Noninvasive assessment of cardiac output in critically ill patients by analysis of the finger blood pressure waveform

Objective: To assess whether the measurement of cardiac output by computer-assisted analysis of the finger blood pressure waveform can substitute for the thermodilution method in critically ill patients. Design: Prospective data collection. Setting: Emergency department in a 2000-bed inner city hospital. Patients: Forty-six critically ill patients requiring invasive monitoring for clinical management were prospectively studied. Interventions: Under local anesthesia a 7-Fr pulmonary artery catheter was inserted via the central subclavian or jugular vein. Cardiac output was determined by the use of a cardiac output computer and injections of 10 mt ice-cold glucose 5%. Noninvasive cardiac output was calculated from the finger blood pressure waveform by the use of the test software program. Measurements and Main Results: Three hundred twenty-three pairs of invasive and noninvasive hemodynamic measurements were collected in intervals of 30 mins from 46 patients (mean age 61.9 +/- 12.4 yrs; 35 male, 11 female). The average cardiac index during the study period was 2.83 L/min/m(2) (range 0.97 to 5.56). The overall discrepancy between both measurements was 0.14 L/min/m(2) (95% confidence interval: 0.10-0.18, p <.001). Seventy-five (23.2%) measurements had an absolute discrepancy >+/-0.50 L/min/m(2). Noninvasive and invasive comparisons of mean differential cardiac output were out of phase for 9.7% of all readings. Conclusion: Computer-assisted analysis of finger blood pressure waveform to assess cardiac output is not a substitute for the thermodilution method due to a high percentage (23.2%) of inaccurate readings; however, it may be a useful tool for the detection of relative hemodynamic trends in critically ill patients.