Table 1.

Baseline and procedure characteristics

Baseline	Sex, age, body mass index (kg/m2), American Society of Anaesthesiologists (ASA) physical status score, smoking status, peripheral vascular disease, diabetes, (metastatic) cancer, congestive heart disease, (pulmonary) hypertension, chronic obstructive pulmonary disease, immunosuppressant use, peripheral oxygen saturation (%), glucose (mg/dL), indication for surgery, emergency procedure
Preoperative	Use of preoperative antibiotic prophylaxis (dose and agent), timing of preoperative antibiotic prophylaxis, use of mechanical bowel preparation, haemoglobin (g/L), use of antibiotic bowel preparation, cytostatic chemotherapy, radiotherapy, use of preoperative skin preparation prophylaxis (dose and agent), timing of preoperative skin preparation prophylaxis
Intraoperative	Surgical procedure(s), organ involvement, contamination (Centers for Disease Control and Prevention wound classification61), laparoscopic surgery, mean arterial pressure (mm Hg), haemoglobin (g/L), heart rate (beats/min), haemodynamic monitoring method, haemodynamic management algorithm, crystalloid infusion (mL), colloid Infusion (mL), red cell transfusion (units), duration of surgery (min), duration of anaesthesia (min), mean core temperature (°C)*, lowest core temperature (°C)*, duration hypothermia (<35°C), mean net fluid supplementation (mL/kg/hour), arterial oxygen saturation (%), peripheral oxygen saturation (%), subcutaneous oxygen tension (mm Hg), muscle oxygen tension (mm Hg), partial pressure of arterial oxygen (mm Hg), mean FiO2 (%), mean positive end-expiratory pressure (PEEP) (cmH2O), ventilator flow (L/min), peak airway pressure (mm Hg), plateau pressure (mm Hg), tidal volume (mL/kg predicted body weight), respiratory frequency, vasopressor agent, vasopressor agent used (mg), glucose (mg/dL), use of general anaesthesia, use of spinal or epidural anaesthesia, use of mechanical ventilation, use of nitrous oxide, total blood loss (mL), fluids (mL), end tidal CO2
Postoperative	Use of postoperative antibiotics (dose and agent), postoperative antibiotic duration (days), cytostatic chemotherapy, radiotherapy, haemoglobin (g/L), visual analog scale (VAS) pain score, use of postoperative oxygen suppletion (duration, method and FiO2), haemoglobin (g/L), peripheral oxygen saturation (%), partial pressure of arterial oxygen (mm Hg), subcutaneous oxygen tension (mm Hg), muscle oxygen tension (mm Hg), glucose (mg/dL), National Nosocomial Infections Surveillance System (NNIS) Score,62 surgical site infection risk score,63 use of drains
Oxygen administration and monitoring	Total duration and concentration of oxygen exposure during the preoperative/intraoperative/postoperative period (timing of initiation, concentration, duration), oxygen supply and mode of administration (intubation, use and type of face mask, nasal prongs), carrier gas (N2, N2O, medical or room air), protocol-defined target or range of partial pressure of arterial oxygen (mm Hg) or peripheral oxygen saturation (%)

*Direct measurement or its approximation by peripheral measurement.