Application Of Central Retinal Artery Ultrasonography To Assess Cerebral Perfusion Pressure In The Perioperative Period Of Traumatic Brain Injury

PART1 Correlation Between The Hemodynamic Parameters of Central Retinal Artery Measured by Ultrasound and Intracranial Pressure and Cerebral Perfusion Pressure in Patients with Traumatic Brain InjuryObjectives This study aimed to investigate the correlation between hemodynamic parameters of central retinal artery measured by ultrasound and intracranial pressure and cerebral perfusion pressure in patients with traumatic brain injury during the perioperative period.Methods The included 55 patients with Traumatic Brain Injury(TBI)who had undergone invasive Intracranial Pressure(ICP)monitoring(TBI group),an additional 15 healthy volunteers(normal group)were enrolled.The hemodynamic parameters of the Central Retinal Artery(CRA)for the subjects(TBI group and normal group)were obtained by ultrasound and compared the CRA hemodynamic parameters between the two groups(Peak Systolic Flow Velocity(PSV),End-Diastolic Flow Velocity(EDV),Pulsatility Index(PI)and Resistance Index(RI)),compared the correlation between the hemodynamic parameters of CRA and ICP,and Cerebral Perfusion Pressure(CPP).CPP of ?70mmHg was regarded as low cerebral perfusion pressure,applied the Receiver Operating Characteristic Curve(ROC)to determine the accuracy and threshold of PI and RI in diagnosing low cerebral perfusion pressure,and found the best index for evaluating low cerebral perfusion pressure.Results Compared with the normal group,the CRA hemodynamic parameters of the TBI group were significantly different in EDV,PI,and RI.In the TBI group,the PSV measured by ultrasound was not correlated with ICP and CPP,while EDV was negatively correlated with ICP(r=-0.557,P<0.01),and positively correlated with CPP(r=0.708,P<0.05).PI,RI were positively correlated with ICP(0.476 vs.0.479,P<0.05),and negatively correlated with CPP(-0.655 vs.-0.656,P<0.01).The correlation between CRA hemodynamic parameters(EDV,PI,RI)and CPP was higher than that of ICP(0.708 vs.-0.557,-0.655 vs.0.476,-0.656 vs.0.479,P values<0.001).When CPP of ?70mmHg was regarded as low cerebral perfusion pressure,the area under the ROC of PI and RI for evaluated low cerebral perfusion pressure was 0.863vs.0.851,and the threshold was 0.97 vs.0.64,but the specificity of PI predicted that low cerebral perfusion pressure is higher than RI(66.7%vs.50.0%).Conclusion EDV,PI,RI,as CRA hemodynamic indicators,measured by ultrasound are correlated with ICP and CPP.They can assess the perioperative cerebral perfusion state of TBI patients.But low cerebral perfusion pressure predicted by PI has higher level of specificity than RI(66.7%vs.50.0%),which is considerable in clinical application.Part2.Correlation Between Central Retinal Artery Pulsatility Index Measured by Ultrasound and Cerebral Perfusion Pressure in A New Zealand Rabbit Intracranial Hypertension ModelObjectives This study aimed to investigate the correlation between central retinal artery pulsatility index measured by ultrasound and cerebral perfusion pressure changes in an intracranial hypertension rabbit model.Methods 30 healthy adult New Zealand rabbits were randomly divided into TBI group and normal group.In the TBI group,an intracranial hypertension rabbit model was made by epidural balloon water injection,and the invasive ICP and CPP values were monitored.The PI of the rabbit central retinal artery was measured by ultrasound.By continuously injecting physiological saline into the balloon,the changing trend of PI during the gradual decline of CPP was observed,and the correlation between PI and ICP and CPP was compared.Results The epidural balloon water injection method can simulate the gradual decline of CPP:CPP was relatively constant in the early stage of balloon water injection.As the balloon volume further increased,CPP gradually decreased,and PI gradually increased.PI was exponentially correlated with ICP and CPP.PI was positively correlated with ICP(r=0.653,P<0.001),PI and CPP were negatively correlated(r=-0.639,P<0.001).Conclusions The central retinal artery pulsatility index measured by ultrasound can reflect the changes of cerebral perfusion pressure of the rabbits modal with intracranial hypertension in real-time.The pulsatility index was negatively correlated with cerebral perfusion pressure of traumatic brain injury,but its application value needs to be further studied.Part3.Application of Central Retinal Artery Pulsatility Index Measured by Ultrasound in Predicting The 28 Days Prognosis of Neurological Function in Patients with Traumatic Brain Injury After SurgeryObjectives This study aimed to explore the value of ultrasound measurement of central retinal artery pulsatility index in predicting the 28 days' prognosis of neurological function in patients with TBI after surgery.Methods 82 TBI patients who had undergone invasive Intracranial Pressure(ICP)monitoring were enrolled from June 2018 to June 2020.All patients were continuously monitored for CPP changes after surgery,and the central retinal artery PI was monitored by ultrasound.The average PI(PIm)and CPP values of every 24 hours within 72 hours after the operation were collected,and the 28 days neurological function prognosis(GOS)of the patients was followed up after the surgery.According to the GOS score at 28 days after surgery,TBI patients were divided into good prognosis group(GOS score? 3 points)and poor prognosis group(GOS<3 points),and PIm values at different time points(24 h,48 h,72 h)were predicted for worse nerves functional prognosis used in the analysis of receiver operating characteristic curve.The best prediction time point and PIm threshold were found based on the maximum AUC area.Results The PIm value of TBI patients was negatively correlated with the GOS value(r=-0.584,P<0.001).When the PIm value ?0.97 was regarded as low cerebral perfusion pressure,the larger number of occurrences of low cerebral perfusion pressure within 72 hours,the more patients had lower GOS scores.The PIm at 72 h after surgery has the largest area under the receiver operating characteristic curve(AUC=0.881,P<0.001)for predicting the prognosis of neurological function in patients with TBI.When the 72 h PIm threshold was 0.925,the sensitivity for the diagnosis of poor prognosis(GOS<3)was 71.4%,and the specificity was 75%.Conclusions The 72 h value after surgery of central retinal artery PIm measured by ultrasound can predict the prognosis of neurological function in 28 days after TBI,which has significant clinical applications.