Hypotension

 

Reviewed by Clinical Guidelines Committee
April 2012
Clinical Guidelines Back Newborn Services Home Page
Normal Blood Pressure Importance of Low Blood Pressure Blood Pressure to Aim For Fluctuation in Blood Pressure
Blood Pressure in PPHN Assessment of end Organ Perfusion Treatment of Low Blood Pressure References

Normal Blood Pressure

Blood pressure increases over the first hours, then days after birth. Very low birth weight babies often have a low blood pressure, especially on the first day. Infants with low Apgar scores or requiring assisted ventilation tend to have lower BPs, while those whose mothers were hypertensive or who received antenatal steroids have higher BPs. There are poor relationships between blood pressure and either cardiac output or blood volume in preterm infants 1, 2 . Systemic vascular resistance is of great importance.

In very low birth weight infants, patent ductus arteriosus may contribute to low blood pressure, even in the first few days, and its closure may result in an increase in BP 3, 4, 5 .

Importance of Low Blood Pressure

Cardiac output and end organ perfusion cannot be directly measured as yet in neonatal
patients. Blood pressure is widely accepted as one of a set of parameters used in assessing
cardiovascular stability. Reduced SVC flow (as a measure of cerebral blood flow) is associated
with a significant increase in mortality, NEC and neurodevelopmental impairment (small study)
in infants of <30 weeks 6. 7. 8

There is controversy as to how active to be in treating a low blood pressure in a small sick baby. There are several publications linking low BP with poor outcome. There may be reporting bias in these publications. It is possible that the duration of low blood pressure (perfusion)
is more relevant than the actual point measurement. No-one has yet shown that treating low blood pressure improves outcome.

Some have found a correlation between periods of hypotension and IVH 9, 10 . Miall-Allen also showed an association between MBP <30 and IVH, ischaemic lesions or death 11 . Low found a relationship between low BP and hypoxaemia and a poor neuro-developmental outcome 12 . The association between a low BP and IVH was not supported by D’Souza 13 .

Blood Pressure to Aim For

Miall-Allen 11 used a mean BP of 30mm as her cut off irrespective of size or gestational age. Watkins 9 used his 10th centiles, which were:

For very low birth weight infants, a good rule of thumb is to aim for the baby’s gestational age as the desired minimum mean blood pressure.

Fluctuation in blood pressure

Blood pressure fluctuation may be as important as its absolute value in the development of cerebral lesions and the long term outcome of infants. Blood pressure variability should be minimised as much as possible in the first days of life in very preterm infants. This involves strategies of minimal handling, careful and gradual management changes and avoiding interventions that can cause changes in catecholamine levels and blood pressure.

Blood pressure in Persistent Pulmonary Hypertension

PPHN is associated with poor cardiac function. The ductus arteriosus is often patent so that, with supra-systemic pulmonary artery pressure there is R-L ductal shunting. If systemic pressure can be increased without a corresponding increase in pulmonary pressure, the shunt will lessen and oxygenation improve. There is not much information on the effect of inotropes on pulmonary vascular resistance in sick newborn infants. What there is suggests that dopamine does not produce a selective increase in systemic pressure. 14

However,

Assessment of end organ perfusion

Treatment of low blood pressure

Consider the underlying cause

Normal Saline

  • Give one to two boluses of 10-15ml/kg over 20 minutes.
  • Equal response to 5% albumin infusion but fewer repeat doses of volume were needed and a lower weight gain was seen over 48 hours, with no difference in serum [Na+] in the one trial 15
  • Saline similar to albumin/FFP in effect 16
  • Volume (albumin in the published paper) is less consistent at increasing BP than dopamine and starting dopamine should not be delayed if hypotension persists 17.

Dopamine

  • Start at 5mcg/kg/min and increase incrementally to a maximum of 20mcg/kg/min. 
  • Increases BP. More consistent response, at a lower dose with a bigger increase in BP than dobutamine 18, 19, 20 .

Dobutamine

  • Start at 5mcg/kg/min and increase incrementally to a maximum of 20mcg/kg/min.
  • Dobutamine is added to dopamine in persistently hypotensive infants, when the dopamine dose has been increased to 10-20mcg/kg/min.
  • Some evidence that improves systemic blood flow better than dopamine 20.

4% Albumin

  • This is an alternative to Normal saline.
  • There is limited data on the relative merits of each in the treatment of neonatal hypotension. A small study showed a trend towards increased mortality in those treated with albumin consistent with the findings in larger adult studies 21.

Blood

  • Use ‘whole’ blood as volume support if the baby is also relatively anaemic.
  • If volume expansion is desired, do not give furosemide with the blood.

Hydrocortisone

  • 2.5mg/kg IV 4hrly x 2 then 6hrly x 48 hrs then 0.125mg/kg 6hrly x 48 hrs, then 0.0625 mg/kg 6hrly x 48 hrs. 
  • Not for routine use. Consider in preterm infants with refractory hypotension who may have relative adrenocortical insufficiency 22. Increases BP a little less consistently but to a greater extent than with dopamine 23 .

Dexamethasone

  • 0.1-0.25mg/kg/dose. Studies of dexamethasone for ventilator dependence shows a fairly rapid increase in BP and ability to wean off inotropes  24, 25 .

Adrenaline

  • 100-300 nanograms/kg/minute, incrementally, higher doses occasionally required..
  • May be considered as additional therapy in refractory hypotension such as septic shock or asphyxial cardiac compromise.
  • As effective as dopamine as single therapy at low doses but with increased side effects 26 .
  • Use with caution and only after a decision by a specialist.

Noradrenaline

  • 0.05-0.5mcg/kg/min, incrementally.
  • Primarily raises systemic vascular resistance.
  • It may produce a reflex reduction in cardiac output and can produce coronary artery changes.
  • Very little (if anything) published on its use in the newborn. Use with caution and only after a decision by a specialist 27 .

References

1 Bauer. Arch Dis Child 1993; 69:521-2
2 Kluckow J Pediatr 1996;129:506-12
3 Knight Early Hum Dev 1992;29:287-92
4 Evans Arch Dis Child 1992; 67:1169-73 
5 Evans Arch Dis Child 1993; 68:584-7
6 Osborn. Pediatrics 2003;112:33-39
7 Hunt. J Periatr 2004;145:588-592
8 Osborn. Pediatrics 2007;120:372-380
9 Watkins. Early Hum Dev 1989;19:103-10
10 Moise Pediatrics 1995;95:845-50
11 Miall-Allen  Arch Dis Child 1987;62:1068-9
12 Low Acta Paediatr 1993; 82:433-7)
13 D’Souza (Arch Dis Child 1995; 72:162-7).
14 Feltes. Pediatr Pharmacol.1986;5:261-71
15 So. Arch Dis Child 1997;76:43-7
16 Wright. unpublished
17 Gill. Arch Dis Child 1993;69:284-7
18 Klarr. J Pediatr 1994;125:117-22, 
19 Greenough Eur J Pediatr 1993;152:925-7
20 Osbourn. J Pediatr 2002;140(2):183-191
21 Donn. J Perinatol 2003;23:473-476
22 Watterberg. Ped Res 2002;51(4):422-423
23 Bourchier Arch Dis Child 1997;76:174-8
24 Fauser. Eur J Pediatr. 1992;152:354-6. 
25 Yeh. J Pediatr 1990;117:273-82
26 Valverde. Pediatrics 2006;117(6):e1213-1222
27 Martinez. J Dev Physiol. 1990;13:141-6.