Chapter 22 - Hemodynamics of the neonate following perinatal hypoxic-ischemia and the effects of therapeutic hypothermia

Abstract

Hypoxic-ischemic injury secondary to asphyxia is a common cause of brain injury in neonates, affecting 1–3 infants per 1000 live births. Infants with moderate to severe hypoxic-ischemic injury often have cardiovascular instability, acute pulmonary hypertension (with or without hypoxemic respiratory failure), and myocardial dysfunction affecting organ perfusion. Therapeutic hypothermia further modulates the cardiovascular system in a predictable pattern. Dysregulated cerebral blood flow and oxygen delivery are potential postnatal contributors to brain injury via an ischemia/reperfusion mechanism. This is particularly true in the setting of impaired cerebral autoregulation, which is common in this population. Persistence of right ventricular dysfunction and pulmonary hypertension have both been linked to adverse neurological outcomes at 18–24 months. It is thus important that research is focused on understanding this unique population and the role that the cardiovascular system and its treatment impact brain injury.The clinical cardiovascular exam of patients with HIE may be challenging. This is due both to the residual organ injury and metabolic derangements from the primary injury and the impact of therapeutic hypothermia on vascular tone (vasoconstriction) and organ function. In this chapter we discuss the impact of the primary injury, multiorgan dysfunction, and therapeutic hypothermia on cardiovascular physiology. We will provide clinical “red flags” and highlight the potential value of targeted neonatal echocardiography and/or comprehensive quantitative echocardiography. Finally, we will discuss a suggested management framework and pharmacokinetic considerations which are required due to both temperature and multiorgan dysfunction.