Radiographic Demonstration of Hypoxic Pulmonary Vasoconstriction during One-lung Ventilation.

Abstract

Hypoxic pulmonary vasoconstriction occurs when the microvasculature perfusing hypoxic alveoli vasoconstricts, diverting blood to oxygenated alveoli to match ventilation with perfusion.1 Hypoxic pulmonary vasoconstriction can occur within seconds and reach a maximum intensity within minutes of hypoxia developing. It appears to be triggered by a mitochondrial redox signal secondary to changes in molecular oxygen that activates voltage-gated potassium and calcium channels which results in vasoconstriction.2 One-lung ventilation can acutely cause global alveolar hypoxia and hypoxic pulmonary vasoconstriction in the nonventilated lung. It is estimated that blood flow to a nonventilated lung can be reduced by as much as 50% if the lung is without atelectasis.3The pulmonary angiograms were performed in a patient with a history of hemoptysis in whom a computed tomography angiogram demonstrated a pulmonary pseudoaneurysm with a presumed bronchial fistula in the right lung. The patient was scheduled for embolization with interventional radiology under general anesthesia. Because of concern for potential bleeding, lung isolation with a left-sided double lumen tube was positioned with the right lung open to ambient pressure. Isoflurane 1.1% was used for maintenance anesthesia. After approximately 15 min of one-lung ventilation, a pulmonary angiogram was performed that dramatically revealed selective peripheral microvascular perfusion to the left lung, but almost no microvascular perfusion to the right lung (fig. 1A and Supplemental Digital Content 1, http://links.lww.com/ALN/C912). This limited visualization of the right pseudoaneurysm. Repeat angiogram after 5 min of two-lung ventilation restored symmetric microvascular perfusion (fig. 1B and Supplemental Digital Content 2, http://links.lww.com/ALN/C913). The patient subsequently underwent selective catheterization and coil embolization of the pulmonary artery pseudoaneurysm.The authors declare no competing interests.Pulmonary Angiogram during One-Lung Ventilation, http://links.lww.com/ALN/C912Pulmonary Angiogram during Two-Lung Ventilation, http://links.lww.com/ALN/C913