Impaired Cerebral Autoregulation in Children

Abstract

Managing acute brain injury involves protecting the brain from secondary injury by addressing the mismatch between metabolic demand and cerebral perfusion. Observational studies have associated impaired cerebral autoregulation, a physiological process governing the regulation of cerebral blood flow, with unfavorable neurological outcomes in both pediatric and adult populations. We review the pathophysiology of cerebral autoregulation and discuss methods for assessing and monitoring it in children after acquired brain injury. We also examine the current research investigating the relationship between impaired cerebral autoregulation and outcomes following traumatic brain injury, cardiac arrest, cardiopulmonary bypass, and extracorporeal membrane oxygenation. Furthermore, we outline potential areas for future research in cerebral autoregulation and its clinical implications for pediatric patients with brain injuries.

Keywords: Cardiac arrest; Cerebral autoregulation; ECMO; Pediatrics; Traumatic brain injury.

FIGURE 1.

Cerebral autoregulation curve as described by Lassen. The cerebral autoregulatory capacity, marked with a double arrow, is the range of MAP/CPP over which CBF remains constant. The lower and upper limits of CA mark the boundaries of this range. More recent data have shown a narrower plateau and steeper slope than initially described. CBF, cerebral blood flow; CPP, cerebral perfusion pressure; LLA, lower limit of autoregulation; MAP, mean arterial blood pressure; ULA, upper limit of autoregulation.

FIGURE 2.

Calculation of optimal mean arterial blood pressure. The CA index COx represents the moving correlation coefficient between the cerebral oxygen saturation and MAP. From these data, a U-shaped curve (black line) was constructed to determine the optimal MAP. The vertical gray bars represent the distribution ( ± 1 S.D.) of COx values within each MAP bin. This curve suggests an optimal MAP of 73 mm Hg (blue dashed line). However, CA is preserved within a MAP range of 46-100 mm Hg. A horizontal red dashed line intersects at a threshold of 0.3 (although this may vary depending on the CA index), indicating impaired CA and an increased risk of ischemia (blue area) or edema (red area) below and above these limits. CA, cerebral autoregulation; COx, cerebral oxygenation index; MAP, mean arterial pressure.