What is the tetralogy of Fallot? Is it really four lesions? What is the principal anatomic lesion?

What are the reasons that this child would have received a palliative shunt for his first surgical procedure rather than a definitive repair? Are there any long-term consequences of a Blalock-Taussig shunt (BTS) of importance to you as an anesthesiologist?

The patient is extremely apprehensive and very scared of needles. How will you gain his confidence so that you can perform a physical exam? How will you assess him for volume status and dehydration? Would you expect his hematocrit to be any different today than it was 2 months ago? What do you expect his oxygen saturation to be? Any additional lab studies you would like to see? Any additional diagnostic cardiac information you would like to have? What would you expect to find on echocardiogram?

He has a “tet spell” in the examining room…how do you manage it? What is a “tet spell,” physiologically and anatomically? Why do you choose the maneuvers you choose? Would it be any different in the preoperative holding area? How about in the operating room during induction?

A palliative shunt is typically done in institutions not versed in infant cardiac surgery utilizing cardiopulmonary bypass (CPB) or in resource-limited environments. The long-term adverse consequences of such a shunt would be (1) poor growth of the native pulmonary arteries due to preferential blood flow to one lung, stenosis at the anastomosis site, or chronic low pulmonary blood flow. In the worst case scenario, the branch pulmonary arteries might become discontinuous. (2) Progression of RVH as placement of a shunt does not address RVOT obstruction and thereby does not remove the stimulus for continued hypertrophy.Following a classic BTS, the right arm will not be a reliable source of either noninvasive or invasive BP monitoring as perfusion to the arm is provided via collateral vessels around the shoulder and scapula. Following a modified BTS (graft from innominate artery to right pulmonary artery), accurate blood pressures might be obtainable, but this will have to be determined by comparison with noninvasive pressures from the contralateral arm.

Volume status would be assessed in this child as in any child of similar age. The erythrocytosis associated with cyanosis is progressive; however, hematocrits above 70 % are rare. A baseline oxygen saturation of 60–70 % with desaturation episodes into the 40–50 % range would be expected. A platelet count would be useful as erythrocytosis is associated with thrombocytopenia. A PT and PTT would be useful as chronic cyanosis is associated with poorly defined coagulation abnormalities. It would be necessary to know the status of the pulmonary vasculature. Specifically, it is necessary to know whether the pulmonary arteries are continuous and of normal size. The echocardiogram will demonstrate severe RVH and there will be bidirectional flow across the VSD. It is possible that the flow across the VSD could be entirely right to left with all pulmonary blood flow supplied by the Blalock-Taussig (BT) shunt.

A “tet spell” is simply an exacerbation of the dynamic component of RVOT obstruction that results in increased right to left shunting across the VSD. It will be precipitated by physiologic perturbations that reduce the caliber of the RVOT: (1) reduced venous return and (2) increases in shortening and thickening of the free wall and septum of the RV. Treatment is directed at these causes. Alternatively treatment can be directed toward increasing systemic vascular resistance (SVR) which will reduce right to left shunting at the VSD but does nothing to treat the underlying cause of the “tet spell.” The only difference between the holding area and the operating room is the extent of monitoring, qualified personnel, and drug choices available.