Hyperoxygenation postsurgery benefits in doubt

By Eleanor McDermid

Supplementation with 80% fraction of inspired oxygen during surgery does not reduce patients' risk for surgical site infections (SSIs), research shows.

The randomized, controlled, assessor-blinded ISO₂ trial, which appears in Anesthesiology, tested the effect of hyperoxygenation in patients undergoing routine abdominal, gynecologic, or breast surgery.

The researchers encountered recruitment problems because of publicity surrounding SSIs at the time; the 434 patients in the study represented 94% of the planned sample size. Also, the rate of SSIs within 30 days of surgery was lower than anticipated in the control group, at 7.2%.

This was despite Pascal Thibon (Centre Hospitalier Universitaire de Caen, France) and colleagues ensuring "exhaustive follow up" of patients after discharge, because SSIs occurring after discharge may account for up to 70% of the total number.

The control group received 30% oxygen, while the hyperoxygenation group received 80% oxygen and had a 30-day SSI rate of 6.6% - not significantly different from that in the control group.

Oxygenation was given throughout surgery, but unlike in some previous trials it was not continued postoperatively, because this would have gone against routine clinical practice. The team aimed to maximize the generalizability of the study by keeping to routine practice, "respecting the routine practices of the surgical teams involved."

Nonetheless, the researchers say they can exclude a major effect of hyperoxygenation on infection risk. Also, hyperoxygenation did not increase rates of adverse outcomes. The most common adverse outcome, postoperative nausea and vomiting, occurred in 7.5% of the hyperoxygenation group and 5.3% of the control group, which was not a significant difference.

Rates of adverse effects potentially associated with hyperoxia - dry cough, retrosternal pain, and vision problems - were not increased in the hyperoxygenation group. Desaturation and bradycardia were more common in the control than hyperoxygenation group.

To compensate for the reduced patient sample size in their study, Thibon and team also conducted a meta-analysis of this study plus eight others, including a total of 3359 patients. There was significant heterogeneity among the studies, but they found no indication of even a small effect of hyperoxygenation on risk for SSIs.

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