Non-invasive continuous cardiac output monitoring in thoracic cancer surgery

BACKGROUND Patients scheduled for thoracic cancer surgery are eligible for goal-directed fluid therapy, but cardiac output monitoring remains challenging in that specific setting. OBJECTIVE We aimed to compare cardiac output as measured with chest bioreactance with that measured by calibrated pulse contour analysis; the hypothesis being that both methods would be interchangeable. DESIGN A prospective monocentre observational study. SETTING A tertiary university hospital. PATIENTS Fifty adult patients undergoing thoracic cancer surgery over a one year period. MAIN OUTCOME MEASURES Simultaneous measurements of cardiac index (CI) with bioreactance (CI-NICOM) and arterial pulse contour analysis calibrated by transthoracic echocardiography (CI-PCA) were performed at eight pre-specified intra-operative time points and following fluid challenge and/or vasoactive agents. Relationships between absolute values and changes in CI were assessed by linear regression. Interchangeability was tested with Bland–Altman analysis and percentage error calculation. A four quadrant plot was used to evaluate trending ability. RESULTS There was a significant difference between CI-PCA and CI-NICOM: 2.4 ± 0.8 (range: 0.9 to 5.8) l min −1 m −2 vs. 2.9 ± 0.9 (range: 0.9 to 7.2) l min −1 m −2 , respectively ( P < 0.001). A positive relationship was found between both techniques: y = 0.29x + 2.19; r 2 = 0.08 ( P < 0.001). Taking CI-PCA as the reference method, there was a systematic overestimation of CI-NICOM by 21% (0.5 l min −1 m −2 ) and limits of agreement were large: -2.49 to 1.47 l min −1 m −2 . The percentage error was 77% and concordance rates were 75 and 70% with and without an exclusion zone of 0.5 l min −1 m −2 . CONCLUSION Chest bioreactance is feasible and well tolerated in patients undergoing thoracic surgery for cancer. When compared with calibrated PCA over a wide range of CI values, the technique is moderately correlated, not interchangeable, and provides moderate trending ability. TRIAL REGISTRATION NCT04251637.