Blood pressure disorders encountered in neonates, monitoring of blood pressure and normal ranges.
The recognition and treatment of hypotension is particularly important to avoid complications such as cerebral ischaemic injury or intraventricular haemorrhage.
In general hypotension is often due to a combination of:
- abnormal peripheral vasoregulation
- myocardial dysfunction
The first line of treatment is volume administration with 10-20 mL/kg normal saline, which should be limited to this amount to avoid complications, especially in preterm infants.
Refractory hypotension should be treated with a dopamine infusion and occasionally followed by an adrenaline infusion and corticosteroids although the latter should only be administered in a tertiary neonatal intensive care unit (NICU).
Unless the baby has an in-dwelling arterial line, the only reliable and accurate way of measuring blood pressure indirectly is by using the oscillometric method.
Non-invasive BP measuring
To minimise errors of non-invasive BP measurements, the following guidelines are recommended:
- The preferred site is the right arm; however, forearm, calf or thigh may be used providing correct cuff size used.
- Cuff width to arm (or calf) circumference ratio as indicated on cuff.
- If possible, obtain BP measurement during quiet or sleep state.
- Obtain average of two or three measurements if making management decisions.
- Use mean BP to monitor changes as this is less likely to be erroneous.
- Non-invasive BP may overestimate BP measurements in very low birthweight (VLBW) or at lower levels.
In-dwelling arterial lines
To minimise errors when using in-dwelling arterial lines, the following factors should be considered:
- Narrow catheters will underestimate systolic BP.
- Occlusion of the tip of the catheter (vessel wall or clot) may dampen wave and underestimate BP.
- Even small air bubbles may have an effect on measurement.
- Peripheral lines read higher than umbilical lines.
- Complications may occur and include:
- thrombus formation
'Normal' neonatal blood pressure values
Points to note:
- Blood pressure increases with:
- postnatal age (especially in the first 72 hours of life).
- Blood pressure may be affected by gender especially on the first day of life.
- There is no significant difference between arm and calf blood pressure in normal infants.
- It is difficult to define 'normal' BP values in ELBW infants.
- In clinical practice, the infant's blood pressure is generally considered to be adequate as long as urine output (> 1 mL/kg/hr) and capillary refill (< 3 seconds) are within normal limits and there is no metabolic acidosis.
- In general all preterm infants, after 72 hours of age, should have a mean blood pressure above 30 mmHg.
However, these are not reliable indicators of tissue perfusion.
Arbitrary definitions of hypertension are as follows:
- term infant: systolic > 90 mmHg, diastolic > 60 mmHg
- preterm infant: systolic > 80 mmHg, diastolic > 50 mmHg.
Blood pressure ranges in neonates
Low birthweight infants
|Birthweight (g)||Systolic range (mmHg)||Diastolic range (mmHg)|
Preterm infants by gestation
|Gestation (wk)||Systolic range (mmHg)||Diastolic range (mmHg)|
Preterm infants by age
|Day||Systolic range (mmHg)||Diastolic range (mmHg)|
|Age||Systolic (mmHg)||Diastolic (mmHg)||Mean (mmHg)|
|Day 1 (asleep)||70+/-9||42+/-12||55+/-11|
|Day 1 (awake)||71+/-9||43+/-10||55+/-9|
|Day 3 (asleep)||75+/-11||48+/-10||59+/-9|
|Day 3 (awake)||77+/-12||49+/-10||63+/-13|
|Day 6 (asleep)||76+/-10||46+/-12||58+/-12|
|Day 6 (awake)||76+/-10||49+/-11||62+/-12|
Clinical features of hypotension may include:
- mottling of the skin
- prolonged capillary refill time
- cool extremities
- reduced urine output.
The major causes of hypotension include:
- blood loss
- disseminated intravascular coagulation (DIC)
- third space losses with necrotising enterocolitis (NEC)
- cardiogenic shock
- congenital heart disease
- cardiomyopathy or myocarditis
- air leak (for example, pneumothorax)
- adrenal haemorrhage or acute adrenal crisis (congenital adrenal hypoplasia)
- drug effects.
Hypertension may occur in up to 3 per cent of NICU admissions.
It is usually due to renal or cardiovascular abnormalities.
Clinical features of hypertension are often non-specific but may include:
- feeding difficulties
- unexplained tachypnoea
- seizures (rare)
- mottling with signs of congestive heart failure.
The major causes of hypertension include:
- Renal artery stenosis/hypoplasia
- Coarctation of the aorta
- Abdominal aortic atresia
- Polycystic kidney disease
- Renal obstruction and hydronephrosis
- Acquired renal parenchymal causes
- Severe acute tubular necrosis
- Cortical necrosis secondary to asphyxia
- Thromboembolic renal artery or vein complications secondary to umbilical catheterisation
- Endocrinological disorders
- Congenital adrenal hyperplasia
- Salt and water overload
- Other causes include
- Neonatal abstinence
- Some medications such as aminophylline
- Metablastic nephroma
Investigation of neonatal hypertension might include:
- urea, electrolytes and creatinine
- plasma renin activity
- thyroid function tests
- chest x-ray
- renal ultrasound
- four limb blood pressure measurements (a differential pressure between the upper and lower limbs is suggestive of coarctation of the aorta) – an echocardiogram would then be warranted.
Treatment of hypertension
- Relates to
- severity of hypertension
- underlying cause.
- Medications might include:
- angiotensin-converting enzyme inhibitors
- calcium channel blockers
- Other approaches:
- relief of pain
- discontinuation of medications potentially causing hypertension.
Care must be taken in treating neonatal hypertension to avoid precipitous falls in blood pressure, which may be associated with further complications particularly in preterm infants.
Areas of uncertainty in clinical practice
Definitions of 'normal' blood pressure in low birthweight and preterm infants are based on small numbers. Although these are 'healthy' infants, a variety of devices have been used to produce the measurements.
There is very good evidence to suggest that blood pressure cannot necessarily be equated with normal systemic flow or a normal circulating blood volume.
As a general rule, the lower limit of mean BP in mmHg on the day of birth is approximately equal to gestational age in weeks.
- Fanaroff JM, Fanaroff AA. Blood pressure disorders in the neonate: Hypotension and hypertension. Sem Fetal Neonatal Med 2006;11:174-81
- Noori S, Seri I. Pathophysiology of newborn hypotension outside the transitional period. Early Hum Dev 2005;81:399-404
- Kent AL, Chaudhari T. Determinants of Neonatal Blood Pressure. Curr Hypertens Rep 2013;15:426-32
- Lee J, Rajadurai VS,Tan KW. Blood pressure standards for very low birthweight infants during the first day of life. Arch Dis Child Fetal Neonatal Ed 1999;81: F168-F170
- Nuntnarumit P, Yang W, Bada-Ellzey HS. Blood pressure measurements in the newborn. Clin Perinatol 1999;26:981-996
- Puchalski Mary L. Should Blood Pressure be measured in Newborn Infants. May 04,2011
- Rennie, JM. (2012). Appendix 4. In: Rennie, JM and Robertson Rennie & Robertsons Textbook in Neonatology. 5th ed. London: Elsevier Limited. 1301-1305.
- Taeusch HW, Ballard RA. Avery's Diseases of the Newborn 7th Ed. W.B. Saunders Company, Philadelphia. 1998
- Flynn, J.T. Etiology, clinical features, and diagnosis of neonatal hypertension. Wolters Kluwer Health. UpToDate 2014
Other reading/web links
- Bauer K, Linderkamp O, Versmold. Systolic blood pressure and blood volume in preterm infants. Arch Dis Child 1993;69:521-2
- Kluckow M, Evans, N. Relationship between blood pressure and cardiac output in preterm infants requiring mechanical ventilation. J Pediatr 1996;129:506-12
Last updated 03 Oct 2018
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First published: February 2016
Last web update: October 2018
Review by: February 2019
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