ABSTRACT
Regional cerebral blood flow is directly proportional to the Doppler velocity time
integral of flow in corresponding cerebral arteries. This study was performed to determine
whether an acute change in the velocity time integral of cerebral blood flow occurs
in newborns with pulmonary hypertension who experience an acute improvement in pulmonary
hemodynamics and gas exchange at the onset of inhaled nitric oxide therapy. Twenty-two
newborns with lung disease and an oxygenation index >25 were treated with 10 to 20
parts per million inhaled nitric oxide. Measurements of heart rate, blood pressure,
arterial blood gases, right and left ventricular planimetry, and Doppler ultrasonography
were performed before and after 30 to 60 minutes of therapy. Nitric oxide inhalation
was associated with a significant acute change in arterial blood pressure, pH, arterial
carbon dioxide tension, arterial oxygen tension, proportion of right-to-left ductal
shunt, estimated systolic pulmonary arterial pressure, and right ventricular diastolic
and systolic areas. In the middle cerebral artery, peak systolic flow velocity (49
± 5 vs. 41 ± 4, cm/sec), diastolic flow velocity (21 ± 3 vs. 14 ± 3, cm/sec), and
the velocity time integral (10.3 ± 1.1 vs. 7.9 ± 1.1, cm) all decreased (p <0.05). These changes only occurred in a subgroup of 17 patients who experienced
an improvement in arterial oxygen tension ≥10 mmHg. The velocity time integral of
flow in the middle cerebral artery is acutely decreased in newborns with pulmonary
hypertension who experience an acute increase in oxygenation after the onset of inhaled
nitric oxide.
KEYWORD
Cerebral circulation - Doppler ultrasonography - echocardiography - ductus arteriosus
- nitric oxide - persistent pulmonary hypertension of the newborn
