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Title: The effect of blood pressure on the cerebral blood flow of preterm infants
Author: Jayasinghe, Dulip
ISNI:       0000 0001 3589 5658
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2007
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During the early postnatal period, some preterm infants experience periods of hypoxia, hypotension or both. Hypotension is associated with significant cerebral lesions and contributes to morbidity and mortality. The aetiology of the lesions is thought to be secondary to a loss of Cerebral Blood Flow (CBF) autoregulation, resulting in a pressure-passive CBF. Treatment of hypotension may require the use of inotropic agents that may also affect CBF. CBF can be measured by a number of techniques; one quantitative method is the intravenous 133Xe technique. To investigate the effects of blood pressure on the CBF of preterm infants, CBF was measured before and after treatment of hypotension. Infants received, in a stepwise manor, volume replacement, a dopamine. infusion of 5 JJ9/kg/min then randomisation between 10 JJ9/kg/min of dopamine (Group 1), or the addition of dobutamine infusion at 10 JJg/kg/min (Group 2). Analysis was performed in two stages; the infants were grouped according to blood pressure during acquisition of serial CBF estimates and analysed for the presence of autoregulation; secondly, the effect of inotropes on CBF was modelled. Sixty-one CBF recordings were obtained from 16 infants. Five infants were normotensive during CBF estimation, 11 were hypotensive at least once. CBF-MABP reactivity (95% CI) of the normotensive group was 1.9% (-0.8% to 4.7%) I mmHg llMABP; hypotensive group 1.9% (0.8% to 3.0). The PaCOz-CBF reactivity of the normotensive infants was 11.1% (6.8% to 15.5%) I KPa llPaCOz, that of the hypotensive infants was 4.1% (-5.0% to 14.1%). Twelve infants received at least 5 JJ9/kg/min of dopamine, 5 were SUbsequently randomised to Group1, 5 randomised to Group2. When the effects of MABP, PaC02 , postnatal age, dose of dopamine and dobutamine were modelled on CBF, MABP (2.1% (95% CI1.13.3%)/ mmHg L\MABP; p=0.0003) and postnatal age (1.1% (95% CI 0.12.1 %)/hour L\postnatal age; p=0.03) were found to be significant predictors of change in CBF. The 95% CI of MABP-CBF reactivity of the normotensive infants encompassed 0, interpreted as intact autoregulation, the lower CI of the hypotensive group did not, which was interpreted as absent autoregulation. Inotropes were not observed to affect CBF directly but could through increase in MABP via pressure-passive CBF.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available