Changes in end-tidal CO2 could predict fluid responsiveness in the passive leg raising test but not in the mini-fluid challenge test: A prospective and observational study

Abstract

Objective: The objective is to explore the value of end-tidal carbon dioxide (ETCO2) in replacing cardiac index for evaluating fluid responsiveness during the passive leg raising (PLR) test and mini-fluid challenge (mini-FC).

Methods: Patients experiencing septic shock and who were on mechanical ventilation in an intensive care unit were divided into responder and nonresponder groups according to whether their cardiac index increased by more than 10% after the FC. Before and after those tests, the changes in ETCO2, central venous pressure, heart rate, mean arterial pressure, pulse pressure, and cardiac output were recorded.

Results: Of the 48 patients in the study, 34 had fluid responsiveness according to the changes in cardiac output or stroke volume. The ΔCI and ΔETCO2 in the responder group were larger than the changes in the nonresponder group during the PLR test (1.1 ± 0.7 vs 0.2 ± 0.4 L/min per square meter, 3.0 ± 3.0 vs 0.5 ± 2.5 mm Hg; P < .05) but not during mini-FC. ΔETCO2 greater than or equal to 5% during the PLR test predicted fluid responsiveness with 93.4% specificity and 75.8% sensitivity in a receiver operating characteristic curve. The area under the curve was 0.849 (95% confidence interval, 0.739-0.930). ΔETCO2 greater than or equal to 3% during the mini-FC predicted fluid responsiveness with 93.4% specificity and 33.3% sensitivity in a receiver operating characteristic curve, and the area under the curve was 0.781 (95% confidence interval, 0.646-0.915).

Conclusions: The changes in ETCO2 may predict fluid responsiveness during the PLR test in patients with septic shock, but similar results were not found with the mini-FC.

Keywords: ETCO(2); Fluid responsiveness; Passive leg raising test.