Episodes of apnea and bradycardia in the preterm newborn: impact on cerebral circulation.

The effect of episodes of apnea with bradycardia on cerebral circulation was studied during 101 episodes in 15 premature infants. The objectives of the study were to determine whether important alterations occur in cerebral hemodynamics with apnea and bradycardia and whether such alterations relate to systemic hemodynamic events. The transcutaneous Doppler technique was used to measure blood flow velocity in the anterior cerebral arteries. With episodes of apnea complicated by mild-to-moderate bradycardia (heart rate less than 120 or greater than 80), a decrease in diastolic flow velocity was noted with little or no change in systolic flow velocity. With episodes complicated by severe bradycardia (heart rate less than 80), the diastolic flow velocity fell to the electronic base line, and a progressive decrease in systolic flow velocity also was observed. Accompanying the changes in cerebral blood flow velocity were similar changes in arterial blood pressure. These data suggest potential deleterious hypoxic-ischemic effects on brain from apnea with severe bradycardia in the preterm infant.