Supplemental Oxygen During and After Surgery
Supplemental Oxygen During and After Surgery and the Risk of Surgical Wound Infection
What is the problem and what is known about it so far?
Surgical wound infections prolong hospitalization by an average of 1 week and substantially increase the cost of care. These infections are possibly the most common serious complication of surgery. Defense against infectious agents (bacteria) requires oxygen therefore interventions that increase tissue oxygen may reduce infection risk.
Why did the researchers do this particular study?
A study in 2000 showed that providing 80% oxygen throughout surgery and 2 hours after surgery decreased infection risk by half compared with patients who were on 30% oxygen. However, a study in 2004 concluded the opposite. This particular study was done to retest the hypothesis that supplemental oxygen during surgery decreases the risk of wound infection.
Who was studied?
300 subjects aged 18 to 80 years who underwent colorectal surgery in 14 hospitals in Spain were enrolled. Subjects who had an expected surgery time of less than 1 hour, fever or existing signs of infection, diabetes mellitus, HIV infection, weight loss greater than 20% in the previous 3 months, serum albumin less than 30 g/L, and white blood cell count less than 2500 cells/ml were excluded.
How was the study done?
Subjects who underwent colorectal surgery were randomly assigned to an oxygen/air mixture with a fraction of inspired oxygen (FIO2) of 30% or 80% during surgery and 6 hours after surgery. The surgical team including those who evaluated the wound for infection and the patients were not informed of the group assignments. Surgical wounds were assessed daily for infection. Wounds were considered infected when they met Centers for Disease Control and Prevention definitions. The attending surgeon controlled use of pain medications, initiation of feeding, initiation of walking, and the length of hospitalization. Only infections diagnosed in the first 14 days after surgery were included. Patients discharged before 14 days were monitored daily in an outpatient clinic.
What did the researchers find?
143 subjects received 30% FIO2 and 148 received 80% FIO2 during and after surgery. Surgical site infection occurred in 35 patients given 30% FIO2 and 22 patients given 80% FIO2. The risk of infection was 39% lower in the 80% FIO2 group compared to the 30% FIO2 group. Patients with infections had significantly longer hospital stays and delays to walking. None of the other outcomes such as use of pain medications, initiation of feeding, initiation of walking, and length of hospitalization varied significantly between the two groups.
What were the limitations of the study?
The chances of getting a wound infection depend on numerous factors, including the type of procedure, duration of anesthetic, and body temperature and as expected these were not identical in all subjects. Another limitation is that only infections that occurred in the first 15 days after surgery were considered. It is possible that subsequent infections may have occurred.
What were the implications of the study?
Supplemental 80% FIO2 during and for 6 hours after colorectal surgery reduced wound infection risk by almost 50% compared to the group that received 30% FIO2. This result is consistent with most data already published. Supplemental oxygen does not appear to add any new risks to the patient, costs little, and should be considered part of ongoing quality improvement activities related to surgical care. Further research is needed to determine if these results apply to patients undergoing other surgical procedures.
Summarized by Carl Kapadia, College of Medicine, University of Vermont
Summarized from "Supplemental Perioperative Oxygen and the Risk of Surgical Wound Infection: A Randomized Controlled Trial." Belda, F.J. et al., Journal of the American Medical Association, October 26, 2005, Volume 294, Number 16, pages 2035-2042.
