Determination of Brain Death

219 Determination of Brain Death



Teresa L. Smith Jacobs, Thomas P. Bleck


Determination of death by neurologic criteria is a clinical diagnosis. After certain prerequisites are met, there are three essential components to the determination: irreversible coma or unresponsiveness, absence of brainstem reflexes, and apnea. Before the diagnosis is made, it is essential to rule out alternative causes for the patient’s neurologic status, including hypothermia, drug-induced coma, and severe metabolic disarray.



image Prerequisites


Determination of death can be made in patients who continue to have cardiac function during mechanical ventilation in the appropriate clinical scenario. A clear irreversible cause must be known based on history, brain imaging, or cerebrospinal fluid examination. Determination of death by neurologic criteria cannot be made in patients with a temperature below 36°C or in those who may have drug intoxications or poisoning without a confirmatory study indicating the absence of intracranial blood flow. If neuromuscular junction blocking agents have been administered, electrical stimulation should be performed to document the presence of transmission at the neuromuscular junction. Severe acid-base, electrolyte, or endocrine abnormalities also cannot be present.



image Unresponsiveness


The examination shows that the patient has no eye movements or motor response to verbal or noxious stimulation, with the exception of spinally mediated responses. Standard points of pressure application for administration of noxious stimuli are nailbeds, supraorbital nerve, and temporomandibular joint.1



image Absence of Brainstem Reflexes



Pupillary Response


Pupillary responsiveness should be assessed using a bright flashlight. Using an ophthalmoscope allows for magnification of the iris and pupil so that even a subtle response can be detected. Pupils are usually mid-position (4-6 cm in diameter); rarely, they may be more dilated if spinal sympathetic pathways are intact.



Facial Sensation and Motor Response


A very gentle stimulus such as a wisp of cotton should be gently touched to the cornea of each eye individually. We prefer to use a small squirt of saline from the plastic containers used for saline administration during airway suctioning, as saline will not harm the cornea. In patients with a diagnosis of death by neurologic criteria, no blink will be induced. There can be no grimace to painful stimuli or jaw reflex.



Gag and Cough Reflexes


Patients being examined for a determination of death by neurologic criteria will all be on ventilatory assistance. The gag response can be difficult to determine in patients with endotracheal tubes in place. The endotracheal tube itself should not be maneuvered to stimulate a gag response, as this could lead to tracheal damage; a tongue blade should be used instead. Cough in response to deep bronchial suctioning should be sought. Absence of these responses is required for a determination of death by neurologic criteria.



Assessment of Eye Movements



Cervico-Ocular Reflexes (“Doll’s-Eyes Maneuver”)


This maneuver is only performed in the absence of cervical instability. With the eyes held open, the head should be briskly turned from side to side (mid-position to 90 degrees), looking for any eye movements. If an endotracheal tube is in place, it should be moved together with the head movements to avoid tracheal damage or unplanned extubation. No eye movements occur in patients with a diagnosis of death by neurologic criteria. The term doll’s eyes refers to the expected horizontal movement in the direction opposite to the head movement, indicating that the brainstem centers for conjugate horizontal gaze are functional, but the cerebral cortex is not controlling them. However, the likelihood of inaccurate use of this term is so great that it should be avoided.



Vestibulo-Ocular Reflexes (“Cold Calorics”)


Once the absence of the cervico-ocular reflex is determined, or in circumstances in which it cannot be tested owing to cervical instability, caloric testing should be performed. First, the tympanic membranes are examined for perforations and to ensure no obstructions are present. The caloric test is sufficiently important, however, that it should proceed when death by neurologic criteria is being proved even if a perforation is present. The head of the bed should be elevated to 30 degrees. Ice-cold water, 50 mL, should be placed in a syringe. Soft tubing connected to the syringe (for instance, from a butterfly intravenous line) should be inserted into the external auditory canal, and the water irrigated into the ear while the patient’s eyelids are held open. In cases of coma with intact brainstem pathways, the eyes should deviate toward the side of the cold water instillation. Absence of any eye movement will be present in a case of death by neurologic criteria. The eyes should be scrutinized for 1 minute after the cessation of icewater irrigation. After 5 minutes, the identical procedure should be repeated for the opposite ear.

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Jul 7, 2016 | Posted by in CRITICAL CARE | Comments Off on Determination of Brain Death

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