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

STUDY OBJECTIVE

To compare cardiac index (CI) 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 CI 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%. CIPA, CIPC, and CITD were determined, and changes in CI (DeltaCI) were calculated. Fluid load was repeated until no increase in stroke volume index (DeltaSVI <10%) was achieved.

MAIN RESULTS

Regression analysis between CIPA/CIPC, CIPA/CITD, and CIPC/CITD revealed r2 = 0.92, r2 = 0.92, and r2 = 0.98. Regression analysis between DeltaCIPA/DeltaCIPC, DeltaCIPA/DeltaCITD, and DeltaCIPC/DeltaCITD revealed r2 = 0.57, r2 = 0.67, and r2 = 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 DeltaCIPA/DeltaCIPC, DeltaCIPA/DeltaCITD, and DeltaCIPC/DeltaCITD resulted in m = -1.01%, SD = 6.51%; m = -0.83%, SD = 5.80%; and m = -0.33%, SD = 4.65%, respectively.

CONCLUSION

Compared with pulmonary artery thermodilution, arterial pulse contour analysis reflects relative changes in CI during rapid changes of preload with clinically acceptable accuracy.