• Lígia de A Maia, Cynthia S Samary, Milena V Oliveira, Cintia L Santos, Robert Huhle, Vera L Capelozzi, Marcelo M Morales, Marcus J Schultz, Marcelo G Abreu, Paolo Pelosi, Pedro L Silva, and Patricia Rieken Macedo Rocco.
• From the *Laboratory of Pulmonary Investigation, Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Centro de Ciências da Saúde, Rio de Janeiro, Brazil; †Department of Anesthesiology and Intensive Care Therapy, Pulmonary Engineering Group, University Hospital Dresden, Technische Universität Dresden, Dresden, Germany; ‡Department of Pathology, Faculty of Medicine, University of São Paulo, São Paulo, Brazil; §Laboratory of Cellular and Molecular Physiology, Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Centro de Ciências da Saúde, Rio de Janeiro, Brazil; ‖Department of Intensive Care Medicine and the Laboratory for Experimental Intensive Care and Anesthesiology (L.E.I.C.A), Academic Medical Centre at the University of Amsterdam, Amsterdam, the Netherlands; and ¶Department of Surgical Sciences and Integrated Diagnostics, IRCCS AOU San Martino-IST, University of Genoa, Genoa, Italy.
• Anesth. Analg. 2017 Oct 1; 125 (4): 1364-1374.

BackgroundIntraoperative mechanical ventilation may yield lung injury. To date, there is no consensus regarding the best ventilator strategy for abdominal surgery. We aimed to investigate the impact of the mechanical ventilation strategies used in 2 recent trials (Intraoperative Protective Ventilation [IMPROVE] trial and Protective Ventilation using High versus Low PEEP [PROVHILO] trial) on driving pressure (ΔPRS), mechanical power, and lung damage in a model of open abdominal surgery.MethodsThirty-five Wistar rats were used, of which 28 were anesthetized, and a laparotomy was performed with standardized bowel manipulation. Postoperatively, animals (n = 7/group) were randomly assigned to 4 hours of ventilation with: (1) tidal volume (VT) = 7 mL/kg and positive end-expiratory pressure (PEEP) = 1 cm H2O without recruitment maneuvers (RMs) (low VT/low PEEP/RM-), mimicking the low-VT/low-PEEP strategy of PROVHILO; (2) VT = 7 mL/kg and PEEP = 3 cm H2O with RMs before laparotomy and hourly thereafter (low VT/moderate PEEP/4 RM+), mimicking the protective ventilation strategy of IMPROVE; (3) VT = 7 mL/kg and PEEP = 6 cm H2O with RMs only before laparotomy (low VT/high PEEP/1 RM+), mimicking the strategy used after intubation and before extubation in PROVHILO; or (4) VT = 14 mL/kg and PEEP = 1 cm H2O without RMs (high VT/low PEEP/RM-), mimicking conventional ventilation used in IMPROVE. Seven rats were not tracheotomized, operated, or mechanically ventilated, and constituted the healthy nonoperated and nonventilated controls.ResultsLow VT/moderate PEEP/4 RM+ and low VT/high PEEP/1 RM+, compared to low VT/low PEEP/RM- and high VT/low PEEP/RM-, resulted in lower ΔPRS (7.1 ± 0.8 and 10.2 ± 2.1 cm H2O vs 13.9 ± 0.9 and 16.9 ± 0.8 cm H2O, respectively; P< .001) and less mechanical power (63 ± 7 and 79 ± 20 J/min vs 110 ± 10 and 120 ± 20 J/min, respectively; P = .007). Low VT/high PEEP/1 RM+ was associated with less alveolar collapse than low VT/low PEEP/RM- (P = .03). E-cadherin expression was higher in low VT/moderate PEEP/4 RM+ than in low VT/low PEEP/RM- (P = .013) or high VT/low PEEP/RM- (P = .014). The extent of alveolar collapse, E-cadherin expression, and tumor necrosis factor-alpha correlated with ΔPRS (r = 0.54 [P = .02], r = -0.48 [P = .05], and r = 0.59 [P = .09], respectively) and mechanical power (r = 0.57 [P = .02], r = -0.54 [P = .02], and r = 0.48 [P = .04], respectively).ConclusionsIn this model of open abdominal surgery based on the mechanical ventilation strategies used in IMPROVE and PROVHILO trials, lower mechanical power and its surrogate ΔPRS were associated with reduced lung damage.

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