|Reviewed by Clinical Guidelines Committee|
|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|
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 .
Cardiac output and end organ perfusion cannot be directly measured as yet in
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
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 .
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.
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.
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
Consider the underlying cause
|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|
|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.|