Noninvasive Ventilation After Coronary Artery Bypass Grafting in Subjects With Left-Ventricular Dysfunction

BACKGROUND: The use of noninvasive ventilation in patients with left-ventricular dysfunction may increase cardiac performance by decreasing inspiratory effort and left-ventricular afterload. The aim of the present study was to evaluate the acute effects of noninvasive ventilation on central-venous oxygen saturation (S_cv̄O2) and blood lactate in subjects with left-ventricular dysfunction during the early postoperative phase of coronary artery bypass grafting.

METHODS: This study included 100 subjects during the postoperative phase of elective coronary artery bypass grafting. Blood samples, at 5 time points, were collected to assess tissue perfusion markers (ie, S_cv̄O2 and blood lactate) as follows: (1) the intraoperative period (after anesthesia induction); (2) 20 min after ICU arrival, under intermittent mandatory ventilation; (3) 20 min after extubation with spontaneous breathing; (4) after 1 h of noninvasive ventilation; and (5) 20 min after discontinuation of noninvasive ventilation.

RESULTS: A significant increase in the blood lactate and a drop in the S_cv̄O2 were observed on arrival to the ICU compared with intraoperative values (P < .001). After extubation, during spontaneous breathing, the S_cv̄O2 significantly decreased (P = .02), whereas the blood lactate increased, although not significantly (P = .21) compared with intermittent mandatory ventilation on arrival to the ICU. During the application of noninvasive ventilation, the S_cv̄O2 significantly increased (P = .048) and the blood lactate significantly decreased (P = .008) compared with spontaneous breathing values after extubation. After noninvasive ventilation discontinuation, the S_cv̄O2 and blood lactate did not change compared with measures taken during noninvasive ventilation; higher values of S_cv̄O2 were maintained compared with those obtained after extubation (P < .001).

CONCLUSIONS: The acute application of noninvasive ventilation improved S_cv̄O2 and decreased the blood lactate in subjects with left-ventricular dysfunction during the early postoperative phase after coronary artery bypass grafting.