Comparison between capnodynamic and thermodilution method for cardiac output monitoring during major abdominal surgery An observational study

BACKGROUND Cardiac output (CO) monitoring is the basis of goal-directed treatment for major abdominal surgery. A capnodynamic method estimating cardiac output (COEPBF) by continuously calculating nonshunted pulmonary blood flow has previously shown good agreement and trending ability when evaluated in mechanically ventilated pigs. OBJECTIVES To compare the performance of the capnodynamic method of CO monitoring with transpulmonary thermodilution (COTPTD) in patients undergoing major abdominal surgery. DESIGN Prospective, observational, method comparison study. Simultaneous measurements of COEPBF and COTPTD were performed before incision at baseline and before and after increased (+10 cmH(2)O) positive end-expiratory pressure (PEEP), activation of epidural anaesthesia and intra-operative events of hypovolemia and low CO. The first 25 patients were ventilated with PEEP5 cmH(2)O (PEEN, while in the last 10 patients, lung recruitment followed by individual PEEP adjustment (PEEPadi) was performed before protocol start. SETTING Karolinska University Hospital, Stockholm, Sweden. PATIENTS In total, 35 patients (>18 years) scheduled for major abdominal surgery with advanced hemodynamic monitoring were included in the study. MAIN OUTCOME MEASURES AND ANALYSIS Agreement and trending ability between COEPBF and COTPTD at different clinical moments were analysed with Bland-Altman and four quadrant plots. RESULTS In total, 322 paired values, 227 in PEEP5 and 95 in PEEPadj were analysed. Respectively, the mean COEPBF and COTPTD were 4.5 +/- 1.0 and 4.8 +/- 1.1 in the PEEP5 group and 4.9 +/- 1.2 and 5.0 +/- 1.0 l min(-1) in the PEEPadj group. Mean bias (levels of agreement) and percentage error (PE) were -0.2 (-2.2 to 1.7) l min(-1) and 41% for the PEEP5 group and -0.1 (-1.7 to 1.5) l min(-1) and 31% in the PEEP(adj )group. Concordance rates during changes in COEPBF and COTPTD were 92% in the PEEP5 group and 90% in the PEEPadj group. CONCLUSION COEPBF provides continuous noninvasive CO estimation with acceptable performance, which improved after lung recruitment and PEEP adjustment, although not interchangeable with COTPTD. This method may become a tool for continuous intra-operative CO monitoring during general anaesthesia in the future.