Brain death

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Criteria

  • Known proximate cause of condition
  • Exclusion of complicating medical conditions (severe electrolyte, acidbase, or endocrine disturbance)
  • No drug intoxication/poisoning
  • Core temperature >32C (90F)
  • Cerebral unresponsiveness
  • Absence of brain stem relexes (see below)
  • Apneic (see below)
  • Irreversible condition (+/- repeat exam in 6hrs)

Brain Stem Reflexes

  • Pupils (CN 2 sensory, CN 3 constriction)
    • no response to light (fixed and mid-dilated)
  • Ocular movement (CN 8 sensory, CN 6 lat rectus)
    • Oculocephalic reflex (+Doll's Eyes)
      • eyes should move to maintain forward fixation as head is turned.
    • 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.
      • 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)
  • Paryngeal (CN 9/10)
    • gag (tounge blade) or suction.
  • Tracheal (CN 10)
    • endotracheal suction (In intubated patients only)

Apnea Testing

  • Prerequisites:
    • Clinical Criteria
    • Core temperature >32 C (actual temperature value > 32 varies by institution) with corrected electrolytes. > 36.5C is preferred.
    • SBP >90
    • Nl PCO2 (>40)
    • Nl PO2 (preoxiginate >200)
  • Test:
    • check baseline ABG (ensure PCO2 <40mmHg to maximate target PCO2 rise)
    • Connect pulse ox, disconnect ventilator, place nasal cannula in ET (at carina), and place on 100% O2 at 6LPM.
    • Physician able to declare brain death (typically neurology/neurosurgery) will observe for respiratory movements
    • Draw ABG at 8 min. Observe for PCO2 rise >20mmHg over 8 minutes with no respiratory movement -->positive apnea test (supports brain death)
      • Pos test = 20 increase over baseline (typically 60) ensure to blow down CO2 to ~40 to enable 20mmHg rise. Typical rise is 3mmHg per minute
  • Considerations
    • Abort the test (reconnect ventilator) if SBP <90 or sig O2 desat (can draw ABG at that time, with same criteria as above).
    • Must perform 2 exams 6 hours apart in addition to apnea test.

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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.
    • Hypothyroid - T4 20 microgram T4 IV bolus then T4 at 10 micrograms/hr. (This causes hyperkalemia so administer 10U regular insulin with 1 amp 50% detrose before IV bolus)
    • Hypoinsulinemia- Insulin drip, titrate to maintain gluciose 80-110 with q1hr checks
    • Hypocortisol - treatment - 15mg/kg IV bolus qd empirically.
  • Hypotension
    • Place a- line with goal SBP > 90 MAP > 60
      • If goals are not met a continuous caridac index monitor (Vigileo or PICCO) may be indicated. Goals are CI > 2.5 and UOP >1ml/kg/hr start dobutamine/milrinone drip.
      • If MAP < 60 despite adequate CI, start peripheral pressor (phenylephrine or norepinepherine).
    • Place central line with CVP goals >5
    • Maintain fluids at 1.5-2ml/kg/hr. Choice of fluids include NS for Na < 155, 1/2NS for Na 156-165, D5W if Na > 165.
  • Screening labs
    • HIV 1/2, HTLV 1,2, RPR, Toxo IgG, CMV IgG, EBV IgV, VZV IgG, HSV 1-2, Hepatitis A,B,C.
    • LFT's,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

Adapted from One-Legacy