Abstract
It is generally assumed that one reason why white matter injury is common in preterm infants is the relatively poor vascular supply.AimTo examine whether blood flow to the white matter is relatively more reduced at low blood pressure than is blood flow to the brain as a whole.MethodsThirteen normoxic preterm infants had blood flow imaging on 16 occasions with single-photon emission computed tomography (SPECT) using 99Tc labelled hexa-methylpropylenamide oxime (HMPAO) as the tracer. Gestational age was 26–32 weeks. Transcutaneous carbon dioxide was between 4.7 and 8.5 kPa and mean arterial blood pressure between 22 and 55 mmHg.ResultsThere was no statistically significant direct relation between white matter blood flow percentage and any of the variables. Using non-linear regression, however, assuming a plateau over a certain blood pressure threshold and a positive slope below this threshold, the relation to white matter flow percentage was statistically significant (p = 0.02). The threshold was 29 mmHg (95% confidence limits 26–33).ConclusionOur analysis supports the concept of periventricular white matter as selectively vulnerable to ischaemia during episodes of low blood pressure.
Highlights
Brain injury in preterm infants involves predominantly white matter, and the periventricular zone is at particular risk
The vascular anatomy was used to explain this by describing periventricular white matter as a vascular end-zone [1] at special risk for ischaemia
Cerebral blood flow (CBF) is moderately low before major intracranial haemorrhage [2,3], and low CBF is weakly associated with neurodevelopmental deficit [4,5]
Summary
To demonstrate an association between white matter injury and ischaemia or low cerebral blood flow. Another problem is that if blood flow to the white matter is selectively decreased, this will not be easy to detect with a measure of global CBF as is obtained by xenon clearance or near infrared spectroscopy. Cerebral white matter blood flow and arterial blood pressure tracer was injected intravenously in a dose of 4 MBq ⁄ kg body weight within 30 min from preparation.
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