Cardiac index measurements during rapid preload changes: a comparison of pulmonary artery thermodilution with arterial pulse contour analysis

Study Objective: To compare cardiac index (Cl) values obtained by pulmonary artery thermodilution (CIpA), arterial thermodilution (CITD), and arterial pulse contour analysis (CIPC) during rapid fluid administration, as accurate and rapid detection of Cl changes is critical during acute preload changes for guiding volume and vasopressor therapy in critically ill patients, and the accuracy of CIPC during acute changes in loading condition is currently unknown. Design: Prospective clinical study. Setting: Cardiac surgical intensive care unit of a university hospital. Patients: Seventeen American Society of Anesthesiologists (ASA) physical status II and III patients, aged 32 to 76 years, with normal left ventricular function during the early postoperative period after elective coronary artery bypass graft surgery. Measurements: After baseline determinations of CIPA, CIPC, and CITD were made, fluid loading was performed using 10 mL times body mass index of hydroxyethyl starch 6%. Cl-PA, CIPC, and CITD were determined, and changes in CI(Delta CI) were calculated. Fluid load was repeated until no increase in stroke volume index (Delta SVI < 10 %) was achieved. Main Resuts: Regression analysis between CIPA/CIPC, CIPA/CITD, and CIPC/CITD revealed r(2) = 0.92, r(2) 2 = 0.92, and r(2) = 0.98. Regression analysis between Delta CIPA/Delta CIPC, Delta CIPA/Delta CITD, and Delta CIPC/Delta CITD revealed r(2) = 0.57, r(2) = 0.67, and r(2) = 0.74, respectively. Bland-Altman analysis was used to determine accuracy and precision of the 3 methods compared. The mean differences (m) and SD between Delta CIPA/Delta CIPC, Delta CIPA/,Delta CITD, and Delta CIPC/,Delta CITD resulted in m = -1.01%, SD = 6.51%; m = -0.83%, SD = 5.80%; and m = -0.33%, SD = 4.65%, respectively.