What are the general anesthetic considerations for the common cardiac lesions?
Associated extracardiac defects are present in 5–50% of children with congenital heart disease. In 17–18%, the defect is part of a syndrome or chromosomal anomaly. Genitouri-nary tract anomalies are among the most common lesions and are present in 4–15% of patients with congenital heart disease. Major chromosomal anomalies with associated car-diac lesions of anesthetic significance are Down (trisomy 21), Turner, Noonan, and DiGeorge syndromes.
All patients with shunt lesions are at risk for air emboli to the systemic circulation irrespective of their usual shunting pattern. A left-to-right shunt may transiently reverse due to the earlier relaxation of the left ventricle compared with the right ventricle. Additionally, upon sud-den obstruction to right ventricular output due to an air embolus, a left-to-right shunt will convert to a right-to-left shunt pattern. Therefore, the intravenous (IV) line should be meticulously debubbled and then rechecked after warming of the operating room, since this may have caused nitrogen to come out of solution in the IV fluid, forming additional hazardous bubbles. All IV lines should be con-nected while the IV fluid is flowing freely. In addition, all syringes should be cleared of air. Prior to injecting into an intravenous line, a small amount of fluid should be aspi-rated into the syringe to clear any air that may be in the needle or injection port. A recommended technique is to dilute any given medication such that 1 mL consists of a unit dose. With this technique, aspiration of IV fluid into the syringe will not significantly change the drug concen-tration. These precautions are important in any patient in whom a communication exists between the systemic and pulmonary circulations, regardless of the presence or absence of pulmonary outflow obstruction.
The majority of patients with congenital heart disease, pre- or post-correction or palliation, require antibiotic prophylaxis for the prevention of bacterial endocarditis prior to any surgical, diagnostic, or dental procedure that may result in bacteremia. Routine oral endotracheal intu-bation and flexible bronchoscopy do not require prophy-laxis. However, manipulation of the genitourinary tract does. Current recommendations as published by the American Heart Association are listed in Table 69.2.