 to 88 mmHg), mean PAP (20 to 14 mmHg), PCWP (10 to 7.5 mmHg), and RAP (4.5 to 2.5 mmHg) to decrease moderately but no further changes were effected by the subsequent general anaesthesia. SVR and PVR were not influenced by either epidural or by general anaesthesia. CI (3.6 to 3.41 . min-1 . m-2), LVSWI (67 to 52 p . m-1), and cardiac minute work index (55 to 40 J . min-1 . m-2) decreased during latency of complete spread but were no further influenced by general anaesthesia. The haemodynamic changes of neuroleptanaesthesia were almost identical to those of the combined epidural-general anaesthesia. For the operation which followed, a continuous infusion of 0.125 per cent plain bupivacaine (0.25 ml/kg X h) via epidural catheter (in combination with N2O/O2-anaesthesia) was sufficient for complete analgesia in the epidural group. These findings lead to the conclusion that a small bolus volume and a low concentration of bupivacaine result in good anaesthesia while avoiding serious haemodynamic alterations.