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

Abstract

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 cmH2O) 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 PEEP 5 cmH2O (PEEP5), while in the last 10 patients, lung recruitment followed by individual PEEP adjustment (PEEPadj) 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 PEEPadj 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.

Trial registration: Clinicaltrials.gov identifier: NCT03444545.

Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the European Society of Anaesthesiology and Intensive Care.

Figures

Fig. 1

Patient flow chart

Fig. 2

Event line displaying cardiac output measured with the capnodynamic (COEPBF) and transpulmonary thermodilution (COTPTD) methods in the PEEP5 (left) and PEEPadj (right) groups in patients who successively completed all the steps in the protocol in the correct order.

Fig. 3

Bland–Altman plots for 322 paired values from all included patients (top – blue dots), 227 paired values in PEEP5 (middle – purple dots), and 95 paired values in PEEPadj (bottom – pink dots) for COEPBF versus COTPTD.

Fig. 4

Four-quadrant plots for PEEP5 (a) showing 96 paired delta values and PEEPadj (b) showing 41 paired delta values displayed by the capnodynamic method (COEPBF) and transpulmonary thermodilution (COTPTD) from all interventions.

Fig. 5

A continuous trace of various haemodynamic parameters from one patient with a sudden blood loss (600 ml) from a large pelvic artery and an ongoing resuscitation with fluids and increase in norepinephrine.