Acquired right-to-left intracardiac shunts and severe hypoxemia.

Critically ill hypoxemic patients without significant radiological changes on the chest x-ray present a diagnostic and therapeutic problem. Three patients with patent foramen ovale and a patient with a spontaneously closed congenital ventricular septal defect which reopened due to ischemic changes in the ventricular septum are presented. In reviewing the literature, we could not find this type of presentation. Their hypoxemia was associated with right-to-left intracardiac shunts demonstrated by dye dilution cardiac output curves. Because of the risk of systemic embolism associated with a right-to-left intracardiac shunt, air bubbles and particulate material in the intravenous infusion should be avoided. Use of anticoagulants may be beneficial. High inspired oxygen concentration may not correct the associated hypoxemia. The detection of these shunts is easily done at the bedside.