1.
Definition
a)
Serum
antibodies that become active at decreased body temperature
b)
Produce
agglutination or hemolysis (via complement) of r.b.c.
c)
Are
directed towards antigens on the r.b.c.
2.
Characteristics
a)
Thermal
amplitude
i)
Temperature
below which the Ab become activated
ii)
As
temperature drops below this thermal amplitude, the Ab activity increases
exponentially
iii)
This
activity reverses as rewarming occurs
b)
Titre
i)
High
titre of Ab are clinically more significant
c)
Complement
activation with hemolysis can only occur if the temp is cold enough for
agglutination but still warm enough for complement activation
d)
Agglutination
may or may not be reversible
e)
Heparinisation
& dilution of blood by CPB circuit offer little/no protection against
agglutination
3.
Laboratory testing
a)
Often
see agglutination when doing routine X-matching at room temp
b)
Initially
screen at 4°C — if negative no further screening required; if positive require
to determine thermal amplitude
c)
Thermal
amplitude measured by subjecting samples to several different temperatures (eg
4°C, 15°C, 22°C & 37°C)
d)
—
eg, positive results at 4°C & 15°C but negative at 22°C & 37°C indicate
a thermal amplitude between 15°C & 37°C
4.
Development
a)
May
be transient associated with viral infections [postpone surgery for several
weeks]
b)
May
be chronic eg not associated with recent viral infection
5.
Clinical signs
a)
Rarely
seen as usually only see agglutination well below body temp
b)
Acrocyanosis
of digits, tip of nose & ears
6.
Signs on CPB
a)
Undiagnosed
in hypothermic CPB
i)
Haemoglobinuria
ii)
Intravascular
agglutination [more likely due to inadequate heparinisation]
iii)
Agglutination
in cold blood cardioplegia circuit
iv)
May
proceed to multiorgan damage due to gangrene from prolonged vascular occlusion
with r.b.c. agglutination
7.
CPB management
a)
Most
important technique — use of normothermic or mildly hypothermic CPB at
temperatures above the thermal amplitude
b)
Warm
blood cardioplegia
c)
Cold
crystalloid cardioplegia (induction achieved with warm crystalloid cardioplegia
to wash all rbc out of the myocardium)
d)
Septal
temperature monitoring of reduced myocardial temp
e)
Warming
of fluids, blood etc
f)
Warming
inspired gases
g)
Plasmapheresis
with high thermal amplitude patients
h) Use of arterial filters
i) Bleeding propensity?
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