Postoperative hyperlactataemia and preoperative cardiopulmonary exercise testing in an elective noncardiac surgical cohort: a retrospective observational study()

BACKGROUND: Blood lactate concentration in the postoperative period is a marker of physiological stress and a predictor of complications and mortality. Cardiopulmonary exercise testing (CPET) is a common preoperative risk stratification tool. We aimed to investigate the association between preoperative CPET results and postoperative lactate concentration with postoperative mortality after major noncardiac surgery. METHODS: We analysed data from patients undergoing major noncardiac surgery in a tertiary UK centre between 2007 and 2014 who had preoperative CPET and postoperative lactate measurements. Univariate and multivariate analyses were performed to assess the association between lactate concentration, CPET results, or both and mortality. RESULTS: We analysed data from 1075 patients. A mean lactate concentration >2 mM in the first 12, 24, and 48 h after surgery was associated with odds ratios (ORs) and 95% confidence intervals (CIs) for 30-day mortality of 3.9 (2.1–7.3; P<0.005), 4.5 (2.4–8.4; P<0.005), and 6.1 (3.3–11.5; P<0.005), respectively. The dichotomous CPET variable, ventilatory equivalence for CO(2) (V̇E/V̇(co2); cut-off 34), was associated with increased risk of 30-day mortality (OR 2.5; 95% CI: 1.3–4.8; P<0.005). In a multivariable model, hyperlactataemia and poor V̇E/V̇(co2) retained their significant associations with 30- and 90-day mortality when adjusted for age, BMI, and surgical risk. When looking at the combined effect of the dichotomous hyperlactataemia in the first 24 h (cut-off 2 mM) and preoperative V̇E/V̇(co2), the OR for 30-day mortality was 11.53 (95% CI: 4.6–28.8; P≤0.005). CONCLUSIONS: Our study suggests that postoperative hyperlactataemia and preoperative poor V̇E/V̇(co2) are independently associated with an increased risk of mortality after major noncardiac surgery.