Optimizing Cerebral Autoregulation May Decrease Neonatal Regional Hypoxic-Ischemic Brain Injury

Abstract

Background: Therapeutic hypothermia provides incomplete neuroprotection for neonatal hypoxic-ischemic encephalopathy (HIE). We examined whether hemodynamic goals that support autoregulation are associated with decreased brain injury and whether these relationships are affected by birth asphyxia or vary by anatomic region.

Methods: Neonates cooled for HIE received near-infrared spectroscopy autoregulation monitoring to identify the mean arterial blood pressure with optimized autoregulatory function (MAPOPT). Blood pressure deviation from MAPOPT was correlated with brain injury on MRI after adjusting for the effects of arterial carbon dioxide, vasopressors, seizures, and birth asphyxia severity.

Results: Blood pressure deviation from MAPOPT related to neurologic injury in several regions independent of birth asphyxia severity. Greater duration and deviation of blood pressure below MAPOPT were associated with greater injury in the paracentral gyri and white matter. Blood pressure within MAPOPT related to lesser injury in the white matter, putamen and globus pallidus, and brain stem. Finally, blood pressures that exceeded MAPOPT were associated with reduced injury in the paracentral gyri.

Conclusions: Blood pressure deviation from optimal autoregulatory vasoreactivity was associated with MRI markers of brain injury that, in many regions, were independent of the initial birth asphyxia. Targeting hemodynamic ranges to optimize autoregulation has potential as an adjunctive therapy to hypothermia for HIE.

Keywords: Brain injury; Cerebral blood flow; Hypoxia; Hypoxic-ischemic encephalopathy; Neonates.

Figure 1

The distribution of neonates’ mean arterial blood pressure (MAP) during hypothermia (A), rewarming (B), and normothermia (C). Means with SD are shown.

Figure 2

The neonates’ optimal mean arterial blood pressure (MAP) values (A), the percentage of each period spent with blood pressure below (B), within (C), or above (D) optimal MAP, and the maximal blood pressure deviation below (E) or above (F) optimal MAP. Means with SD are shown. Each circle represents one neonate.