Supplemental Perioperative Oxygen to Reduce the Incidence of Surgical-Wound Infection

Supplemental Perioperative Oxygen to Reduce the Incidence of Surgical-Wound Infection – Brief Article

George Allen

R Greif et al The New England Journal of Medicine Vol 342 (Jan 20, 2000) 161-167

Surgical wounds are the second most frequently reported site of nosocomial infections. Approximately 500,000 surgical wound infections, now more commonly referred to as surgical site infections (SSIs), occur annually, accounting for 3.7 million additional hospital days for patients and more than $1.6 billion in additional hospital costs. Consequently, as SSIs continue to be an important cause of morbidity and mortality worldwide, prevention continues to demand the attention of international, national, and local health care authorities, hospital administrators, and personnel at all levels of the perioperative milieu.

We have long known that oxidative killing (ie, destruction by oxidation) is an important defense against bacteria that cause SSIs. It also is known that oxidative killing depends on the partial pressure of oxygen (ie, oxygen tension) in contaminated tissue and that an effective method of increasing oxygen tension in inadequately perfused tissue is to increase the concentration of inspired oxygen. These researchers, therefore, tested the hypothesis that supplemental oxygen administered during the perioperative period will decrease the incidence of SSIs.

Methodology. A multicenter study was conducted in three European countries. Five hundred patients between 18 and 80 years of age undergoing elective major colorectal surgical procedures were assigned randomly to receive 30% or 80% inspired oxygen during their procedure and for two hours after surgery. Patients with a recent history of fever, infection, serious malnutrition, or bowel obstruction and those undergoing only a minor colorectal procedure (eg, polypectomy, isolated colostomy) were excluded from the study. All patients underwent standard bowel preparation with an electrolyte solution protocol the night before surgery and received antibiotic prophylaxis and standardized anesthesia induction protocol. After induction and placement of the endotracheal tube, each patient was assigned to one of two groups through the use of a set of computer-generated random numbers.

Patients in one group received 30% oxygen and 70% nitrogen, and patients in the other group received 80% oxygen and 20% nitrogen until immediately before extubation. Oxygen then was increased to 100%. Oxygen concentrations were returned to assigned levels as soon as deemed safe by the anesthesia care provider and continued for two hours postoperatively using a non-rebreathing mask. Anesthesia care providers were aware of the treatment group assignments.

Cardboard shields were placed over flow meters and relevant monitors to prevent surgical staff members from determining the fraction of inspired oxygen.

Results. Chi-square tests were used to compare the number of SSIs in each group, and multiple logistic regression analysis was used to determine predictive risk factors. Arterial oxygen saturation, partial pressure of arterial oxygen, subcutaneous oxygen tension, and muscle oxygen tension were significantly higher in patients in the group that received 80% oxygen (P = .001). The incidence of SSIs was halved for patients in this group. In the 80% oxygen group, 13 out of 250 patients developed SSIs (rate 5.2, 95% confidence interval, 2.4% to 8.0%) compared with 28 out of 250 patients in the 30% oxygen group (rate 11.2, 95% confidence interval, 7.3% to 15.1%). Multiple logistic regression analysis revealed that only the use of 30% oxygen correlated significantly with the risk of infection (odds ratio 2.3, 95% confidence interval, 1.2% to 4.6%).

Discussion. This study demonstrates that supplemental oxygen administered during surgery and for one to two hours postoperatively using a nonrebreathing mask effectively reduced the risk of SSIs by more than 50%. Previous studies demonstrate that for a patient with normal peripheral perfusion, the subcutaneous oxygen tension is related linearly to the arterial oxygen tension and that there is an inverse correlation between subcutaneous tissue oxygen tension and the incidence of SSI. These studies suggest that supplemental oxygen should be given for one to two days after surgical procedures, Other studies reveal that supplemental oxygen administered through nasal prongs had no effect on SSIs; however, these researchers show that using a nonrebreathing mask for two hours after surgery was effective in reducing the rate of SSIs. Consequently, the use of a nonrebreathing mask is essential and as few as two hours during the postoperative period is required; however, additional studies are needed to determine the optimum length of time that supplemental oxygen should be continued postoperatively.

Considering the substantial costs associated with SSIs and the finding that there is only minor, if any, additional cost required to use 80% oxygen, supplemental oxygen administered during surgery and a short recovery period using a nonrebreathing mask can be implemented easily by perioperative personnel. Implementing such a process carries with it the potential for significantly reducing the incidence of SSIs and positively affecting the documented weighty cost of SSIs.




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