Neuroprotection: Protection of the Threatened Infant Brain, 4/1998

The perinatal period—the period including labor, delivery and the 24-36 hours after delivery—is one of the specific times in which the infant's brain is subject to risk of immediate injury. The process of being born and separated from the maternal environment can be threatening to the infant's brain. Fortunately, modern obstetrical and neonatal care is able to reduce this threat to a minimum. However, the trauma of even a normal delivery in which there is relatively little overt injury can be a trigger that results in permanent brain damage; this occurs when the health of the infant's brain is already problematic because of events that occurred during pregnancy.

Interventions are being explored that when used either during labor and delivery or in the immediate neonatal period might protect the threatened infant's brain from the stress of the perinatal period. This area of research is called neuroprotection.

There are two general approaches to neuroprotection being explored: drugs and hypothermia.

Drugs: The delivery process and the neonatal period when the infant is adjusting to a new environment are periods when the infant brain is under stress. For the first time, the infant is completely dependent upon its own body mechanisms for survival. The developing brain is particularly vulnerable to this stress. If the baby is born prematurely and the infant brain is underdeveloped; or the baby is of low birth weight (less than 5 1/2 lbs.); or is the result of a difficult delivery; or is a twin, a triplet or more; or whose growth and development has been threatened during intra-uterine life, the infant's brain cells can be exceptionally vulnerable to injury during the adjustment to extra-uterine life.

However, there is evolving evidence that threatened nerve cells in the brain may be able to be protected if drugs are used that protect the metabolic processes of these threatened cells. A number of drugs are under study to see if neuroprotection can be provided. Among them are steroids, excitatory amino acid inhibitors and magnesium. None of these have yet been demonstrated to be universally useful, although some give promise of effectiveness in very specific situations. This is an exciting and promising field of research and offers promise of neuroprotection.

Hypothermia: Hypothermia is the process by which the baby's body temperature is lowered below the normal. This can be done by immersing the baby in cold water, placing ice around its body or by cooling its blood. An even more direct approach is the cooling of only the infant's head either by circulating cold water over the skull or the cooling of the blood flowing to the brain. As a result, the infant's metabolism is "slowed down", its metabolic needs are diminished, and there is an increase in the time available to remove the stressful stimuli. Hypothermia is not an innocuous procedure in that it can have negative effects on heart and liver function. Animal studies demonstrate that the adverse effects can be controlled. However, the specific indications for either body or brain cooling have not yet been established and the issues of "how cool" and "for how long" in human infants are still to be worked out. Hypothermia is already being used during surgery on infants for the repair of congenital disorders of the heart; thus information is being accumulated that will be of use in neuroprotection.

Comment

Protecting the infant's brain and having a longer period of time available to correct for factors threatening the infant's brain, offer promise of reducing the occurrence of developmental brain damage or of reducing the severity of damage. Neuroprotection is an exciting area of research which the UCP Research and Educational Foundation is helping to develop.