Use of the heart lung machine as a
cell saver
Cell saving versus cell washing
Homologous blood collection for
heart surgery
Post operative chest drainage
collection & treatment for transfusion
Intra operative cell salvage
includes collecting, concentrating and washing shed blood in the operating
room.
Salvage begins when shed blood is
obtained from the operating site and immediately mixed with an anticoagulant (usually 30,000 units of heparin per
litre of 0.9% normal saline or citrated dextrose) near the suction tip.
The anticoagulated blood is stored
in a collection reservoir, where a 120 micron filter removes tissue, clots,
orthopaedic cement and other macro debris, and stores blood for
processing.
A simple push of a button activates
the automatic process. A volume of 400 to 700 mls of blood is pumped into a
spinning centrifuge. The centrifuge force in the bowl captures the red blood
cells and concentrates them. The centrifugal force separates the red blood cell
from the plasma and other waste products. Plasma overflows from the bowl into
the waste bag, taking with it white cells, platelets, free haemoglobin,
irrigation fluids, activated clotting factors and cell debris.
A light sensor detects when the
centrifuge bowl is full of red blood cells (225mls concentrated to a
Haematocrit above 50%), thereby activating the wash cycle. Sterile normal
saline is pumped through the red blood cells within the centrifuge bowl,
washing the packed red cells.
It takes 1-1.5 litres to wash away
the unwanted elements such as soluble activated clotting factors, proteolytic
enzymes, potassium, heparin, red cell debris and free haemoglobin. Orthopaedic
procedures have more debris to remove and therefore require more washing
(usually 1.5-2 litres).
At the completion of the wash cycle,
packed red cells suspended in saline (> 50% Hct) are pumped from the
centrifuge bowl into a reinfusion bag. The washed red cells are reinfused back
into the patient using a 40 micron filter in the usual manner. These processed
red cells contain no clotting factors and no anticoagulants. The entire process
takes less than 10 mins.
Approximately 50% of the shed red
blood cells are saved.
1.
Blood
salvage from operative sites
a)
Cardiotomy
b)
Venting
i)
Concerns
a)
Emboli
(1)
Particulate
(2)
Gaseous
b)
Haemolysis
2.
Concentration
of red cells
a)
Haemoconcentrator
3.
Limited
dilution of potassium
a)
Haemoconcentrator
with NaCl replacement
4.
Residual
blood at end of CPB can be collected and then concentrated and washed by a
centrifugal cell saver prior to reinfusion into patient
Cell saving
with NO washing
Rationale:
Dilution of the returned
blood in the vascular system of the patient makes unwashed drainage safe and
practical
Cell saving
with washing
Rationale:
Unwashed drainage containing
blood is dangerous if given intravenously because of the presence of activated
clotting factors, activated complement and proteolytic enzymes from injured
white cells. Resulting in leukocyte aggregation in lungs (ARDS) and DIC.
1.
Preoperative donation
a)
Safe
& effective
b)
<
1% side effects (which are minor anyway)
c)
Reduction
in use of homologous blood products
d)
Ideal
3—4 units for CABG
e)
?
longevity of platelets & other clotting factors
2.
Pre CPB phlebotomy
a)
Intraoperative
haemodilution by phlebotomy
b)
May
reduce requirement for homologous blood products
c)
Spares
platelets & other blood components from interacting with circuitry
i)
Clinical
studies show inconclusive results on postoperative blood losses & platelet
function
d)
Hct
should be > 0.35 prior to phlebotomy
e)
Dependent
of patient’s size & Hct may remove 1—2 units (500—1000ml)
f)
Accomplished
1) prior to heparinisation using CPD
2) just prior to CPB via venous line
g)
Concern
viz. Left main dx, severe CAD etc
3.
Intraoperative blood salvage
(cell saver)
a)
Blood
lost prior to heparinisation
b)
Blood
lost post protamine administration
c)
Usage
of a CPD or heparinised cardiotomy suction system
d)
Collected
blood is filtered, concentrated (spun) and washed prior to reinfusion
4.
Platelet rich plasma
a)
Harvest
of platelet rich plasma by plasmapheresis prior to CPB
b)
Aspirated
from a large bore cannula in subclavian, jugular or femoral veins
c)
Immediately
after centrifugation (optional)
i)
Red
cells may be returned to maintain Hb levels
ii)
Platelet
poor plasma returned to maintain intravascular volume
d)
Immediately
after termination of CPB & protamine
i)
Platelet
rich plasma is returned to aid in haemostasis
e)
Expensive
f)
Controversial
& inconclusive effects on reducing postoperative blood loss and need for
homologous blood products
g)
Risks
i)
Hypotension
2° hypovolaemia
a)
Treat
(1)
vasopressors
(2)
reduction
in aspiration rate
(3)
colloid/fluid
administration
ii)
Reduced
O2 carrying capacity of blood as manifested
a)
Hypotension
b)
Tachycardia
c)
ST-elevation
d)
Treat
(1)
100
% FiO2
(2)
Stop
aspiration
(3)
Return
rbc/ add homologous blood
(4)
Begin
CPB
iii)
Inadvertent
CPD administration
a)
Hypotension
b)
Treat
(1)
Calcium
(2)
Fluids
iv)
Infection
a)
Maintain
sterile technique
v)
Relative
contraindications
a)
Left
main dx or equivalent
b)
Left
ventricular dysfunction
c)
Anaemia
d)
Thrombocytopaenia?
e)
Heparin
therapy?
f)
Emergent
surgery
·
Blood
collected from both the pleural cavities & the mediastinum can be reinfused
into the patient
·
The
blood collected from these sites does not clot due to defibrination of the
blood in contact with the heart and lungs
·
Blood
from the mediastinum has a lower Hct, higher free Hb, higher platelet count and
a higher fibrinogen content than whole blood
·
Although
autotransfusion of this blood elevates plasma free Hb and haemoglobinuria, no
adverse effect on the renal system, pulmonary, hepatic or any other system
occurs
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