Definition

1. 
   

   Blood pressure reference data in newborn infants are limited, but a systolic or diastolic blood pressure or a mean arterial blood pressure >95th percentile should be regarded as hypertension.

   
   
2. 
   

   Blood pressure increases over gestation and during the first days of life.

   
   
   
   
   1. 
      

      Therefore, birthweight, gestational age, and postnatal age need to be taken into account when assessing blood pressure recordings.

      
      
   2. 
      

      A term infant with a systolic blood pressure >90 mm Hg, a diastolic blood pressure >65 mm Hg, or a mean arterial pressure of >70 mm Hg should be regarded as hypertensive.

      
      
   3. 
      

      Corresponding figures for very preterm infants (<32 weeks) are >75, >50, and >60 mm Hg.

Prevalence

Hypertension is uncommon in early neonates.

1. 
   

   In a large study based on NICU admissions, 1% were coded with the diagnosis of hypertension.

Pathophysiology

1. 
   

   Blood pressure depends on cardiac function, vascular resistance, and sodium and water balance.

Risk factors

1. 
   

   Several factors and neonatal morbidities may contribute to blood pressure elevation, such as

   
   
   
   
   1. 
      

      Fluid overload

      
      
   2. 
      

      Renal disease

      
      
   3. 
      

      Cardiovascular disorders including structural malformations

      
      
   4. 
      

      Lung disease

      
      
   5. 
      

      Endocrine/metabolic disturbances

   
   
2. 
   

   The use of umbilical artery catheters is associated with an increased risk of thromboembolism causing hypertension.

   
   
3. 
   

   Increased autonomic stress due to pain or discomfort is common in the infant undergoing intensive care, and may also lead to high blood pressure.

   
   
4. 
   

   Neurologic injury or seizures.

   
   
5. 
   

   Irritability (during assessment).

   
   
6. 
   

   Neonatal abstinence syndrome.

   
   
7. 
   

   Medications, including caffeine, theophylline, corticosteroids, vitamin D intoxication, inotropes, or certain maternal drugs.

Clinical presentation

Hypertension is almost always detected due to routine monitoring of blood pressure, most accurately when measured invasively through umbilical or peripheral arterial catheter.

Diagnosis

Hypertension should be defined as systolic/diastolic blood pressure above >95th percentile for gestational age and postnatal age, recorded on three separate occasions. It should be assessed when the infant is calm and with the appropriate-sized cuff, if not being measured invasively.

Management

1. 
   

   Nonpharmacological

   
   
   
   
   1. 
      

      Optimizing nursing care and relieving stress, pain, and discomfort could reduce blood pressure.

   
   
2. 
   

   Pharmacological

   
   

   Published data on pharmacological therapy are limited.

   
   
   
   
   1. 
      

      The severely hypertensive, symptomatic infant (usually blood pressure far above the 99th percentile, Table 16-1 should be treated in the NICU with intravenous administration of blood pressure–lowering drugs.

      
      
   2. 
      

      It is important to monitor the blood pressure closely during pharmacologic treatment, preferably using an indwelling arterial line, and to avoid large and rapid reductions in BP.

      
      
   3. 
      

      Severe, symptomatic hypertension should be treated, using calcium channel blockers as first line of treatment.

      
      
   4. 
      

      ACE inhibitors reduce blood pressure in infants, but the risk of a drastic BP reduction should be considered due to the activation of the renin-angiotensin system during infancy.

      
      
   5. 
      

      β-Blocking agents and nitroprusside have also been proven useful.

   
   
3. 
   

   Surgical

   
   

   Surgical treatment is only indicated if the underlying cause of hypertension is surgically treatable, eg, coarctation of the aorta or neoplasias.

Early developmental/therapeutic interventions

1. 
   

   Very preterm infants or babies with severe brain injuries, who are autonomically unstable, may benefit from a minimal stimulation environment.

   
   
2. 
   

   Sudden changes in blood pressure should be avoided in very preterm infants, especially in the first week of life, due to risk of intraventricular hemorrhage (IVH).

Prognosis

In the majority of cases, hypertension is secondary to other disease or to increased autonomic stress due to pain or discomfort. Consequently, the prognosis depends on the underlying problem.

1. 
   

   Despite a need for antihypertensive intervention during intensive care, most infants do not need continued drug treatment during infancy.

   
   
2. 
   

   Preterm infants face an increased risk of hypertension from infancy to adulthood. Whether this risk is related to the severity of illness during intensive care or related to the preterm birth per se is not known.

Definition

Hypertension is defined as a systolic or diastolic blood pressure >95th percentile for age, sex, and body size, measured on three occasions.

1. 
   

   Blood pressure rises during the first 2 weeks of postnatal life and then stabilizes.

   
   
2. 
   

   Blood pressure data in relation to gestational age, which may serve as reference curves during convalescent care from 2 weeks of age, are found in Table 16-1

Prevalence

The prevalence of hypertension in healthy newborns has been reported to be low. In healthy NICU graduates, the incidence of hypertension is higher, but still is reported to be only 2.6%.

Pathophysiology

1. 
   

   Blood pressure depends on cardiac function, vascular resistance, and sodium and water balance.

Risk factors

1. 
   

   The most common causes of hypertension in infancy are renal vascular or renal parenchymal disease.

   
   
2. 
   

   Among infants born very preterm, bronchopulmonary dysplasia (BPD) is frequently associated with hypertension and both right and left-ventricular cardiac hypertrophy.

   
   
3. 
   

   A risk factor common to many NICU graduates is that they have had umbilical artery catheters. A known complication of umbilical artery catheters is aortic or renal arterial thrombosis, causing hypertension.

   
   
4. 
   

   Neonatal asphyxia or sepsis may be associated with acute tubular and cortical necrosis, and are risk factors for renal vein thrombosis.

   
   
5. 
   

   Less frequent causes of hypertension in infants may be coarctation of the aorta, neonatal abstinence syndrome (especially iatrogenic and s/p ECMO), congenital adrenal hyperplasia, hyperaldosteronism, hyperthyroidism, or neoplasias, such as Wilms tumor, neuroblastoma, or pheochromocytoma.

   
   
6. 
   

   In NICU graduates, the risk and severity of hypertension seem to be associated with the severity and duration of neonatal illness.

Clinical presentation

Hypertension in infancy is usually asymptomatic and often detected as a consequence of routine monitoring of blood pressure.

1. 
   

   Left-ventricular hypertrophy or heart failure on echocardiography or signs of hypertensive retinopathy during routine ophthalmological screening may also lead to the discovery of severe hypertension.

   
   
2. 
   

   Feeding difficulties, apnea, tachypnea, lethargy, irritability, or seizures can also be symptoms of hypertension and are indications for blood pressure measurements.

Diagnosis

1. 
   

   Blood pressure measurements in neonates

   
   

   Infants born preterm and other NICU graduates should have their blood pressure checked regularly during the convalescent care.

   
   

   A standardized protocol has been recommended to increase the reproducibility of blood pressure readings in neonates.

   
   
   
   
   1. 
      

      The infant should be lying, prone, or supine.

      
      
   2. 
      

      An appropriately sized blood pressure cuff should be placed on the upper right arm, 1.5 hours after feeding or medical intervention. In neonates, a proper cuff size is one where the cuff width to arm circumference ratio is 0.44 to 0.55. An overview of appropriate cuff sizes for children is given in Table 16-2.

      
      
   3. 
      

      The infant should then be left undisturbed for 15 minutes before three successive blood pressure readings are taken at 2-minute intervals.

      
      
   4. 
      

      The infant should be asleep or in quiet awake state.

   
   
2. 
   

   Diagnosis of hypertension

   
   

   The finding of an elevated blood pressure during convalescent care should be confirmed with repeated measurements.

   
   
   
   
   1. 
      

      At NICU discharge, a blood pressure at the 90th to <95th percentile should be checked again at the next follow-up visit.

      
      
   2. 
      

      A blood pressure more than 5 mm Hg above the 95th to the 99th percentile (stage 1 hypertension) should be rechecked within 7 to 14 days or earlier if symptomatic.

      
      
   3. 
      

      A patient having a blood pressure more than 5 mm Hg above the 99th percentile (stage 2 hypertension) should be referred to a pediatric hypertension specialist within a week, or earlier if symptomatic.

   
   
3. 
   

   Clinical examination

   
   

   When investigating an elevated blood pressure, a full physical examination including blood pressure measurements in both arms and legs, palpation of peripheral pulses, weight, and length.

   
   
   
   
   1. 
      

      Special attention should be paid to the presence of any abdominal masses that could reveal a Wilms tumor, neuroblastoma, polycystic kidney disease, or masses that could compress the renal arteries causing hypertension.

   
   
4. 
   

   Additional investigations

   
   

   When hypertension is confirmed, further investigation should include full blood count, electrolytes (sodium, potassium, chloride, and calcium), blood urea nitrogen, creatinine, plasma glucose, thyroid function test, cholesterol and triglycerides, urinalysis, chest x-ray, and renal ultrasound with Doppler. Additional investigations, such as echocardiography, abdominal ultrasound, plasma renin activity, aldosterone, and cortisol are sometimes indicated depending on initial findings and the severity of hypertension.

Management

The management of hypertension during inpatient convalescent care depends on the severity and the underlying cause.

1. 
   

   Nonpharmacological treatment

   
   
   
   
   1. 
      

      Normal growth should be aimed for, avoiding malnutrition.

      
      
   2. 
      

      Both breast milk and formula have low sodium content. Breast milk feeding has long-term beneficial effects on blood pressure.

      
      
   3. 
      

      Avoid a high sodium intake when starting solid foods.

      
      
   4. 
      

      Pain and other stressors should be relieved.

      
      
   5. 
      

      If current medications are likely to contribute to hypertension, dose adjustments or discontinuation of medication should be considered.

   
   
2. 
   

   Pharmacological

   
   
   
   
   1. 
      

      The severely hypertensive, symptomatic infant (usually blood pressure far above the 99th percentile, Table 16-1 should be transferred to the NICU for treatment with intravenous administration of blood pressure–lowering drugs (see Section I).

      
      
   2. 
      

      Infants with blood pressure recordings >99th percentile can be regarded as candidates for antihypertensive drug therapy, but drug of choice and route of administration (IV/PO) should be discussed with a colleague experienced in treating hypertension in infancy.

      
      
   3. 
      

      There is a lack of evidence for treatment of asymptomatic hypertension without target-organ damage in this age group.

      
      
   4. 
      

      Asymptomatic hypertension constantly above the 99th percentile, or infants with severe hypertension in remission, can be treated orally.

      
      
   5. 
      

      β-Blockers are contraindicated in infants with BPD, but diuretics may improve both lung function and blood pressure.

      
      
   6. 
      

      Calcium channel blockers could be used as first line of treatment.

      
      
   7. 
      

      ACE inhibitors should be used with caution in this age group because of the risk of an uncontrolled drop in blood pressure. They have also been suggested to impair nephron development.

   
   
3. 
   

   Surgical

   
   

   Coarctation of the aorta, renal artery stenosis, and tumors are managed surgically.

Discharge

1. 
   

   Teaching

   
   
   
   
   1. 
      

      Parents should be taught the importance of giving the baby their antihypertensive medication, even if he or she is not showing symptoms.

      
      
   2. 
      

      Parents should be advised of possible symptoms suggestive of hypertension (or hypotension)—poor feeding, irritability, lethargy, etc.

   
   
2. 
   

   Monitoring

   
   
   
   
   1. 
      

      Because infants with hypertension are generally asymptomatic, routine monitoring of blood pressure should be done at routine intervals upon discharge.

      
      
   2. 
      

      Primary care providers should be made aware of the need for routine monitoring, as well as having them verify that they have the appropriate-sized blood pressure cuff to obtain accurate measurements.

      
      
   3. 
      

      Guidelines for goal blood pressures should be passed along to the PCP upon discharge.

   
   
3. 
   

   Medication plan

   
   
   
   
   1. 
      

      Pediatricians and follow-up providers should be given guidelines as to whether or not to weight-adjust antihypertensive medications, at what dosing, how frequent, etc.

      
      
   2. 
      

      In general, unless the infant has an underlying cause for hypertension or continues to have a blood pressure greater than the 95th percentile then allow the child to outgrow the therapeutic dose.