Right ventricular function during weaning from mechanical ventilation after coronary artery bypass grafting: effect of volume loading

Objective: The study was designed to investigate the right ventricular (RV) reaction to weaning from mechanical ventilation (MV) in patients with and without volume loading after coronary artery bypass grafting (CABG). Design: Controlled study. Setting: Surgical intensive care unit in a university hospital. Patients: 18 patients were randomized in two groups, Control group (n = 9) and Volume group (n = 9), when the established criteria for weaning from the respirator were satisfied. Intervention: During MV, patients in the Volume group received in rapid (10-min) 6 ml/kg infusion of a 6% hydroxyethyl starch preparation. Measurements and results: Hemodynamic parameters were measured using a combined right ventricular (RV) ejection fraction-oximetry pulmonary artery catheter at T0 (during MV: baseline), T1 (during MV: 10 min after volume loading or at the same time in the Control group), T2 [after 20 min of spontaneous ventilation (SV)]. In the Control group, RV volumes did not differ throughout the study, while cardiac index (CI) and RV stroke work index (RVSWI) increased from T1 to T2. In the Volume group, RV volumes increased from T0 to T1, further increasing from T1 to T2, whereas CI increased only from T0 to T1. In this group, RVSWI increased from T0 to T1 in 8/9 patients and from T1 to T2 in 6/9 patients. Conclusions: An increase in RV volumes with a concomitant increase in RVSWI was observed in high preload patients when going from MV to SV, suggesting a preserved RV function during weaning from MV in this group compared with control patients. The depression in RV contractility observed in some patients suggested that rapid volume expansion before weaning from MV in CABG patients must be done carefully.