This randomized controlled trial is to investigate if SmtO2-guided management on top of the usual care, compared with the usual care only, during laparoscopic hysterectomy significantly reduces the incidence of PONV.

Postoperative nausea and vomiting (PONV) remains prevalent despite the institution of various prophylactic measures. The incidence of PONV in female patients undergoing laparoscopic gynecological surgery is up to 50% with and 70% without the administration of antiemetics, respectively. The consequences of PONV range from patient discomforts, postoperative complications, prolonged hospitalization, to increased health care costs. Among the multiple risk factors, suboptimal gastrointestinal (GI) perfusion or oxygenation may be responsible for some cases of PONV; however, this speculation remains to be confirmed.5 Optimal tissue oxygenation, the balance between tissue oxygen consumption and supply, is essential for the integrity of any tissue bed that is metabolically active. However, GI oxygenation cannot be directly and continuously monitored in patients at this time. Whether there is an organ which can be used as a surrogate of the GI system, meaning that the tissue oxygenation of this surrogate organ not only can be monitored and that it also correlates with that of the GI system, is an intriguing question. Currently, tissue oxygenation can be measured using near-infrared spectroscopy (NIRS) in patients. The recent advancements of this technology enable the accurate monitoring of the oxygenation within many tissue beds depending on the location of the oximetry probe.

The recent cohort study demonstrated that there is a close relationship between muscular tissue oxygen saturation (SmtO2) and PONV in patients undergoing robotic laparoscopic hysterectomy (manuscript accepted and in production). Multiple thresholds based on threshold, AUC, and multivariable analyses are able to differentiate the risk of PONV. The following SmtO2 thresholds were found to correlate with a reduced risk of PONV: 20% above baseline; while the following thresholds correlate with an increased risk of PONV: 5% below baseline, 15% below baseline, and 20% below baseline, < 70%, < 65%, and < 60%. Taken together, our study suggests the potential therapeutic targets for PONV prophylaxis may be to maintain SmtO2 > 70% and above baseline.

In this study, the investigators aim to investigate if intraoperative care guided by SmtO2 monitoring reduces the incidence of PONV after laparoscopic hysterectomy.

Inclusion Criteria:

1. Age 18-65 years
2. Non-smoker
3. ASA I-III
4. Elective laparoscopic procedure involving hysterectomy

Exclusion Criteria:

1. Refuse to participate
2. Emergent surgery
3. Bowel resection planned
4. Vaginal or abdominal (open) hysterectomy
5. Chemotherapy or radiotherapy before surgery
6. Significant neuro, cognitive, or psychologic disease: stroke with neurologic deficit, dementia, schizophrenia, or any condition that makes meaningful postoperative follow-ups impossible
7. Significant cardiovascular disease: low-output cardiac failure defined as a preoperative left ventricular ejection fraction < 30%, active coronary artery disease, symptomatic valvular disease, symptomatic arrhythmia with or without pacemaker and/or AICD placement
8. Significant pulmonary disease: COPD requiring home oxygen therapy, severe asthma requiring steroid treatment, other pulmonary conditions requiring home oxygen therapy
9. Severe hepatic dysfunction being evaluated for liver transplantation or with a Child-Pugh Class C classification
10. Severe renal dysfunction requiring renal replacement therapy
11. Muscular pathologies such as dystrophy, atrophy, and weakness
12. Skin conditions incompatible with the adhesive oximetry probe (e.g., delicate or tattooed skin)
13. Current or previous smoker
14. ASA Physical Score ≥ IV

It is female patients whom are receiving hysterectomy.

Individual participant data are available to the editorial office of the journal to which the manuscript is submitted upon request.

Both patients and outcomes assessor are blinded to group assignment.