To the Editor:—
I read with interest the review article of Dr. Mauermann and Dr. Nemergut1about the anesthesiologist's role in preventing surgical site infection (SSI).
The authors deal with hypothermia and write, “The incidence of SSI was 5.8% in the normothermic group and 18.8% in the hypothermic group. The patients who developed SSIs required hospital stays nearly 1 week longer than those who did not develop a SSI, indicating that these were clinically significant complications ” (italics added).
They also review the role of hyperoxia to reduce SSI and write, “Both of these studies found statistically significant reductions in the rates of SSIs in the 0.8 fraction of inspired oxygen (Fio2) group versus the 0.3 Fio2group.” They correctly cite the two studies2,3that found that 80% oxygen could halve surgical site infection versus 30% oxygen; they also cite another study4that found that 80% oxygen increased surgical site infection versus 35%. But surprisingly, they do not report whether the impressive reduction in SSI using 80% oxygen found in those two studies reduced clinically significant complications.
Greif et al. 2report a 54% relative risk reduction of SSI using 80% versus 30% oxygen. However, patients who received 80% oxygen had 12.2 days of hospitalization versus 11.9 days among those who received 30% oxygen. Moreover, no difference was found for time to first solid food intake or staples removed.
Belda et al. 3report a 39% relative risk reduction of SSI using 80% versus 30% oxygen. Again, consistently with the lack of clinically significant benefit, there was no difference in days of hospitalization, time to solid food intake, or staples removed.
The authors conclude that “… high inspired oxygen levels in the perioperative period confers some benefit in reducing the incidence of SSIs.” They do not report, however, the lack of clinically significant benefit.
In contrast with these results, Pryor et al. 4did find clinically significant harm among patients who received 80% oxygen (longer hospital stay, higher reoperation rate). This study, the lack of clinical benefit in the other two studies, and the inexistence of data evaluating more moderate oxygen concentrations (45–60%)5should prevent anesthesiologists from accepting 80% as the ideal perioperative oxygen concentration to improve surgery outcomes.
Hospital General Universitario de Elche, Elche, Alicante, Spain. firstname.lastname@example.org