Identification of Various Perioperative Risk Factors Responsible for Development of Postoperative Hypoxaemia.

Objective: Identification of risk factors that might be responsible for postoperative hypoxaemia, in view of changing profile of surgical patients and better but more complex perioperative care nowadays.

Methods: We conducted a prospective observational study that included patients aged 18-65 years, who underwent elective surgery and required general anaesthesia. Oxygen saturation was monitored before the induction in operating room and continued 72 hours post-surgery. Patients were maintained on room air if SpO2 remained >94%. If SpO2 was between 90% and 94%, then patients were provided oxygen therapy via face mask (flow rate at 5-6 litre min-1 ). If SpO2 was between 89%-85% despite oxygen therapy with face mask, the Bilevel Positive Airway Pressure (BiPAP) was applied. If SpO2 was <85% despite therapy with face mask, or if patient was unable to maintain SpO2 >90% on BiPAP, then patient was intubated, and ventilatory support was provided.

Results: Out of 452 patients, 61 developed SpO2 ≤94% requiring oxygen therapy (13.5%). Oxygen therapy by face mask was required in 51 patients, BiPAP in 8 and ventilatory support with endotracheal intubation in 2. Age, body mass index (BMI), smoking status, presence of preoperative respiratory disease, SPO2 (on room air) at baseline and immediately after the transfer to the post-anaesthesia care unit (PACU) were independently associated with postoperative oxygen therapy.

Conclusion: The risk of postoperative hypoxaemia was highest in patients aged 51-65 years, BMI higher than 30, current and former smokers, pre-existing respiratory disease, chronic obstructive pulmonary disease, patients with 96% oxygen saturation or less at baseline or after shifting to PACU. The type of surgical incision, duration of surgery and dose of opioids administered were not independent risk factors.