Objective: Stroke volume variation as measured by the analysis of the arterial pressure waveform enables prediction of volume responsiveness in ventilated patients with normal cardiac function. The aim of this study was to investigate the ability of monitoring stroke volume variation to predict volume responsiveness and to assess changes in preload in patients with reduced left ventricular function after cardiac surgery.
Design: Prospective study.
Setting: University hospital.
Patients: Fifteen mechanically ventilated patients with a left ventricular ejection fraction <0.35 (study group) and 15 patients with an ejection fraction >0.50 (control group) after coronary artery bypass grafting following admission to the intensive care unit.
Interventions: Volume loading with 10 mL of hetastarch 6% times body mass index. If stroke volume index increased >5%, successive volume loading was performed until no further increase in stroke volume index was reached.
Measurements and main results: Stroke volume variation, central venous pressure, pulmonary artery occlusion pressure (PAOP), and left ventricular end-diastolic area index (LVEDAI) were measured at baseline and immediately after each volume loading step. In both groups, stroke volume variation at baseline correlated significantly with changes in stroke volume index caused by volume loading (p <.01). Further, changes in stroke volume variation as a result of volume loading correlated significantly with the concomitant changes in stroke volume index in both groups (p <.01). Using receiver operating characteristic analysis, in the study group areas under the curve for stroke volume variation, PAOP, central venous pressure, and LVEDAI did not differ significantly. In the control group, the area under the curve for stroke volume variation was statistically larger than for PAOP, central venous pressure, and LVEDAI.
Conclusions: Continuous and real-time monitoring of stroke volume variation by pulse contour analysis can predict volume responsiveness and allows real-time assessment of the hemodynamic effect of volume expansion in patients with reduced left ventricular function after cardiac surgery.