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.