Pro: low tidal volume is indicated during one-lung ventilation.

Pro: Low Tidal Volume Is Indicated During One-Lung Ventilation Peter Slinger, MD, FRCPC Since the introduction of one-lung ventilation (OLV) as a standard practice during thoracic surgery in the first half of the last century, anesthesiologists have had to deal with the problem of maintaining adequate intraoperative arterial oxygenation while ventilating only one of the patient’s lungs. Evolution in this management has been one of the great success stories in the practice of anesthesiology, as the incidence of hypoxemia during OLV has declined from 20%–25% in the 1970s (1) to 1% today (2). This can be attributed to several advances, including the use of fiberoptic bronchoscopy for double-lumen endobronchial tubes and bronchial blocker positioning and the use of newer volatile anesthetics that cause less inhibition of hypoxic pulmonary vasoconstriction and less shunt during OLV than older volatile anesthetics (3). Oxygenation with 1 MAC of the newer volatile anesthetics is equivalent to that seen during total IV anesthesia (4). Further success with management of OLV can be attributed to ventilation strategies that minimize atelectasis. One prevalent approach is ventilation with large tidal volumes. Common teaching in fact has been to use similar tidal volumes (10–12 mL/kg) for both two-lung ventilation and OLV (5). The incidence of hypoxemia during routine OLV has become so infrequent that the question arises whether these large tidal volumes may injure the lung. Acute lung injury (ALI) after pulmonary resection has been described since the use of OLV for thoracic surgery became routine. The most publicized report is a compilation of 10 cases after pneumonectomy published in 1984 (6), which focused on the role of IV overhydration as a cause of post-pneumonectomy pulmonary edema. Subsequently, there have been several reviews of this topic identifying a variety of other potentially causative factors for ALI, such as the administration of freshfrozen plasma, mediastinal lymphatic damage, inflammation, and oxygen toxicity (7). The most thorough study to date (8) is a retrospective survey of 806 pneumonectomies that found 21 cases (2.5%) of postpneumonectomy pulmonary edema, which represents one of the lowest incidences reported of this complication. There were no differences in perioperative fluid balance between post-pneumonectomy ALI (positive fluid balance at 24 h: 10 mL/kg) versus matched pneumonectomy controls (positive fluid balance at 24 h: 13 mL/kg). These authors used rigorous fluid restriction compared with other reports (9) (e.g., 24-h positive balance: 21 9 mL/kg), suggesting that limiting intraoperative fluids might decrease but not eliminate ALI. Further reports demonstrate improved survival from post-pneumonectomy pulmonary edema, likely as a result of improved postoperative management of established cases (10). Post-pneumonectomy ALI (11) has been found to have a bimodal distribution of onset. Late cases (10/37, 27%) presented 3–10 days postoperatively and were secondary to obvious causes such as bronchopneumonia and aspiration. “Primary” ALI (27/37, 73% of cases) presented on From the Department of Anesthesia, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada. Accepted for publication April 4, 2006. No reprints will be available form the author. Address correspondence to Peter Slinger MD, Department of Anesthesia, 3EN, Toronto General Hospital, 200 Elizabeth St., Toronto, ON, Canada M5G 2C4. Address e-mail to peter.slinger@uhn.on. ca. Copyright © 2006 International Anesthesia Research Society DOI: 10.1213/01.ane. 0000223701.24874. c8