High-altitude adaptation as a protective factor against postoperative pulmonary complications in liver resection: a prospective matched cohort study

Abstract

Background: High-altitude adaptation (HAA), induced by chronic hypoxia, has clinically significant cardioprotective effects; however, its impact on postoperative pulmonary complications (PPCs) in patients undergoing liver resection remains uncertain.

Methods: We conducted a single-center prospective matched cohort study enrolling 292 consecutive patients undergoing elective liver resection. Patients were divided into two groups based on their long-term residential altitude: high-altitude group (≥ 1500 m) and plain group (< 1500 m). Propensity score matching (1:2 ratio) was applied to control for confounding factors, including demographic variables, clinical characteristics, preoperative oxygen saturation, ARISCAT score, and surgical factors. The primary outcome was the incidence of PPCs within 7 days after surgery. Secondary outcomes included the severity of PPCs, surgical complication grading, and length of hospital stay. Statistical analysis was performed using R software and SPSS 22.0.

Results: After matching, 212 patients were included in the analysis. The incidence of PPCs within 7 days postoperatively in the high-altitude group was significantly lower than that in the plain group (61.5% vs. 76.1%, RR 0.80, 95% CI 0.66-0.98, P = 0.024). Furthermore, the high-altitude group showed milder complication severity and a shorter hospital stay (6 [4-8] vs. 7 [5-11] days, P = 0.005). Multivariate logistic regression analysis showed that HAA was an independent protective factor against PPCs (OR 0.31, 95% CI 0.12-0.83, P = 0.020). Further exploratory analysis revealed that during hepatic pedicle clamping, blood glucose levels remained more stable in the high-altitude group ([9.30 [7.25-11.90] vs. 10.95 [7.90-14.00] mmol/L, P < 0.001), with lower lactate accumulation after multiple clamps (1.55 [1.10-2.17] vs. 1.70 [1.10-2.50] mmol/L, P = 0.042).

Conclusion: HAA may reduce the incidence and severity of PPCs after liver resection, potentially due to enhanced metabolic stability associated with chronic hypoxia in high-altitude residents.

Trial registration: This study is registered with ChiCTR (ID: ChiCTR2200061915), registered on July 11, 2022.

Keywords: Blood glucose; High-altitude adaptation; Lactic; Liver resection surgery; Postoperative pulmonary complications.

Fig. 1

CONSORT flow chart. ASA: American Society of Anesthesiologists, ARISCAT Score: Assess Respiratory Risk in Surgical Patients in Catalonia Score

Fig. 2

Severity grade of postoperative pulmonary complications within the first 7 d after surgery

Fig. 3

Multivariate Logistic Regression of Postoperative Pulmonary Complications. BMI: Body Mass Index. ^a: The low incidence of conversion to open surgery prevented the model from accurately estimating the effect of this category, resulting in complete separation

Fig. 4

Changes in Patients’ Intraoperative Blood Gas Parameters. a Changes in patients’ intraoperative blood glucose levels. b Changes in patients’ intraoperative blood glucose levels with increasing number of clamps. c Changes in patients’ intraoperative lactic acid levels. d Changes in patients’ intraoperative lactic acid levels with increasing number of clamps. Data are presented as median with interquartile range (IQR). Asterisks indicate statistical significance between the two groups, with P-values denoted as *, P < 0.05; **, P < 0.01