What are the types of deceased donors
Heart-beating: Brain stem death
diagnosed
Non-heart-beating: brain stem death cannot
be diagnosed
What are the brain stem
death criteria
•
Pre-conditions
– structural
disease consistent with brain stem death (haemorrhage,
tumour, and infarct) and
Apnoea.
•
Exclusions
– Free of neuromuscular blocking agents (confirmed on nerve
conduction),
anaesthetic agents, drugs, alcohol, metabolic problems
(hypoglycaemia), hypothermia,
Uremia and encephalopathy excluded
•
Clinical tests –
apnoea (despite PaCO2>6.65), corneal reflex, gag reflex, pupillary
reflex, vestibuol-ocular
reflex, oculo-cephalic relex (Doll’s
Eyes).
Tested
twice by two ICU physicians on separate occasions. Other tests EEG, Cerebral angio, brain stem evoked
potentials are not
required.
What are the contra-indications
to donation
•
Infection –
HIV and history of TB.
Even
in presence of systemic sepsis the risk of transmission of
bacterial infection
appears
small.
Transplantation is acceptable if blood
cultures are negative for 72 hours or the organisms is known (along with its sensitivity)
and treated before procurement.
Donors
with serological evidence of past
HBV and HCV
infection may be used for
recipients who are themselves already
infected with
these viruses or immunized against
HBV
•
Malignancy – except
non-melanoma skin cancer and primary brain tumour.
•
Previous
medical problems – Donors with DM or HTN may still donate
as depending on degree of organ damage
•
Dysfunction of
specific organs -
the tests of function in the donor at the time of brain
stem death may
be imperfect predictors of organ function in the recipient:
o
Significant
elevations of creatinine predispose to delayed graft function
o
History
of cirrhosis contra-indicated
liver procurement,
but the values of LFT and PT in donor immediately before
procurement are
imperfect predictors of function
o
Cardiac dysfunction requiring high dose
inotropes or causing
arrhythmia is
a
contra-indication to cardiac Tx
o
DM and pancreatitis
contra-indicated Pancreas Tx.
What are the
physiological consequences of brainstem
death
•
Loss of sympathetic tone leading to
hypotension –
may need inotropes to correct
•
Hypothermia –
warmed fluids, heating blanket
•
Loss of ADH from post-pituitary leading
to DI with
high volume, dilate urine,
hypernatremia and increasing serum osmolality. Treat with
dextrose infusion and
desmopressin infusion
•
Loss of ant. Pituitary hormones leading
to low T4/T4, cortisol deficiency. Infusions of steroids
and T3 have been
used
•
Coagulopathy
related to hypothermia
•
Without
donor maintenance 62% of donors will have cardiac arrest at 24
hours and 90% at
72 hours.
What are the components
of UW solution
•
Organ
preservation is achieved by cold
storage which
reduces energy requirements
•
Organ preservation solutions extend
organ survival in cold storage.
•
The
most commonly used is UW solution, Preservation
solutions contain
o
impermeable solutes (lactobionate,
raffinose and hydroxyethyl
starch) that
minimize cellular
swelling by providing a hyperosmolar
extracellular
environment.
o
Adenosine to
provide precursors for ATP synthesis
o
Allopurinol for
inhibition of Xanthine oxidase in reperfusion injury
o
Glutathione as a
free-radical scavenger
o
Phosphate for
buffering H+ ions.
o
Mg and Dexamethasone
for membrane stabilization.
•
UW solution allows storage of kidneys
for 48 hours, livers and
pancreas for 24 hours and 12 hours for bowel.
•
Heart is preserved in cold
hyperkalaemic cardioplegia solution for up to 4 hours.
•
Lungs are preserved with hypothermia,
inflation and intracellular-type solution such as
Euro-Collins or UW.