Hemodynamic effects of passive leg raising: an echocardiographic study in patients with shock

To determine the effects of passive leg raising (PLR) on hemodynamics and on cardiac function according to the preload dependency defined by the superior vena cava collapsibility index (ΔSVC).

Forty patients with shock, sedated and mechanically ventilated, were included. Transesophageal echocardiography was performed. At baseline (T1), two groups were defined according to ΔSVC. Eighteen patients presenting a ΔSVC > 36%, an indicator of preload dependency, formed group 1, whereas 22 patients (group 2) exhibited a ΔSVC < 30% (not preload-dependent). Measurements were then performed during PLR (T2), back to baseline (T3), and after volume expansion (T4) in group 1 only. At T1, ΔSVC was significantly higher in group 1 than in group 2, 50 ± 9% and 7 ± 6%, respectively. In group 1, we found a decrease in ΔSVC at T2 (24 ± 9%) and T4 (17 ± 7%), associated with increased systolic, diastolic and arterial pulse pressures. Cardiac index also increased, from 1.92 ± 0.74 (T1) to 2.35 ± 0.92 (T2) and 2.85 ± 1.2 l/min/m² (T4) and left ventricular end-diastolic volume from 51 ± 41 to 61 ± 51 and 73 ± 51 ml/m². None of these variations was found in group 2. No change in heart rate was observed.

Hemodynamic changes related to PLR were only induced by increased cardiac preload.