brain death ( bd ) in the popular belief is that someone 's brain stops functioning , even though their heart may be kept beating using a machine .
thus , the concept of bd is closely linked to the birth of modern intensive care medicine .
after brain function had ceased , the somatic function being sustained by mechanical ventilation for a long time .
so in many countries , the law provides that treatment can be legitimately removed from a patient who was diagnosed bd , and the donation of organs for transplantation can start . in this regard ,
a definition of  irreversible coma  was presented for death by an ad hoc committee of the harvard medical school . then in 1976 , guidance on the diagnosis of brain (
stem ) death was published by the united kingdom conference of medical royal colleges and their faculties . in 1979 ,
a memorandum stated that bd equated with the death of the whole person by this commission . in 1995 , the american academy of neurology ( aan ) issued guidelines on the diagnosis of bd in order to standardize its practice parameters . this guidance was the basis for the development of the statutes of death in each state in the united states and formed the basis of bd definitions in other countries .
the latest criterion in the united states is the update of the 1995 aan guideline on determining of bd , which was published in 2010 . despite the general consensus on the concept of bd , its definition still varies widely between countries . in china ,
, a draft of the determination of bd in adults was published in national medical journal of china . in 2009 ,
the revised draft was published in chinese journal of cerebrovascular disease . in 2013 , 
criteria and practical guidance for the determination of bd in adults ( bqcc version )  was published in chinese medical journal .
the 2009 version of bd criteria is completely the same as the 2013 version . in this study
, we observed the application of the chinese criteria of bd in a neurological intensive care unit ( neuro icu ) . at the same time , we compare generally accepted bd criteria for diagnosis between china and the united states in order to know its diagnostic effectiveness .
from january 1 , 2012 , we began to evaluate patients in the neuro icu of beijing tiantan hospital , who were applied for bd diagnosis .
the evaluations of bd were done by several neurologists who worked in the neuro icu .
we used two criteria for bd diagnosis that were criteria of the united states and chinese criteria . in summary ,
the criteria of the united states consist of four steps : ( 1 ) prerequisites : definite and irreversible coma whose cause should be excluded drug , hypothermia , alcohol , and other laboratory abnormal values ; ( 2 ) examination : absence of brainstem reflexes ; ( 3 ) the apnea test result is positive ; and ( 4 ) ancillary tests can be used when uncertain about the clinical examination or when the apnea test can not be performed .
the criteria in china also consist of four steps : ( 1 ) the clinical examination confirm the bd diagnose , including deep coma , absence of brainstem reflexes and no spontaneous ( spont ) respiration ; ( 2 ) confirmatory tests should fulfill two of the three which include transcranial doppler ( tcd ) , electroencephalogram ( eeg ) , and somatosensory evoked potential ( sep ) ; ( 3 ) the apnea test is positive ; and ( 4 ) a repeat determination should be done 12 h later after the 1 time .
if patients were in a coma and ventilated by nonautonomy breathing mode , they would be applied for the evaluation for bd and enrolled in this study .
first of all , the cause of coma should be known and excluded drug , hypothermia , and alcohol .
they should have normal body temperature and blood pressure ( bp ) , no acidosis .
the brainstem reflexes included corneal reflexes , pupillary reflexes , oculocephalic reflexes , oculovestibular reflexes , and cough reflexes .
no matter what the test result was , confirmatory tests were done continuously which were sep , eeg , and tcd .
if the results of tests for patients all fulfilled the criteria of bd , a repeat determination should be done 12 h later .
ventilator should be adjusted to provide normocarbia ( paco2 3445 mmhg ) and hyperoxia ( pao2 200 mmhg ) .
if respiratory movements are absent in 10 min and paco2 is 60 mmhg or 20 mmhg over a baseline , apnea can be confirmed . the determination of bd in confirmatory tests as follows : ( 1 ) short - latency sep of median nerve shows that bilateral n9 and ( or ) n13 exist , while p14 , n18 , and n20 are absent ; ( 2 ) eeg shows electrical silence ; and ( 3 ) tcd sonography shows that the blood flows of intracranial anterior and posterior circulation demonstrate reverberating flow , small systolic spike , or absence of blood flow signal .
the reactions of the physicians and families were recorded which meaning believes or unbelieves and the changes of treatment or not .
the chinese criteria of bd diagnoses have been officially published in the national journals which represent the legal status of this evaluation . at the same time , each steps of the evaluation have been already used in the clinical for years .
however , we informed the patients families about the bd evaluation and obtained their consent before evaluations .
the age , time , and money were expressed as a mean  standard deviations ( sd ) .
paired t - test was used to assess the statistical significance of changes in time and money .
all statistical analyses were used spss 19.0 software ( spss inc . , chicago , il , usa ) .
from january 1 , 2012 to october 8 , 2013 , there were 37 patients which were applied for bd evaluation in the neuro icu of beijing tiantan hospital , who were a coma , being ventilated and no spont breathing .
they were 21 males , 16 females , with a mean age of 58.86  12.54 years ( ranging from 37 years to 96 years ) .
all patients were definite coma and excluded of diseases due to drug , hypothermia , and alcohol .
the cause of coma were known as subarachnoid hemorrhage ( sah , 18 patients , 48.6% ) , intracerebral hemorrhage ( ich , 8 patients , 21.6% ) , cerebral ischemia ( ci , 9 patients , 24.3% ) , brain stem tumor ( 1 patients , 2.7% ) , and intracranial infection ( 1 patients , 2.7% ) .
features of the study population bd : brain death ; sah : subarachnoid hemorrhage ; ich : intracerebral hemorrhage ; ci : cerebral ischemia ; sd : standard deviation . before the clinical examination , all patients had normal body temperature ( core temperature > 36c ) and bp ( systolic bp 100 mmhg ) except 1 patient who had low bp .
although 33 patients needed to do apnea tests , only 25 patients did the tests because others could not provide normocarbia ( paco2 3445 mmhg ) and hyperoxia ( pao2 200 mmhg ) .
the mean paco2 after 10 min stopping ventilators was 73.89  11.51 mmhg ( range 60.1098.50 mmhg ) . there were 2 patients who seemed to be recovered in spont breathing .
when the ventilator mode changed to spont mode , patients could remain spont breathing by machine .
all the 2 patients repeated the apnea tests and got the positive results ( paco2 61.6 mmhg and 77.6 mmhg , respectively ) .
confirmatory tests were completed differently because it was only necessary to have 2 positive results of the 3 tests for bd diagnosis .
one patient who had decompressive craniotomy ( dc ) did not complete eeg because there were no places for the electrodes .
twenty - five patients had positive results of eeg , and the positive rate was 100% .
the positive rate of sep was the same as eeg ( 16 patients , 100% ) .
the each part of evaluation results of bd in 37 patients , % ( n / n ) in chinese criteria , repeated tests should be done 12 h after the first evaluation .
complete  means the finishing rate of the test in all patients who had done the test . 
positive  means the positive rate of the test in all patients who had completed the test .
tcd : transcranial doppler ; eeg : electroencephalogram ; sep : somatosensory evoked potential ; bd : brain death .
as we know the evaluation of bd contains several steps , we followed the program one by one .
as we have described above in detail , in all 37 patients , 1 patient was excluded because of low bp .
in all 33 patients , we need to complete one or more tests including the apnea test , tcd , eeg , and sep . the highest selection rate of the test was tcd , and the rate was 89.2% . while the completed rates were higher in eeg and sep than the other two test ( 96.2% , 94.1% , 90.9% , and 80.0% ) .
thirty - three patients were diagnosed bd by criteria of the united states . according to the standards of the united states ,
only 9 patients were diagnosed bd by chinese criteria . as we showed in table 3 , 23 patients had two positive results of ancillary tests
. there were 14 patients who had positive results of apnea test at the same time .
two of them were chose to give up treatments after their families knowing about the bd diagnosis .
that might be the reasons why the diagnose rate were such low in chinese criteria .
the bd diagnostic procedures and positive cases in two criteria , n the positive rate of chinese criteria for bd was 24.3% and the criteria of the united states were 89.2% .
the use of time and money in the usa criteria was obviously fewer than that in chinese criteria ( p = 0.000 ) [ table 4 ] .
compare of the criteria of the united states and china in the practice * p = 0.000 , there were a significant differential between two groups .
but when we did the apnea test again , we confirmed that they were bd . some doctors doubted if the criteria of the united states is right .
the families of patients all believed the bd diagnosis while 8 patients families could not believe that bd was equal to real death .
the mean time was 2.69  2.42 days ( range 110 days ) [ table 4 ] .
in china , the diagnosis of bd and donation of organs are under development . although the chinese criteria were published in the authoritative magazine since 2009 , those were not used widely in the intensive care unit ( icu ) .
are the chinese criteria for bd so difficulty ? can we just use the usa criteria ? in order to answer the above questions , we compared the bd evaluations between criteria of china and the united states in a sequential series of patients in neuro icu of beijing tiantan hospital .
as a neurologist , he or she knew exactly what the irreversible coma was and how to make judgments to the cause of the coma . also , they could do brainstem reflexes accurately
. the pupillary , corneal , and cough reflexes were often tested , and doctors were skilled in checking them .
it should be noted that patient should have normal body temperature ( core temperature > 36c ) and bp ( systolic bp 100 mmhg ) .
one patient did not do the bd evaluation because he could not reach the levels .
as we see , there were 4 patients had blood flow in the middle cerebral artery .
that meant you can not exclude bd even after blood flow found in tcd . and
. the brain condition could not complete tcd which included the poor temporal windows and craniotomy . in 33 patients who planned to have cd ,
eeg to determinate bd had some difficulties because the examination was done in the icu . the environment exits
too many electric inferences . when the sensitivity is increased to 2 v , it will take much time to get rid of inferences .
an apnea test is mandated by law or recommended by professional guidance in many countries .
in fact , the apnea test had some danger that 5 patients were suspended because they became unstable or desaturases in the test .
but the complete rate was 80% that reflected most patients can afford the apnea test .
when the ventilator mode changed to spont , patients could remain spont breathing by machine .
all the 2 patients repeated the apnea tests and got the positive results ( paco2 61.6 mmhg , and 77.6 mmhg , respectively ) .
repeated assessments were chosen in many countries , presumably to minimize the risk of diagnostic errors .
this is contrary to bd criteria of the united states which stipulate that only a single examination is required . in chinese criteria
although the repeat tests increased accuracy , they prolonged the time of diagnoses . in our study , 5 patients did not wait for 12 h for another determination of bd .
we compared the determination of bd in china with that in the united states . in all 37 patients , more patients
were confirmed bd by criteria of the united states than the chinese criteria ( 89.2% vs. 24.3% ) . if the apnea test was positive , the patient can be diagnosed bd . as we showed in table 3 ,
all of the above reasons make the diagnosis of bd by criteria of the united states more quickly , cheaper , and high diagnostic rate . the mean use of time in criteria of the united states was 52.27 min ( < 1 h )
the mean use of time in chinese criteria was 990 min ( 16 h and 30 min ) .
the use of time and money in criteria of the united states was obviously fewer than that in chinese criteria ( p = 0.000 ) . after comparing with criteria of the united states
, can we draw the conclusion that chinese criterion is poorer than criterion of the united states ?
the second reason is that the organ donation is rare in the neuro icu . in our study , there were no cases of organ donation .
the advantage of bd diagnosis is that the families and hospitals can stop unnecessary treatment . yet
, there were also some families who could not believe that bd was equal to real death .
they asked for continuous active treatments . in our study , some patients lived on ventilators for 10 days .
if a patient can not complete apnea test , some ancillary test can be performed to determinate bd . in our study and other studies in china
when the confirmatory tests of these patients are all according with bd , we can not exclude the diagnosis of bd .
although we need accuracy , can these patients be confirmed bd ? or we can use 3 confirmatory tests to take the place of apnea test .
the secondary thing is about the number of confirmatory tests . in order to be more accuracy ,
the bd diagnosis will be difficult to finish in time when organ donations increase in the future . if patients have apnea test , and one confirmatory test can confirm bd , it will be more convenience than now . there are some limitations in our study .
the subjects in the study were most of the patients with cerebrovascular diseases since beijing tiantan hospital is good at the treatment of cerebrovascular diseases .
the subjects we observed were sah , ich , and ci , who were older in age .
we are not sure whether our results can apply to the brain trauma and other neurological diseases . in conclusion
, we observed the application of chinese criteria of bd in 37 patients from neuro icu .
we found that bd evaluations in chinese criteria were safety and feasible . a neurologist could fulfill the tests .
compared with the bd criteria of the united states , chinese criteria were stricter , lower positive rate , more cost in money and time , and more reliable by families and doctors .
each of the two criteria has both advantages and disadvantages . with the more experiences we have in the future
 background : criteria for determining brain death ( bd ) vary between china and the united states . 
 we reported the results of an investigation designed to compare procedures to determine bd in two countries.methods:the latest criteria in the united states were published in 2010 . 
 the latest criteria in china were published in 2009 . 
 we used these two types of bd criteria to evaluate patients who were considered to be bd . 
 the time , cost , and accuracy of the diagnosis were compared.results:from january 1 , 2012 to october 8 , 2013 , there were 37 patients which were applied for bd evaluation in the neurological intensive care unit of beijing tiantan hospital . 
 the cause of coma were known as subarachnoid hemorrhage ( 18 patients , 48.6% ) , intracerebral hemorrhage ( 8 patients , 21.6% ) , cerebral ischemia ( 9 patients , 24.3% ) , brain stem tumor ( 1 patient , 2.7% ) , and intracranial infection ( 1 patient , 2.7% ) . the clinical examinations were done for all of the patients except 1 patient who had low blood pressure . 
 three patients had brainstem reflexes that were excluded from bd . 
 twenty - five patients had apnea tests , and 20 tests were completed that were all positive . 
 confirmatory tests were completed differently : transcranial doppler ( 30 patients , positive rate 86.7% ) , electroencephalogram ( 25 patients , positive rate 100% ) , and somatosensory evoked potential ( 16 patients , positive rate 100% ) . 
 thirty - three patients were diagnosed bd by criteria of the united states . 
 only 9 patients were diagnosed bd by chinese criteria . 
 the use of time and money in the usa criteria was obviously fewer than those in chinese criteria ( p = 0.000).conclusion : compared with bd criteria of the united states , chinese criteria were stricter , lower positive rate , more cost in money and time , and more reliable by families and doctors . 
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