A 25-year-old man sustained a head injury during a motor vehicle accident. He is currently comatose and intubated in the intensive care unit. He has no significant medical problems except for mild asthma. His urine drug screen was negative; however, his blood alcohol level was above the legal limit. He works as a bartender and frequently binges on hard liquor and beer. A non-contrast head CT at the time of admission revealed a hyperdense, extra-axial, space-occupying, right-sided lesion, which was subsequently drained. He was sedated with a propofol infusion, but it was discontinued 12 hours ago.
His temperature is 37 C (98.6 F) , pulse is 80/min, blood pressure is 130/85 mm Hg, and respirations are 18/min. He is currently on volume assist-control ventilation with an FiO₂ of 40%, tidal volume of 500 cc, and PEEP of 5 cm H₂O. He is not triggering the ventilator. The general physical examination is unremarkable except for a hemi-craniectomy along the right side of the head. He is comatose on neurological examination. Cranial nerve and motor responses are absent.
His arterial blood gas analysis shows a pH of 7.42, PaCO₂ of 36 mm Hg, and PaO₂ of 101 mm Hg.
Which of the following is essential in establishing the diagnosis of brain death in this patient?

Question

Quizplus · Accepted Answer

When clinical criteria suggest brain death, the best next step is apnea testing. Patients must be hemodynamically stable with a body temperature > 36 C (97 F), normal pH, and normal PaCO₂/PaO₂ levels. Apnea testing objectively confirms brainstem failure if the patient cannot generate spontaneous breaths or trigger the ventilator in response to elevated PaCO₂ levels > 10 minutes after disabling control mode (Choice E). clinical criteria 11ec193a_9709_2838_853d_197f40e05156_MD0002_00 Patients are first pre-oxygenated with 100% oxygen for 10 minutes using existing ventilatory support, and then mechanical ventilation is discontinued. However, they should continue to passively receive 100% oxygen while the chest and abdomen are observed for spontaneous respirations for approximately 10 minutes. If spontaneous respirations are observed, the apnea test is negative and the patient is not brain dead. A positive test is defined as no spontaneous respirations and requires another clinical brain death examination for confirmation. In addition, repeat ABG must confirm that the PaCO₂ was > 60 mm Hg or that it increased > 20 mm Hg from the baseline ABG. Patients who cannot tolerate apnea testing or have inconclusive results require ancillary diagnostic tests to confirm brain death. (Choice A) The atropine response test involves administering atropine and observing for an increase in heart rate (> 3%). Although the vagal nucleus in the medulla may be one of the last functions lost in brain death, the atropine response test provides a limited assessment and has not been well validated for confirming brain death. (Choice C) Cerebral blood flow testing (e.g., cerebral angiogram or cerebral scintigraphy) is the gold standard test for brain death confirmation, but it is highly invasive and not used routinely as the initial step for diagnosing brain death. Cerebral blood flow testing may be used in patients with an unreliable clinical examination or bedside apnea test. (Choice D) Current guidelines do not recommend EEG with ECI protocol for brain death confirmation, as it is susceptible to excessive artifact from other electrical devices in the ICU that make it less reliable. In addition, EEG is very sensitive to the effects of sedative medications and metabolic derangements, and therefore can be easily confounded by those variables. Educational objective: Brain death can be suggested by clinical criteria (e.g., coma, absent cranial nerve reflexes and motor responses, CT/MRI brain imaging consistent with a devastating CNS event, etc.). Two clinical brain death examinations and apnea testing are recommended and considered appropriate for brain death diagnosis. Every attempt should be made to remove all confounding variables that can interfere with obtaining a reliable clinical examination and bedside apnea test. __________ References: An update on brain death criteria: a simple algorithm with complex questions. (http://www.ncbi.nlm.nih.gov/pubmed/21881464) The diagnosis of brain death. (http://www.ncbi.nlm.nih.gov/pubmed/19881172)

A 25-Year-Old Man Sustained a Head Injury During a Motor