Study On The Application Of Pressure Reactivity Index In Monitoring The Cerebral Autoregulation After Subarachnoid Hemorrhage

PART Ⅰ:ASSESSMENT OF CEREBRAL AUTOREGULATION IN SUBARACHNOID HAEMORRHAGE BY PRESSURE REACTIVITY INDEXObject: Dysfunction of cerebral autoregulation is one of the pathophysiological mechanisms that cause severe secondary brain damage after subarachnoid haemorrhage(SAH).Pressure Reactivity index(PRx)have been confirmed to represent the level of cerebral autoregulation but are still inadequately understood in SAH patients.The goal of this study is to explore how PRx changes in patients with integrated cerebrovascular reactivity and individualized autoregulation-guided CPP management by PRx.Method: The study objects were established as low-grade subarachnoid haemorrhage and unruptured aneurysm patients,which had both clipping of intracranial aneurysm and intracranial pressure(ICP)monitoring.ICP and arterial blood pressure(ABP)were measured continuously by high-fidelity manometer systems,PRx was calculated and collected by Neumatic computer system.According to new infarction occurred or not during the monitoring period,patients were divided into ischemic group and control group.Results: 31 patients were monitored in NICU.including ICP,ABP,CPP,and PRx.The correlation curve between PRx and CPP was observed to be a specific ‘M-shaped curve’.The optimal CPP(CPPopt)was defined as the valley of the coreation curve of CPP-PRx.The lower CPP and upper CPP limits of autoregulation(LLA and ULA)were defined as 2 vertices of“Mshaped curve” and WLA(within CPP limits of autoregulation)was defined as the CPP range between LLA and ULA.No statistically significant differences in amount of CPP LLA,CPP ULA,WLA range,nor CPPopt were found between aSAH group and unruptured aneurysm group.Mean ICP was significantly higher in those that ischemia(12.91 ± 5.71 mm Hg,p=0.01).The mean CPP LLA,CPP ULA and CPPopt in the ischemia group were significantly higher than control group(70.91±12.21 mm Hg vs59.25±7.12 mm Hg,p=0.006;97.27±8.17 mm Hg vs 92.50±6.18 mm Hg,p=0.03;81.36±13.43 mm Hg vs 70.42±6.89 mm Hg,p=0.01).The WLA range in the ischemia group was decreasing comparing with control group(26.36±9.51 mm Hg vs 32.25±6.34 mm Hg,p=0.01).Conclusion: The “M-shaped curve” reflects the hemodynamic changes caused by cerebral autoregulation.Deviation of CPP from the autoregulation guided individual and flexible thresholds is related to postoperative cerebral ischemia.Individualized autoregulation-guided CPP management by PRx may be a better strategy instead of single thresholds of CPP.PART Ⅱ:HYPOPERFUSION ASSESSED BY PRESSURE-REACTIVITY INDEX IS ASSOCIATED WITH DELAYED CEREBRAL ISCHEMIA AFTER SUBARACHNOID HAEMORRHAGEObject: Dysfunction of cerebral autoregulation is one of the pathophysiological mechanisms that causes delayed cerebral ischemia(DCI)after subarachnoid haemorrhage(SAH).Pressure Reactivity index(PRx)have been confirmed to reflect the level of cerebral autoregulation and used to derive optimal cerebral perfusion pressure(CPPopt).The goal of this study is to explore the associations between autoregulation,CPPopt,PRx and DCI.Method: Continuous intracranial pressure(ICP),arterial blood pressure(ABP)and cerebral perfusion pressure(CPP)signals acquired from 61 aSAH patients were retrospectively analyzed.PRx was calculated and collected by Neumatic computer system.The CPP at the lowest PRx was determined as the CPPopt.The duration of a hypoperfusion event(d HP)was defined as the cumulative time that the PRx was > 0.3 and the CPP was< CPPopt.The duration of CPP more than 10 mm Hg below CPPopt(ΔCPPopt <-10 mm Hg)was also used to assess hypoperfusion.d HP and time with ΔCPPopt <-10 mm Hg was compared between DCI group and control group,utilizing univariate and multivariate logistic regression.The modified Rankin Scale(mRS)was assessed prognosis at 3 months,and logistic regression and ROC analysis were used for predictive power for unfavorable outcomes(m Rs 3-5).Results: Data from 52 patients were included in the final analysis of61 patients.The mean %d HP in DCI was 29.23%,and 10.66% in control.The mean %ΔCPPopt <-10 mm Hg was 22.28%,and 5.90% in control.The %d HP(p<0.001)and the %ΔCPPopt <-10 mm Hg(p<0.001)was significantly longer in the DCI group.In multivariate logistic regression model,%ΔCPPopt <-10 mm Hg and %d HP were independent risk factor for predicting DCI and unfavorable outcomes.Conclusion: The increase of duration of hypoperfusion events and duration of CPP below CPPopt over 10 mm Hg,evaluated as time of lowered CPP,is highly indicative of DCI and unfavorable outcomes.