Chapter 61

### I. PROBLEM

An infant has a systolic blood pressure (BP) of >95 mm Hg. Normal blood pressure values depend on the infant's gestational age, postnatal age, and birthweight. Hypertension is commonly defined as a BP >2 standard deviations above normal values for age and weight, but other definitions exist. The Task Force on Blood Pressure Control in Children defines hypertension as 95% percentile or above on 3 separate occasions. For a rapid reference of blood pressure ranges for premature and term infants see Table 65–1. For estimated BP levels at the 95th and 99th percentiles in infants after 2 weeks of age see Table 61–1. For other detailed BP values see Appendix C. Normal blood pressure increases with birthweight, gestational age, and postconceptional age.

Table 61–1.   ESTIMATED BLOOD PRESSURE LEVELS AT THE 95th AND 99th PERCENTILES IN INFANTS AFTER 2 WEEKS OF AGE

### II. IMMEDIATE QUESTIONS

1. How was the BP taken? Verify that the BP reading is correct and the hypertension is real. As the first reading is usually the highest, it is best to take 2–3 confirmatory measurements. BP rises when the infant is feeding, sucking, or in an upright position. BP is lower in the prone versus supine position. Measure when the infant is calm. Most BP data is from measurements taken from the right arm.

1. Blood pressure cuff size is important; it should encircle two-thirds of the length of the upper extremity. If the cuff is too narrow, the BP will be falsely elevated. The American Academy of Pediatrics (AAP) recommendations for BP cuff bladder width are as follows: newborn—4 cm; infant—6 cm. For length: newborn—8 cm; infant—12 cm. Maximum arm circumference: newborn—10 cm; infant—15 cm.

2. BP reading from an indwelling catheter (radial or umbilical artery) is the most accurate (gold standard) of all methods. If measurements are taken by means of an umbilical artery catheter (UAC), be certain that the catheter is free of bubbles or clots and the transducer is calibrated; otherwise, erroneous results will occur.

3. Automated oscillometric devices (electronic pressure sensor), common in the neonatal intensive care unit (NICU), can give lower pressures than intra-arterial catheters.

4. BP protocols have been established to standardize blood pressure measurement in infants. One suggested by Nwankwo is to measure BP 1.5 hours after ...

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