Organ donation..Organ support after brain death

Physiological derangements after brain death are an extension of those which occur with severe brain injury.

Initial dysautonomia and catecholamine release -> labile HT and tachycardias
Subsequent hypotension due to neurogenic decrease in SVR and / or myocardial dysfunction
Neurogenic diabetes insipidus
Non-cardiogenic pulmonary oedema
Hyperglycaemia
Coagulopathy
Poikilothermia

Management includes

a) Ventilatory control:

Optimum ventilation strategy uncertain. Recommended aims:

·PaO2 > 100mmHg

·PaO2:FiO2 > 250

·PaCO2 35 - 45mmHg

·Avoid pulmonary congestion

·Methylprednisone 15mg/kg may improve oxygenation

·Regular routine turning and tracheal toilet

b) Circulatory control:

·Volume replacement - crystalloids tend to pulmonary oedema, starch compounds impair graft function

·Inotrope support . Adrenalin promotes hyperglycaemia, but may reduce acute graft rejection.Dobutamine ineffective.

·Short acting ß-Blocker may be used for significant tachycardias. Clonidine will not work once brain dead.

·Vasopressin 1iU IV bolus + 0.01 - 0.04iU/kg/hour IVI controls diabetes insipidus (V2 receptor) and may lower inotrope requirements (V1 receptor).

Corticosteroid may smooth haemodynamics

c) Metabolic control

·Diabetes insipidus is managed with intermittent dDAVP 2 - 4 ucg q2-6hr IV (acts at V2 receptor only) or a

Vasopressin infusion at 0.01 - 0.04iU/kg/hour (acts at V1 and V2 receptors) to maintain U/O between

0.5 - 3 ml/kg/hr.

·Hyperglycaemia is managed with insulin IVI

·Electrolytes are kept within normal ranges by usual methods.

·Temperature kept 35 - 37C. Prevents left shift of Hb-O2 dissociation curve.

·Sick euthyroid pattern may occur but replacement does not improve haemodynamics.

·Corticosteroid (methylprednisone 15mg/kg) may smooth haemodynamics, reduce transplant immunogenicity and improve transplanted lung function.

·Hormonal optimisation (methylprednisone + vasopressin + T3 or T4) may improve donor transplant rates,

esp cardiac transplant. Recommended in UK based on retrospective analysis in 2003.

d) Renal support

Maintaining haemodynamic and metabolic control, improves donor kidney outcome and reduces graft rejection and recipient mortality.

e) Hepatic support

·Maintaining nutritional support lessens hepatic glycogen depletion. Dextrose and insulin or enteral nutrition.

·Maintaining serum Na < 155mmol/L reduces graft failure.

·Haemodynamic support minimises hepatic ischaemia Determining cardiac

sedationstation