SYSTEMIC HYPERTENSION IN THE PREMATURE AND TERM NEONATE

OKOJIE EGHONGHON, MD AND MONESHA GUPTA-MALHOTRA, MB, BS

Introduction

Neonatal hypertension was initially described in the 1970s¹ and is of utmost concern to the neonatologist. Hypertension in the neonatal period is usually secondary, rather than being essential.² There are limited studies on neonatal hypertension especially in the premature. There is not much focus on neonates with hypertension and universal blood pressure (BP) screening was not recommended in neonates.³ In most newborns hypertension is discovered on routine BP measurement in the neonatal intensive care units (NICUs).² This review serves to highlight the etiology, method of diagnosis and management of hypertension in the premature and term neonate.

Epidemiology

Previous studies showed the incidence of hypertension in NICU to be 0.81% to 1.3%.^2,4 A more current report put the incidence of hypertension in the neonates without congenital heart defects (CHDs) to be 1%.⁵ The incidence of treated hypertension was reported to be similar between preterm (1.4%) and term (1%) infants.² The length of stay in the NICU was found to be significantly higher in both term and preterm infants with treated hypertension compared to controls.²

Etiology and Pathophysiology

Neonatal BP is largely determined by factors related to the neonate, the mother, or a combination of both.⁶ The causes of hypertension in the neonate may be classified into secondary causes of hypertension similar to older children, but unique perinatal risk factors that a neonate is exposed in the NICU, particularly the premature baby below 28 weeks of gestation, should be taken into consideration.² The phenotype of neonatal hypertension in term infant differs from that in preterm infant: term infants in comparison to preterm infants are diagnosed with hypertension earlier, have a shorter duration of stay in the NICU, and have a higher incidence of resistant hypertension.²

Maternal Causes

The nature of the intrauterine environment may predispose the growing fetus to development of hypertension in the neonatal period. Fetal exposure to illicit substances such as cocaine⁷ and heroin has been shown to induce neonatal hypertension due to its effect on the developing kidneys.⁸ Exposure to prenatal steroids such as glucocorticoids in utero has also been found to be associated with development of hypertension.⁹ Seliem et al found that steroids given in the antenatal period to accelerate lung maturity were associated with an 8-fold increase in the risk of developing neonatal hypertension.¹

Maternal essential hypertension and maternal gestational hypertension are linked to a higher BP in neonates. There have been different reports on the association of preeclampsia and the development of hypertension in the neonate. Holland et al described a lack of association between preeclamsia and elevated systolic BP in neonates.¹⁰ However, some other studies have found elevated BPs in neonates born to preecclamptic mothers. Swarup et al found that infants >29 weeks born to mothers with preeclampsia had higher BP.¹¹ Amini et al also found that systolic and diastolic BPs were significantly higher in babies born to mothers with preeclampsia than those without.¹²

Neonatal Factors

Neonatal hypertension may be related to perinatal risk factors such as umbilical artery catheterization, or other secondary causes for hypertension such as renal parenchymal abnormalities, urinary outlet obstruction, endocrinopathies and tumors, among other factors similar to older children.¹³

Perinatal risk factors     Several of the neonates in the NICU are premature and thus are exposed to these perinatal risk factors related to prolonged intensive care management and prematurity. Of the infants with sustained high BP leading chronic systemic hypertension that require therapy in the NICU, 74% were found to be premature.² Among the perinatal risk factors, the 3 most significant contributors to systemic hypertension were found to be bronchopulmonary dysplasia, steroids for bronchopulmonary dysplasia and patent ductus arteriosus (PDA), both of which are associated with prematurity.² Conditions that lead to chronic low cardiac output with renal hypoperfusion can cause systemic hypertension in the perinatal period.

Renovascular thromboembolism.     Thromboembolism of the aorta and/or the renal arteries associated with umbilical catheterization is a major cause of hypertension in the NICU. Neal et al initially found an association between umbilical artery catheterization and development of thrombi.¹⁴ Other studies demonstrated the presence of hypertension who had undergone umbilical artery catheterization.^15,16 It is thought that thrombosis during umbilical artery catheterization results from disruption of the vascular endothelium, which in turn leads to renovascular occlusion with the release of renin and, therefore, the elevation of BP. Other studies have tried to determine factors that influence the development of thrombosis associated with catheter placement. One study found that umbilical artery catheterization, left in place for a longer duration in situ, was associated with an increased risk of thrombosis formation.¹⁷

Bronchopulmonary dysplasia.     Hypertension due to bronchopulmonary dysplasia was initially studied by Abman et al, who concluded that systemic hypertension is a significant problem in infants with bronchopulmonary dysplasia; they found elevated systolic BP on at least 3 different occasions in 13 of 30 infants. The onset of hypertension usually followed discharge and responded to the use of antihypertensive medications.¹⁸ Another study supported these results in that they found that the incidence of hypertension in very low birth weight infants with bronchopulmonary dysplasia was almost twice the overall incidence of hypertension in the control population.¹⁹ Development of hypertension with bronchopulmonary dysplasia has been shown to correlated the use of steroids and bronchodilators.²⁰ Furthermore, chronic hypoxemia causes hypertension similar to that seen with sleep apnea.

Extracorporeal membrane oxygenation (ECMO).     Development of hypertension secondary to baroreceptor stimulation has been found to occur during ECMO in neonates.⁵ Sell et al found systolic hypertension greater than 90 mmHg in 38 of the 41 newborns treated with ECMO.²¹

Total parental nutrition.     Prolonged total parenteral nutrition may lead to the development of hypertension, and this may be due to water or solute (such as calcium and salt) overload.^8,22

Medications.     Medication induced hypertension usually resolves when the offending drug is withdrawn. For example, the use of dexamethasone and aminophylline have been discovered to elevate BP.²³ Indomethacin administration in the neonatal period, used in the treatment of a PDA, is also associated with renal hypoperfusion, which may lead to the development of hypertension.¹ Adrenergic medications and caffeine can cause vasoconstriction and elevate the BP. Renal toxicity from certain medications (antibiotics) and/or infections may lead to hypertension as well.

Chronic pain.     The presence of pain including postoperative pain should not be overlooked in the assessment of hypertension in the NICU, and simple analgesia will be useful in managing the elevated BP.²³

PDA.     The presence of a PDA has been linked to the development of hypertension in neonates, which could result from thrombosis of the renal artery.^24,25 Significant shunting from the PDA can cause chronic steal from systemic blood flow and cause chronic renal hypoperfusion and renal ischemia. Studies have found a PDA to be a risk factor associated with the development of hypertension in infants.^2,4

Secondary causes     Similar to older children, many diseases and malformations have been associated with hypertension among neonates; the most common being renal abnormalities.

1. Tumors.     Tumors in the neonatal period, such as Wilms, tumor, neuroblastoma and nephroblastic nephroma, may present with hypertension by either direct compression of the renal vessels and ureters or the release of vasoactive peptides.^22,26

2. Renal abnormalities.     Renal parenchymal diseases, such as congenital polycystic kidney disease syndrome, which could be autosomal dominant or recessive, are other causes of neonatal hypertension. Both variants could present in the newborn period with hypertension and enlarged kidneys. Acquired renal parenchymal disease, such as acute tubular necrosis and cortical necrosis, usually due to asphyxia are other causes of hypertension in the neonatal period.²⁷ Beyond the renal parenchyma, obstruction along the renal tract has been linked to the development of hypertension. Ureteral obstruction along any point may lead to hypertension, even in the absence of arterial compression.

3. Endocrinopathies.     Endocrine disorders in neonatal period such as congenital adrenal hyperplasia²⁸

Stay updated, free articles. Join our Telegram channel

Join