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

Transcranial Doppler Sonography in Pediatric Neurocritical Care: A Review of Clinical Applications and Case Illustrations in the Pediatric Intensive Care Unit

Transcranial Doppler sonography is a noninvasive, real-time physiologic monitor that can detect altered cerebral hemodynamics during catastrophic brain injury. Recent data suggest that transcranial Doppler sonography may provide important information about cerebrovascular hemodynamics in children with traumatic brain injury, intracranial hypertension, vasospasm, stroke, cerebrovascular disorders, central nervous system infections, and brain death. Information derived from transcranial Doppler sonography in these disorders may elucidate underlying pathophysiologic characteristics, predict outcomes, monitor responses to treatment, and prompt a change in management. We review emerging applications for transcranial Doppler sonography in the pediatric intensive care unit with case illustrations from our own experience.

Scintigraphy as a confirmatory test of brain death

The concept of "brain death" was introduced to medicine in the second half of the 20th century, when technological advancements began to allow sustaining cardiorespiratory functioning of the body in the absence of brain function. Although physicians generally agree that a patient can be declared brain dead when the loss of brain function is total and irreversible, different approaches have been taken to define what constitutes brain death. A thorough clinical examination is essential to the diagnosis. The role of confirmatory tests differ among countries in the world but generally are indicated when a specific part of the clinical examination cannot be performed or is deemed unreliable. Under certain circumstances, confirmatory tests can be used to shorten the clinical observation. Of the confirmatory tests recommended by the American Academy of Neurology and the American Academy of Pediatrics, cerebral scintigraphy is a safe, reliable, and widely available alternative. Once the radiopharmaceutical is properly compounded, cerebral scintigraphy can be performed rapidly and can be interpreted in a straightforward manner. It is tolerant of metabolic aberrations and pharmacologic intoxicants. It is not affected by electrical interference, and the presence of skull defects or scalp trauma do not preclude its performance. The radiopharmaceuticals used in scintigraphy have no deleterious effects on potential donor organs. Cerebral radionuclide angiography has been highly sensitive. Either cerebral planar scintigraphy or cerebral scintitomography with Tc-99m hexamethylpropyleneamineoxime also are highly sensitive, but, in addition, appear to be 100% specific.

Electrocerebral silence with preserved but reduced cortical brain perfusion

Isoelectric electroencephalogram in conformance with clinical findings is strongly suggestive of brain death. In clinical practice, isoelectric electroencephalogram in not-brain-dead patients is rarely seen. We report on a 53-year-old patient who suffered ischaemic encephalopathy after cardiopulmonary arrest. He had residual brainstem function with sufficient spontaneous breathing and evidence of cerebral blood flow on single photon emission computed tomography scan, but his electroencephalogram was isoelectric. He survived this condition for more than 7 weeks. This case demonstrates that isoelectric electroencephalogram can not be equated with brain death, and that in prognostic assessment both clinical findings and supportive technical methods are mandatory.

Care of the potential pediatric organ donor

Although all of this information may create the impression that caring for a potential organ donor is an exceedingly complex task, in the authors' experience, this often is not true, and much energy can--and should--be devoted to the care of the bereaved family. Of crucial importance are the early recognition of brain death and the consequent radical switch of the treatment goal from preservation of the patient's brain and life to preservation of organs for the lives of others. Care for the donor is the natural extension of care for a critically ill or injured patient. During the foregoing discussion, the authors had to stress the absence of sound evidence on many points. Because many reports originate from transplant centers dedicated to a specific organ, gaining a comprehensive view on management options in the ICU further is hampered. Thus, this situation leaves another field in which investigations originating from pediatric intensivists could provide evidence urgently needed to make optimal choices. The next decade should see the thyroid hormone controversy solved by at least one controlled prospective study and the differential applicability of inotropic, vasoactive, or fluid-centered strategies. It seems self-evident that only graft survival and related parameters can form adequate endpoints for future studies.

Evaluating brain death with positron emission tomography: case report on dynamic imaging of 18F-fluorodeoxyglucose activity after intravenous bolus injection

A dynamic positron emission tomography (PET) study of the head was performed over 1 hour after the intravenous bolus administration of 18F-fluorodeoxyglucose (18F-FDG) to a 18-year-old patient with the clinical diagnosis of brain death. This dynamic PET study was performed on the seventh day after a severe posttraumatic closed-head injury. No intracerebral uptake or retention of tracer was noted, consistent with a diffuse absence of brain metabolism. A small amount of tracer was noted to slowly rise over time within the sagittal sinus, indicating that visualization of sagittal sinuses on technetium 99m-diethylene-triaminepentaacetic acid planar images could provide a falsely negative scintigraphic evaluation for the presence of brain death. It is concluded that PET FDG imaging may be a useful technique in evaluating patients for brain death.

The physiological changes associated with brain death--current concepts and implications for treatment of the brain dead organ donor

The profound physiological disturbances associated with severe intracerebral pathology have long been recognized. These changes have also been described in the brain dead potential organ donor but have only been studied since the early 1980s. Physiological disturbances in the brain dead organ donor result in a diffuse vascular regulatory injury and a diffuse metabolic cellular injury. The net result of these changes is an inexorable deterioration of all organs and eventual "cardiovascular death" of the patient. This paper reviews these physiological changes and the effect they may have on solid transplantable tissues, and discusses the management of brain dead organ donor with regard to these changes. Current concepts of brain death and how they may affect the interpretation of the observed physiological changes are also reviewed.

Effect of sudden episodic intracranial hypertension on the electroencephalogram in a child with head injury

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