Obstetric parameters and Doppler findings in cerebral circulation as predictors of 1 year neurodevelopmental outcome in asphyxiated infants.

OBJECTIVE: To establish the association of cardiotocography (CTG) and other obstetric parameters with pulsed Doppler findings in cerebral arteries during the first day of life, and to compare the cerebral artery Doppler with other determinants of asphyxia in predicting 1-year neurological outcome in asphyxiated full-term infants. STUDY DESIGN: Cerebral blood flow velocity (CBFV) were measured from the anterior cerebral (ACA) and basilar (BA) arteries in 30 asphyxiated and 30 healthy-term infants using pulsed Doppler ultrasonography at approximately 24 h of age. CTG, cord artery pH, Apgar scores, biochemical asphyxia markers and symptoms of hypoxic-ischemic encephalopathy (HIE) were compared with the Doppler findings in respect of the ability to predict the outcome, defined by death or impaired neurological performance at 1 year of age. RESULT: In all, 20% of the asphyxiated infants but none in the control group had increased peak systolic CBFVs (mean+3 s.d.) in the ACA or BA. The sensitivity of increased systolic CBFV to predict abnormal outcome in the asphyxia group was 83%, specificity 95% and the sensitivity of the combination of HIE grade from 2 to 3 and increased systolic CBFV in the ACA or BA was 100% and specificity was 95%, respectively. Pathological CTG and low cord artery pH or low Apgar scores showed low predictive power. CONCLUSION: Grade from 2 to 3 HIE and the systolic CBFV (mean+3 s.d.) in the ACA or BA by Doppler ultrasound seemed to predict the outcome in asphyxiated infants at 1 year of age better than CTG, acid basement status, Apgar scores or asphyxia markers. If an increase of more than +3 s.d. in the systolic CBFV does not occur within the first 24 h of life, a good 1-year neurological outcome may be anticipated.

Regulation of heart rate variation by the autonomic nervous system in neonatal lambs.

We studied the role of the autonomic nervous system in the regulation of heart rate variation (HRV) in 12 chronically instrumented neonatal lambs. HRV was quantified from ECG tracings by computing periodic HRV distributions at frequencies of 0.02-1.00 Hz, using power spectral analysis of heart rate, and also by HRV indices. Heart rate declined more during the 1st than the 2nd mo after birth. Multiple regression analysis showed that the heart rate responses to vagal and to beta-adrenergic blockade had an independent negative association both with age and with the initial mean heart rate, whereas the overall HRV response had a positive association with age. Vagal blockade led to a 70-80% decrease in the beat-to-beat HRV in all lambs (p less than 0.001). The overall HRV indices decreased by 40-65% in lambs (less than 30 d old (p less than 0.001) and about 30% in those greater than 30 d old (p less than 0.05). In the power spectrum the greatest decrease was seen in the high-frequency components of HRV. beta-Blockade led to a decrease of about 50% in all HRV (p less than 0.001) in the younger lambs, without frequency selection. In the older lambs, it had no effect on the beat-to-beat HRV, but the overall HRV (coefficient of variance) decreased maximally by 40% (p less than 0.01), with a significant reduction in the low-frequency components of HRV. These results suggest that in the regulation of HRV after birth dual control via the autonomic nervous system is most important. In the older lambs, developmental changes result in precise regulation of the fast heart rate fluctuations mainly by the vagal division, whereas the slow fluctuations are partially regulated by the vagal and beta-adrenergic divisions.