375.4 📋 章末速蚘 Summary

375.4.1 🔑 䞀句話瞜結

Brain death (death by neurological criteria, DNC) = irreversible cessation of ALL brain function including brainstem → legally + ethically equivalent to cardiopulmonary death; AAN 2023 consensus (combined adult + pediatric — latest guideline); three criteria — (1) irreversible coma of known etiology + (2) absent brainstem reflexes + (3) apnea; confounders must be excluded — hypothermia (core temperature ≥ 36°C) + drug intoxication/sedatives (clearance, levels) + neuromuscular blockade (train-of-four) + severe metabolic/electrolyte/acid-base/endocrine disturbance + severe hypotension (SBP ≥ 100 mmHg, vasopressors OK) + adequate ventilation (PaO2 ≥ 200, PaCO2 35-45 baseline); clinical examination components — (1) coma (unresponsive, no purposeful movements, no grimacing, no posturing — spinal reflexes can be present); (2) absent brainstem reflexes — pupillary (bilateral fixed, mid-position or dilated 4-9 mm), corneal, oculocephalic doll’s eyes (NOT done if C-spine concern), oculovestibular cold calorics (no eye movement with 50 mL ice water in each ear, intact TM), gag, cough (tracheal suction), facial grimace, jaw jerk; (3) apnea test — pre-oxygenate 100% × 10 min + confirm baseline PaCO2 35-45 + disconnect ventilator + provide O2 + observe 8-10 min + ABG → positive (confirms apnea): PaCO2 ≥ 60 mmHg OR ↑ ≥ 20 mmHg from baseline with NO respiratory effort; abort if hemodynamic instability/hypoxia/arrhythmia; examinations — 1 in adults (most US states), 2 in children with age-specific intervals (7-30 days: 24 hr; 31 days-1 year: 12 hr; > 1 year: 12 hr); ancillary tests when needed (apnea contraindicated, confounders persist, exam incomplete) — EEG (electrocerebral silence < 2 ÎŒV ≥ 30 min) + cerebral blood flow studies (conventional 4-vessel angio gold standard historically, radionuclide HMPAO, CTA with brain death protocol increasingly used, MR angiography) + transcranial Doppler (TCD — oscillating flow, systolic spikes) + SPECT/PET; spinal reflexes can persist after brain death — Lazarus sign (complex spinal movements), triple flexion, plantar reflex — DO NOT preclude diagnosis; organ donation — DBD (donation after brain death) vs DCD (donation after circulatory death) with separation of declaration from donation + family consent + brain death maintenance (hemodynamic support, hormone replacement levothyroxine/vasopressin/methylprednisolone, glucose control, temperature); communicating with families — clear/compassionate, “brain death = death”, consider religious accommodations (NY, NJ allow); disorders of consciousness (DOC) spectrum — coma (eyes closed, unarousable) → UWS/vegetative state (eyes open + sleep-wake + no awareness + brainstem reflexes intact; persistent 1 mo → permanent 3 mo non-traumatic / 12 mo traumatic) → MCS/minimally conscious state (inconsistent signs of awareness — visual tracking, command following intermittent; better prognosis) → emergence to communication; locked-in syndrome (pseudocoma) — awake + aware + quadriplegic + anarthric + preserved vertical eye movements + blinking + ventral pontine lesion (often basilar artery occlusion); akinetic mutism — awake + no movement/speech + bilateral frontal lesions; covert consciousness (cognitive-motor dissociation, 15-20% of apparent UWS) — fMRI/EEG paradigms show awareness without behavioral signs (“imagine playing tennis”); CRS-R (Coma Recovery Scale-Revised) for standardized DOC assessment; vegetative state misdiagnosis ~ 40% in clinical examination alone; treatment for DOC — limited evidence, amantadine (some benefit in TBI) + sleep cycle regulation + sensory stimulation + specialized rehab。

375.4.2 💊 治療粟芁 (適甚斌 brain death management for organ donation)

  • hemodynamic supportvasopressors (norepinephrine, vasopressin) + fluids + target MAP > 60-70 mmHg
  • hormone replacement (brain death physiology — loss of hypothalamic regulation)vasopressin for DI 0.5-4 units/h + levothyroxine 20 ÎŒg bolus + 10 ÎŒg/h + methylprednisolone 15 mg/kg + insulin glucose control
  • ventilationlung-protective if intent to donate lungs + adequate PEEP
  • temperaturenormothermia
  • DOC treatment limitedamantadine 100-200 mg BID (some benefit in TBI for emergence) + sleep cycle regulation (melatonin) + environmental enrichment + sensory stimulation + specialized neurorehabilitation
  • family communicationbrain death = death; mechanical ventilation temporarily maintains organ function; cultural/religious considerations; ethics consultation if needed

375.4.3 🎯 盧醫垫的考前提醒

  1. Brain death definition: irreversible loss of ALL brain function INCLUDING BRAINSTEM (whole-brain criteria — US, many countries); legally + ethically equivalent to cardiopulmonary death; AAN 2023 consensus latest guideline
  2. Three criteria (memorize): (1) irreversible coma of known etiology + (2) absent brainstem reflexes + (3) apnea (positive apnea test)
  3. Confounders MUST be excluded before brain death determination: hypothermia (core ≥ 36°C) + drug intoxication/sedatives + neuromuscular blockade + severe metabolic/electrolyte disturbance + severe hypotension (SBP ≥ 100 mmHg, vasopressors OK) + severe endocrine disturbance
  4. Brainstem reflexes (ALL must be absent): pupillary + corneal + oculocephalic (doll’s eyes) + oculovestibular (cold caloric) + gag + cough (tracheal suction) + facial grimace + jaw jerk
  5. Apnea test positive (confirms apnea): PaCO2 ≥ 60 mmHg OR ↑ ≥ 20 mmHg from baseline AND NO respiratory effort observed during 8-10 min after disconnecting ventilator + pre-oxygenation
  6. Ancillary tests when needed (apnea contraindicated, confounders persist, exam incomplete): EEG (electrocerebral silence < 2 ÎŒV ≥ 30 min) + cerebral blood flow studies (CTA increasingly used, conventional angio gold standard historically, radionuclide HMPAO, TCD oscillating flow/systolic spikes)
  7. Spinal reflexes can persist after brain death — Lazarus sign, triple flexion, plantar reflex — DO NOT preclude diagnosis; family education important
  8. Disorders of consciousness (DOC) spectrum: coma → UWS (vegetative — eyes open + sleep-wake + no awareness) → MCS (minimally conscious — inconsistent signs) → emergence; locked-in syndrome (pseudocoma — awake + aware + preserved vertical gaze + ventral pontine lesion); covert consciousness (15-20% of apparent UWS — fMRI/EEG paradigms detect awareness)
  9. UWS prognosis: persistent at 1 month → permanent at 3 months non-traumatic / 12 months traumatic; MCS better prognosis than UWS; some recover years later especially traumatic
  10. Organ donation framework: DBD (donation after brain death) vs DCD (donation after circulatory death) — separation of declaration from organ donation procedures + family consent + brain death maintenance (hemodynamic + hormone replacement levothyroxine/vasopressin/methylprednisolone); religious accommodations (NY, NJ allow); consider cultural sensitivity in family communication