In acute respiratory distress syndrome (ARDS), ventilation with a low tidal volume (VT) reduces mortality compared to a conventional VT.[1,2] Recent studies have shown that ventilation with a conventional tidal volume is also associated with sustained cytokine production in the lungs in patients without lung injury at the onset of mechanical ventilation.[3–6] Furthermore, incidences of lung injury have been reported after major surgery in those without any pre-existing lung diseases. In those studies,[3–6] the protective ventilation strategy consists of low VT ventilation, relatively high positive end-expiratory pressure (PEEP), and lung recruitment maneuver. During hepatectomy, however, surgeons require low PEEP to reduce bleeding from cut surface of the liver. Our question was: when high PEEP, one part of lung protective approaches, is unavailable, does the low tidal volume ventilation strategy have utility? To answer the question, we proposed a study that aimed to evaluate the effect of low tidal volume ventilation during surgery under the condition with a restricted PEEP level (3 cmH2O).
We conducted a prospective, randomized controlled study on patients undergoing hepatic surgery under two different VT ventilation conditions assigned randomly to determine whether low VT ventilation reduces lung injury and improves lung physiology during hepatic surgeries. The primary outcome of the present study was the change in pro-inflammatory cytokine concentrations in the lungs. Secondary outcomes were oxygenation during and immediately after the surgery and the duration of hospital stay after the surgery. We hypothesized that (a) proinflammatory mediators increase in the circulation after hepatic surgery with the Pringle maneuver that causes a temporal hepatic blood flow interruption; (b) airway inflammation is induced when a conventional VT is used during surgery; and (c) compared to conventional VT ventilation, low VT ventilation during hepatectomy reduces airway inflammation and prevents lung injury under a condition of a limited PEEP.
BMC Anesthesiol. 2016;16(47) © 2016 BioMed Central, Ltd.