375.3 🏥 內科專科考前版

375.3.1 Recent Updates

375.3.1.1 AAN 2023 Consensus (Adult + Pediatric)

  • Combined guideline
  • Standardizes approach across ages
  • Stricter requirements for ancillary tests
  • Emphasis on training + competency
  • Communication with families

375.3.1.2 Updates from 2010

  • More attention to confounders
  • Hypothermia threshold (≥ 36°C)
  • Drug clearance considerations
  • Ancillary test standards

375.3.2 Mechanistic Deep Dive

375.3.2.1 Whole-Brain vs Higher-Brain Criteria

  • US + many: whole-brain (including brainstem)
  • UK: brainstem death
  • Higher-brain (cortex only): proposed but not legal anywhere
  • Different philosophical frameworks

375.3.2.2 Brain Death Maintenance Physiology

  • Loss of hypothalamic regulation
  • Diabetes insipidus (often)
  • Hemodynamic instability
  • Hypothermia
  • Coagulopathy
  • Hyperglycemia

375.3.2.3 Hormone Replacement

  • Vasopressin (DI)
  • Levothyroxine
  • Methylprednisolone
  • Insulin
  • Goals: organ preservation

375.3.3 High-Yield Specialist Points

375.3.3.1 CTA for Brain Death

  • Becoming more available
  • Specific protocols
  • Absence of cerebral perfusion
  • Faster than nuclear scan
  • Increasingly accepted

375.3.3.2 Cardiopulmonary Death After Brain Death

  • Usually occurs days
  • Cardiac arrest follows brain death

375.3.3.3 Cognitive-Motor Dissociation

  • Awareness without behavioral signs
  • fMRI command following
  • “Imagine playing tennis” paradigm
  • EEG-based methods also
  • 15-20% of “vegetative” patients

375.3.3.4 Coma Recovery Scale-Revised (CRS-R)

  • Standardized assessment
  • 6 subscales
  • Distinguishes UWS from MCS
  • Multiple assessments recommended (variability)

375.3.3.5 Vegetative State Misdiagnosis

  • ~ 40% in clinical examination alone
  • Use CRS-R + advanced techniques
  • Repeat assessments

375.3.3.6 Late Recovery from MCS

  • Some recover years later
  • Especially traumatic etiology
  • Less common from UWS

375.3.3.7 Disorders of Consciousness Treatment

  • Limited evidence
  • Amantadine (some benefit in TBI)
  • Sleep cycle regulation
  • Environmental enrichment
  • Sensory stimulation
  • Specialized rehab

375.3.3.8 Apnea Test Risks

  • Hypotension
  • Hypoxia
  • Pneumothorax (from PEEP loss)
  • Cardiac arrhythmia
  • Arrest
  • Have ABG ready, vasopressors

375.3.3.9 Drug Clearance

  • Generally 5 half-lives
  • Check levels if available
  • Some drugs (BZDs in renal/hepatic failure) prolonged

375.3.3.10 Hypothermic Brain Injury

  • Especially post-cardiac arrest
  • Need normothermia for brain death determination
  • Rewarming + 24 hr observation typical

375.3.3.11 Brain Death in Pregnancy

  • Continued maintenance for fetal viability
  • Ethical and legal considerations
  • Case-by-case

375.3.4 Pearls

  • Whole-brain criteria for brain death
  • 3 elements: irreversible coma + absent brainstem + apnea
  • Confounders must be excluded
  • Apnea test: PaCO2 ≥ 60 or ↑ ≥ 20 without breathing
  • Ancillary tests: EEG, cerebral blood flow when needed
  • Spinal reflexes can persist
  • DOC spectrum: coma → UWS → MCS → locked-in
  • CRS-R for assessment
  • Covert consciousness in some “UWS”
  • Brain death maintenance for organ donation
  • Family communication essential