FETAL RESPONSES TO ACUTE MATERNAL COCAINE INJECTION IN SHEEP

Maternal cocaine abuse has been associated with neonatal neurological and neurobehavioral problems of unknown pathogenesis. We administered a single intravenous dose of cocaine (2 mg/kg) to 12 unanesthetized pr egnant sheep; their fetuses had been catheterized in utero 2 days befo re the study. We measured fetal cerebral blood flow (CBF), cerebral me tabolic rate of O2 (CMR(O2)), mean arterial blood pressure (MAP), and blood gases before and 2, 5, 15, and 30 min after maternal cocaine inj ection. Fetal CBF increased by 37 +/- 33% (mean +/- SD) at 5 min and r eturned to baseline by 15 min. Regional brain blood flow changes paral leled CBF changes with the greatest increases occurring in cerebellum (54 +/- 43%) and brain stem (54 +/- 52%). Cerebral vascular resistance was decreased for cerebellum (22%) and brain stem (19%) but was uncha nged for cerebral hemispheres and caudate. Increased CBF at 5 min was associated with a 20 +/- 9% increase in fetal MAP and a 38 +/- 13% dec rease in fetal arterial O2 content. Fetal CMR(O2), was unchanged. Ther e was a decrease in fetal intestinal blood flow at 2 min, an increase in myocardial, adrenal, and renal blood flow at 5 min, and no change i n placental blood flow. Maternal cocaine injection causes fetal hypoxe mia, hypertension, and increased CBF. Possible mechanisms for cerebral vasodilation (in some areas) include hypoxemia, impaired autoregulato ry response to increased blood pressure, and/or direct or indirect vas cular effects of cocaine or its metabolites.