Reducing Surgical Wound Infections with Supplemental Oxygen
Reducing Surgical Wound Infections with Supplemental Oxygen
Abstract & Commentary
Synopsis: In a randomized trial, supplemental 80% oxygen was associated with a 54% reduction in surgical site infections among patients undergoing colorectal surgery.
Source: Greif R, et al. Supplemental perioperative oxygen to reduce the incidence of surgical-wound infection. N Engl J Med 2000;342:161-167.
Greif and colleagues randomized 500 patients undergoing elective colorectal resection to receive either 30% or 80% oxygen during surgery and for two hours after extubation. The presence or absence of wound infection during the first 15 days post- operatively was assessed using uniform criteria by physicians who were unaware of treatment group assignment. Subsets of patients underwent intraoperative determination of subcutaneous and intramuscular oxygen tension during surgery.
Case and control groups were evenly distributed as to the study on the efficacy of nosocomial infection control (SENIC) and national nosocomial infection surveillance system (NNISS) scores and had identical predicted infection rates. Of the 250 patients assigned to receive 80% oxygen, 13 (5.2%) had wound infections, compared with 28 patients assigned to receive 30% oxygen (11.2%). The absolute difference between the groups was 6% (CI = 95, 1.2- 10.8%). There were six postoperative deaths in the group receiving 30% oxygen, compared with one in the group receiving 80% oxygen (P = 0.13). Mean subcutaneous oxygen tension was significantly higher in patients receiving 80% oxygen compared with those receiving 30% oxygen (109 mm Hg vs 59 mm Hg; P < 0.001), as was muscle oxygen tension (49 mm Hg vs 25 mm Hg; P < 0.001). Although the overall duration of hospitalization was not significantly different between the two groups, patients with wound infections were hospitalized for a mean of 18.7 days compared with 11.4 days for those without infection (P < 0.001).
Comment by Robert Muder, MD
Wound infections are major complications of surgical procedures, increasing morbidity, length of stay, and cost. Colorectal surgery is relatively high risk, with infection rates of 4-13% reported by the NNISS.1 It is generally believed that the immediate perioperative period is the critical window in which wound infection is established. Thus, prophylactic antibiotics are most effective when administered immediately before skin incision.2 Oxidative killing of bacteria by neutrophils requires production of superoxide radicals. The rate of generation of these radicals is dependent on the local partial pressure of oxygen. Tissue oxygenation is disrupted during surgery because of vascular injury and thrombosis. Aggravating factors include hypovolemia, hypotensions, and systemic hypoxia.
Greif et al demonstrated that maintaining high perioperative tissue oxygen tension through administration of 80% supplemental oxygen resulted in a 50% decrease in surgical wound infections. Although the study was meticulously performed, I have a few minor criticisms. It does not appear that prophylactic antibiotic administration was standardized; it would have been reassuring to have seen data on the drugs and timing of administration for both study groups. In addition, the wound infection rate in the patients receiving 30% oxygen was substantially higher (11.2%) than that predicted by the NNISS index (6.3%). Finally, the duration of follow-up was 15 days. If the effect of higher concentrations of oxygen was to delay rather than prevent wound infection, the difference between the two groups might have been smaller.
However, brief administration of 80% oxygen is without known or observed detrimental side effects; it is not particularly expensive. I believe that the data presented in this study are fairly convincing and would agree that patients undergoing intestinal surgery should receive supplemental 80% oxygen. Whether patients undergoing other types of procedures should receive increased oxygen concentrations is uncertain. For example, joint replacement surgery is associated with infection rates of 1-2% or less in many centers. It would be difficult to demonstrate a significant reduction due to any intervention without a large study group. On the other hand, infections of prosthetic joints lead to prolonged disability and multiple subsequent surgical procedures. A small decrease in infection rates due to a simple and inexpensive intervention may prove to be extremely cost effective. This would be a worthy area of investigation should anyone be up to the task of conducting such a trial.
References
1. Gerberding J, et al. Am J Infect Control 1999;27: 520-532.
2. Classen DC, et al. N Engl J Med 1992;326:281-286.
Which of the following statements is correct?
a. Perioperative administration of supplemental 80% oxygen has been shown to reduce the risk of surgical wound infection after hysterectomy.
b. It has been demonstrated that all patients undergoing placement of a joint prosthesis should receive supplemental 80% oxygen.
c. Supplemental 80% oxygen reduced the incidence of surgical wound infections after colorectal surgery by approximately one-half.
d. Bacterial killing by neutrophils is optimal at reduced oxygen tension.
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