The Study Of The Change Of Cerebral Oxygen Metabolism In The Process Of Establishment Of Brain Death Animal Models

Objective:To observe the change of AJDO2、DPCO2and DPCO2/AJDO2in the process of establishment of brain death animal models, evaluating the significance and value of AJDO2、DPCO2and DPCO2/AJDO2for severity evaluation of patients with trauma brain injury and the diagnosis of brain death.Methods:On the basis of classic method of increasing epidural intracranial pressure, Codman intracranial pressure monitoring probes were implanted in12landrace pigs invasively, the brain death models were established by increasing epidural intracranial pressure with a rate of0.5mL/min injected into the Foley balloon catheter under real-time monitoring of the intracranial pressure. Brain death is identified as the irreversible cessation of all brain functions and is diagnosed according to a standard which requires the following criteria:゛bsence of corneal reflex;゛bsence of pupillary light reflex;③the animals are non-response to pricking the head and face;④TCD shows surge waves, nail waves or no blood stream signal;⑤electroencephalography documenting the absence of spontaneous or induced brain electric activity;⑥atropine test is negative;(7)positive apnea test result(absence of respiratory drive with Pco2>60mmHg and pH<7.4).Date collectionThe HR, ICP, MAP and EEG are monitored continuously in the progress, the spectrum and mean velocity of MCA, blood gas analysis of external carotid artery and of internal jugular are monitored discontinuously. PO2、PCO2、pH、SO2and Hb are recorded to calculate AJDO2and AejDO2,DPCO2and DPejCO2,DPC02/AJDO2and DPejC02/AejDO2Statistical analysisMeasurement data is expressed by mean±standard deviation, and is analyzed by SPSS19.0Statistical Analysis Software, a P<0.05is considered as statistically significant.1. Cerebral blood flow was reduced stepwise in the animals by inducing intracranial hypertension with consequently cerebral perfusion pressure reduction: CBF100%,70%-100%of baseline,30%-70%of baseline and0%-30%of baseline. To analyze the difference of AJDO2, DPCO2, and DPCO2/AJDO2between groups by analysis of variance.2. To analyze the difference between SjvO2and SejO2, AJDO2and AejDO2, DPCO2and DPejCO2, DPCO2/AJDO2and DPejCO2/AejDO2before increasing epidural intracranial pressure, the diagnosis of brain death and after the diagnosis of brain death separately by t-test.Results:1.12experimental landrace pigs, one died of anesthetic accident,11were successfully induced model of brain death, the success rate was100%. With effective respiratory and circulatory support the brain death models can maintain31.3±4.7h.2. AJDO2of3.92±0.64vol%, DPCO2of6.11±1.43mmHg, and a ratio of1.57±0.64with the normal cerebral perfusion pressure; a coupled increased of AJD02(5.86±1.21vol%) and DPCO2(10.33±1.83mmHg) with no change in ratio(1.62±0.81) when CPP is70～100%of the baseline; AJDO2of4.31±0.77vol%with an increased in DPCO2(11.48±2.32mmHg) and correspondingly higher ratio(2.81±0.53), in this phase, CPP is30～70%of the baseline; when the CPP is0-30%of the baseline, there is a decrease of AJDO2(1.38±0.35vol%) and of DPCO2(5.06±0.65mmHg) with a further ratio increase(4.12±1.07).3. Before the diagnosis of brain death, it is statistics significance at difference between SjvO2and SejO2, AJDO2and AejDO2, DPCO2and DPejCO2, DPCO2/AJDO2and DPejCO2/AejDCO2.After the diagnosis, there is no statistical differences between SjvO2and SejO2, AJDO2and AejDO2, DPCO2and DPejCO2, DPCO2/AJDO2and DPejCO2/AejDO2.Conclusion:1. This method of inducing brain death model is easy to operate and has a higher success rate, the vital signs of the model which can be maintained for a long time and easily to be standardized change stably in the progress.2. It is possible to discovery ischemic and anoxia and to detect whether it is compensatory or decompensated early on by combining changed of AJDO2, DPCO2and DPCO2/ADO2, providing basis on animals for the estimate of illness, adjustment of treatment, assessment of prognosis.3. After the diagnosis of brain death, the blood gas analysis showed typical change in internal jugular vein bulb, which may have the value of evaluating on cerebral blood flow and metabolism in patients with brain death.