15.12 Brainstem Death

Question 1

A 20-year-old patient who satisfies the criteria for brainstem death has been accepted as an organ donor.
a) List the main adverse cardiovascular changes associated with brainstem death. (5 marks)

Answer 1

1&raquo_space; Brainstem ischaemia.

2&raquo_space; Catecholamine release
causing hypertension;
tachycardia;
increased systemic vascular resistance
and pulmonary vascular resistance
(causing pulmonary oedema);

myocardial ischaemic damage and necrosis;
other organ vasoconstriction
and consequent damage.

3. > > Reflex baroreceptor-
   mediated bradycardia.

4&raquo_space; Progression of brainstem ischaemia
and infarction and foramen magnum herniation
results in loss of vasomotor centres
and spinal cord sympathetic outflow.

5&raquo_space; Ischaemia of the pituitary
results in diabetes insipidus.
Intravascular depletion contributes
to cardiovascular instability.

6. > > Vasodilatation, bradycardia, asystole.

Question 2

b) What are the physiological goals (with values) required to ensure optimisation of this donor? (7 marks)

Answer 2

> > PaO2 greater than 10 kPa.

> > PaCO2 5–6.5 kPa.

> > pH greater than 7.25.

> > MAP 60–80 mm Hg.

> > CVP 4–10 mm Hg.

> > Cardiac index greater than 2.1 l/min/m2.

> > Central venous oxygen saturation greater than 60%.

> > SVRI 1800–2400 dyne s/cm5/m2.

> > Temperature 36–37.5°C.

> > Blood glucose 4–10 mmol/l.

> > Plasma sodium less than 150 mmol/l.

> > Urine output 0.5–2 ml/kg/h.

Question 3

c) Outline the measures and drugs that may be used to achieve these goals. (8 marks)

Answer 3

Respiratory:
» Recruitment manoeuvres.

> > Lung protective ventilation strategy
(PEEP 5–10 cm H2O,
peak inspiratory pressure 25 cm H2O,
tidal volume 6–8 ml/kg).

> > Keep fraction of inspired oxygen ideally below 0.4.

> > 30–45 degree head-up positioning
ensure adequate cuff inflation;

continue airway suctioning,
regular position changing and physiotherapy.

Cardiovascular:
» Site central venous catheter
(ideally right side) and
arterial line (ideally left side) for
monitoring and therapy.

> > Cardiac output and urine output
monitoring to direct fluid management –
excess fluid to be avoided.

> > Commence vasopressin infusion
if vasopressor required, wean off
catecholamine infusions.

> > Commence dopamine or dobutamine
if goals not met with vasopressin.

Endocrine:
» Methylprednisolone.
» Insulin infusion.
» DDAVP or vasopressin if
excessive urine output due to diabetes insipidus.

Haematological:
» Physical and pharmacological
prophylaxis of thromboembolism.

Metabolic:
» Maintain normothermia
using active warming if necessary.