Hypoxia During Thoracic Surgery: Practical Advice for the Anesthesiologist

Abstract

Double-lumen tubes or bronchial blockers are used to provide one-lung ventilation (OLV) in patients undergoing lung, esophageal, thoracic vascular, minimally invasive cardiac, and occasionally mediastinal surgery. During OLV, an intrapulmonary shunt may result in hypoxemia related in part to collapse of the nondependent lung and increased atelectatic areas in the dependent lung. Hypoxemia by definition is a decrease in oxygen saturation (SpO2) to less than 90% 4 or an arterial oxygen tension (PaO2) of less than 60 mmHg when the patient is being ventilated at an inspired oxygen fraction (FiO2) of 1.0. 5 The incidence of hypoxemia during OLV has been reported to be 1 to 10%. This relative infrequency is related in part to advances with routine use of a fiberoptic bronchoscope for optimal placement of lung isolation devices. It is also attributable to the introduction of newer volatile anesthetics that cause less inhibition of hypoxic pulmonary vasoconstriction (HPV) in a dose-dependent manner and less venous admixture during OLV. This review focuses on the predictors of hypoxia during OLV, the pathophysiology of HPV, protective ventilation maneuvers to restore or improve arterial oxygenation, the effects of anesthetics on hypoxia and inflammation, and cerebral desaturation episodes and hypoxia during OLV.