Neurosurgery notes/Other specialities/ITU/Random/Brainstem death

Brainstem death

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Ancillary confirmatory tests

General

  • Once brainstem death has been diagnosed, cessation of the heart beat follows within a short period. This has been confirmed and validated in published series.
  • If there is seizure then it is not brainstem death

Who can be tested

  • Age
    • Paeds < 37 weeks
      • Cannot do brainstem testing
    • Paeds > 38 week
      • Have special guidelines
    • Paeds > 2 months to adults any age
  • There must be an identifiable aetiology causing brain damage.
    • This may be intra- or extra-cranial.
  • No reversible cause for absent brainstem reflex
  • The patient must be deeply unconscious
  • The patient must be apnoeic, needing mechanical ventilation.
    • This condition must not be secondary to the effect of sedative drugs of neuromuscular blockade.
    • This may require testing through
      • Nerve stimulator to show intact neuromuscular transmission.
      • Tendon reflexes can also demonstrate intact transmission.

When can you test

  • >6 hrs after last positive brainstem reflex
  • >24 hrs after last positive brainstem reflex, where aetiology primarily anoxic damage

Who can do the test

  • 2 doctors who have held full registration with the GMC > 5 y, one of whom should be a consultant.
    • Neither should be a member of the transplant team.
      • Clinical Leads for Organ Donation can carry out testing and are likely to have significant expertise.
    • None should have a conflict of clinical interest

How many time it should be done

  • Two sets of tests should be performed to remove the risk of observer error.
    • The two doctors may perform the tests together or separately and although no defined time interval has to elapse between the tests, it should be of sufficient duration to reassure the patient’s next-of-kin.
  • 2nd test can be done immediately after the first test
  • The time of death is recorded at the end of the first test indicates brain death.

Exclude

  • Hypothermia
    • Core temperature should be over 34°C for > 24 hrs
  • Sedative and muscular relaxant agents
    • Off for > 24 hrs
    • Use antagonist
      • Flumazenil
      • Naloxone
    • Check blood levels of the drug
      • Midazolam < 10mcg/L,
      • Thiopentone < 5mg/L
    • For muscle relaxant
      • Peripheral nerve stimulation
  • Electrolyte abnormalities
    • Na, K, Mg, PO₄
    • Correct them
    • Use vasopressin for DI if required
  • Hyper/hypoglycaemia
    • Keep between 3-20
  • Hypoxia
    • Keep PaO₂>10
  • Hypercabia
    • Keep PaCO₂ <6.0
  • Potentially reversible circulatory, metabolic and endocrine disturbances must have been excluded as the cause of the continuing unconsciousness.
    • Some of these disturbances may occur as a result of the condition rather than the cause and these do not preclude the diagnosis of brain stem death.

The test

  1. Light reflex
      • Pupils must be fixed in diameter and not responsive to incident light.
      • Cranial nerves II, III
  1. Corneal reflex
      • There must be no corneal reflex (avoid damaging the cornea).
      • Cranial nerves V, VII
  1. Vestibulo-ocular reflexes (Caloric testing)
      • No eye movements occur following the slow injection of at least 50mls of ice cold water over 1 min into each external auditory meatus.
      • Check for any movement of the eyes.
      • Normal reflex is slow phase to the left and fast phase to the right
        • If the cold water is injected to left side
      • Access to the tympanic membrane should be confirmed by otoscopy.
        • Injury or pathology may prevent this test being performed on both sides – this does not invalidate the test.
      • Cranial nerves VIII, III.
  1. Gag/pharyngeal reflex
      • Use a spatula or Yankauer sucker or laryngoscope to stimulate the posterior pharynx.
      • Cranial Nerves IX, X
  1. Cough/tracheal reflex
      • No cough or other reflex should occur in response to bronchial stimulation by a suction catheter being passed down the endotracheal tube to carina.
      • Cranial Nerves IX, X.
  1. Pain reflex in cranial nerve
      • Supraorbital pressure
      • Cranial Nerves V,VII.
      • Reflex limb and trunk movements (spinal reflexes) can be present
  1. Apnea test
      • Hypoxia should be prevented by pre-oxygenation and insufflation of oxygen through a tracheal catheter/nasal cannula
      • Technique
        • FiO₂ of 1.0 for about 10 min,
        • Reduce RR to slowly increase PaCO₂-45 mmHg/6.0 kPa
        • Disconnect pt from the ventilator.
          • In patients with chronic CO₂ retention, or those who have received intravenous bicarbonate, it recommended that PaCO₂ is allowed to rise to above 6.5 kPa.
        • Confirm on ABG but use end tidal PaCO₂ to monitor
      • Check any spontaneous respiration during a minimum of 5 (five) minutes continuous observation following disconnection from the ventilator

No respiratory movements should occur in response to disconnection from the ventilator.

  • Cannot be done in
    • High cervical cord injury affecting C3-C5 causing diaphragmatic paralysis apnea testing is not reliable,
      • Brain stem death will have to be confirmed using absence of other brain stem reflexes and ancillary investigations.

Management

  • Standard medical care must be continued in those in whom brain stem death has not been conclusively established and may be continued after this in order to maintain the condition of organs for donation. This may include maintaining fluid and electrolyte balance or haemodynamic parameters.
  • Initiating mechanical ventilation in those patients thought to have irremediable brain damage, who stop breathing before brain stem death testing can occur, is only justified if it is of benefit to the patient.
    • It is unlawful for this to occur in order to preserve organ function.

Pitfalls in brain death determination

  • Movement of body parts after brain death.
    • May occur as long as 32 hours after brain death.
    • Many are mediated by spinal cord discharges as it undergoes cell death.
    • Documented observations include
      • Facial movements,
      • Finger tremor,
      • Repetitive leg movements,
      • Sitting up.
    • These movements are often repetitive, usually stereotypical, and do not change with changing stimuli.
  • The appearance of breathing.
    • This typically occurs with a ventilator that is set to trigger on detecting respiratory effort.
    • Ventilators may be sensing air movement created by transmission of arterial pulses of the great vessels to the lung or actions of a chest tube.

Distinguishing features of reduced states of consciousness

State
Awareness
Wakefulness
Eyes/visual tracking
Communication
Locked‑in syndrome
Yes, consistent
Sleep/wake cycles
Open eyes, can track objects
Consistently using vertical eye movement
Minimally conscious state
Inconsistent but reproducible
Sleep/wake cycles
Open eyes, can track objects
Inconsistent but reproducible, intelligible words, gestures
Vegetative state
No
Sleep/wake cycles
Open eyes, no visual tracking
None, no command following, random vocalization only
Coma (e.g. anesthesia, brain death)
No
No
No
None

Localising signs

  • Such as cranial nerve lesions may be seen, depending upon the site of any lesion or injury.
  • False localising signs
    • CN3
      • Stretching of the oculomotor nerve over the tentorium cerebelli, usually by herniation of the uncus or another expanding lesion.
    • CN6
      • The abducens nerve, with its long intracranial course, is stretched by swelling.
  • Cardiovascular changes
    • Cushing response
    • Hypothalamic and pituitary failure causes a reduction in thyroid hormone synthesis and secretion, which contributes to the cardiovascular changes,
  • Diabetes insipidus
    • Lack of anti-diuretic hormone
  • Loss of thermoregulation with hypothermia being the usual finding.