Application Of Ultrasound Measurement Of Optic Nerve Sheath Diameter In Brain Death Monitoring

Objective:Brain death(BD)involves different pathological processes,but ultimately,it may be due to brain edema and elevated intracranial pressure(ICP),leading to cerebral hernia.Ultrasound measurement of optic nerve sheath diameter(ONSD)is a new noninvasive technique for assessing high ICP.The purpose of this study was to evaluate the clinical value of ultrasound detection of ONSD in monitoring BD.Methods:Part Ⅰ(The value of ONSD measured by ultrasound in the evaluation of brain death):From December 2021 to May 2022,patients with deep coma(Glasgow Deep Coma scale score of 3)and BD who had increased intracranial pressure due to central nervous system diseases in the intensive care unit were collected.Healthy volunteers who came to our hospital for physical examination and excluded intracranial lesions were recruited.ONSD was detected by ultrasound in healthy control group,deep coma patients and BD patients.After comparison between groups,a receiver operating characteristic(ROC)curve was used to determine the optimal ONSD threshold for assessing BD.Part Ⅱ(Clinical significance of ONSD in dynamic assessment of critically ill patients):From June 2022 to December 2022,patients with deep coma(Glasgow Deep Coma scale score of 3)who had increased intracranial pressure due to central nervous system diseases in the intensive care unit were collected.ONSD was measured daily during hospitalization until patient experienced BD or discharge.The t test was used for comparison between groups.Results:Part Ⅰ:1.A total of 35 healthy control patients(74.3%male)were enrolled,with an average age of 48±11 years.There were 20 patients(85%male)in the deep coma group,with an average age of 49±10 years.Forty patients(85%male)in the BD group were enrolled,with a mean age of 49±10 years.2.The ONSD in the BD group was significantly higher than that in the healthy control group(6.57±0.50 VS 3.78±0.65,P<0.05).The ONSD in the BD group was higher than that in the deep coma group(6.57±0.50 VS 5.83±0.52,P<0.05).According to Wilcoxon’s rank sum test,the differences among the three groups were statistically significant(P<0.001),and the differences between the following two groups were also statistically significant:brain death group-deep coma group(Z=-4.454,P<0.001),deep coma group-healthy control group(Z=-6.002,P<0.001),and brain death grouphealthy control group(Z=-7.434,P<0.001).3.Between healthy controls and deep coma groups with elevated intracranial pressure,the area under the curve of the ROC curve for ICP increase assessed by ONSD was 0.990(95%CI:97.2-100%).The optimal threshold was 5.18 mm,with sensitivity 90%and specificity 100.0%.4.Between deep coma groups and BD groups,the area under the curve of the ROC curve for BD assessed by ONSD was 0.855(95%CI:75.9-95.1%).The optimal threshold was 6.39 mm,with sensitivity 70%and specificity 80%.Part Ⅱ:1.A total of 27 patients with deep coma(3 points on the Glasgow Coma Scale)were included in the study.ONSD and transcranial doppler sonography(TCD)were measured daily during hospitalization.Finally,there were 21 patients with BD(Group A)(17 with subarachnoid hemorrhage,2 with craniocerebral trauma,and 2 with massive cerebral infarction).Six patients with non-BD(Group B)(4 cases of subarachnoid hemorrhage,2 cases of brain injury).2.In group A,with the deepening of coma,the pulsatility index of TCD gradually increased,and the average blood flow velocity gradually decreased until shock wave or spike wave or cerebral blood flow arrest appeared.From admission to confirmed BD,the ONSD increased(5.88±0.30 VS 6.34±0.33,P<0.05,95%CI:0.348-0.571).And during the first 24 hours after admission,the ONSD showed an increasing trend(6.02±0.30 VS 5.88±0.3,P<0.05,95%CI:0.019-0.105).3.In group B,during daily TCD monitoring,there was no significant change in pulsatility index.In addition,there was no significant difference in ONSD from admission to discharge(5.64±0.26 VS 5.60±0.11,P=0.546,95%CI:-0.134-0.224).The ONSD at 24 hours after admission was not statistically different from that at admission(5.63±0.14 VS 5.60±0.11,P=0.205,95%CI:-0.027-0.097).4.Comparing the ONSD changes in group A and group B during the first 24 hours after admission,it was found that the ONSD changes in group A were greater than those in group B(0.14±0.09 VS 0.035±0.06,P=0.008,95%CI:0.031-0.187).Conclusion:Ultrasound detection of ONSD is helpful in evaluating patients with BD and deep coma ONSD may has clinical value in the dynamic evaluation of the condition of critically ill patients.