Supplemental oxygen given during and after colorectal resection reduces the incidence of surgical wound infection by half, according to a double-blind study published in the New England Journal of Medicine (2000;342:161).
Dr Robert Grief (department of anaesthesiology and intensive care medicine, Donauspital, Austria) and colleagues explain that the most important defence against surgical pathogens is destruction by oxidation, with bactericidal activity of neutrophils mediated by oxidative killing. Resistance to infection depends on the partial pressure of oxygen in the wound and can thus potentially be improved by increasing the arterial oxygen tension beyond that required to saturate blood. The researchers say that an easy method of improving oxygen tension in adequately perfused tissue is to increase the inspired concentration.
In their study, 500 adults undergoing colorectal resection were randomly assigned to receive 30 per cent or 80 per cent inspired oxygen, given by mask, during and for two hours after the operation. Anaesthetic treatment was standardised and all patients received prophylactic antibiotic therapy. Wounds were evaluated daily until the patient was discharged and then two weeks after surgery at a clinic visit. Wounds with culture-positive bacterial pus were considered to be infected.
The researchers found that surgical wound infections occurred in 13 out of the 250 patients who received 80 per cent oxygen, compared with 28 of the 250 patients given 30 per cent oxygen. No significant difference in the infection rate between smokers and non-smokers was seen. They comment that, because the costs of, and risk associated with, supplemental peri-operative oxygen are trivial, the provision of supplemental oxygen appears to be a practical method of reducing the incidence of surgical wound infections.
Commenting on the study, Mr David Rosin (consultant surgeon, St Mary's hospital, Imperial College School of Medicine) told The Journal on February 9 that the study was very interesting and that giving high oxygen during anaesthesia for reducing the incidence of surgical wound infections was new. However, he had some reservations about the design of the study. He was concerned that the wounds had been looked at daily, which, although the same for both groups, could have induced infection. He further questioned whether actually administering oxygen directly onto the wound would also be effective.