Abstract
Background/Aim: Selective head cooling (SHC) is a promising therapy for hypoxic-ischaemic brain damage (HIBD) in neonates. Disturbance of cerebral blood flow (CBF) plays an important role in neonatal HIBD. Safe application of SHC will depend on a better understanding of the effects of hypothermia on CBF which is influenced by temperature. This research aimed to study dynamic changes in CBF following SHC in newborn piglets.
Methods: Sixteen newborn piglets, 5 to 7 day old, were randomly assigned to one of the following groups: SHC in normal piglets (n= 4), SHC after HI (n= 6) and normal temperature after HI (n= 6). HI was induced using temporary occlusion of the bilateral carotid arteries and mechanical ventilation with low concentration of oxygen (6%) for 30 minutes. In SHC nasopharyngeal temperature was reduced to 35 °C, and then to 32 °C. During HI and SHC, heart rate, respiratory rate, arteria blood pressure, SpO2, blood glucose and haemoglobin were monitored. CBF was measured with colour microspheres before HI (as baseline) and 2, 4 (35 °C), 6 (32 °C ) and 8 hours (rewarming) after HI.
Results: During HI and SHC, no differences in arteria blood pressure, SpO2, blood glucose and haemoglobin were seen among the three groups studied. In normal piglets during SHC, global CBF decreased to 68% and 50% of baseline at 35 °C and 32 °C, respectively, particularly in temporal lobe, parietal lobe, brainstem and cerebellum. In normal temperature newborn piglets after HI, global CBF was decreased to 78% and 60% of baseline at 2h and 4h, respectively, after HI, particularly in temporal lobe, parietal lobe, hippocampus and thalamus. In SHC piglets after HI, similar decrease in global CBF was observed at the same time point at 35 °C and 32 °C, but local CBF was increased at 35 °C, particularly in the hippocampus, striatum and thalamus. At 32 °C, however, local CBF tended to decrease, particularly in the cerebellum, brainstem and parietal lobe.
Conclusion: Global CBF was decreased in piglets at 2h and 4h after HI. The decrease was not influenced by SHC, although global CBF was decreased in normal piglets during SHC. Local CBF in HI piglets during SHC was improved at 35 °C, and tended to decrease when temperature was reduced to 32 °C. Thus, after HI although SHC does not improve global CBF, it improves local CBF when the temperature remains at 35 °C.
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Chen, G., Shao, X. & Jiang, Z. 121 Dynamic Changes In Cerebral Blood Flow During Selective Head Cooling In Newborn Piglets. Pediatr Res 56, 484 (2004). https://doi.org/10.1203/00006450-200409000-00144
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DOI: https://doi.org/10.1203/00006450-200409000-00144