What is the difference between a single-inlet and a double-inlet ventricle? Why would it matter? What are the morphologic components of any ventricle? Is it important to your anesthetic management to understand the outlet component? Is there a difference whether or not the outlet component is concordant or discordant with the ventricular morphology? Why?

What is a bidirectional Glenn shunt? How does it differ from a Fontan procedure? In what way are the differences relevant for anesthesia? Are there any specific differences with regard to anesthesia for venous to pulmonary artery shunts compared to systemic arterial to pulmonary artery shunts such as the modified Blalock-Taussig shunt (mBTS) or Waterston shunt? When would it matter?

Of what significance are the exercise history and the hematocrit? What if he was simply short of breath with exertion but had a hematocrit of 45 %? What if the hematocrit was 57 % and he was short of breath at rest? Does this patient need to come into the hospital the night before surgery for intravenous hydration? Why/why not? What would your choice of fluid be? Full maintenance rate, one-half maintenance? Why?

Should this patient receive a premedication prior to coming to the operating room? What if he was extremely apprehensive? What would be the potential advantage? If the patient became profoundly sedated and difficult to arouse to anything except vigorous shaking, would that be a problem? Why?

A double-inlet ventricle is one in which both AV valves drain into one ventricle resulting in complete mixing of systemic and pulmonary venous blood. Subsequent delivery of this mixed blood to the systemic and pulmonary circulations then occurs in parallel (not series) from one ventricle. These two features are the basis of single ventricle physiology. The morphological components of a ventricle are the inlet, the body, and the outlet. The right “ventricle” is composed of only an outlet portion and communicates with the left ventricle via a bulboventricular foramen (BVF). Transposition of the great vessels (TGV) refers specifically to the anatomic circumstance wherein there is concordance of the atrioventricular connections associated with discordance of the ventriculoarterial connections. Corrected transposition (C-TGV) refers specifically to the anatomic circumstance wherein there is discordance of the atrioventricular connections associated with discordance of the ventriculoarterial connections. In the case of single ventricle physiology, concordance or discordance of the ventriculoarterial connections becomes academic as systemic and arterial flow is derived from one ventricle. The relevant issue is whether the outflow to either circulation from the single ventricle is obstructed. In the case described here, there is potential for subpulmonary obstruction at the level of the BVF and pulmonary outflow tract.

A classic Glenn shunt is an end-to-end anastomosis of the superior vena cava (SVC) to the right pulmonary artery (RPA) in which the RPA is separated from the main PA. Thus all pulmonary blood flow is derived from the SVC to RPA anastomosis. A bidirectional Glenn (superior cavopulmonary anastomosis) is currently the procedure of choice. It involves an end-to-side anastomosis of the SVC to the right pulmonary artery in which the RPA is in continuity with the main PA and LPA. Thus all pulmonary blood flow is derived from the SVC to RPA and LPA anastomosis. All IVC blood is delivered to a common atrium (mixing with pulmonary venous blood) following a Glenn shunt. These shunts are dependent on systemic venous pressure (SVC pressure) to provide pulmonary blood flow and not on systemic arterial pressure as is the case with systemic to pulmonary artery shunts such as the mBTS (usually graft between innominate artery and RPA) or Waterston shunt (ascending aorta to RPA anastomosis).

The hematocrit is consistent with adequate pulmonary blood flow and systemic oxygen delivery as there is no compensatory erythrocytosis. The good exercise tolerance is consistent with preserved ventricular function and chronotropic reserve such that cardiac output and systemic oxygen delivery can be increased. In patients with a palliated congenital heart lesion, loss of chronotropic reserve may be a component of impaired exercise tolerance. A hematocrit of 57 % and shortness of breath would warrant further evaluation, specifically an echocardiogram to evaluate ventricular function, AV valve regurgitation, and patency of the Glenn pathway. Cardiac catheterization would be necessary to rule out decompressing venous collaterals from the Glenn pathway to the IVC or directly to the pulmonary venous system. These collaterals would diminish pulmonary blood flow and increase right to left shunting (systemic venous blood to the common atrium). In addition, cardiac catheterization would delineate the extent of pulmonary arteriovenous malformations (AVMs); these are a source of intrapulmonary right to left shunting (systemic venous blood delivered directly to the pulmonary veins). These AVMs develop in patients with Glenn shunts due to a lack of hepatic venous blood being delivered to the lungs.