Acid-Base Balance in Pediatric Congenital Heart Patients

Abstract

Acid-base balance in children with congenital heart disease before and after heart surgery is of paramount importance. In general, newborns have a reduced ability to cope with metabolic acidosis, especially under parenteral nutrition. Changes in arterial pCO₂ and pH determine changes in pulmonary vascular resistances, which may trigger serious hemodynamic problems in the balance between systemic and pulmonary circulation and in case of critical pulmonary blood flow (cavopulmonary connection, Fontan circulation). In patients with tetralogy of Fallot, acidosis and hypercapnia are triggers of tet-spell crisis.

In addition to these peculiar factors, after heart surgery in congenital patients, the acid-base balance is a marker of the adequacy of cardiac output to sustain the metabolic needs. Metabolic acidosis and hyperlactatemia are among the most important indirect markers of a poor cardiac output. Maintenance of a normal acid-base balance guarantees against the risk of electrolyte concentration changes (viz., potassium) which may in turn lead to arrhythmic complications. This chapter offers a brief overview of the acid-base balance in the general physiologic setting and in the particular conditions involved in the intensive care management of congenital heart children.