Hypertension in newborn infants primarily is of renal origin, although cardiac, endocrine, and pulmonary causes have been described as well.
Renovascular problems that may lead to neonatal hypertension include renal venous thrombosis and renal artery stenosis secondary to fibromuscular dysplasia. Many infants with FMD may have main renal arteries that appear fairly normal on angiography but demonstrate significant branch vessel disease that can cause severe hypertension.
Numerous congenital renal parenchymal abnormalities can lead to hypertension in the newborn period. For example, patients with autosomal dominant or autosomal recessive polycystic kidney disease (PKD) may present in the newborn period with severe nephromegaly and hypertension.Additional renal parenchymal causes of hypertension in the newborn period include severe acute tubular necrosis, interstitial nephritis, and cortical necrosis.
Therefore, the pathophysiology depends on the organ system involved. For example, hypertension related to renal emboli primarily is a high renin form of hypertension, whereas the hypertension associated with bronchopulmonary dysplasia (BPD) is likely related to hypoxia. Such differences in pathophysiology are very important because they can guide the clinician with respect to evaluation and treatment.
Blood pressure in newborn infants is influenced by various factors, including birthweight, gestational age, and postconceptual age.
In most newborns, hypertension is discovered on routine monitoring of vital signs. Other presentations of neonatal hypertension to be aware of in acutely ill infants include congestive heart failure (CHF) and cardiogenic shock, which are potentially life threatening. Fortunately, these consequences of hypertension gradually resolve with appropriate BP reduction. In the less acutely ill infant, feeding difficulties, unexplained tachypnea, apnea, lethargy, irritability, or seizures may constitute symptoms of unsuspected hypertension. In older infants who have been discharged from the nursery, unexplained irritability or failure to thrive may be the only manifestations of hypertension.