Hypertension

 

Reviewed by Clinical Guidelines Committee
January 2016
Clinical Guidelines Back Newborn Services Home Page
Normal Blood Pressure Epidemiology Causes of Hypertension Investigations
  Treatment References  

Definition

Hypertension is defined as elevation in systolic blood pressure in a neonate which is ≥95th percentile for age, weight and gender on 3 separate occasions1, 2. This is a statistical definition. Clinically we are likely to investigate and / or treat hypertension only if the blood pressure is persistently ≥99th percentile. Other factors such as pain control etc. need to be taken into consideration before commencing investigation.

Normal Blood Pressure in Neonates

BP in neonates (preterm and term) admitted to NICU varies with gestational age, chronological age, post-conceptual age (corrected gestation), and birth weight. Hence it is difficult to define normal BP and hypertension in neonates.

Epidemiology

By definition, 5% of neonates will have hypertension, but the reported incidence in infants admitted to neonatal units ranges from 0.2-3.0%5. Hypertension is unusual in otherwise healthy term infants and routine BP measurement is not advocated. Hypertension is much more common in infants with BPD, PDA or those with indwelling UACs, with up to 9% developing hypertension 5. Other risk factors for hypertension are antenatal steroids, maternal hypertension, and postnatal ARF 6.

The gold standard for blood pressure measurement is an appropriately calibrated intra-arterial catheter. Both umbilical and radial arterial blood pressure correlate with aortic blood pressures 7. However, for babies who do not have or require invasive monitoring, the most frequently used technique is via an oscillometric manometer (e.g Dinamap). Blood pressure should be taken preferably in right upper arm, when babies are quietly awake and not feeding (systolic BP is 5mmHg lower in sleeping babies and is higher after a feed) with an appropriate sized cuff  8. The cuff bladder should measure 2/3rd of the length of the extremity, and 0.44 to 0.55 of the arm circumference  8. If the choice is difficult, err on the side of choosing a larger as compared to a smaller cuff. After cuff placement, infant is left undisturbed for 15 minutes. 3 successive BP readings are obtained at 2-min intervals.

Table 1. Estimated BP values in well infants > 2 weeks of age from 26 - 44 weeks postconceptional age5

Postconceptional age 50th percentile 95th percentile 99th percentile

44wks

SBP
DBP
MAP

 

88
50
63

 

105
68
80

 

110
73
85

42wks

SBP
DBP
MAP

 

85
50
62

 

98
65
76

 

102
70
81

40wks

SBP
DBP
MAP

 

8o
50
60

 

95
65
75

 

100
70
80

38wks

SBP
DBP
MAP

 

77
50
60

 

92
65
75

 

100
70
80

36wks

SBP
DBP
MAP

 

72
50
59

 

87
65
72

 

92
70
71

34wks

SBP
DBP
MAP

 

70
40
50

 

85
55
65

 

90
60
70

32wks

SBP
DBP
MAP

 

68
40
48

 

83
55
62

 

88
60
69

30wks

SBP
DBP
MAP

 

65
40
48

 

80
55
65

 

85
60
68

28wks

SBP
DBP
MAP

 

60
38
45

 

75
50
58

 

80
54
63

26wks

SBP
DBP
MAP

 

55
30
38

 

72
50
57

 

77
56
63

 

Figure 1. Systolic and diastolic blood pressures (Mean and 95% confidence intervals) on Day1 at various gestational ages4

Causes of Neonatal Hypertension

  1. Renal
  1. Cardiovascular
  1. Endocrine
  1. Chronic Lung Disease
  1. Medications
  1. Neurological
  1. Miscellaneous / multifactorial

Investigations5

First Line Investigations:
 

  1. Repeat your clinical examination
  1. 4-limb blood pressures
  1. Electrolytes, urea, and creatinine
  2. Urinalysis protein, creatinine, microalbumin
  3. Renal and aortic ultrasound scan with dopplers (mention hypertension on the request form)
  4. Chest radiograph (if cardiac murmur or signs of congestive cardiac failure)

Second (and Third) Line Investigations (when clinical picture is suggestive):

  1. Echocardiogram to exclude coarctation or interrupted aortic arch.
  1. Plasma renin activity
  1. Plasma cortisol, aldosterone, or thyroxine (as indicated)
  2. Urine VMA/HVA
  3. Cranial ultrasound or MRI if any suspicion of an intracranial cause
  4. Renal radionucleotide study
  5. Renal angiography may be required for ongoing suspicion of renovascular disease

Treatment 5

  1. Removal of any iatrogenic cause
  2. Treatment of underlying cause e.g. cardiac, endocrine etc.
  3. Antihypertensive treatment should be commenced after discussion with the on-call neonatologist. Some commonly used medications and their doses are listed in the table below(5,9)

Class

Drug

Recommended
Dose

Comments

Reference

Alpha / Beta
adrenergic
antagonists
Labetolol

Oral

 

Doses from one month of
age

1 2 mg/kg three to four
times a day

Ref 9
But doses are
from one month of age

Labetolol

IV

 

IV Hypertensive emergencies
500 micrograms/kg/hour
adjusted at intervals of at
least 15 minutes, according
to response; to a maximum
of 4 mg/kg/hour

Ref 9,10
Beta-adrenergic antagonists Propranolol

Oral

  250 micrograms/kg three
 times daily, increasing if
necessary to a maximum of
2 mg/kg three times daily
Ref 9
Calcium channel blockers Amlodipine

Oral

  Doses from one month of age
100 200 micrograms/kg
once daily
increasing if necessary at
intervals of 1-2 weeks up to
400 micrograms/kg
once daily.
Ref 9
Vasodilators  Hydralazine

Oral

  250 -500 micrograms/kg
every 8 12 hours, increase
 as necessary to a maximum
of 2 3 mg/kg every 8 hours
Ref 9,10

 

Hydralazine

IV

 

  IV Slow IV Injection
100 500 micrograms/kg
every 4 6 hours,
as necessary. Maximum of
3 mg/kg daily.
Continuous IV Infusion
preferred route for cardiac patients
12.5 50 micrograms/kg/hour.
Maximum 2 mg/kg daily.
Ref 9

Ref 10
states that IV labetalol
is more effective
in the initial urgent
control of acute
hypertensive crisis

 

  1. Consider discussing with either a paediatric nephrologist or a paediatric cardiologist (depending on underlying cause).

References

1 Watkinson M. Hypertension in the newborn baby. Archives of Disease in Childhood Fetal and Neonatal Edition. 2002;86(2):F78-F81.
2 National High Blood Pressure Education Program Working Group on High Blood Pressure in C, Adolescents. The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents. Pediatrics. 2004;114(2 Suppl 4th Report):555-76.
3 Batton B, Li L, Newman NS, Das A, Watterberg KL, Yoder BA, et al. Evolving blood pressure dynamics for extremely preterm infants. J Perinatol. 2014;34(4):301-5.
4  Zubrow AB, Hulman S, Kushner H, Falkner B. Determinants of blood pressure in infants admitted to neonatal intensive care units: a prospective multicenter study. Philadelphia Neonatal Blood Pressure Study Group. Journal of perinatology: official journal of the California Perinatal Association. 1994;15(6):470-9.
5 Dionne JM, Abitbol CL, Flynn JT. Hypertension in infancy: diagnosis, management and outcome. Pediatric nephrology. 2012;27(1):17-32.
6 Seliem WA, Falk MC, Shadbolt B, Kent AL. Antenatal and postnatal risk factors for neonatal hypertension and infant follow-up. Pediatr Nephrol. 2007;22(12):2081-7.
7 Gevers M, Hack WW, Ree EF, Lafeber HN, Westerhof N. Calculated mean arterial blood pressure in critically ill neonates. Basic Res Cardiol. 1993;88(1):80-5.
8 Flynn J. Etiology, clinical features and diagnosis of neonatal hypertension. 2014 [cited 2015, March 29th.]. Available from: http://www.uptodate.com/contents/etiology-clinical-features-and-diagnosis-of-neonatal-hypertension.
9 New Zealand Formulary for Children. http://www.nzfchildren.org.nz/
10 Neonatal Formulary 6: Drug Use in Pregnancy and the First Year of Life (ed. Hey). http://onlinelibrary.wiley.com/book/10.1002/9781444329773