Brain death in children: Part II

Determining Brain Death

PURPOSE OF REVIEW

Major complexities exist in the assessment of a patient with a catastrophic neurologic disorder that might have progressed to loss of all brain function. The determination of brain death and initial management of the potential organ donor is one of the major key tasks of the neurologist. This article addresses the potential for errors, mimickers, and uncertainties associated with ancillary tests for determining brain death.

RECENT FINDINGS

Major professional neurologic organizations including the American Academy of Neurology have published guidelines for the determination of brain death in both adults and children. Checklists are now available to assist physicians in the assessment of the patient.

SUMMARY

The clinical diagnosis of brain death in a patient with a catastrophic brain injury is determined by a comprehensive clinical examination that involves at least 25 individual assessments. It requires excluding confounding factors first (to confirm futility), examining the patient carefully with special attention to signs of brainstem function, and, finally, performing an apnea test. Once a patient is declared brain dead, organ donation may proceed after consent is obtained.

Brain death

The diagnosis of brain death should be based on a simple premise. If every possible confounder has been excluded and all possible treatments have been tried or considered, irreversible loss of brain function is clinically recognized as the absence of brainstem reflexes, verified apnea, loss of vascular tone, invariant heart rate, and, eventually, cardiac standstill. This condition cannot be reversed - not even partly - by medical or surgical intervention, and thus is final. Many countries in the world have introduced laws that acknowledge that a patient can be declared brain-dead by neurologic standards. The U.S. law differs substantially from all other brain death legislation in the world because the U.S. law does not spell out details of the neurologic examination. Evidence-based practice guidelines serve as a standard. In this chapter, I discuss the history of development of the criteria, the current clinical examination, and some of the ethical and legal issues that have emerged. Generally, the concept of brain death has been accepted by all major religions. But patients' families may have different ideas and are mostly influenced by cultural attitudes, traditional customs, and personal beliefs. Suggestions are offered to support these families.

Clinical report—Guidelines for the determination of brain death in infants and children: an update of the 1987 task force recommendations

OBJECTIVE

To review and revise the 1987 pediatric brain death guidelines.

METHODS

Relevant literature was reviewed. Recommendations were developed using the GRADE system.

CONCLUSIONS AND RECOMMENDATIONS

(1) Determination of brain death in term newborns, infants and children is a clinical diagnosis based on the absence of neurologic function with a known irreversible cause of coma. Because of insufficient data in the literature, recommendations for preterm infants less than 37 weeks gestational age are not included in this guideline. (2) Hypotension, hypothermia, and metabolic disturbances should be treated and corrected and medications that can interfere with the neurologic examination and apnea testing should be discontinued allowing for adequate clearance before proceeding with these evaluations. (3) Two examinations including apnea testing with each examination separated by an observation period are required. Examinations should be performed by different attending physicians. Apnea testing may be performed by the same physician. An observation period of 24 hours for term newborns (37 weeks gestational age) to 30 days of age, and 12 hours for infants and chi (> 30 days to 18 years) is recommended. The first examination determines the child has met the accepted neurologic examination criteria for brain death. The second examination confirms brain death based on an unchanged and irreversible condition. Assessment of neurologic function following cardiopulmonary resuscitation or other severe acute brain injuries should be deferred for 24 hours or longer if there are concerns or inconsistencies in the examination. (4) Apnea testing to support the diagnosis of brain death must be performed safely and requires documentation of an arterial Paco(2) 20 mm Hg above the baseline and ≥ 60 mm Hg with no respiratory effort during the testing period. If the apnea test cannot be safely completed, an ancillary study should be performed. (5) Ancillary studies (electroencephalogram and radionuclide cerebral blood flow) are not required to establish brain death and are not a substitute for the neurologic examination. Ancillary studies may be us d to assist the clinician in making the diagnosis of brain death (i) when components of the examination or apnea testing cannot be completed safely due to the underlying medical condition of the patient; (ii) if there is uncertainty about the results of the neurologic examination; (iii) if a medication effect may be present; or (iv) to reduce the inter-examination observation period. When ancillary studies are used, a second clinical examination and apnea test should be performed and components that can be completed must remain consistent with brain death. In this instance the observation interval may be shortened and the second neurologic examination and apnea test (or all components that are able to be completed safely) can be performed at any time thereafter. (6) Death is declared when the above criteria are fulfilled.

Differential involvement of the brain in neonatal asphyxia: a pathogenic explanation

Multiple cystic lesions in brain parenchyma supplied by the anterior cerebral circulation is a recognized pattern of cerebral injury associated with hypoxic-ischemic encephalopathy in the term infant. This report presents a series of seven infants (gestational age, 39.3 +/- 2.8 weeks; range, 36 to 44 weeks) who developed multicystic encephalomalacia in the distribution of the anterior cerebral circulation after severe neonatal asphyxia. Cerebral imaging and pathologic studies demonstrate relative preservation of the cerebellum, brain stem, and cerebral structures supplied by the vertebrobasilar circulation. Compared to the vertebrobasilar vasculature, the anterior cerebral vessels in the term infant have dense sympathetic innervation. Asphyxia, a potent sympathetic stimulator, may induce vasoconstriction in the anterior circulation and differentially accentuate the effects of hypoxia/ischemia on cerebral tissue.

Prognostic significance of prehospital cardiac or pulmonary resuscitation in paediatric burns patients

Cardiac or pulmonary arrest at the scene of a house fire can be associated with cerebral anoxia in burn patients, and this may influence further treatment decisions. Our experience with such patients supports an aggressive initial approach to resuscitation in paediatric burn patients with a history of prehospital cardiac or respiratory arrest.

Dissociation of cerebral blood flow, glucose metabolism, and electrical activity in pediatric brain death. Case report

A 2-month-old infant demonstrated clinical brain death 48 hours after suffering a closed head injury accompanied by cardiac arrest. Two nuclear cerebral blood flow (CBF) studies demonstrated normal perfusion. On the 11th day following injury, cerebral electrical activity ceased and a normal glucose metabolic gradient between gray and white matter was documented on positron emission tomography. Autopsy revealed widespread necrosis with mononuclear cell infiltrates throughout all cerebral cortical layers. Nine children have previously been described with clinical brain death, electrocerebral silence, and evidence of CBF by radionuclide scan. The dissociation between cerebral electrical activity and blood flow may be explained by an increase in cranial volume allowed by the expansile neonatal skull, preventing both intracranial hypertension and a reduction in perfusion pressure. The persistence of glucose metabolism may be associated with the presence of inflammatory microglial cells in the ischemic cortex. The authors conclude that persistence of CBF and glucose metabolism in brain-dead children may not indicate neuronal survival. If repeated neurological examinations with or without electroencephalography support the diagnosis of brain death, the presence of CBF and glucose metabolism should not alter this conclusion.

The function of the hypothalamo-pituitary axis in brain dead patients

In order to find out the function of the hypothalamo-pituitary axis in brain dead patients, pituitary and hypothalamic hormone concentrations were measured and several anterior pituitary releasing tests were carried out in 39 brain dead patients. In addition, cerebral blood flow measurements were simultaneously performed. In almost all cases, the blood concentration of pituitary and hypothalamic hormones were above the sensitivity of the assay. Anterior pituitary releasing tests indicated that efficient functions of the hypothalamus were severely suppressed, while the normal secretory mechanism of the anterior pituitary was partially preserved in brain dead patients. Histological changes of hypothalamic neurons varied from barely detectable ghost cells to nearly normal cells even in the same case. Although, the remaining circulation seemed not to be sufficient enough to maintain integrated hypothalamo-pituitary function, as shown by the examinations of cerebral blood flow, the presence of hypothalamic hormones in the systemic circulation suggests that these hormones were released and carried from the hypothalamus by minimal flow which is preserved even after the diagnosis of brain death.

Brain-death criteria currently used by pediatric intensivists

A survey was done to identify how pediatric intensivists determine brain death in children. Forty-nine pediatric intensive-care units (PICUs) were surveyed. The questionnaire explored the following areas: 1) clinical and confirmatory studies performed, 2) types of physicians involved, and 3) reevaluation intervals. Thirty-four centers responded to the questionnaire. Sixty-nine percent were children's hospitals, and 94% were university affiliates. The mean number of PICU beds was 17, with a mean admission rate of 890 patients per year, and the mean mortality rate for these units was 6%. There was general agreement on the sufficiency of clinical examination to determine cortical and brain-stem function. All the pediatric intensivists noted that a positive apnea test, absent cephalic reflexes, fixed and dilated pupils, and no motor response to pain were reliable signs of brain death. Radionuclide cerebral-flow scan and EEG were the confirmatory tests routinely used. Most physicians (77%) felt a second clinical examination was required within 12 to 24 hours. The opinion of more than one physician, one of whom was a neurospecialist, was required in 80% of the surveyed institutions.

[Diagnosis of brain death in the newborn and the child]

The purpose of this article was to sum up the problems raised by diagnosis of brain death in the child through a review of the literature. The clinical and paraclinical criteria of the diagnosis are considered in terms of the respective value and complementarity of different examinations. The fact that organ removal has become increasingly frequent in the child requires a rapid and reliable determination of the irreversibility of brain damage. The guidelines set up after conferences in which American authors participated to reach a consensus opinion relate to the child's age, the etiology, of the coma and the results of various paraclinical examinations. The diagnostic value of these examinations is assessed and the limitations of the various approaches are considered, particularly as regards certain etiologies in the newborn. It is suggested that it would be useful to inquire into the different diagnostic means used in France with respect to this difficult problem. Finally, the ethical and moral problems raised by some recent practices such as organ removal in anencephalic patients are discussed.

The effects of the falling therapeutic and subtherapeutic barbiturate blood levels on electrocerebral silence in clinically brain-dead children

In a retrospective study at a large children's hospital, we identified 92 children who had received barbiturates that were simultaneously discontinued at the time they were being evaluated for brain death in the presence of electrocerebral silence and clinical brain death by physical exam. Of these 92 children, 67 had barbiturate levels that were monitored from initial therapeutic or subtherapeutic levels. Repeat EEGs were obtained in 76 patients, and in all electrocerebral silence and clinical brain death (by exam) persisted despite the lower barbiturate levels. The study suggests that therapeutic and subtherapeutic barbiturate levels have no effect on the outcome of children who fulfill the criteria for brain death.

Anencephaly: clinical determination of brain death and neuropathologic studies

Twelve liveborn anencephalic infants were serially examined to determine if they would meet our clinical criteria for whole brain death within a 7-day period: Protocol 1 infants (6) received intensive care including intubation from birth; and Protocol 2 infants (6) received intensive care during the period in which death was imminent. Brain death was determined by absence of brainstem function, including loss of all cranial nerve responses and sustained apnea (PCO2 greater than 60 torr) for 48 hours with confirmation of findings by an outside consulting child neurologist. The initial examinations of these 12 infants revealed spontaneous movements and startle myoclonus (12), suck, root, and gag responses (7), increased tone (8), deep tendon reflexes (9), absent pupillary responses (9), absent oculocephalic and corneal responses (6), absent auditory/Moro responses (7), and nonvisualization of the optic nerve (8). Mild depression of neurologic function occurred during the first several days of life; subsequently, the infants' responses were easier to elicit and more sustained. Only 2 infants met the clinical criteria for brain death. Neuropathologic findings indicated that observed complex motor responses were not based upon cortical activity because no infant had a normally-formed cerebrum. Brainstem neuronal activity may have accounted for these motor responses in some patients but even at this level neurons were scanty or absent. Our findings suggest that, although rare, clinical brain death can be determined in liveborn anencephalic infants; ophthalmologic and otologic developmental abnormalities may confound examination of cranial nerve function; and absence of cortical neurons supports the widely held opinion that these infants do not experience sensation.

Anesthetic management of neonatal cardiac transplantation

Anesthetic management of thirteen neonatal heart transplant patients is reviewed. Donor management, preoperative, operative and early postoperative management is discussed. Ten of 13 patients in this series survived the operation and appear to be developing normally.

Massive brain stem necrosis in the human neonate: presentation of three cases with review of the literature

In neonates suffering hypotensive or asphyxial episodes, the brain stem is particularly vulnerable to selective neuronal necrosis. Typically, the pattern is one of generalized neuronal necrosis within well-defined brain stem cranial nerve nuclei, or random neuronal degeneration within the reticular formation. More recently, isolated cases of severe partial or total cystic necrosis of the brain stem reticular formation have been recorded. The pathogenesis is poorly understood at this time, but may be similar to the less severe (but more often recognized) nuclear or focal neuronal loss. Three infants are presented in which severe necrosis of the brain stem occurred. In each, the clinical setting was one of sudden and abrupt worsening of the patient's cardiovascular status.

Hypoxemia and hemodynamic changes during the hypercarbia stimulation test

The hypercarbia stimulation test is a valuable technique to document the absence of brainstem responsiveness to elevated levels of carbon dioxide (PCO2); however, its application has been limited by concern that hypoxemia may induce cardiovascular instability. We investigated hemodynamic and oxygen (PO2) changes in 19 patients: group 1 (17 patients) had no spontaneous ventilations at PCO2 values ranging from 37-129 torr; group 2 (2 patients) had spontaneous ventilations at less than 38 torr. Group 1 was separated into 2 subgroups: A (10 patients) with PO2 greater than 153 torr and B (7 patients) with PO2 less than 80 torr. Hemodynamic changes (less than 10% variation in baseline pulse and blood pressure) occurred in 9 of 10 patients in group 1A and all patients in Group 1B. Mean differences in pulse and blood pressure changes between these groups were not significant; therefore, pulse and blood pressure changes are not predictive of hypoxemia and hypercarbia is not necessary to induce spontaneous ventilation in patients with intact medullary function.