Effect of mild hypothermia of different duration on cerebral vasospasm following subarachnoid hemorrhage in dogs

Abstract

Objective To investigate the effect of mild hypothermia of different duration on cerebral vasospasm following subarachnoid hemorrhage(SAH)in dogs.Methods Adult healthy mongrel dogs of both sexes weighing 14-20 kg were used in this study.SAH was induced by 2 injections of non-anticoagulated autologous blood0.5 ml/kg into foramen magnum at an interval of 48 h.Thirty dogs were randomly divided into 5 groups(n = 6each): group Ⅰ control(group C);group Ⅱ SAH;group Ⅲ,Ⅳ,Ⅴ SAH+8,16,32 h mild hypothermia(guoup H8 h,H16 h,H32 h).In control group artificial cerebro-spinal fluid(ACSF)0.5 ml/kg was injected into foramen magnum instead of autolegous blood.In group Ⅲ,Ⅳ,Ⅴ the dogs were cooled after the second intra-foramen magnum injection via an endovascular cooling device to 33.5℃(rectal temperature)which was maintained for 8,16 and 32 h respectively.The overall neurological performance was categorized(OPC)and scored(0 = normal.4 = coma),plasma and CSF concentrations of ET-1 and NO_2~-/NO_3~- were measured and the change in the diameter of cerebral basilar artery was determined by CT angiography before first intra-foramen magnum injection and at 5,12 and 19 d after the second injection.Results The OPC score and plasma and CSF concentrations of ET-1 were significantly increased while plasma and CSF NO_2~-/NO_3~- concentrations and diameter of cerebral basilar artery were significantly decreased after the second injection as compared with the baseline before1st injection in group SAH,H8 h and H_16 h.The OPC scores and plasma and CSF ET-1 concentrations were significantly lower while plasma and CSF NO_2~-/NO_3~- concentrations were significantly higher and the diameter of cerebral basilar artery was significantly larger in group H_16 h and H_32 h than in group SAH.Conclusion Mild hypothermia(33.5℃)maintained for 16-32 h can attenuate the cerebral vasospasm by decreasing plasma and CSF ET-1 concentration and increasing plasma and CSF NO concentration,leading to the balance between cerebral vascular constriction and dilatation. Key words: Hypothermia,induced; Subarachnoid hemorrhage; Vasospasm,intracranial