RESUMO
For major operative procedures in the lower abdomen and many orthopedic procedures such as total hip replacement, a combination of general and epidural anesthesia is used. In order to investigate the hemodynamic effects of such a combination in 14 geriatric patients aged 63-80 years who were undergoing total hip replacement, cardiovascular monitoring was established by an arterial line and a pulmonary artery catheter. The epidural anesthesia was achieved with bupivacaine 0.5% in a dose calculated to obtain a block up to Th 6. General anesthesia was then induced and maintained with midazolam, fentanyl, pancuronium bromide, and a 2:1 nitrous oxide-oxygen mixture. Hemodynamic measurements were established before and 30 min after induction of the epidural anesthesia and 20 min after the induction of general anesthesia. After bupivacaine was injected the loss of sympathetic tone produced a systolic arterial blood pressure decrease from 174 +/- 22 to 136 +/- 28 mmHg (p less than 0.05) and a decrease in heart rate from 73 +/- 12 to 66 +/- 10 min-1 (p less than 0.05). The cardiac index did not change, but the peripheral vascular resistance decreased significantly. Because intravenous fluids were given simultaneously, preload could be maintained. Oxygen delivery and oxygen extraction did not change. During general anesthesia a significant drop in cardiac output was observed from 3.0 +/- 0.6 l/min.m2 to 2.3 +/- 0.4 l/min.m2 (p less than 0.05). The systolic arterial blood pressure decreased to as low as 95 +/- 17 mmHg (p less than 0.05) and oxygen delivery decreased from 500 +/- 125 ml/min.m2 to 323 +/- 84 ml/min.m2 (p less than 0.05).