Experimental Study In Establishment Of Acute Intracranial Hypertension Model And The Effect Of Intracranial Hypertension Upon Pattern And Parameter Of TCD

【objectives】To establish the animal model of acute intracranial hypertension., investigate thechanges of transcranial Doppler patterns in raised intracranial pressure, detect thecorrelations between intracranial pressure, cerebral perfusion pressure and theparameters of TCD and establish the regression equations of ICP and CPP, observe thechanges of transcranial Doppler flow patterns at the last stage of extremeintracranial hypertension before rabbits'death so that the necessaryexperimental evidence will be provided to clinical experience for monitoring ICP andCPP and diagnosing brain death using transcranial Doppler non-invasively.【Methods】Acute intracranial hypertension was induced by inflating the balloons inserted intothe epidural space of rabbits. New Zealand white rabbits were randomly divided intotwo groups. The balloons of experimental group (n=20) animals were inflatedprogressively and the control group's (n=8) were not. Blood flow velocity wasmeasured with transcranial Doppler and intracranial pressure, arterial pressure wasmeasured continuously in both groups until the animals died.【Results】1 With progressive increase of intracranial pressure five characteristic flow patternswere observed, appearing in the following order: high resistance pattern, systolic flow,retrograde diastolic flow, very small systolic flow and zero flow.2 With progressive increase in intracranial pressure, cerebral perfusion pressuredropped. TCD parameter showed a significant correlation with ICP and CPP. There areinverse linear relationships between ICP and Vs, Vd, Vm. RI is linear related to ICP andPI is exponential related to ICP. There are linear relationships between CPP and Vs, Vd,Vm. RI is inversely linear related to CPP and PI shows a inverse exponntial correlationwith CPP. 3 At the last stage of extreme intracranial hypertension Doppler sonogramsshowed three characteristic flow patterns in the following sequence: retrograde diastolicflow, very small systolic flow and zero flow. Retrograde diastolic flows are multiformrelated to the phases of brain death. Very small systolic flow showed two shapes:systolic-spike and small systolic triangular. 【Conclusions】 Analysing patterns and parameters of TCD may be helpful for evaluating ICP andCPP qualitatively or half-quantitatively. According to three characteristic flow patterns,brain death can be diagnosed reliably.