Cardiovascular effects of ketamine in humans with cervical or lumbar epidural blockade

To examine the effect of sympathectomy induced by epidural blockade on the cardiovascular effects of ketamine anesthesia, the authors compared the changes in arterial blood pressure (AP) and heart rate (HR) following intravenous administration of ketamine in patients who had cervical epidural anesthesia (n = 18), lumbar epidural anesthesia (n = 16), or light general anesthesia alone (n = 16). Ketamine, 2 mg/kg, iv, produced statistically significant increases in both AP and HR in all patients studied. However, the per cent increases in systolic AP in the cervical group were statistically less than those in the lumbar epidural group and control groups (P less than 0.05), which did not significantly differ from each other. The changes in HR following ketamine in the cervical group were significantly less than those in the other two groups (at 3-10 min following ketamine) (P less than 0.05). These results indicate that the cardiovascular stimulatory effects of ketamine are suppressed partially by a high level of epidural anesthesia but not by a low level of epidural blockade. Since patients with cervical epidural anesthesia had an analgesic level extending between C4 and Th8, the above attenuative effects of epidural blockade may be considered to be attributable to cardiac sympathectomy induced by a high level of epidural anesthesia.