To the Editor:
We read with a great interest the article by Canet et al. 1regarding pulmonary complications after surgery. The authors have evaluated the incidence of this frequent adverse event and its risk factors in more than 2,000 patients. They found that postoperative pulmonary complications occur in 5% of patients and identify several patient-related (e.g. , age, low preoperative SpO2, acute respiratory infection during the month before surgery, preoperative anemia) and surgical-related risk factors (e.g ., upper abdominal or intrathoracic surgery, emergency surgery, procedure duration). It is noteworthy that anesthesia was not identified as a risk factor for postoperative pulmonary complications. Instead, the authors1considered only two categories for this variable (i.e. , general vs . regional anesthesia).
Some patients may receive a combination of general and regional anesthesia that aims to decrease postoperative pain and postoperative diaphragmatic dysfunction, thereby reducing risk of pulmonary complications. A large randomized controlled trial has observed that combined epidural and general anesthesia after major surgery decreases postoperative pulmonary complications.2Meta-analysis has also demonstrated that epidural analgesia that lasts more than 24 h decreases the risk of pneumonia.3General anesthesia combined with epidural analgesia is not equivalent to general anesthesia alone.
General anesthesia is also characterized by the need for ventilatory support. However, the ventilatory “setting” may be different from to one patient to another, as shown in large epidemiologic studies performed in the intensive care unit.4However, similar multicenter studies are lacking for surgical patients receiving general anesthesia in the operating room.4Ventilator-induced lung injury was first described in patients with acute lung injury and acute distress respiratory syndrome.5Experimentally, ventilator-induced lung injury has been demonstrated in animals without previous lung injury.5In the context of ventilation for anesthesia, several authors6,7have observed that use of large tidal (more than 10 ml/kg) or high pressure during general anesthesia may influence pulmonary complications. Thus, ventilatory setting as well as other strategies used in operative anesthesia (e.g ., fluid administration, analgesia management) usually comprise the “black box” in cohort studies that evaluate risk factors for postoperative pulmonary complications. It is necessary to consider that anesthesia management (i.e ., ventilator settings, fluid administration, drugs, techniques used) may have a positive—but also negative—impact on the risk of postoperative pulmonary complications. More data on the practice of anesthesiologists are required.
*Tenon Teaching Hospital, Assistance Publique Hôpitaux de Paris, Université Pierre et Marie Curie-Paris, Paris, France. emmanuel.marret@tnn.aphp.fr
