FIGURE 96.2 Neonatal blood pressure norms based on gestational age A: Systolic blood pressure norms B: Diastolic blood pressure norms (Reprinted with permission by Springer, from Zubrow AB, Hulman S, Kushner H, et al Determinants of blood pressure in infants admitted to neonatal intensive care units: a prospective multicenter study J Perinatol 1995;15(6):470–479; permission conveyed through Copyright Clearance Center, Inc.) Hypertension is confirmed after serial accurate measurements reveal consistent elevations above 95% for age and weight The most common causes of neonatal hypertension include umbilical artery catheterization, renovascular disease, parenchymal renal disease, and chronic lung disease of prematurity Additionally, coarctation of the aorta, hyperthyroidism, congenital adrenal hyperplasia (CAH), and increased intracranial pressure can cause neonatal hypertension and can be life threatening if left untreated Most infants with hypertension are asymptomatic When symptoms are present, they are often nonspecific (lethargy, poor feeding, apnea) and not necessarily correlate with the degree of hypertension Initial evaluation should include blood pressure measurement in all four extremities, urinalysis, urine culture, blood urea nitrogen, serum creatinine, electrolytes, and calcium It is important to note that the absence or presence of hematuria, proteinuria, or azotemia vary in this age group and cannot be used in isolation to diagnose renovascular disease If the history and physical examination are suggestive of endocrine, neurologic, or intoxication causes of hypertension, additional testing may be needed Renal ultrasonography (US) with Doppler evaluation should also be included to evaluate for renovascular and parenchymal disease Echocardiography should be considered to assess left ventricular function Determining when to institute pharmacotherapy for hypertension is based on the underlying etiology, severity of hypertension, and presence of symptoms The decision to initiate therapy should be done in consultation with pediatric nephrologist FIGURE 96.3 Neonatal blood pressure norms based on birth weight A: Systolic blood pressure norms B: Diastolic blood pressure norms (Reprinted with permission by Springer, from Zubrow AB, Hulman S, Kushner H, et al Determinants of blood pressure in infants admitted to neonatal intensive care units: a prospective multicenter study J Perinatol 1995;15(6):470–479; permission conveyed through Copyright Clearance Center, Inc.) Hypotension in a neonate can result from volume depletion, hemorrhage, sepsis, or cardiac failure Detecting hypotension in the preterm or SGA infant can be challenging, as noninvasive monitoring can routinely overestimate blood pressure values It is imperative to treat hypotension aggressively to prevent end- organ damage and multisystem organ failure First-line treatment is to provide intravascular replacement with iso-osmotic fluids, typically normal saline, or packed red blood cells in the setting of acute hemorrhage Typical resuscitation volumes are 10 mL/kg over 30 minutes, with more judicious use in the premature infant Excessive volume expansion in the preterm neonate is associated with higher morbidity; therefore early administration of pressors is necessary if there is a limited response to volume Treatment of hypotension should be directed at improving perfusion and cardiac function, rather than aiming for a desired blood pressure value This is of particular importance in conditions that widen the pulse pressure, where systolic pressures are adequate but the mean arterial pressure underestimates perfusion pressure Temperature Rectal thermometry is considered the reference standard for measurement of body temperature in neonates However, it is important to note that mechanical trauma from rectal thermometry in a newborn can result in peritonitis and abscess formation, and should be performed with caution It is also contraindicated in patients with neutropenia Similarly, infants receiving active intervention for temperature control require continuous thermometry that is better accomplished with electronic axillary thermometry Temperature readings may vary according to the site measured so that reference ranges should be interpreted with its specific set of normal values In general, hypothermia in a neonate occurs when the temperature is less than 36.5°C, and fever occurs when temperatures exceed 38°C Infants have a very large ratio of surface area to body mass, low fat stores, and immature thermoregulatory centers, all of which leave them at increased risk for cold stress Neonates naturally respond to cold stress by becoming hypermetabolic, vasoconstricted, hyperactive, tachycardic, tachypneic, and acidotic Heat loss after a week of life commonly occurs through radiation, and is greatly influenced by ambient temperature, humidity, and the temperature of surfaces to which the infant is exposed Therefore, whenever possible, it is important for the clinician to minimize exposure to cold air and surfaces during examination or observation by placing the baby under an open radiant heater Hyperthermia or fever is most often noted as a sign of hypermetabolism in a septic infant However, hypothermia can also be a sign of sepsis, due to a markedly diminished response to bacterial pyrogens in neonates (see Chapter 31 Fever ) ... hypertension, and presence of symptoms The decision to initiate therapy should be done in consultation with pediatric nephrologist FIGURE 96.3 Neonatal blood pressure norms based on birth weight A: Systolic