Muscular tissue oxygen saturation during robotic hysterectomy and postoperative nausea and vomiting: exploring the potential therapeutic thresholds.

The relationship between muscular tissue oxygen saturation (SmtO2) during surgery and postoperative nausea and vomiting (PONV) remains to be determined. Patients undergoing robotic hysterectomy participated in this prospective cohort study. SmtO2 of the brachioradialis muscle in the forearm was continuously monitored during surgery. Thresholds based on relative changes or absolute values were systematically assigned. The relationship between thresholds and PONV was investigated based on threshold analysis (i.e., exceeding or not exceeding a threshold), area under the curve analysis (i.e., the size of the area enclosed by the SmtO2 trace and threshold), and multivariable analysis by accounting for recognized PONV risk factors. PONV occurred in 35 of 106 patients (33%). Based on the multivariable analysis, the SmtO2 threshold of 20% above baseline correlated with less PONV (OR 0.39; 95% CI 0.16-0.93; p = 0.034), and the following values correlated with more PONV: 5% below baseline (OR 2.37; 95% CI 1.26-4.45; p = 0.007), 20% below baseline (OR 16.08; 95% CI 3.05-84.73; p = 0.001), < 70% (OR 2.86; 95% CI 1.17-6.99; p = 0.021) and < 60% (OR 6.55; 95% CI 1.11-38.53; p = 0.038). Our study suggests that a potential therapeutic goal for PONV prophylaxis may be to maintain SmtO2 at > 70% and above baseline.