brain stem function but no brain activity

#Brain stem function but no brain activity series#

This lack of blood flow to the brain usually results in widespread cell anoxia and death. Reduction of blood flow to the brain is usually created when the intracranial pressure is greater than the mean arterial pressure, thus lowering the cerebral perfusion pressure to a point that sufficient blood flow into the brain ceases. Regardless of the primary insult to the brain, tissue death occurs from brain anoxia by one of several mechanisms: severe blood hypoxemia (ie, lethal reductions in nutrient or oxygen blood content) severely impaired perfusion (eg, widespread edema, elevation of intracranial pressure the cessation of blood flow to the brain and brainstem) or toxic neuronal injury.Ĭerebral blood flow is particularly important when considering a diagnosis of brain death.

Brain death may be frequently seen as a consequence of aneurysmal subarachnoid hemorrhage, intracerebral hemorrhage or infarct, cardiac arrest, and severe head injury. The cause of brain death itself is variable, and can be a result of traumatic events or numerous medical conditions. 4 Two clinical findings are necessary to confirm this irreparable condition of the brain: coma (with a known cause), and absence of brainstem reflexes. 3īrain death was defined in 1995 by the American Academy of Neurology as the irreversible cessation of function of the brain, including the brainstem. It is also important to understand some neurologic states can mimic brain death. These circumstances must be considered before brain death determination can proceed. Medical conditions possibly complicating the clinical assessments include severe acidosis/alkalemia, body temperature irregularities, drug intoxication, poisoning, neuromuscular blockade, and a locked-in syndrome. The recognition of confounding factors, proper interpretation of appropriate neurologic imaging, and performance of any confirmatory examination and testing should be considered when determining brain death. 2 In general, the declaration of brain death usually requires that the cause of brain injury is known, the irreversibility of the injury is certain, and important neurological signs of brain function are absent. However, despite more than half a century of the general acceptance of brain death as a medical concept, clear consensus regarding brain death determination is still lacking. 1 The rationale for this distinction was that the former represented human existence, while the latter was viewed simply as biological existence. The concept of brain death was first described in the medical literature in 1959, and was an attempt to separate the cessation of meaningful neurological function from the cessation of cardiorespiratory function. The purpose of this report is to provide an overview of apnea testing and discuss issues related to the administration and safety of the procedure. While apnea testing is not new, it still lacks consensus standardization regarding the actual procedure, monitored parameters, and evidence-based safety measures that may be used to prevent complications. A “positive” test is defined by a total absence of respiratory efforts under these conditions. This procedure requires close monitoring of a patient as all ventilator support is temporarily removed and Pa co 2 levels are allowed to rise.

As a consequence, apnea testing is an important component of brain death assessment. The drive to breathe in the setting of an intense ventilatory stimulus (ie, respiratory acidosis) is a critical marker of brainstem function.

#Brain stem function but no brain activity series#

These findings are coupled with a series of confirmatory tests, and the diagnosis of brain death is established based on consensus recommendations.

The key findings in brain death are unresponsiveness, and absence of brainstem reflexes in the setting of a devastating neurological injury. Strong knowledge of neurophysiology and an understanding of brain death etiology must be used to confidently determine brain death. The diagnosis of brain death is a complex process.