ASPHYXIA

Anatomic Changes

Asphyxia (i.e., decreased PaO₂ and pHa and increased PaCO₂ ) occurs when gas exchange by the placenta (fetus) and by the lung (neonate) is inadequate or when there is right-to-left shunting of blood in the heart or lungs. The large quantities of metabolic acids produced are partially buffered by bicarbonate.^[30] In utero, asphyxia is caused by maternal hypoxia, decreased placental-umbilical blood flow, and fetal heart failure. Maternal hypoxia is caused by maternal cyanotic congenital heart disease, congestive heart failure, or respiratory failure. Asphyxia is caused by maternal hypotension, catecholamine secretion, abruptio placentae, or placental disease (e.g., fibrosis, calcification, infarction, infections) or by reduced placental-umbilical blood flow.