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Subcutaneous oxygen partial pressure is one of several determinants of surgical site infections (SSIs). However, tissue partial pressure is difficult to measure and requires invasive techniques. We tested the hypothesis that early postoperative tissue oxygen saturation (StO2) measured with near-infrared spectroscopy predicts SSI.We evaluated StO2 in 116 patients undergoing elective colon resection. Saturation was measured near the surgical incision, at the upper arm, and at the thenar muscle with an InSpectra™ tissue spectrometer model 650 (Hutchinson Technology Inc., Hutchinson, MN) 75 minutes after the end of surgery and on the first postoperative day. An investigator blinded to StO2 assessed patients daily for wound infection. Receiver operating characteristic curves were used to analyze the performance of StO2 measurements as a predictor of SSI.In 23 patients (≈20%), SSI was diagnosed 9 ± 5 days (mean ± SD) after surgery. Patients who did and did not develop an SSI had similar age (48 ± 14 vs 48 ± 15 years, respectively; P = 0.97) and gender (female:male, 15:8 vs 46:47, respectively), but patients who developed SSI weighed more (body mass index 32 ± 7 vs 27 ± 6 kg/m2; P < 0.01). StO2 at the upper arm was lower in patients who developed SSI than in those who did not develop SSI (52 ± 22 vs 66 ± 21; P = 0.033), and these measurements had a sensitivity of 71% and specificity of 60% for predicting SSI, using StO2 of 66% as the cutoff point.StO2 measured at the upper arm only 75 minutes after colorectal surgery predicted development of postoperative SSI, although the infections were typically diagnosed more than a week later. Although further testing is required, StO2 measurements may be able to predict SSI and thus allow earlier preventive measures to be implemented.