Brain death: determination with brain stem evoked potentials and radionuclide isotope studies

Ancillary investigations for death determination in infants and children: a systematic review and meta-analysis

PURPOSE

We performed a systematic review and meta-analysis to determine the diagnostic test accuracy of ancillary investigations for declaration of death by neurologic criteria (DNC) in infants and children.

SOURCE

We searched MEDLINE, EMBASE, Web of Science, and Cochrane databases from their inception to June 2021 for relevant randomized controlled trials, observational studies, and abstracts published in the last three years. We identified relevant studies using Preferred Reporting Items for Systematic Reviews and Meta-Analysis methodology and a two-stage review. We assessed the risk of bias using the QUADAS-2 tool, and applied Grading of Recommendations Assessment, Development, and Evaluation methodology to determine the certainty of evidence. A fixed-effects model was used to meta-analyze pooled sensitivity and specificity data for each ancillary investigation with at least two studies.

PRINCIPAL FINDINGS

Thirty-nine eligible manuscripts assessing 18 unique ancillary investigations (n = 866) were identified. The sensitivity and specificity ranged from 0.00 to 1.00 and 0.50 to 1.00, respectively. The quality of evidence was low to very low for all ancillary investigations, with the exception of radionuclide dynamic flow studies for which it was graded as moderate. Radionuclide scintigraphy using the lipophilic radiopharmaceutical 99mTc-hexamethylpropyleneamine oxime (HMPAO) with or without tomographic imaging were the most accurate ancillary investigations with a combined sensitivity of 0.99 (95% highest density interval [HDI], 0.89 to 1.00) and specificity of 0.97 (95% HDI, 0.65 to 1.00).

CONCLUSION

The ancillary investigation for DNC in infants and children with the greatest accuracy appears to be radionuclide scintigraphy using HMPAO with or without tomographic imaging; however, the certainty of the evidence is low. Nonimaging modalities performed at the bedside require further investigation.

STUDY REGISTRATION

PROSPERO (CRD42021278788); registered 16 October 2021.

Relationships Between Resting Energy Expenditure and Transcranial Doppler Measurements in Patients With and Without Brain Death

Introduction Brain metabolism deteriorates during brain death, suggesting that cerebral metabolic measurements could serve as a prognostic factor. The application of transcranial Doppler can be useful in evaluating patients evolving to brain death. Resting energy expenditure is lower than expected in patients with brain death, and this is caused by the decrease in cerebral blood flow and consequently lower oxygen supply. The primary aim of this retrospective study is to investigate the early metabolic changes in patients with clinical criteria of brain death and examine if these changes are related to a gradual decrease in blood flow velocities in the middle cerebral artery. Methods All consecutive patients from 1st June 2018 to 30th April 2022, admitted to the ICU with brain injury and a GCS ≤ 8, were included retrospectively in the study. Patients were allocated into two groups: Group A, patients without clinical signs of brain death (n = 32), and Group B, patients with brain death (n = 34). In each group, three sets of metabolic measurements were performed concomitantly with cerebral blood flow velocities using transcranial Doppler (a) upon admission to the ICU, (b) once hemodynamic stabilization was obtained, and (c) 48 hours after their hemodynamic stabilization or when brain death was confirmed by clinical criteria. Resting energy expenditure (REE) measurements were performed using a metabolic computer. Cerebral blood flow velocities were measured after a period of 30 min using a 2-MHZ 2D ultrasound probe. Results Brain-dead patients had a significant decrease in their metabolic parameters as the cerebral blood flow velocities recorded with the transcranial Doppler deteriorated, (REE Group A = 1667.65 ± 597 vs Group B = 1376.12 ± 615, p = 0.05 and REE predicted Group A = 113.19 ± 44.9 vs Group B = 93.29 ± 41.5, p = 0.066 for measurement 1; REE Group A = 1844 ± 530.9 vs Group B = 1219.97 ± 489, p < 0.001 and REE predicted Group A = 124.38 ± 39 vs Group B = 81.35 ± 30.4, p < 0.001 for measurement 2; REE Group A = 1750.97 ± 414, p < 0.001 and REE predicted Group A = 116.38 ± 19.2 vs Group B = 56.09 ± 19.6, p < 0.001 for measurement 3). Multiple stepwise regression analysis revealed a strong relationship between age, the worsening of the blood flow velocities pattern, and the decrease in REE (multiple R = 0.264, F = 5.55, p = 0.009). Furthermore, a statistically significant correlation was found between temperature and REE (correlation coefficient = 0.500, 0.674, 0.784 for measurements 1, 2, and 3, respectively, and p < 0.001 for all measures). Conclusions In brain-dead patients, the gradual decrease in cerebral blood flow leads to a decrease in REE as well as thermogenetic control. These changes can be detected early after the patient's admission to the ICU.

Diagnosis of brain death

Brain death (BD) should be understood as the ultimate clinical expression of a brain catastrophe characterized by a complete and irreversible neurological stoppage, recognized by irreversible coma, absent brainstem reflexes, and apnea. The most common pattern is manifested by an elevation of intracranial pressure to a point beyond the mean arterial pressure, and hence cerebral perfusion pressure falls and, as a result, no net cerebral blood flow is present, in due course leading to permanent cytotoxic injury of the intracranial neuronal tissue. A second mechanism is an intrinsic injury affecting the nervous tissue at a cellular level which, if extensive and unremitting, can also lead to BD. We review here the methodology of diagnosing death, based on finding any of the signs of death. The irreversible loss of cardio-circulatory and respiratory functions can cause death only when ischemia and anoxia are prolonged enough to produce an irreversible destruction of the brain. The sign of such loss of brain functions, that is to say BD diagnosis, is fully reviewed.

Specificity of Radionuclide Brain Blood Flow Testing in Brain Death: Case Report and Review

Brain blood flow tests with diffusible radiopharmaceuticals are often done as an ancillary test in brain death (BD). We report a case of an infant with absent brain blood flow on an anterior planar image despite persistent breathing and extensor posturing. We reviewed the literature from 1980 to 2008 using MEDLINE and PubMed to determine the sensitivity and specificity of these tests in the diagnosis of BD. Search terms were any combination of: brain death; and single photon emission computed tomography (SPECT), radiopharmaceuticals, technetium Tc 99m exametazime, or organotechnetium compounds. The sensitivity of absent brain blood flow on planar imaging for clinically confirmed BD is 119/153 = 77.8% [95% CI 70.5%—83.7%]; and the specificity is 41/41 (100%) [95% CI 92.6%—100%]. For clinically confirmed BD, the sensitivity of SPECT is 107/121 (88.4%) [95% CI 81.4%—93.1%], and specificity is 12/12 (100%) [95% CI 78.4%—100%]. For contrast angiography confirmed BD, the sensitivity of SPECT is 34/34 (100%) [95% CI 91.2%—100%]; the specificity could not be estimated as there were no patients without clinical BD having both tests. Case reports emphasized the possibility of isolated posterior-fossa blood flow, which would not be detectable using non-diffusible radiopharmaceuticals, or without a lateral view using diffusible agents. We conclude that patients having an ancillary radiopharmaceutical brain blood flow test for BD should have anterior and lateral views without exception. Larger numbers of patients both with and without BD (but with severe brain injury) must be studied to determine the sensitivity and specificity of these tests.

Tc-99m-HMPAO SPECT in the diagnosis of brain death in children

BACKGROUND

The diagnosis of brain death is based on both clinical and laboratory findings. However, diagnosis of brain death is still contentious and reliable tests are required. Early recognition and declaration of the diagnosis is the main goal, which is important for discontinuation of life support and organ donation for transplantation. In order to achieve this goal, competent diagnostic procedures should be performed. In this paper the authors review the diagnosis of brain death in eight children from different age groups, with an emphasis on factors concerning the reliability, use and appropriate application time of Tc-99m-HMPAO single photon emission computed tomography (SPECT) in early diagnosis in infants and newborns.

METHODS

Eight patients who fulfilled the clinical criteria of brain death underwent Tc-99m HMPAO SPECT and electroencephalogram (EEG) monitoring.

RESULTS

All patients had electrocerebral silence on EEG recordings. Six patients showed lack of perfusion in cerebrum in their first SPECT, however, newborns needed a second image for a confirmed diagnosis.

CONCLUSION

In infants, SPECT has a high reliability for confirmed diagnosis of brain death; however, in newborns the application time is important for an accurate diagnosis.

99mTc-HMPAO SPECT in the diagnosis of brain death

OBJECTIVE

To evaluate the effectiveness of single proton emission tomography (SPECT) with 99mTc-HMPAO in the diagnosis of brain death (BD).

DESIGN

Prospective study in comatose and brain-dead patients.

SETTING

Neurologic ICU.

PATIENTS AND METHODS

Fifty comatose patients (age range: 10 days-75 years) were submitted to SPECT study. In 21 of them (42%) reversible factors (e.g., influence of drugs affecting the central nervous system) were present. Thirty-eight patients were clinically brain-dead, while the remaining 12 were tested both in pre-terminal conditions and after the clinical onset of BD.

INTERVENTIONS

Brain SPECT following i.v. injection of 99mTc-HMPAO (300-1100 MBq), using a 4-headed gamma-camera (20 min, 360 degrees, 88 images).

MEASUREMENTS AND RESULTS

All patients tested in pre-terminal conditions showed preserved brain perfusion. Two of them had flat EEGs despite the absence of any reversible cause of coma; three patients survived, but remained in persistent vegetative states. SPECT confirmed the diagnosis of BD in 45 out of 47 patients (95.7%), clearly showing the arrest of brain perfusion (picture of "empty skull"); in two clinically brain-dead children (aged 10 days and 12 months, respectively) weak perfusion of the basal ganglia, thalamus and/or brain stem was still present, precluding the diagnosis of BD; both of them died a few days later.

CONCLUSIONS

Our results confirm the reliability of SPECT in the diagnosis of BD. A problem arises about its effectiveness in brain-dead children, but this seems to be a matter of definition of BD and cerebral viability, rather than a limit of SPECT.

[The use of EEG in the diagnosis of brain death in France]

Scientific and modern conception of brain-death is rather recent, thus making possible organ transplantations. During the past three decades clinical criteria for brain-death have been defined. Electroencephalography (EEG) appears to be a complementary tool as it permits brain-death assessment. In France laws enforced respectively in 1968, 1978, 1991 and 1996 provide a framework for brain-death evaluation before organ transplantation and include EEG recording. Advantages and pitfalls of EEG in the diagnosis of brain-death are considered as this technique may be unreliable. Only evoked potential recordings can allow assessment and confirmation of brain stem death, which is a mandatory criterion. We recommend simultaneous EEG and either brain stem auditory or somatosensory evoked potential recordings to strengthen clinical criteria of brain-death and definitely prove it using objective electrophysiological criteria.

Reversibility of severe brain stem dysfunction in children

The very popular concept of brain death can lead to a defeatist attitude when confronted by a patient with severe brain stem dysfunction. This problem is compounded by the constant controversy surrounding the establishing of criteria to determine brain death. Many young doctors tend to accept the precondition of irreversibility as being any condition that is not explicitly listed in the examples of potentially reversible conditions. In children, however, with compressive brain stem dysfunction, decompressive surgery can lead to a reversal of the dysfunction. In the last three years, we have had the opportunity to observe 5 children who were deeply comatose and apnoeic. All were suffering from compression of the brain stem and experienced dramatic return of brain stem function following emergency decompression. The implications of these findings on the therapeutic attitude towards compressive brain stem lesions in children are exposed. In children with severe brain stem dysfunction, and no evidence of brain stem destruction, decompressive surgery should be undertaken before a diagnosis of brain death is considered.