Critical Care Medicine

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Critical Care Medicine:
Case Reports

Pharmacologic exposure of an occult atrial septal defect

Mackenzie, Iain M. DM, MRCP, FRCA; Banning, Adrian MD, MRCP; Dyar, Oliver MRCPI, FRCA

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Objective: To describe the diagnostic technique used to identify the presence of a symptomatic interatrial shunt obscured by normal intracardiac pressures and to discuss the unusual findings in this case and their relevance to the investigation of patients with unexplained hypoxemia.

Design: Case report.

Setting: Intensive care unit of a university teaching hospital.

Patient: A patient with a variant of the platypnea-orthodeoxia syndrome.

Interventions: Intravenous administration of metaraminol.

Measurements and Main Results : Clinical examination and routine investigations ruled out pneumonia or myocardial infarction as a cause of respiratory failure, and pulmonary angiography was normal other than for the demonstration of an interatrial communication. Repeated transthoracic echocardiograms failed to indicate the presence of a significant interatrial shunt that was eventually detected following temporary shunt reversal with intravenous metaraminol and confirmation by bubble-contrast transesophageal echocardiography and right heart catheter studies.

Conclusions: Symptomatic right-to-left intracardiac shunt may occur in patients with normal intracardiac and pulmonary artery pressures. The presence of a significant shunt cannot be ruled out by transthoracic echocardiography without the use of bubble contrast.

© 2001 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins

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