Pulse Wave Transit Time Measurements of Cardiac Output in Septic Shock Patients: A Comparison of the Estimated Continuous Cardiac Output System with Transthoracic Echocardiography

BACKGROUND: We determined reliability of cardiac output (CO) measured by pulse wave transit time cardiac output system (esCCO system; CO(esCCO)) vs transthoracic echocardiography (CO(TTE)) in mechanically ventilated patients in the early phase of septic shock. A secondary objective was to assess ability of esCCO to detect change in CO after fluid infusion. METHODS: Mechanically ventilated patients admitted to the ICU, aged >18 years, in sinus rhythm, in the early phase of septic shock were prospectively included. We performed fluid infusion of 500ml of crystalloid solution over 20 minutes and recorded CO by EsCCO and TTE immediately before (T0) and 5 minutes after (T1) fluid administration. Patients were divided into 2 groups (responders and non-responders) according to a threshold of 15% increase in CO(TTE) in response to volume expansion. RESULTS: In total, 25 patients were included, average 64±15 years, 15 (60%) were men. Average SAPSII and SOFA scores were 55±21.3 and 13±2, respectively. ICU mortality was 36%. Mean cardiac output at T0 was 5.8±1.35 L/min by esCCO and 5.27±1.17 L/min by CO(TTE). At T1, respective values were 6.63 ± 1.57 L/min for esCCO and 6.10±1.29 L/min for CO(TTE). Overall, 12 patients were classified as responders, 13 as non-responders by the reference method. A threshold of 11% increase in CO(esCCO) was found to discriminate responders from non-responders with a sensitivity of 83% (95% CI, 0.52-0.98) and a specificity of 77% (95% CI, 0.46-0.95). CONCLUSION: We show strong correlation esCCO and echocardiography for measuring CO, and change in CO after fluid infusion in ICU patients.