Chapter 54

1. Problem. An infant has a systolic blood pressure (BP) >90 mm Hg. Hypertension is defined as a BP >2 standard deviations above normal values for age and weight, but the definition can vary widely (see Appendix C.). Others define neonatal hypertension as a systolic BP >95th percentile for age and sex on three separate occasions. It can also be defined as a systolic BP >90 mm Hg and a diastolic BP >60 mm Hg in full-term infants; for premature infants, the values are systolic >80 mm Hg and diastolic >50 mm Hg. The values for normal BP are given in Appendix C (infants [C-1], premature infants[C-2] and infants weighing 401–1000 g [C-3]).

2. Immediate questions

1. How was the BP taken? Make sure the BP reading is correct and the hypertension is real. Doppler flow ultrasonography is the most reliable noninvasive method of measurement. The size of the cuff 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. If measurements are taken by means of an umbilical artery catheter, be certain that the catheter is free of bubbles or clots and the transducer is calibrated; otherwise, erroneous results will occur. BP reading from an indwelling catheter is the most accurate of all methods. BP rises when the infant is feeding, sucking, or in an upright position.

1. Is an umbilical artery catheter in place, or has one been in place in the past? Umbilical artery catheters are associated with an increased incidence of renovascular hypertension. There is no relation between the duration of catheter placement and the development of hypertension. The hypertension is probably related to the thrombus formation, which leads to disruption of the vascular endothelium of the artery. The following conditions are risk factors to thrombus formation in the aorta: bronchopulmonary dysplasia (BPD), patent ductus arteriosus, hypervolemia, and certain CNS disorders. Improved catheters and the use of heparin have helped decrease the incidence of thrombus formation.

1. Are symptoms of hypertension present? Infants with hypertension may be asymptomatic or may have the following symptoms: tachypnea, cyanosis, seizures, lethargy, increased tone, apnea, abdominal distention, fever, and mottling. They may also have congestive heart failure (CHF) and respiratory distress.

1. What is the BP in the extremities? The BP in a healthy infant should be higher in the legs than in the arms. If the pressure is lower in the legs, coarctation of the aorta may be the cause of the hypertension.

1. What is the birthweight and postnatal age of the infant? Normal BP values increase with increasing birthweight and age. Values rise ~1–2 mm Hg/day during the first week of life and then ~1–2 mm Hg/week over the next 6 weeks.

1. Is the infant in pain or agitated? Pain from an invasive procedure, crying, agitation, or suctioning can cause a transient rise in BP. The systolic pressure can be 5 mm Hg lower in sleeping infants.

1. Does the infant have BPD, patent ductus ...

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