Controversies in the diagnosis and management of hypotension in the newborn infant

Although close to half of the newborns admitted to neonatal intensive care units receive treatment for "hypotension," the normal physiologic blood pre ssure range ensuring appropriate organ perfusion in the neonate is unknown. Thus, the decision to treat hypotension in the newborn is based on statist ically defined gestational and postnatal age-dependent normative blood pres sure values and physicians' beliefs rather than on data bearing physiologic reference. Dopamine is the most widely used sympathomimetic amine in the t reatment of neonatal hypotension, and it is more effective than dobutamine in raising blood pressure. Volume administration is less effective in the i mmediate postnatal period, and its extensive use is associated with signifi cant untoward effects, especially in preterm infants. During the course of their disease, some of the sickest hypotensive newborns become unresponsive to volume and presser administration. This phenomenon is caused by the des ensitization of the cardiovascular system to catecholamines by the critical illness and relative or absolute adrenal insufficiency. The findings that steroids rapidly upregulate cardiovascular adrenergic receptor expression a nd serve as hormone substitution in cases of adrenal insufficiency explain their effectiveness in stabilizing the cardiovascular status and decreasing the requirement for presser support in the critically ill newborn with vol ume- and presser-resistant hypotension. Finally. despite recent advances in our understanding of the pathophysiology and management of neonatal hypote nsion, there are few data on the impact of the treatment on organ blood flo w and tissue perfusion and on neonatal morbidity and mortality. (C) 2001 Li ppincott Williams & Wilkins.