| Selective head cooling (SHC) is a promise therapy for hypoxic-ischemic brain damage (HIBD) in neonates. Disturbance of cerebral blood flow (CBF) and cerebral oxygenation metabolism play an important role in HIBD of neonate. CBF and cerebral oxygenation are influenced by temperature, and thus changes in CBF and cerebral oxygenation metabolism at states of hypothermia are a major problem involving in hypothermia safety. Research in this field is of important significance to clinical use of hypothermia.Part OneClinical study of Change in cerebral blood flow and cerebral oxygenation in neonates Hypoxic-ischemic brain damage during selective head coolingClinical study one: Change in cerebral blood flow velocity Objective: To study serial change in CBFV during SHC and rewarming in neonates with HIBD. Methods: thirty-eight neonates with moderate-severe HIBD were assigned randomly to one of the following groups: SHC group(n=18)with nasopharyngeal temperature maintained 34℃ and normal temperature group (n=20)with rectum temperature maintained about 36℃. Both groups were observed 84h. CBFV of middle cerebral artery(MCA) was measured with transcranial Doppler(TCD) before therapy and at 12h, 24h, 48h, 72 and 84 house after birth。Seven normal neonates served as control group. Result: At 0~6h after birth, Vs,Vd and Vm of MCA of neonates with HIBD were lower, and RI was higher than control. During 6~12h, no difference was observed between two groups. But at 12~48h, Vs,Vd and Vm were lower in neonates with HIBD. Compared to the control group , Vs,Vd and Vm of MAC in SHC group were lower at 0~6h after birth. But no difference was observed during 12~48h after birth. Compared to normal temperature group, Vs,Vd and Vm of MAC in SHC group were higher at 12~48h. Conclusion: CBFV of MAC in neonates with moderate-severe HIBD was decreased during the first 48h after birth, particularly at 0~6h and 12~48h. The disturbance of cerebral hemodynamics was improved by SHC.Clinical study two :Change in cerebral oxygenation metabolismObjective: To study change in cerebral oxygenation metabolism in neonates with HIBD during SHC. Methods: The subjects and group division were the same as part one. Cerebral oxygenated hemoglobin change (ΔHbO2), deoxygenated hemoglobin change(ΔHb), total hemoglobin(ΔtHb) , oxidized cytochromeaa3(Cytaa3) and tissue oxygen index(TOI) were monitored continuously throughout the study using near infrared spectroscopy(NIRS). Result: In neonates with HIBD, ΔHbD,ΔHbO2 and ΔCytaa3 were lower than normal control after birth later until 60h,but ΔtHb was lower only during 0~6h after birth. ΔHbD andΔHbO2 were lower in SHC group than the control during 0~12h after birth, but ΔtHb was lower only during 0~6h. ΔCytaa3 was lower after birth later until 36h. At 24,36 ,48 and 60 hours after birth, ΔHbO2 in SHB group was higher than in normothermia group, ΔCytaa3 was higher during 36~60 hours. No different was observed among three groups in TOI. Conclusion : ΔHbD andΔHbO2 were more sensitive in reflecting cerebral homodynamic change thanΔtHb; ΔCytaa3 can reflect the change in cerebral oxygenation at cell level. The disturbance of cerebral hemodynamics and cerebral oxygenation metabolism occurred in neonates with HIBD. SHC can improve cerebral hemodynamics and cerebral oxygenation in neonates with HIBD. Part TwoAnimal experiments of change in cerebral blood flow andcerebral metabolic rate during selective head cooling in newborn pig Animal experiments one: Change in CBF in selective head cooling Objective: To study the influence of SHC on CBF in newborn piglets Methods: Sixteen newborn piglets, aged 5~7 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). Nasopharyngeal temperature respectively was reduced to 35℃and then 32℃in SHC. HI was induced using temporary occlusion of the bilateral carotid arteries and mechanical ventilation with low concentration of o...
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