Hypotension

 

 Reviewed by David Knight
December
2000
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 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

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. No-one has shown that treating low blood pressure improves outcome.

Some have found a correlation between periods of hypotension and IVH 6, 7 . Miall-Allen also showed an association between MBP <30 and IVH, ischaemic lesions or death 8 . Low found a relationship between low BP and hypoxaemia and a poor neuro-developmental outcome 9 . The association between a low BP and IVH was not supported by D’Souza 10 .

Blood Pressure to Aim For

Miall-Allen 8 used a mean BP of 30mm as her cut off irrespective of size or gestational age. Watkins 6 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. 11

However,

Treatment of low blood pressure

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 12. 
  • Saline similar to albumin/FFP in effect 13. 
  • Volume (albumin in the published paper) is less consistent at increasing BP than dopamine and starting dopamine should not be delayed if hypotension persists 14.

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 15, 16 .

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.

4% Albumin
  • This is an alternative to Normal saline.
  • There is no data on the relative merits of each in babies outside the immediate newborn period (first couple of days) so use albumin rather than saline in these babies as it is the ‘more established’ treatment.

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. 
  • Increases BP a little less consistently but to a greater extent than with dopamine 17 .

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  18, 19 .

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 20 .

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 Watkins. Early Hum Dev 1989;19:103-10
7 Moise Pediatrics 1995;95:845-50
8 Miall-Allen  Arch Dis Child 1987;62:1068-9
9 Low Acta Paediatr 1993; 82:433-7)
10 D’Souza (Arch Dis Child 1995; 72:162-7).
11 Feltes. Pediatr Pharmacol.1986;5:261-71
12 So. Arch Dis Child 1997;76:43-7
13 Wright. unpublished
14 Gill. Arch Dis Child 1993;69:284-7
15 Klarr. J Pediatr 1994;125:117-22, 
16 Greenough Eur J Pediatr 1993;152:925-7
17 Bourchier Arch Dis Child 1997;76:174-8
18 Fauser. Eur J Pediatr. 1992;152:354-6. 
19 Yeh. J Pediatr 1990;117:273-82
20 Martinez. J Dev Physiol. 1990;13:141-6.
21 Bolande. Exp Mol Pathol. 1996;63:87-100