Neonatal Hypertension Clinical Presentation

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 blood pressure (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.

Focus the history on discovering any pertinent prenatal or postnatal exposures, as well as to the particulars of the infant's nursery course and any concurrent conditions. Review the procedures that the infant has undergone, especially umbilical catheter placement, and analyze the baby's current medication list. If the infant has been discharged from the nursery, the history should also cover symptoms related to possible underlying causes of hypertension (similar to the evaluation of hypertension in older children).

The physical examination should begin with 4-extremity blood pressure (BP) measurements in order to rule out aortic coarctation. Assess the general appearance of the infant and pay particular attention to the presence of dysmorphic features that may indicate an underlying genetic syndrome. Perform careful cardiac and abdominal examinations to rule out congestive heart failure (CHF) or renal anomalies. Examine the genitalia to rule out congenital adrenal hyperplasia (CAH). Neurologic examination may also be helpful, particularly in infants with intraventricular hemorrhage.

Normal blood pressure levels

BP in newborn infants is influenced by various factors, including birth weight, gestational age, and postconceptual age. Excellent data illustrating the importance of these factors were generated by Zubrow et al, who prospectively obtained serial BP measurements from nearly 700 infants admitted to several NICUs in a large metropolitan area over 3 months.^[8] The investigators used these data to define the mean plus upper and lower 95% confidence limits for BP; their data clearly demonstrated increases in BP with increasing gestational age, birth weight, and postconceptual age.

A more recent study of hemodynamically stable premature and term infants admitted to the NICU showed that BPs on day 1 of life correlated with gestational age and birth weight.^[9] However, another study of more than 400 term infants admitted to a postnatal ward in Australia showed no difference in BP on day 1 of life based on birth weight, length, or gestational age.^[10] Thus, there appears to be physiologic differences in premature infants with respect to BP level that need to be taken into consideration when considering whether a particular BP value is normal or elevated.

Data from these studies have recently been summarized by Dionne et al,^{[11, 12]} who generated a table of BP values that can be used in assessing if a neonate’s BP is normal or elevated (see Table 1 below). For older infants, the percentile curves generated by the 1987 Second Task Force on Blood Pressure Control in Childhood remain the most useful reference of normal BP values (see the image below).^[13] These curves allow BP to be characterized as normal or elevated not only by age and sex but also by size, albeit to a somewhat limited extent.

Defining hypertensive-level BP

Hypertension in adults is defined based upon occurrence of hard cardiovascular endpoints such as myocardial infarction, stroke, and death. Since these events occur rarely in the pediatric age group, the definition of hypertension in infants, children, and adolescents is a statistical one based on databases of BP readings obtained in healthy subjects. Thus, BP in the young is considered normal if less than the 90th percentile for age, sex, and height, and is considered hypertensive if it is greater than or equal to the 95th percentile.

For infants, the same definitions should probably be applied, although the available data on normal BP values in infancy is limited. The table summarized below is a useful reference for premature infants, while the Second Task Force curves (see image above) can be used for term and older infants. However, there are obvious shortcomings for both of these references, highlighting the need for additional studies of normal BP in infancy.

Table 1. Neonatal Blood Pressures and Potential Treatment Parameters. Adapted from Dionne et al.* (Open Table in a new window)

*Estimated values for blood pressures after age 2 weeks in infants from 26-44 weeks postconceptual age. The 95th and 99th percentile values serve as a reference to identify infants with persistent hypertension that may require treatment. SBP, systolic blood pressure; DBP, diastolic blood pressure; MAP, mean arterial pressure.