Pathophysiology of newborn hypotension outside the transitional period.

Hypotension is a common diagnosis in neonatal intensive care units. Although there are epidemiological data for normative blood pressure values in preterm and term infants, the ranges of normal blood pressure where adequate organ perfusion is ensured for different gestational and postnatal ages remain unclear. An understanding of the developmentally regulated differences in the physiology and pathophysiology of the neonatal cardiovascular system in comparison to that of mature subjects is important to formulate an appropriate treatment strategy in neonates with circulatory compromise. This article reviews the current understanding of pathophysiology of hypotension and shock in the neonate beyond the transitional period, focusing on hypovolemia, myocardial dysfunction, abnormal peripheral vasoregulation, and relative or absolute adrenal insufficiency with potentially associated down regulation of adrenergic receptors.