Oxygen and anesthesia: what lung do we deliver to the post-operative ward?
Article first published online: 4 APR 2012
© 2012 The Author. Acta Anaesthesiologica Scandinavica © 2012 The Acta Anaesthesiologica Scandinavica Foundation
Acta Anaesthesiologica Scandinavica
Volume 56, Issue 6, pages 675–685, July 2012
How to Cite
HEDENSTIERNA, G. (2012), Oxygen and anesthesia: what lung do we deliver to the post-operative ward?. Acta Anaesthesiologica Scandinavica, 56: 675–685. doi: 10.1111/j.1399-6576.2012.02689.x
- Issue published online: 11 JUN 2012
- Article first published online: 4 APR 2012
- Manuscript Accepted: 21 FEB 2012
- Swedish Research Council 5315
- Swedish Heart-Lung Fund
Anesthesia is safe in most patients. However, anesthetics reduce functional residual capacity (FRC) and promote airway closure. Oxygen is breathed during the induction of anesthesia, and increased concentration of oxygen (O2) is given during the surgery to reduce the risk of hypoxemia. However, oxygen is rapidly adsorbed behind closed airways, causing lung collapse (atelectasis) and shunt. Atelectasis may be a locus for infection and may cause pneumonia. Measures to prevent atelectasis and possibly reduce post-operative pulmonary complications are based on moderate use of oxygen and preservation or restoration of FRC. Pre-oxygenation with 100% O2 causes atelectasis and should be followed by a recruitment maneuver (inflation to an airway pressure of 40 cm H2O for 10 s and to higher airway pressures in patients with reduced abdominal compliance (obese and patients with abdominal disorders). Pre-oxygenation with 80% O2 may be sufficient in most patients with no anticipated difficulty in managing the airway, but time to hypoxemia during apnea decreases from mean 7 to 5 min. An alternative, possibly challenging, procedure is induction of anesthesia with continuous positive airway pressure/positive end-expiratory pressure to prevent fall in FRC enabling use of 100% O2. A continuous PEEP of 7–10 cm H2O may not necessarily improve oxygenation but should keep the lung open until the end of anesthesia. Inspired oxygen concentration of 30–40%, or even less, should suffice if the lung is kept open. The goal of the anesthetic regime should be to deliver a patient with no atelectasis to the post-operative ward and to keep the lung open.