Chapter 103: Neonatal Hypertension

INTRODUCTION

Over the past several decades, we have learned much about neonatal hypertension, resulting in an increased awareness in the modern neonatal intensive care unit (NICU). In healthy term infants, hypertension is exceedingly uncommon,¹ with an incidence of approximately 0.2%. In critically ill infants admitted to the NICU, however, the incidence is higher, with reported rates^{2, 3, and 4} ranging from 0.7% to 3.0%. The diagnosis of hypertension in neonates and infants can be challenging because their normal blood pressure (BP) range is dynamic, varying along with a number of factors, including gestational age, postnatal age, and weight. Despite this, a careful diagnostic evaluation should allow determination of the underlying cause of hypertension in most hypertensive neonates. There are numerous treatment options, and treatment decisions should be tailored individually based on the severity of the hypertension and concomitant disease states. Fortunately, in most infants, hypertension resolves over time, although a small number may have persistently elevated BPs throughout childhood.

DEFINING AND DIAGNOSING NEONATAL HYPERTENSION

Normative Neonatal Blood Pressures

One of the greatest challenges when diagnosing hypertension in neonates is the fact that the normative BP range is dynamic. BPs exhibit a variable pattern, and one must consider gestational age at birth, postnatal or postconceptual age, birth weight, and appropriateness of size for gestational age. In general, BP normally increases with increasing gestational and postconceptual age, as well as with increasing birth weight.^{5, 6, 7, 8, and 9} Not surprisingly, a greater rate of increase is seen in preterm and infants small for gestational age, compared to term neonates. Fortunately, several recent studies have provided normative data that greatly facilitate the identification of neonates with elevated BPs.

Zubrow et al defined mean and upper/lower 95% confidence limits for neonatal BPs based on prospective, serial oscillometric BP measurements from 608 neonates admitted to multiple NICUs.⁹ On day of life 1, systolic and diastolic BPs correlated strongly with birth weight and gestational age. BP progressively increased after birth, most rapidly during the first 5 days (1.6–2.7 mm Hg/d). This increase continued after the fifth day, albeit at more gradual increments (0.15–0.27 mm Hg/d). Most notably, in a multiple-regression analysis, the primary determinant of BP was postconceptual age (Figure 103-1).

In addition, Pejovic et al examined BPs measured by an oscillometric device in 373 hemodynamically stable premature and term neonates to evaluate the influence of gestational age, postnatal age, birth weight, gender, and sleep state on BP.⁸ Systolic and diastolic BPs ...