WBR0234

Author	[[PageAuthor::Mugilan Poongkunran M.B.B.S [1]]]
Exam Type	ExamType::USMLE Step 3
Main Category	MainCategory::Inpatient Facilities
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::A 73 year old male is in ICU on ventilator for three days after cardiac arrest. Still he completely relies on ventilator support. He is unresponsive to verbal and painful stimuli. His vitals are BP: 110/60 mmHg, pulse 64/min and temperature is 99F. After discussing with the family, you plan to take him out of ventilator. You wanted to confirm the diagnosis of brain death with second test within a short observational time. Which of the following would you document to determine that the patient meets the criteria of brain death?]]
Answer A	AnswerA::Absent somatosensory evoked potential upon median nerve stimulation
Answer A Explanation	[[AnswerAExp::Correct : Somatosensory evoked potentials (SSEPs) and brainstem auditory evoked potentials (BAEPs) also have limited utility as ancillary tests. In SSEPs, the bilateral absence of the parietal sensory cortex responses in response to median nerve stimulation is supportive of brain death.]]
Answer B	AnswerB::Absent brainstem auditory evoked potentials to auditory stimuli with unpreserved cochlear response
Answer B Explanation	[[AnswerBExp::Incorrect : The absence of brainstem responses to an auditory stimulus (Waves III to V) in the presence of preserved cochlear response (Wave I) is required for a brainstem auditory evoked potential result to support the diagnosis of brain death. It activates a discrete sensory pathway and extends the electrophysiologic interrogation beyond the EEG to areas of interest in the brainstem.]]
Answer C	AnswerC::EEG with non-specific wave forms
Answer C Explanation	[[AnswerCExp::Incorrect : A flat electroencephalogram (EEG) was a component of brain death.]]
Answer D	AnswerD::Absence of respiratory drive for 5min off the ventilator
Answer D Explanation	[[AnswerDExp::Incorrect : The apnea test is performed after all other criteria for (core temperature ≥36ºC, SBP ≥100 mmHg, PaCO2 35 to 45 mmHg, absence of hypoxia, and euvolemic) brain death have been met). The test is not valid in patients who chronically have high PaCO2 values (CO2 retainers) and in cases of neuromuscular paralysis or high cervical spinal cord lesions. In a positive apnea test there is no respiratory response to a PaCO2 >60 mmHg or 20 mmHg greater than baseline values and a final arterial pH of <7.28. Rise in paCO2 usually happens 10-20mins off ventilator.]]
Answer E	AnswerE::An intermittent cerebral circulation on cerebral Doppler or MR angiography
Answer E Explanation	[[AnswerEExp::Incorrect : Tests demonstrating absent blood flow to the brain are generally accepted as establishing whole brain death. Doppler or MR angiography usually demonstrates absent blood flow at or beyond the carotid bifurcation or Circle of Willis.]]
Right Answer	RightAnswer::A
Explanation	[[Explanation::Brain death implies the permanent absence of cerebral and brainstem functions. There are a number of prerequisites before one can begin considering a patient "brain dead" . • Clinical or neuroimaging evidence of an acute CNS catastrophe that is compatible with the clinical diagnosis of brain death, ie, the cause of brain death should be known. • Exclusion of complicating medical conditions that may confound clinical assessment (no severe electrolyte, acid-base, endocrine, or circulatory (ie, shock) disturbance). • No drug intoxication or poisoning, which may confound the clinical assessment. • Core temperature >36ºC (97ºF). • Normal systolic blood pressure >100 mg Hg. Vasopressors may be required. Educational Objective: References: ]]
Approved	Approved::Yes
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