Neonatal Hypothermia

A Method to Provide Neuroprotection After Hypoxic Ischemic Encephalopathy

Katherine M. Newnam, MS, RN, CPNP, NNP-BC; Donna L. DeLoach, MS, RN, CPNP, NNP-BC

Disclosures

NAINR. 2011;11(3):113-124. 

In This Article

Seizure Management

The infant with HIE is at risk for seizures during acute phase and as the injury evolves. All nurses working in the labor and delivery, newborn nursery, and the intensive care nursery should be educated about the presentation of infant asphyxia and seizures to facilitate implementation of therapeutic hypothermia, which may require infant transport to another facility that provides that level of care.[4]

The timing of the hypoxic insult correlates with the onset of the first seizures. The first seizures typically appear within the first 12 hours after birth if the insult was before labor. A peripartum insult usually causes seizures approximately 18 to 20 hours after birth.[35] Seizure activity may be detectable by electroencephalogram (EEG) but not clinically expressed in approximately two thirds of the infants. Of the one third that were clinically manifested, two thirds of these seizures were either unrecognized or misinterpreted by experienced neonatal staff underscoring the implementation of aEEG in the clinical arena.[35]

The expression of seizures is varied and often subtle. Subtle expressions included slow tongue thrusting, bicycling, boxing and swimming movements, eye deviation, and apnea. Posthypoxic infants exhibit an excessive degree of segmental myoclonus, which can be difficult to distinguish from multifocal seizures. Segmental myoclonus can be seen to some degree in the normal newborn when crying or excited and is often referred to as tremulousness or jitteriness. The nurse should take hold of the affected extremity and flex or extend the joint slightly, which arrests the clonus but does not affect true seizure activity. The rhythmical movements will continue to be felt by the nurse's hand.[28,40]

Seizures are more likely to occur earlier and may initially be resistant to treatment in infants after HIE as compared with other neonatal seizure disorders. In addition, the seizures may increase over the 24 hours that follows, reflecting the reperfusion injury (see Fig 1). The seizures will typically subside in these patients within a few hours to days. This coincides with EEG changes to burst suppression pattern or isoelectric as the injury (apoptosis) and cerebral edema progresses. The EEG is also important in determining the effectiveness of anticonvulsant medications. The increased use of continuous monitoring by EEG has revealed that the most commonly used drugs only suppress the seizure symptoms.[35] Anticonvulsant drugs have not been developed specifically for the treatment of neonatal seizures, in spite of the fact that most seizures begin within the first year of life.[41] There is no current evidence in human experiments that prophylactic use of anticonvulsants improved outcomes in the hypothermic infant.[36] Finally, seizures do not always indicate the long-term outcome will be adversely affected.[41]

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