Prone Positioning in Cardiac Surgery: For Many, But Not for Everyone

Prone positioning is a therapeutic maneuver to improve arterial oxygenation in patients with acute lung injury that is not implemented in most centers performing adult cardiac surgery. The aim of this study was to review our experience with prone positioning to assess the effects of this maneuver in patients with postoperative acute respiratory failure. From 2010-2014, 127 adult patients with postoperative acute respiratory failure were treated with prone positioning in addition to specific therapy. Univariate and multivariate logistic regression analyses were performed to identify independent risk factors associated with in-hospital mortality. In-hospital mortality was 22.8% (n = 29). No significant differences were observed in preoperative risk factors between patients who survived (S) and those who died (D), except for age (62.7 ± 11.2 vs 70.2 ± 11.3; P = 0.007-at multivariate analysis P = 0.03, odds ratio [OR] = 1.1/year). Preproning values of PaO₂/FiO₂ were significantly different between groups (D vs S: 115 ± 46 vs 150 ± 56; P = 0.006), but only preproning FiO₂ remained highly significant at multivariate analysis (D vs S: 0.82 ± 0.18 vs 0.67 ± 0.16; P = 0.001, OR = 1.07; with FiO₂ > 0.75 vs < 75, OR = 19.6). D showed a higher improvement of PaO₂/FiO₂ immediately after prone positioning (207 ± 100 vs 219 ± 90, P = 0.56; within-group analysis between preproning and 1 hour after proning: S-P = 0.49, D-P = 0.019; at 12 hours: 286 ± 123 vs 240 ± 120, P = 0.06; within-group analysis between 1 hour and 12 hours after proning: S-P = 0.15; D-P = 0.17; between groups-P = 0.05). D had higher peak WBC count (26 ± 9.8 vs 17.7 ± 5.9×10³/mL; P = 0.0001) and a higher rate of low output syndrome (15 vs 9 patients-51.7% vs 9.2%; P = 0.0001). At multivariate analysis, white blood cell count: P = 0.005, OR = 1.11/10³ white blood cell; low output syndrome: P = 0.0002, OR = 20.5. In conclusion, our results show that prone positioning, if performed early, is a safe and effective adjunct measure for patients with postoperative acute hypoxemic respiratory failure of noncardiogenic origin.