An experiment was carried out in nine piglets within 24 h after
birth (control group: four,
nicardipine group: five) for the purpose of evaluating the effects of a
calcium antagonist,
nicardipine, on cerebral blood flow changes induced by
asphyxia neonatorum. Under respiratory control with a
mechanical ventilator, the animals were exposed to
hypoxia. The inspiratory
oxygen level was lowered at 15 min intervals from 0.08 to 0.06 and then to 0.05. When
bradycardia (heart rate; 60/min or less) was observed, 100%
oxygen,
adrenaline, and
sodium bicarbonate were administered for
resuscitation.
Nicardipine was administered at a dosage of 10 micrograms/kg via bolus injection 30 min after the
resuscitation. It was administered thereafter at a rate of 10 micrograms/kg per h. The cerebral blood flow was measured using a
laser Doppler velocimeter. The cerebral blood flow, electroencephalograph (EEG), blood pressure, and heart rate were continuously measured for 120 min after the
resuscitation. In the control group, the mean arterial pressure 35 min after the
resuscitation was 60 mmHg or more. However, the cerebral blood flow was lower than the prehypoxia value in the animals with a mean arterial pressure of 75 mmHg or less. In the
nicardipine group, the mean arterial pressure was lower, but the cerebral blood flow was higher than the prehypoxia value and
cerebral ischemia was not induced. The mean arterial pressure 120 min after the
resuscitation was 72.0 +/- 8.2 mmHg in the control group, while it was 56.7 +/- 7.5 mmHg in the
nicardipine group. It was significantly lower in the latter.(ABSTRACT TRUNCATED AT 250 WORDS)