Adults with an untreated intracardiac shunt present a unique challenge to the critical care nurse. The disease process necessitates an understanding of cardiac anatomy and physiology in order to determine the etiology of the cardiac defect and resulting shunt. An understanding of fluid and pressure dynamics is also of importance since anatomic shunting alters usual adult hemodynamics. Arterial and mixed venous oximetry monitoring is most helpful in determining the response to therapies. One must rethink some of the hemodynamic goals that are traditionally used in caring for adults with primary left ventricular dysfunction. Therapeutic response is usually limited to a narrow hemodynamic range. Many of these patients have superimposed health problems such as atherosclerosis, hypertension, and cigarette smoking. Therefore, the critical care nurse is confronted with caring for a patient with unique problems that test creativity and assessment skills.