Anemia of Prematurity - Portal Neonatal

History:
CLINICAL Section 3 of 10
• Defining hypertension in the newborn
o In determining the level of BP that should be considered hypertensive for a newborn
infant, keep in mind that just as BP in older children has been demonstrated to
increase with increasing age and body size, numerous studies have demonstrated
that BP in newborns increases with both gestational and postconceptual age as well
as with birthweight.
o The most recent study demonstrating this principle is a 1995 study by Zubrow and
associates, who prospectively obtained serial BP measurements from nearly 700
infants admitted to several NICUs in a large metropolitan area over a period of 3
months. They used these data to define the mean plus upper and lower 95%
confidence limits for BP for the infants who were studied; their data clearly
demonstrated increases in BP with increasing gestational age, birthweight, and
postconceptual age. Based on these data, an infant's BP is considered elevated if it
falls above the upper limit of the 95% confidence interval for infants of similar
gestational or postconceptual age and size. The curves generated by Zubrow's study
have been widely published and should be consulted in assessing whether a newborn
has hypertension.
o For older infants found to be hypertensive following discharge from the nursery, the
percentile curves generated by the Second Task Force on Blood Pressure Control in
Childhood appear to be the most useful. These curves, which can be found in many
reference texts and handbooks, 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.
Hypertension in this age group is defined as BP elevation higher than the 95th
percentile for infants of similar age, size, and sex.
• 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 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.
• Patient history: Focus the history on discovering any pertinent prenatal 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.
Physical: Issues pertinent to the physical examination in neonates with hypertension can be divided
into two categories, the first being proper blood pressure measurement, and the second being other
components of the physical examination.
• Blood pressure measurement
o Proper identification of hypertension in the newborn requires accurate BP
measurement. Fortunately, in most acutely ill infants, BP is usually monitored directly
via an indwelling arterial catheter, either in the radial or umbilical artery. This method
provides the most accurate BP readings and is clearly preferable to other methods. In
infants who do not have indwelling umbilical lines, automated oscillometric devices
are an acceptable alternative method of BP measurement.