Cardiopulmonary exercise testing and length of stay in patients undergoing major surgery

Abstract

We read with interest the review published in Anaesthesia analysing studies that assessed the value of cardiopulmonary exercise testing (CPET) in evaluating risk in patients undergoing non-cardiopulmonary surgery [1]. Cardiopulmonary exercise testing is increasingly used in the pre-operative assessment of patients undergoing major surgery. Studies have shown a relationship between pre-operative CPET values and mortality [2], postoperative complications and length of hospital stay [3]. Our aim was to determine whether CPET measures might predict postoperative length of stay in both the critical care unit and hospital, in patients undergoing major surgery. We hoped CPET might then assist in better planning and organisation of peri-operative care. We retrospectively analysed data of all 325 patients who had undergone CPET at a large tertiary centre over a 26-month period (January 2008 to March 2010). To achieve some homogeneity in our sample, we selected a subgroup of patients undergoing major vascular or upper gastro-intestinal surgery for further analysis (n = 112). We acquired length of stay data from critical care admission records, hospital notes and discharge letters. We then estimated Spearman correlation coefficients for typical pre-operative CPET measures (anaerobic threshold, peak oxygen consumption and ventilatory equivalents for carbon dioxide (VE/VCO2)) and postoperative length of stay for critical care and hospital. A value of p < 0.05 was considered significant (two-sided). Two out of the 112 patients (1.8%) undergoing major vascular or upper gastro-intestinal surgery died. Median (IQR [range]) length of stay in critical care was 70 (46–110 [18–928]) h and in hospital was 10 (7–15 [3–51]) days. There were no significant correlations between any of the CPET measures and length of stay in either critical care or hospital (Table 1). Therefore, in our series, pre-operative CPET data were not useful in predicting lengths of stay in critical care or hospital. Our negative results may be explained by two reasons. Firstly, the factors influencing a patient’s length of stay are numerous and complex, for example a lack of beds, day of the week, social circumstances and the patient’s surgical team. Secondly, although efforts were made to correct for patients’ heterogeneity, this could have been improved further by comparing patients undergoing more similar procedures, for example, upper gastro-intestinal surgery only, as previous authors have suggested that different types of surgery may differ in sensitivity to CPET values [1]. We look forward to the results of further studies looking in more detail at the outcomes of surgical patients who have undergone pre-operative CPET testing. No external funding and no competing interests declared. Previously posted at the Anaesthesia Correspondence website: http://www.anaesthesiacorrespondence.com. Published with the permission of the Trust's Caldicott guardian.