Validation of preoperative cardiopulmonary exercise testing-derived variables to predict in-hospital morbidity after major colorectal surgery.

Abstract

In single-centre studies, postoperative complications are associated with reduced fitness. This study explored the relationship between cardiorespiratory fitness variables derived by cardiopulmonary exercise testing (CPET) and in-hospital morbidity after major elective colorectal surgery. Patients underwent preoperative CPET with recording of in-hospital morbidity. Receiver operating characteristic (ROC) curves and logistic regression were used to assess the relationship between CPET variables and postoperative morbidity. Seven hundred and three patients from six centres in the UK were available for analysis (428 men, 275 women). ROC curve analysis of oxygen uptake at estimated lactate threshold (V˙o₂ at θ^_L ) and at peak exercise (V˙o_2peak ) gave an area under the ROC curve (AUROC) of 0·79 (95 per cent c.i. 0·76 to 0·83; P < 0·001; cut-off 11·1 ml per kg per min) and 0·77 (0·72 to 0·82; P < 0·001; cut-off 18·2 ml per kg per min) respectively, indicating that they can identify patients at risk of postoperative morbidity. In a multivariable logistic regression model, selected CPET variables and body mass index (BMI) were associated significantly with increased odds of in-hospital morbidity (V˙o₂ at θ^_L 11·1 ml per kg per min or less: odds ratio (OR) 7·56, 95 per cent c.i. 4·44 to 12·86, P < 0·001; V˙o_2peak 18·2 ml per kg per min or less: OR 2·15, 1·01 to 4·57, P = 0·047; ventilatory equivalents for carbon dioxide at estimated lactate threshold (V˙_E /V˙co₂ at θ^_L ) more than 30·9: OR 1·38, 1·00 to 1·89, P = 0·047); BMI exceeding 27 kg/m² : OR 1·05, 1·03 to 1·08, P < 0·001). A laparoscopic procedure was associated with a decreased odds of complications (OR 0·30, 0·02 to 0·44; P = 0·033). This model was able to discriminate between patients with, and without in-hospital morbidity (AUROC 0·83, 95 per cent c.i. 0·79 to 0·87). No adverse clinical events occurred during CPET across the six centres. These data provide further evidence that variables derived from preoperative CPET can be used to assess risk before elective colorectal surgery.