Effect of epidural blockade and oxygen therapy on changes in subcutaneous oxygen tension after abdominal surgery

The effect of oxygen therapy (37% by face mask) and epidural local anesthetic blockade (9 ml 0.5% bupivacaine at Th9-11 level) on wound oxygenation was evaluated in eight otherwise healthy patients undergoing elective colorectal resection. The patients were monitored continuously for subcutaneous oxygen tension, arterial oxygen saturation, heart rate, and skin temperature on the day after operation, and arterial blood for gas analysis was drawn every 15 min during the study. A fluid challenge (10 ml saline/kg body wt) did not alter any of the measured values. The epidural blockade did not change any of the measured values. Oxygen therapy before epidural blockade increased median subcutaneous oxygen tension from 60 to 71 mmHg (P < 0.02) and, after epidural blockade, from 64 to 71 mmHg (P < 0.02) Time to reach steady state in subcutaneous oxygen tension with oxygen therapy was 30 (15-55) min without epidural blockade and 15 (10-20) min with blockade (P < 0.03). In conclusion, epidural local anesthetic blockade did not increase subcutaneous oxygen tension with or without oxygen therapy after elective uncomplicated major abdominal surgery.