Brain death

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Criteria

  • Known proximate cause of condition
  • Cerebral unresponsiveness
  • Absence of brain stem relexes (see below)
  • Apneic (see below)
  • Irreversible condition (+/- repeat exam in 6hrs)
  • Exclusion of complicating medical conditions:
    • Severe electrolyte abnormalities
    • Acid-base derrangement
    • Endocrine disturbance
    • Hemodynamic compromise, with age-adjusted vital sign "normals" in pediatric patients
    • Drug intoxication/poisoning
    • Core temperature < 32 C (90 F)
    • Locked-in syndrome
    • Guillain-Barre syndrome involving all peripheral and cranial nerves
  • Be aware of hospital or state regulations such as:
    • Two separate clinical exams performed by two different physicians at least one hour apart
    • Agreement of brain death between two physicians documenting findings from exam, apnea testing, confirmatory testing
    • Observation period between clinical exams varies when brain death determined in children < 1 year of age[1]
      • 2 mo - 1 yr, waiting period between exams should be at least 24 hours
      • 7 days - 2 mo, waiting period should be at least 48 hours
      • No reliable criteria for children < 7 days

Brain Stem Reflexes

  • Severe facial trauma may make CN testing difficult
  • Pupils (CN 2 sensory, CN 3 constriction)
    • No response to light (fixed and mid-dilated)
  • Ocular movement (CN 8 sensory, CN 6 lateral rectus)
    • Oculocephalic reflex (positive Doll's Eyes)
      • Eyes should move to maintain forward fixation as head is turned
      • Do not perform if cervical spine injury is suspected
    • Oculovestibular reflex (aka "Cold Calorics")
      • (Irrigation with 60cc cold water to ears on intact tympanic membrane and observe for deviation of eyes/fast beat nystagmus. Allow 5 minutes between either side.
      • Clotted blood or cerumen in auditory canal may influence response to cold calorics
      • Cortex injured but brainstem intact = eyes deviate toward cold ear
      • Brainstem injured = no eye deviation at all
  • Corneal reflex (CN 5 sensory, CN 7 motor/blinking)
    • Drip saline flush into eye
    • Progress to direct stimulation on sclera with gauze if no response above (DO NOT scrape cornea)
  • Pharyngeal (CN 9/10)
    • Gag (tongue blade) or suction.
  • Tracheal (CN 10)
    • Endotracheal suction (In intubated patients only)
  • Spontaneous body movements observed at any point during the brain death exam may represent spinal reflexes, up to ~20%[2]
    • May be difficult to discern from respiratory effort
    • Findings may include pronation-extension reflex, abdominal reflex, flexion reflex, the Lazarus sign, periodic leg movements
    • Should not be misinterpreted as brain stem function
    • Evidence of brain death comes from consistent clinical exam and imaging

Apnea Testing

  • Prerequisites:
    • Clinical Criteria
    • Core temperature >32 C (actual temperature value > 32 varies by institution) with corrected electrolytes
    • > 36.5 C is preferred
    • SBP >90
    • Nl PaCO2 (>40)
    • Nl PaO2 (preoxygenate >200)
  • Test:
    • Check baseline ABG (ensure PaCO2 < 40 mmHg to maximize target PaCO2 rise)
    • Connect pulse ox, disconnect ventilator, place nasal cannula in ET (at carrina), and place on 100% O2 at 6 LPM
    • Physician able to declare brain death (typically neurology/neurosurgery) will observe for respiratory movements
    • Draw ABG at 8 min. Observe for PaCO2 rise >20 mmHg over 8 minutes with no respiratory movement →positive apnea test (supports brain death)
      • Positive test = 20 increase over baseline (typically 60) ensure to blow down CO2 to ~40 to enable 20 mmHg rise. Typical rise is 3 mmHg per minute
  • Considerations
    • Abort the test (reconnect ventilator) if SBP <90 or significant SpO2 desat (can draw ABG at that time, with same criteria as above)
    • Must perform 2 exams 6 hours apart in addition to apnea test

Confirmatory Studies[3]

  • When apnea testing or CN testing difficult
    • Severe facial trauma preventing CN testing
    • High cervical cord injury making apnea testing impossible
    • Hemodynamically too unstable or significant lung injury making apnea testing impossible
  • Diagnostics must be done to evaluate for cerebral blood flow or activity
    • Cerebral angiography, nuclear imaging, CTA, or MRA
    • EEG monitoring

Organ Donation

  • Decisions over suitability of a donor typically are left to established organizations that differ for each hospital
  • General contraindications
    • Any kind of cancer (EXCEPT skin cancers other than melanoma, certain primary brain tumors). Essentially this means only cancers with very low risk of metastasis are acceptable
    • Any kind of systemic infection or communicable incurable disease
    • Active Fungal disease (Cryptoccous, Aspergillus, Histoplasma, Coccidioides, Candidemia, invasive yeast
    • Active Bacterial infection (Tb, sepsis)
    • Viral infections HIV, HTLV, rabies, reactive HbsAg, West nile, SARS, enterovirus, HSV, VZV, EBC etc)
  • The general goals with organ donation are organ preservation by maintaining: 1) Physiologic levels of neuro mediated hormones, 2) Blood pressure, 3) Obtaining Screening labs
  • Pan-hypopituitary state
    • Diabetes insipidus
      • Clinical: DI typically presents with UOP >5cc/kg/hr. Urine Spec Grav: < 1.005, serum Na > 145 or serum osmolality > 305mg/dL
      • Treatment: Frequent Na monitoring. Bolus vasopressin 0.5U IV then drip with goal of 0.5U/h. Titrate to UOP 1-2ml/kg/h
    • Hypothyroidism - 20 mcg T4 IV bolus, then T4 at 10 mcg/hr, which may cause hyperkalemia so administer 10 U regular insulin with 1 amp 50% dextrose before IV bolus
    • Hypoinsulinemia - Insulin drip, titrate to maintain glucose 80-110 with q1 hr checks
    • Hypocortisol, adrenal insufficiency - treatment - 15 mg/kg IV bolus qd empirically
  • Hypotension
    • Place arterial line with goal SBP > 90, MAP > 60
      • If goals are not met. a continuous cardiac index monitor (Vigileo or PICCO) may be indicated. Goals are CI > 2.5 and UOP > 1 ml/kg/hr
      • Consider starting inotropes, to include dobutamine or milrinone
      • If MAP < 60 despite adequate CI, start peripheral pressor (phenylephrine or norepinepherine)
    • Place central line with CVP goals > 5 mmhg
    • Maintain fluids at 1.5-2 ml/kg/hr. Choice of fluids include NS for Na < 155, 1/2-NS for Na 156-165, D5W if Na > 165
  • Screening labs
    • HIV 1/2, HTLV 1 and 2, RPR, Toxoplasma IgG, CMV IgG, EBV IgG, VZV IgG, HSV 1 and 2, Hepatitis A/B/C
    • LFTs, amylase, lipase, CBC, coagulation profile
  • Special Considerations
  • Heart often experiences stunning myocardium secondary to neurogenic sympathetic surge. Often will lower EF with some myocyte necrosis and troponin leak. Order q6hr serial cardiac enzymes, then repeat echo. Very often heart will recover after initial stunning period

See Also

References

  1. New York State Department of Health and New York State Task Force on Life and the Law. Guidelines for Determining Brain Death. November 2011. https://www.health.ny.gov/professionals/hospital_administrator/letters/2011/brain_death_guidelines.htm.
  2. Han S-G, Kim G-M, Lee KH, Chung C-S, Jung K-Y. Reflex Movements in Patients with Brain Death: A Prospective Study in A Tertiary Medical Center. Journal of Korean Medical Science. 2006;21(3):588-590.
  3. J Brady Scott, Michael A Gentile, Stacey N Bennett, MaryAnn Couture and Neil R MacIntyre. Respiratory Care March 2013, 58 (3) 532-538.