An 18-year-old man is on mechanical ventilation after sustaining severe head trauma in a motor vehicle collision. The patient is unresponsive to various stimuli. Blood pressure is 108/60 mm Hg and heart rate is 110/min. After monitoring the patient for 24 hours, the physician decides to do a bedside assessment of brain death. Which of the following can be observed in a patient with brain death?

Question

An 18-year-old man is on mechanical ventilation after sustaining severe head trauma in a motor vehicle collision.  The patient is unresponsive to various stimuli.  Blood pressure is 108/60 mm Hg and heart rate is 110/min.  After monitoring the patient for 24 hours, the physician decides to do a bedside assessment of brain death.  Which of the following can be observed in a patient with brain death?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d553_84a9_bc81_61e18807212f_MD0003_00 This patient who sustained severe head injury and has been unresponsive to various stimuli for 24 hours may have sustained brain death. Brain death is defined as the irreversible cessation of all cerebral and brainstem activities and is a legally acceptable definition of death. In adults, the most common cause of brain death is traumatic brain injury. Brain death is a clinical diagnosis. Although specific criteria may vary by country or state, essential components for making the diagnosis of brain death typically include: Clinical criteria: evidence (eg, history, clinical, neuroimaging) of a devastating cause and absence of confounding factors (eg, hypothermia, intoxication, paralytics) Neurologic examination: coma and absence of all cerebral and brainstem activity, including cranial nerve reflexes (ie, brainstem reflexes) such as pupillary light reaction and oculovestibular reaction (Choices C and D). Motor responses originating in the brain, including purposeful movement, facial grimacing, and decerebrate/decorticate posturing, should also be absent. In contrast, movements originating in the spinal cord (eg, deep tendon reflexes such as the monosynaptic patellar reflex) may still be observed even if brain death is present. If the neurologic examination is consistent with brain death, the patient can be removed from the ventilator for an apnea test. A positive apnea test confirms brain death by documenting an absent respiratory response (ie, nonfunctioning medullary respiratory centers) to a PaCO₂ >60 mm Hg (or >20 mm Hg above baseline) and a final arterial pH <7.28 (Choice E). Sometimes additional confirmatory tests are used. ₂ confirmatory tests (Choice B) Atropine administration primarily increases heart rate by blocking the effects of the vagus nerve (ie, parasympathetic stimulation) on the heart. In brain death, vagal activity is already lost due to absent brainstem and cranial nerve function; therefore, additional vagal blockade (eg, atropine) typically has little effect on heart rate. Educational objective: Brain death, an irreversible loss of all brain function, is a clinical diagnosis based on clinical criteria and neurologic examination. Essential findings include coma, absent cranial nerve reflexes and brain-originating motor responses, and apnea. Movements originating in the spinal cord (eg, deep tendon reflexes) may be present. References: Diagnosis of brain death. (http://www.ncbi.nlm.nih.gov/pubmed/21577338) The diagnosis of brain death. (http://www.ncbi.nlm.nih.gov/pubmed/19881172) Performing the brain death examination and the declaration of pediatric brain death. (http://www.ncbi.nlm.nih.gov/pubmed/31073455) Ancillary studies in evaluating pediatric brain death. (http://www.ncbi.nlm.nih.gov/pubmed/31073456)

An 18-Year-Old Man Is on Mechanical Ventilation After Sustaining Severe