Brainstem death
Definition
- Irreversible cessation of all functions of the brain
- Loss of capacity for consciousness and for ventilation (brainstem)
Criteria for diagnosis of brainstem death
- Apnoeic coma of known aetiology - must exclude metabolic (hyglycaemia, hypothyroid), drug intoxication, hypothermia
- Absent cranial nerve reflexes - pupillary (II, III), corneal (III, V), vestibulo-ocular, pharyngeal (IX, X), bronchial (X)
- Absent motor response to painful stimuli within cranial nerve distribution
- Absence of spontaneous respiration with permissive hypercapnoea (PaCO2 > 8kPa) following oxygenation
Tests should be performed on 2 separate occassions by 2 medical practitioners registered for more than 5 years (and competent in field).
Tests should not be performed by members of the transplant team
(Difficult to perform in brainstem encephalitis, ocular trauma)
Physiological Changes in Brainstem death
- Loss of pituitary function
- Loss of vasopressin / ADH release - diabetes insipidus, hypernatraemia, small brain cells; 4ml/kg/hr urine loss - corrected temporarily with IV dextrose +/- aAVP infusion
- Loss of anterior pituitary hormone production
- TSH loss; hypothyroidis
- Loss of temperature regulation at hypothalamic level
- Hypothermia, exacerbated by loss of motor/metabolic activity - managed by warming
- Coagulopathy
- Disorderd autonomic system
- Initial hypertension - immediate increase in sympathetic activity
- Hypotension from loss of sympathetic vascular tone
