Vasoactivity of the major intracranial arteries in newborn infants.

Blood flow to the head and arms was measured by a new volumetric Doppler technique in 30 preterm infants and 10 full term infants. At least 80% of this blood flow is considered to perfuse the brain. At the same time mean blood velocity in the middle and anterior cerebral arteries was measured by Duplex Doppler scanning. While blood flow to the head and arms remained substantially constant in both groups over the first 48 hours of life (60 ml/100 g brain weight/min), blood velocity doubled in both cerebral arteries in the preterm group. The term infants had higher blood velocities in both arteries at all times, but the velocities also increased over 48 hours, although to a lesser extent than in the preterm group. These findings imply that the major intracranial arteries are themselves vasoactive, being dilated at birth and subsequently constricting, possibly as an autoregulatory response to rising arterial blood pressure. While vasodilated, the cerebral arteries will be less efficient at damping pressure transients, placing preterm infants at particular risk of periventricular haemorrhage during the early hours of life. The implications for possible approaches to the prevention of cerebral haemorrhage are discussed.     

Circadian blood pressure pattern in full-term newborn infants

A fully automatic noninvasive device (Dinamap) was used for monitoring blood pressure (BP) and heart rate repetitively over 48 h in 21 full-term newborn infants (9 males and 12 females), aged 4 days in order to clarify the occurrence of a circadian rhythm (CR). The data collected were analyzed by computer statistical analysis. Mean values and standard error of BP and heart rate measured at hourly intervals in males and females were computed and plotted as chronograms. However, each newborn infant was analyzed for a CR of BP and heart rate by the single cosinor fit of a 24-hour cosine curve. The analysis of the chronograms revealed that the values of systolic and diastolic BP show an hour-by-hour significant fluctuation in male infants, but not in female infants. CR development of BP is present only in a minority of newborn infants and reveals sex and interindividual differences. CR of heart rate is absent in all infants. The physiological significance of these findings was discussed, and the importance of knowing the physiological variances of BP in infants in order to obtain a correct clinical evaluation was stressed.     

Cerebrospinal fluid amino acid levels in newborn infants with intracranial hemorrhage

Cerebrospinal fluid (CSF) amino acid levels including excitatory amino acids (i.e. glutamate and aspartate) in 25 preterm and 18 full-term newborn infants with no serious disease except intracranial hemorrhage (ICH) were measured. ICH was detected in 13 preterm and six full-term infants on the basis of the clinical, lumbar puncture (LP) and cranial ultrasonography (CraUSG) findings. Twelve preterm and 12 full-term infants who were neurologically healthy comprised the control group. The mean concentration of CSF amino acids did not differ between preterm and full-term infants. The CSF concentrations of taurine, threonine, glycine, alanine, valine, isoleucine, leucine, tyrosine and phenylalanine in preterm infants, and threonine, aspartic acid and alanine in full-term infants were significantly elevated in infants with ICH. These abnormalities, especially in preterm infants, are probably related to cerebral hypoxia in CSF amino acid concentrations in newborn infants with ICH.     

Head position in low-risk premature infants. Impact of nursing routines

Head position preference in 15 low-risk pre-term infants studied in relation to conceptional age and nursing routines. A head position preference to the right is evident with respect to the head position imposed by the nurse. The observed spontaneous head position preference might be ascribed to the influence of the foregoing imposed head position, the influence of which diminishes with increasing observation time. After several spontaneous head turnings the low-risk pre-term infants show no head position preference anymore.     

New fontanometer for continuous estimation of intracranial pressure in the newborn.

Intracranial pressure was estimated by a new pneumatic applanation fontanometer in babies in intensive care. A close correlation with cerebrospinal fluid pressure was found on 35 separate occasions. In 12 control babies the mean (SD) fontanelle pressure was 5.2 (2.2) cm H2O, in eight with a hypoxic-ischaemic encephalopathy it was 12.6 (4.3) cm H2O, and in nine with post-haemorrhagic hydrocephalus it was 10.8 (4.3) cm H2O. In four babies monitored continuously over seven days the correlation remained good. The fontanometer enables pressure to be monitored accurately, continuously, and non-invasively in neonates at risk of raised intracranial pressure.     

Measurement of systolic blood pressure in fingers of newborn infants.

The systolic blood pressure in the index finger was measured using a minicuff and a strain gauge both placed around the finger. 122 measurements in four newborn infants were performed during monitoring in an incubator and the systolic blood pressure values obtained were compared with the simultaneously recorded intra-arterial blood pressure in the aorta. Good correlation between direct and indirect pressure values was found. An important advantage is that the measurements do not arouse the infants nor disturb their sleep. The procedure seems suited for further technical development and automatic measurements.