Perioperative Oxygen Administration Reduces Postoperative Wound Infections
Abstract & Commentary
In a multicenter study of postoperative surgical wound infections, Greif and colleagues randomly assigned 500 patients undergoing major colorectal operations to receive either 30% or 80% oxygen during the operation and for two hours thereafter. Anesthetic and postoperative care were standardized. All patients received prophylactic antibiotic therapy. Wounds were evaluated daily until the patient was discharged from the hospital, and again two weeks later. Outcomes studied were the occurrence of surgical wound infection (defined as the presence of culture-positive pus in the wound), the timing of suture removal, and hospital length of stay. Greif et al used a double-blind protocol to ensure that the operating surgeons, the clinicians subsequently assessing the patients’ wounds for infection, and the individuals determining the date of hospital discharge were unaware of which treatment was given.
The two treatment groups each had 250 patients and were well matched in terms of demographics, preoperative health status, duration of operation, core temperature, and other functions. On average, neither patient group was hypoxemic either during or immediately after the operation. Mean intraoperative arterial partial pressure of oxygen (PO2) was 121 ± 34 mm Hg in the patients receiving 30% oxygen and 348 ± 97 mm Hg in those receiving 80% oxygen. Oxygen tensions measured during the two hours postoperatively in which the oxygen therapy continued were 114 ± 35 and 206 ± 91 mm Hg, respectively.
Patients who received the higher concentration of supplemental oxygen during and immediately following surgery had fewer wound infections than those who received less oxygen. The surgical wound infection rates in the two groups were 5.2% (95% CI; 2.4-8.0%) vs. 11.2% (95% CI; 7.3-15.1%), respectively (P = 0.01). There was no difference in preoperative blood leukocyte count, but patients who received 80% oxygen had significantly higher white blood cell counts on postoperative days 1, 3, 6, and 9. Dates of suture removal and duration of hospitalization were similar in the two groups. (Greif R, et al. N Engl J Med 2000;342:161-167.)
COMMENT BY DAVID J. PIERSON, MD, FACP, FCCP
This study, carried out in Austria and Germany, produced results that may initially seem counterintuitive. Why should the administration of a high concentration of supplemental oxygen to patients who are not hypoxemic in the first place have any beneficial effect at all? The question conjures up images of professional football players sucking on oxygen masks on the sideline after a strenuous series of downs. However, there is a major difference between the two situations: The football players do not have fresh major surgical wounds that may be contaminated with infection-causing bacteria.
Whether clinical infection develops after wound contamination by bacteria is affected by what happens in the initial several hours, as the bacteria gain a foothold and begin to multiply. Oxidative killing of bacteria by neutrophils is dependent upon the production of bactericidal superoxide radicals from molecular oxygen. It thus stands to reason that increasing the supply of molecular oxygen in the tissues during these initial hours of vulnerability would have a positive influence on whether the neutrophils could gain the upper hand and turn the tide against overt infection. Whether this is the mechanism for the observed benefit of increasing the inspired oxygen fraction in this study is unknown.
There is no question that preventing surgical wound infections is a good idea. Such infections are known to increase the duration of postoperative hospitalization and overall monetary cost. It is interesting to note, however, that no detectable decreases in hospital length of stay were achieved in this study, despite a halving of the rate of postoperative wound infection. Despite this, administering 80% oxygen to patients undergoing major surgery and for a short time thereafter is inexpensive, seems a safe thing to do, and may benefit patients.
Administering 80% oxygen to patients during and after major colorectal surgery reduced:
a. postoperative wound infection by 50% and mortality by 15%.
b. postoperative wound infection by 50% and average length of stay by two days.
c. postoperative wound infection by 50% without a change in the other measures.
d. postoperative wound infection by 25% without a change in the other measures.
e. None of the above
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