Intraoperative desaturation in pediatric patients at high altitude: incidence, risk factors, and a non-linear body...

Pediatric patients undergoing general anesthesia are vulnerable to intraoperative hypoxemia, and this risk may be magnified at high altitude. However, the specific incidence, risk factors, and dose-response relationships for desaturation in children residing at extreme altitudes (≥3,650 m) remain poorly defined.

This retrospective cohort study included 1,793 consecutive pediatric patients (<12 years) of native Tibetan ethnicity who underwent elective non-cardiothoracic surgery under general anesthesia with mechanical ventilation at an altitude of 3,650 m (Lhasa, China) between January 2020 and October 2025. Intraoperative desaturation was defined as SpO₂ <90% lasting ≥1 min during mechanical ventilation. Multivariable logistic regression, restricted cubic splines, and piecewise regression were used to identify risk factors and nonlinear thresholds.

The overall incidence of intraoperative desaturation was 3.5% (63/1,793). Multivariable analysis revealed that younger age (adjusted OR per one-year increase 0.80, 95% CI: 0.72-0.90), severe underweight (<3rd percentile for age and sex; adjusted OR 4.57, 95% CI: 2.18-9.58), lower preoperative hemoglobin (adjusted OR per 1 g/dL increase 0.85, 95% CI: 0.74-0.98), prolonged mechanical ventilation (adjusted OR per 1 h increase 1.46, 95% CI: 1.24-1.73), and female sex (adjusted OR 1.76, 95% CI: 1.01-3.04) were independent risk factors. A non-linear L-shaped relationship was identified between absolute body weight and desaturation risk (P for non-linearity = 0.004), with an exploratory non-linear safety threshold at 26.95 kg. Below this threshold, each 1 kg increase in weight reduced the risk by 25.6% (adjusted OR 0.744, 95% CI: 0.646-0.857). In unadjusted between-group comparisons, desaturation was associated with higher rates of delayed extubation, a nearly four-fold higher ICU admission rate, and prolonged hospital stay (all P < 0.01).

At extreme high altitude, intraoperative desaturation in pediatric patients is independently driven by younger age, severe underweight, lower hemoglobin, female sex, and prolonged ventilation. The identified L-shaped relationship and the exploratory 26.95 kg inflection point provide growth-based criteria for preoperative risk stratification. Together with the other independent risk factors (younger age, lower hemoglobin, female sex, and prolonged ventilation), these findings underscore the need for individualized, comprehensive perioperative strategies to reduce desaturation and improve outcomes in high-altitude pediatric anesthesia.