Postoperative Wound Oxygen Tension with Epidural or Intravenous Analgesia

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Abstract
Background: Adequate tissue oxygen tension is an essential requirement for surgical-wound healing. The authors tested the hypothesis that epidural anesthesia and analgesia increases wound tissue oxygen tension compared with intravenous morphine analgesia. Methods: In a prospective, randomized, blind clinical study, the authors allocated patients having major abdominal surgery (n = 32) to receive combined general and epidural anesthesia with postoperative patient-controlled epidural analgesia (epidural group, n = 16), or general anesthesia alone with postoperative patient-controlled intravenous analgesia (intravenous group, n = 16). An oxygen sensor and a temperature sensor were placed subcutaneously in the wound before closure. Wound oxygen tension (P(w)O(2)) and temperature were measured continuously for 24 h. Other variables affecting wound tissue oxygenation and visual analogue scale (VAS) pain scores were also documented. Results: Despite epidural patients having lower body temperatures at the end of surgery (35.7 +/- 0.3) versus 36.3 +/- 0.5 degrees C, = 0.004), they had significantly higher mean P(w)O(2) over the 24 h period, compared with the intravenous group (64.4 +/- 14 vs. 50.7 +/- 15) mmHg, mean (SD), 95% CI difference, -22 to -5, = 0.002). Area under the P(w)O(2) -24 h time curve was also significantly higher in the epidural group (930 +/- 278 vs. 749 +/- 257) mmHg x h, 95% CI difference -344 to -18, = 0.03). VAS pain scores at rest and moving were significantly lower in the epidural group at all times. Conclusion: Epidural anesthesia and postoperative analgesia for major abdominal surgery increases wound tissue oxygen tension compared with general anesthesia and intravenous morphine analgesia.