Perioperative Open-lung Approach, Regional Ventilation, and Lung Injury in Cardiac Surgery

Abstract

Background In the Protective Ventilation in Cardiac Surgery (PROVECS) randomized, controlled trial, an open-lung ventilation strategy did not improve postoperative respiratory outcomes after on-pump cardiac surgery. In this prespecified subanalysis, the authors aimed to assess the regional distribution of ventilation and plasma biomarkers of lung epithelial and endothelial injury produced by that strategy. Methods Perioperative open-lung ventilation consisted of recruitment maneuvers, positive end-expiratory pressure (PEEP) = 8 cm H2O, and low-tidal volume ventilation including during cardiopulmonary bypass. Control ventilation strategy was a low-PEEP (2 cm H2O) low-tidal volume approach. Electrical impedance tomography was used serially throughout the perioperative period (n = 56) to compute the dorsal fraction of ventilation (defined as the ratio of dorsal tidal impedance variation to global tidal impedance variation). Lung injury was assessed serially using biomarkers of epithelial (soluble form of the receptor for advanced glycation end-products, sRAGE) and endothelial (angiopoietin-2) lung injury (n = 30). Results Eighty-six patients (age = 64 ± 12 yr; EuroSCORE II = 1.65 ± 1.57%) undergoing elective on-pump cardiac surgery were studied. Induction of general anesthesia was associated with ventral redistribution of tidal volumes and higher dorsal fraction of ventilation in the open-lung than the control strategy (0.38 ± 0.07 vs. 0.30 ± 0.10; P = 0.004). No effect of the open-lung strategy on the dorsal fraction of ventilation was noted at the end of surgery after median sternotomy closure (open-lung = 0.37 ± 0.09 vs. control = 0.34 ± 0.11; P = 0.743) or in extubated patients at postoperative day 2 (open-lung = 0.63 ± 0.18 vs. control = 0.59 ± 0.11; P > 0.999). Open-lung ventilation was associated with increased intraoperative plasma sRAGE (7,677 ± 3,097 pg/ml vs. 6,125 ± 1,400 pg/ml; P = 0.037) and had no effect on angiopoietin-2 (P > 0.999). Conclusions In cardiac surgery patients, open-lung ventilation provided larger dorsal lung ventilation early during surgery without a maintained benefit as compared with controls at the end of surgery and postoperative day 2 and was associated with higher intraoperative plasma concentration of sRAGE suggesting lung overdistension. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Acute Respiratory Distress Syndrome in the Perioperative Period of Cardiac Surgery: Predictors, Diagnosis, Prognosis, Management Options, and Future Directions

“… 28 Moreover, in a prespecified subanalysis, the authors showed that although open lung ventilation improved dorsal ventilation in the short term, this benefit was not sustained and was associated with greater plasma biomarkers of epithelial lung injury, suggesting lung overdistention. 29 It is plausible that an open-lung strategy may cause lung distention under the intraoperative “open-chest” conditions and that alveolar recruitment already was maximized in the control group.…”

Management of Intraoperative Mechanical Ventilation to Prevent Postoperative Complications after General Anesthesia: A Narrative Review

“…Notably, studies focused on RMs during GA do not take into account the recruitability of the lung, which may significantly differ in accordance with patient’s baseline comorbidities and surgical position [ 54 ]. In addition, RMs are usually well tolerated hemodynamically but seem to be not free from the risk of overdistention, as described also in critically ill patients [ 37 ]; a recent RCT, indeed, found higher levels of receptor for advanced glycation end-products, a marker of lung epithelial injury [ 55 ], in patients receiving intraoperative RMs [ 56 ]. Further studies are needed to elucidate which patients should receive intraoperative RM and how.…”

“…Even so, sub-group analysis performed in patients with high baseline ∆P suggest some physiological benefit in RM group. Given that intraoperative RM are not free from risk of alveolar injury [ 56 ], one could argue that RM should be limited to patients with higher ∆P. Even so, recommendations based on strong clinical outcomes are still lacking.…”

Open-lung Ventilation Strategy during General Anesthesia

“…In this issue of Anesthesiology, Lagier et al 7 report on the effects of the open-lung ventilation strategy on the distribution of ventilation and lung injury in a subpopulation of the PROVECS study. In total, 86 patients were investigated, whereby 56 patients were included in the analysis of distribution of ventilation by electrical impedance tomography, and 30 patients were investigated for biomarkers of lung injury.…”

“…Lagier et al 7 provide a number of possible explanations for the lack of consistent beneficial effects, and even potentially harmful effects, of the open-lung strategy in this surgical population: (1) most patients included in this subanalysis had no specific respiratory risk; (2) a semirecumbent position was used, which might have reduced lung collapse; (3) de-airing maneuvers before cardiopulmonary bypass, which were part of the surgical protocol, may have recruited lungs of controls, and cardiopulmonary bypass possibly increased the risk of lung collapse; (4) increased respiratory system compliance after sternotomy may have increased transpulmonary pressures; and (5) lack of individualization of PEEP and level of airway pressure during recruitment maneuvers could jeopardize the benefits of the open-lung ventilation strategy. Although they sound plausible, they can also be challenged.…”