Low cerebral perfusion pressure: an indicator of poor prognosis in asphyxiated term infants

Value of intracranial pressure monitoring of asphyxiated newborn infants

Twenty-three infants suffering the effects of moderate or severe hypoxic-ischaemic encephalopathy were continuously monitored for intracranial pressure (ICP) by means of a subarachnoid catheter for a total of 1083 hours. Cerebral perfusion pressure (CPP) was also continuously monitored for 21 of the infants. The median age at the start of ICP monitoring was 17 hours, and the opening pressure correlated poorly with maximum sustained pressures. Maximum sustained ICP allowed the infants to be divided into three groups: (1) those with no elevation of ICP (nine), of whom two died and five had a normal outcome; (2) those with sustained rises in ICP which were resistent to treatment (nine), of whom seven died and two survivors are severely handicapped; and (3) those in whom the pressure was elevated but could be controlled medically (five), of whom two survived to be quite normal. No infant with a sustained elevation of ICP of 15mmHg or more survived to be normal, nor any who had had a CPP below 20mmHg for one hour or more. Hypotension was the cause of low CPP in most cases. There was a highly significant correlation between sustained elevation of ICP above 10mmHg and poor outcome, but no correlation between outcome and minimum CPP. It was not possible to predict clinically which infants would develop intracranial hypertension, and some infants with very severe perinatal asphyxia did not develop intracranial hypertension, and some infants with very severe perinatal asphyxia did not develop raised intracranial pressure at any time.

Cerebral perfusion pressure monitoring in premature newborns

Cerebral perfusion pressure (CPP), believed to be a major determinant of neurologic outcome, was monitored at the bedside of high-risk premature newborns during the first few days of life. Intraventricular hemorrhage was presumed to have occurred in only one of the seven infants and was associated with ventriculomegaly and early death. The other infants had good neurologic outcomes at age 18 months despite low mean CPPs (less than 30 mm Hg). These low CPPs were determined to be dependent on mean arterial blood pressures and not on intracranial pressures which were low in all infants (and even lower in more premature infants with apnea). Methylxanthine treatment of apnea of prematurity did not apparently change CPP, despite hypothetical effects on cerebral and peripheral vascular tone. Although fairly low CPP can be associated with good neurologic outcome, it may not be useful in monitoring newborn infants.

Advances in neonatal neurology

The recent advances in neonatal neurology which are discussed include i) the improved organization of perinatal medical services, ii) technological advances including ultrasonography, brainstem auditory evoked responses and intracranial pressure monitoring and, iii) new developments in therapeutics. The development of departments of perinatal medicine has meant that neonatal pediatricians and obstetricians now enjoy close links which result in benefit to the fetus. The widespread use of fetal monitoring during difficult births is one result of this. Tertiary level neonatal units in major obstetric centers must be established by health care decision-makers under pressure from their colleagues in paediatric neurology. Ultrasound examination of the neonatal brain is convenient and almost as reliable as CT scanning. Its use in the diagnosis of hemorrhage, CNS malformations, monitoring of infective processes and of progressive hydrocephalus is now well established. Brainstem auditory evoked responses are of value in the early detection of hearing loss and in the assessment of brainstem maturity. They may be useful in the detection of impending damage in patients with hyperbilirubinemia and those under treatment with aminoglycoside antibiotics. Non-invasive intracranial pressure monitoring offers promise in managing post-hemorrhagic hydrocephalus and in prognostication in hypoxic-ischemic brain damage. Neonatal meningitis remains a serious threat. The newer antibiotics to date have not improved the prognosis. For neonatal convulsions, phenobarbitone remains the drug of first choice and is best given intravenously by loading dose.