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408
of the blood refrigerator and its general use. The installation of solar-powered refrigerators is
expensive because it requires skilled labor. However, once correctly installed, solar-powered
blood refrigerators are relatively cheap to maintain. They may also have a freezer section
for storing ice packs, but not for the storage of plasma products. Solar-powered equipment
is useful, but its hold-over time is dependent on the quality of the insulation and, except in
areas with plenty of sunshine, its eciency is limited. Nonetheless, despite their limitations,
solar-powered refrigerators are storing blood in remote, rural communities with no access to
the national electricity grid. Moreover, improvements in solar technology design are on the
horizon.
Medical Laboratory Technology: Volume 1
Power Supply
Voltage regulators (stabilizers)
Severe voltage uctuations in the mains power supply occur in some countries. Voltage
uctuations greater than 15% might damage the electronic components of cold chain
equipment, notably the compressors and motors. The local electrical engineer should advise
if the uctuation exceeds 15%, thus requiring a voltage regulator. A voltage regulator or
stabilizer eliminates eects of voltage uctuation on the power line feeding the cold chain
equipment, i.e., the cold chain equipment draws power through the voltage regulator,
which is normally ed between the power source and the cold chain equipment in order to
ensure a consistent power supply to the compressor. In doing so, any power uctuations are
neutralized by the regulator and a constant power supply reaches the cold chain equipment.
Voltage regulators are therefore necessary to protect sensitive electronic and electrical
equipment such as the compressor from eects of power uctuations.
Stand-by generators
All blood bank refrigerators, freezers, cold rooms and freezer rooms should be connected
to a stand-by electricity generator. Stand-by generators are designed to generate electricity
using petrol or diesel fuel. They are connected to the main electricity supply unit, may be
manually started or automatically switched on when there is a power failure. Ideally, standby generators should have an automatic transfer switch, which turns on the generator when
a power failure occurs.
Generator location and security
A generator should be positioned so that it does not create a re hazard. Typically, it should
be located in a separate building or weatherproof enclosure. The fuel tank should be isolated
and should be surrounded by a low wall or an earth bank to prevent fuel spills from spreading.
Both the generator and the fuel tank should be located in a secure compound to prevent theft.
The fuel ller cap should be locked and the fuel line protected so that it cannot be tampered
with. Fire extinguishers capable of extinguishing fuel oil, engine and electrical res should
be ed close to the generator fuel tank. The type and size of the generator to select and
purchase is a very important issue. The following points need to be taken into account:
• the number of items of equipment to be serviced by the generator.
• the starting and running currents of each piece of cold chain equipment.
• the altitude and ambient temperature where the equipment is to be located.
• if the generator is to run continuously on full power, a generator with a higher energy
output will be required.
• the type of fuel used: diesel-fuelled machines are more robust than petrol.
• the type of cooling for the generator: air-cooled methods are beer than water-cooled
methods.
Collection and Processing of Blood for Transfusion
409
Emergency power supply
Hospital blood banks are generally on the same emergency stand-by generator as the other
critical departments of the hospital such as operating rooms and intensive care units (ICUs).
It is necessary to ensure that most, if not all of the cold chain equipment is wired to the standby emergency generator power source. Stand-alone blood banks require their own standby generators. In some situations, a generator is the only source of power for blood bank
equipment. However, in this section we are assuming that the energy source for the blood
bank equipment is the main energy grid and, therefore, the alternative energy source is a
generator or an alternative site to store blood in an emergency.
Alternative site: It may be necessary to identify other storage sites for blood in an
emergency, i.e., in the event of a long power failure. Depending on the cause or location of
the power failure, it may be necessary to move the equipment to another location within the
hospital where power is available. It may even be necessary to nd a hospital department or
site which already has a stand-by generator as an alternative storage area, such as the ICU.
Temperature monitoring devices: There are many dierent types of temperature monitoring
devices presently in the market. Devices that enable the recall of data are critical in the quality
monitoring of the temperature of blood components in blood cold chain equipment.
Plasma thawers: A plasma thawer achieves a uniform and quality standard of defrosted
plasma for transfusion.
Platelet Agitators
Platelet concentrates are harvested from whole blood by centrifugation or during platelet
aphaeresis. Platelet concentrates are suspended in about 60 mL of plasma. The packs are
continually agitated in a platelet agitator in a room with an ambient temperature between
20–24°C. Incubators are needed if the laboratory is air-conditioned in order that temperatures
are maintained within the desired range. The recommended type is a atbed agitator with
horizontal or vertical agitation, as this ensures no platelet clumping. The key operational
factors of the agitator are the number of strokes per minute (ideally 65 to 75) and the amplitude
of each stroke (ideally 3.6 to 4.0 cm). Platelet agitators are essential in the blood bank as they
ensure proper storage of platelets for transfusion.
Platelet agitators, integrated into an incubator, are also available. The incubator maintains
temperature between 20–24°C and is ed with temperature monitoring devices to ensure
that the temperature is maintained within this range. These devices comprise alarm systems
for motion failure, and temperature display and recording devices for a permanent record of
temperatures reached. Platelet incubators are ideal where there is no air-conditioning in the
laboratory.
Miscellaneous Equipment and Supplies
The laboratory also requires other smaller equipment and supplies to facilitate its functions.
These include:
• Blood collection bags
• Haemostatic clamp (Figure 16.8): This resembles a pair of needle-nosed pliers with a
locking clamp. The haemostat characteristically has long handles and small clamping
pliers that can be held in place by the locking mechanism. The locking mechanism is
typically a series of interlocking teeth; a few on each handle allow the user to adjust the
clamping tension of pliers.
• Plasma separator
• Blood collection monitor (spring balance to weigh the amount of blood collected)
• Ice chests
• Supplies for blood drawing (phlebotomy)
410
• Glassware for preparing and storing reagents
• Volumetric glassware
• Analytical balance
• Dropper boles
• Pasteur pipees
• Water bath
• Desk lamps and magnifying mirrors
• Lighted view box with heat lamps (for red cell typing)
• Hand gloves
• Plastic sealer
Medical Laboratory Technology: Volume 1
reagentS
Reagents for use in the blood transfusion laboratory are available from many commercial
companies. A list of suppliers has been provided in the appendix. However, they are expensive
and many laboratories cannot aord to purchase them in developing countries. These can be
easily prepared in the laboratory with proper care, provided technicians are commied to
prevent contamination and adhere to their quality control measures. The blood grouping
sera retains their potency for 1–2 years when stored at 1–6°C. Antibodies in gamma globulin
(IgG) solution, stored at 4°C, can be used for 20 years. IgM antibodies appear to be less stable.
If commercial reagents are used, one should follow their instructions and discard reagents
after their expiration date.
To prevent bacterial contamination, sera stored at 1–6°C requires some sort of bacteriostatic
agent such as 0.1% sodium azide, which in a nal concentration of 0.01% prevents bacterial
growth. Higher concentration (above 0.3%) has been shown to impact immunohaematological
results. Reagent antisera can be stored at 20°C and as such do not require the addition of any
bacteriostatic agent and retain their potency for many years. Repeated thawing and freezing
is not recommended. Take out the required quantity. After thawing, invert the container
several times before use. The antibodies are usually concentrated in the lower portion of
the frozen sera and may be aached to the ice crystals. Antisera containing human albumin
should not be frozen, but should be stored at 1–6°C.
Antisera
Antisera for use as laboratory reagents may be obtained from individuals (patients or donors)
whose serum contains high-tiered antibodies. It is preferable to obtain serum rather than
plasma in the following way:
• Bleed the donor into a sterile container without anticoagulant.
• Place the container at 37°C for one hour in order to ensure good clot retraction.
• Leave the cloed blood in the refrigerator (1–6°C) overnight in order to allow the
absorption of cold autoagglutinins onto the red cells.
• Centrifuge the container and aspirate the serum into a second sterile container.
Blood grouping reagent sera can also be obtained from plasma when a donor comes for
plasmapheresis. The method of obtaining serum from plasma is described here:
• Centrifuge the anticoagulated blood at 500 G for 15 min.
• Recover the plasma into a second sterile container and return the red cells to the donor
(plasmapheresis). Take 15 mL of plasma and add 15 mL of a solution containing 5.5 g
of calcium chloride (CaCl2.6H2O) and 1.6 g of magnesium chloride (MgCl2.6H2O) in 100
mL of sterile water.
• Place the mixture at room temperature or at 37°C for 15 min.
• Centrifuge the resulting serum at 500 G for 8 min to clarify the serum.
• Recover the serum into a third sterile container.
Collection and Processing of Blood for Transfusion
411
Note Serum obtained by this method of adding excess calcium to neutralize the anticoagulant
(citrate), may contain residual brin or precipitate of the calcium complexes. These might
interfere with the observation of red cell agglutination reactions.
Reagent red cells
Red cells used as laboratory reagents (A, cells, A2 cells, В cells, О cells, screening cells and
control cells) are all stored in the refrigerator at 1–6°C, usually in modied Alsever’s solution.
Alsever's solution
Trisodium citrate (dehydrate) 8.0 g
Dextrose 19.0 g
Sodium chloride 4.2 g
Citric acid (monohydrate) 0.5 g
Distilled water (q.s.) 1000 mL
One volume of this solution is added to one volume of blood.
When stored in the way described, the reagent red cells are usually suciently reactive for
3–4 weeks, although their antigenic and serological reactivity gradually decreases during this
time. It is, therefore, desirable to monitor the reactivity of the red cells at regular intervals.
Antihuman globulin is available commercially and should be purchased from a reliable
supplier. Laboratory preparation of this reagent is not recommended.
preparation of Blood componentS
Most medical laboratory technologists are not involved in the preparation of blood
components in the blood bank. Rather, they are involved in performing blood grouping, blood
typing, cross-matching, identication of undesirable antibodies, and other activities more
immediately related to providing blood components to patients. In the present discussion
we shall provide a general idea of the preparation of blood components, but the details are
obtained from the training programs run by the blood bank.
Clinical Significance of Using Blood Components
Selective transfusion of specic blood components is preferable to the routine use of whole
blood, since the specic fraction can be administered, thus reducing the risk of circulatory
overload and thereby allowing for the ecient treatment of many patients from a single
donation (Table 16.2).
Table 16.2 Commonly used blood components for transfusion
Commonly used blood
components
Whole blood 400–500 m L ( l unit) Massive blood loss*
Packed cells 140–180 mL (70–80% Hct) Symptomatic anaemia*
Fresh frozen plasma 140–180 mL All coagulation factors
Platelets 300 mL (aphaeresis or pooled) Thrombocytopaenia or platelet
*Must be ABO compatible
Quantity Clinical condition
Clinically signicant coagulopathy
present (no platelets)
dysfunction
412
The collection of blood components was made possible by the development of sterile
collection bags with integral tubing as well as by technical advances in high-speed
temperature—controlled centrifugation. It is now possible to process from a single whole
blood donation these components—RBCs (or packed cells), platelets, leukocytes, leukocytepoor (reduced) red cells, plasma and cryoprecipitate as well as plasma, derivatives such as
albumin, factor VIII concentrate and factor II, VII, IX and X concentrates.
Medical Laboratory Technology: Volume 1
Whole blood
Whole blood is the anticoagulated blood where the cloing process is prevented by the use of
the anticoagulant. It has two major components, the liquid component, (which is the plasma)
and the cellular component (which contains the red cells, white cells, and platelets). Each
of these components is useful and used for dierent kinds of transfusion therapies. Whole
blood, by broad denition, is that which is taken from the donor, with none of the various
components removed. In a standard donation, the whole blood contains 450 mL of blood
and 63 mL of CPD. A 10% margin of error is permied for the amount of blood collected.
Various components of blood are collected from the whole blood. If the unit contains less
than 300 mL of blood, it is usually not issued as whole blood although it can be used for
transfusion purposes if collected in a proportionately reduced volume of anticoagulant.
Other blood components should not be made from low volume units.
Whole blood is collected by a phlebotomist or nurse from a healthy donor. The blood
is collected in an anticoagulant solution with or without the addition of nutrients such as
glucose (CPD) or adenine (CPDA). Immediately after collection, blood should be stored in
a refrigerator in the range of 1 to 6°C. The expiration date, after phlebotomy, for CPD is
21 days while for CPDA; it is 35 days. Whole blood collected into heparin must have an
expiration date not exceeding 48 h after phlebotomy. Proper storage conditions are essential
if the survival time of stored red cells is to be optimized. Stored blood undergoes many
biochemical changes and that have contributed to dening the maximum storage time. For
the transportation of whole blood, specially designed blood transport boxes should be used.
The refrigerant recommended for most shipments is wet ice in leak-proof containers, such
as plastic bags. Wet ice from commercial ice-making machines is satisfactory. Super-cooled
cubed ice, canned ice or dry ice should not be used for shipping or storing whole blood or red
cells, as they can create very low temperatures, which may cause red cells in their immediate
vicinity to freeze and undergo haemolysis. Blood shipped by air might freeze if transported
in an unpressurized storage compartment.
Whole blood is indicated when a patient has blood loss severe enough to cause symptoms of
hypovolaemia (i.e., when restoration of blood volume aains the same degree of importance
as restoration of actual cellular elements. In general, there is lile justication for the routine
use of whole blood for transfusion. If all of the constituents of blood are required clinically,
these constituents are provided more eectively by the judicious combination of components
than by a unit of stored whole blood in which the labile contents are reduced in number
or quality. Whole blood is contraindicated for patients with severe chronic anaemia, who
compensate for reduced red cells through an increase in plasma volume. These patients do
not need the plasma in whole blood and might develop transfusion-associated circulatory
overload. This volume overload is more likely to occur in patients with kidney failure or preexisting heart failure. Each unit of whole blood given to an individual weighing 70 kg (155
lb) should increase the haematocrit 3–5% and the haemoglobin 1–1.5 g/dL. This increase may
take several hours to become apparent.
Collection and Processing of Blood for Transfusion
413
Red blood cells (red cell concentrates or packed cells)
If the volume of the plasma is reduced from the whole blood, the resultant uid is rich in
red cells and often referred as ‘packed cells’. It is used in treating patients with symptomatic
anaemia. There are several advantages in the use of RBCs over whole blood. It decreases the
risk of circulatory overload, the incidence of transfusion reactions from donor antibodies is
reduced, the volume of anticoagulant and electrolytes is reduced, and in addition, each blood
donation used as components can serve the needs of more than one recipient.
Units intended for use as RBCs should be collected in blood collection units with integral
transfer containers. On a routine basis, blood may be allowed to sediment at 4°C in a
refrigerator. This is perhaps the most inexpensive way of geing packed cells. The separation
usually takes about an hour. Alternatively, depending on the availability of facilities, whole
blood may be centrifuged in a high-speed refrigerated centrifuge equipped with a swinging
bucket for 5 min at 4100 rpm (5000G) at 4–5°C. Following sedimentation or centrifugation,
the plasma is expressed into the transfer container and the two containers (primary pack and
transfer pack) are separated by sealing and then cuing the integral tubing in such a way
that neither pack will be contaminated (i.e., it remains a closed system). This process can be
undertaken at any time before the expiration date of the blood.
Addition of a second preservative solution to the separated RBCs is recommended for
increased viability of the red cells. This addition should take place as soon as possible and no
later than 24 h after phlebotomy. Addition can be achieved by collecting blood into a primary
bag containing CPD with multiple satellite bags. One of the satellite bags contains 100 mL of
additive solution that consists of saline, dextrose, mannitol and adenine that can be expressed
onto the cells after separation.
Single units of whole blood may be used as RBCs by using a sterile transfer container and
aseptically inserting the cannula of the transfer container into the outlet site of the bag of
blood and then expressing the plasma into the container; however, this is not recommended.
If the procedure is used, it should be remembered that the unit has been entered, and is
therefore open to possible contamination and must be transfused as soon as possible.
While removing the plasma in preparing packed cells, the technician must bear in mind
that 25% of the plasma citrate should be left in the cells in order to ensure optimal red cell
survival. This means that the haematocrit value cannot exceed 80% and that the blood still
ows through an infusion set.
Red blood cells must be stored at 1–6°C after the plasma has been separated. If a ‘closed’
system has been used (without entering the unit) in the preparation of the cell concentrate,
the same expiration time as for the whole blood applies. The shelf-life of packed cells with
additive solution is 42 days.
The critical haemoglobin level that indicates a need for transfusion is generally considered
to be 7 g/dL or lower, except for patients with heart, lung or cerebral vascular disease. The
increase of haemoglobin and haematocrit levels following the transfusion of one unit of
packed red cells is same as that for whole blood (1 g/dL increase), although increases will
be seen more quickly with RBC transfusion because the adjustment in blood volume is less.
Washed red cells
Buy-poor washed red cells are desirable for patients at risk for severe allergic or anaphylactic
transfusion reactions. To prepare this, red cells are rst separated without the buy coat and
then washed with saline in order to remove most of the remaining white cells.
414
Medical Laboratory Technology: Volume 1
Platelet concentrates
Transfusion of platelet-rich plasma is given to patients suering from thrombocytopaenia
(decreased platelet production), patients with bleeding tendency or patients with abnormally
functioning platelets.
Lower temperatures adversely aect platelet function and viability. For this reason, whole
blood meant for preparing platelet concentrate should be kept between 20–24°C. Platelet-rich
plasma must be separated from whole blood by centrifugation within 8 h of phlebotomy. The
bleeding of the donor shall be performed by a single venepuncture giving an uninterrupted
ow of blood with minimum damage to the tissue of the donor.
Both manual and automated methods can be used in the preparation of platelet
concentrates. Platelet concentrates are prepared from individual units of fresh whole blood,
with each unit containing a minimum of 5.5 × 1010 platelets (suspended in approximately 50
mL of plasma). This represents about 60% of platelets contained in one unit of blood. The
manual preparation procedure is as follows:
1. Use integral transfer bags in the whole blood collection by phlebotomy. The satellite
bags are used for separating the plasma that contains platelets.
2. Centrifuge the unit of blood (450 mL) at 2500 rpm (1740 G) for 3 min at 20°C. This should
be done as soon as possible after donation (no more than 8 h), and the unit should not
be chilled below room temperature (20–24°C).
3. The plasma is then expressed into a satellite pack and separated. The red cells are then
refrigerated.
4. In the next step, the plasma is centrifuged at a higher speed, 4100 rpm for 5 min at
20°C. This yields platelet-rich plasma at the boom and platelet-poor plasma at the
top. Platelet-poor plasma is expressed into a second satellite pack, leaving about 50 mL
of platelet-rich plasma on the platelet buon. The platelet-poor plasma may be frozen
and stored as fresh-frozen plasma (FFP), provided this can be accomplished within 8 h
of collection.
5. The platelet buon, which is the platelet-rich plasma, should be re-suspended by placing
the container at room temperature on a slow rotator that allows for gentle agitation until
the platelets are uniformly re-suspended. This takes about 2 h.
Note Platelet concentrates must be handled gently at all times; rough handling or agitation
might result in irreversible aggregation of platelets. Centrifugation speed and time may be
adjusted in order to yield an unclumped platelet without visible haemolysis that meets the
requirement of platelet counts (5.5 × 1010 in 50 mL of plasma).
Storage of platelets
Platelet concentrates should be stored at a temperature between 20 to 24°C with continuous
agitation. This is essential to prevent platelet aggregation which results in loss of viability.
The shelf-life and transport conditions dier according to the type of plastic bag used to
store the component. Platelet concentrates stored between 20 to 24°C maintain their function
and viability beer than refrigerated platelet concentrates. If no platelet agitator or rotator
is available, it is not possible to store platelets. Once prepared, they must be transfused
immediately unless the blood bank has a platelet incubator that keeps the platelet concentrates
at a temperature between 20 and 24°C for up to ve days. Since platelet concentrates are
stored at room temperature, they pose a greater risk for bacterial proliferation. Storage
conditions and expiry dates should also be strictly adhered to in order to prevent septic shock
for the recipient. After the hermetic seal is broken, platelet concentrates should be transfused
as soon as possible, but denitely within a maximum of 4 h of storage between 20 to 24°C.
The time and speed of centrifugation must have been demonstrated to produce a suspension
Collection and Processing of Blood for Transfusion
without visible aggregation or haemolysis. The plasma must have at least 70% of platelets of
the original whole blood unit.
415
Transportation of platelet
Containers for transporting platelets should be equilibrated at a temperature of 20–24°C
before use. A well-insulated container without added ice is often sucient. If outdoor
temperatures are extremely high, special chemical and coolant pouches are available that
may be shipped with platelets to maintain temperatures of approximately 20–24°C for up to
12 h. Also available are containers with a power source that maintains temperatures between
20–24°C. Platelets should reach their destination within 24 h, which is the maximum time
allowed without agitation.
Fresh frozen plasma
If the plasma is quickly frozen, it retains all the coagulation factors. Fresh-frozen plasma is
used primarily for administration to patients with deciencies of cloing factors. It is also
useful to treat patients with liver failure, disseminated intravascular coagulation, vitamin К
deciency, warfarin toxicity or massive blood losses requiring transfusion. It should be noted
that recipients should always receive group-specic fresh-frozen plasma, especially when
the component is to be transfused to infants; in severe emergency circumstances, however,
plasma from group AB donors may be given to recipients of all other blood groups.
It is important that the anticoagulant be constantly and thoroughly mixed with the blood
during donation, because any activation of the coagulation factors lowers the yield of these
factors in the plasma. If diculty is experienced in venepuncture or if the donation time
exceeds 8 min, the unit should not be used for the preparation of fresh-frozen plasma. After
drawing blood, plasma is separated within 8 h after collection and frozen according to the
following procedure:
1. Collect blood in a collection unit (primary bag with anticoagulant) with two integrally
aached transfer containers.
2. Remove any aached pilot tube and centrifuge at 5000G for 5 min at 5°C.
3. Place the unit on plasma expresser, clamp the tubing with a haemostat and dislodge the
bead from the tubing at the satellite pack.
4. Express the haemostat and express the plasma into the satellite pack. Weight the plasma
to determine the volume and record the volume on the bag.
5. Seal the tubing with a dielectric sealer if available or with metal clips 2–3 cm apart,
taking care not to obliterate the segment number of the primary pack. Place another seal
near the satellite pack.
6. Cut the tubing between the two seals close to the RBC container. The tubing may be
coiled and placed against the plasma container where it will be available for crossmatching the plasma.
7. The plasma pack should be labelled with the following information: Volume of plasma,
ABO blood group with Rh type and expiration date. Some laboratories also record the
antibody screening test result.
8. Place the plasma in a protective container in order to avoid cracking or breaking of the
plastic bag, which becomes brile at low temperature. Freeze the bag immediately. The
plasma should be frozen in such a way that evidence of thawing can be determined
(e.g., an indentation into the bag that is visible as long as the unit remains frozen). The
plasma must be frozen solid within 8 h after collection from the donor.
Frozen plasma must be stored below 20°C (preferably below 30°C). It has an expiry date of
one year from the date of collection. This is referred as fresh-frozen plasma or FFP. The FFP
is used in treating patients with bleeding problems. For extended preservation, the plasma
416
can be stored at colder temperatures. Prior to use for infusion, the frozen plasma should be
thawed rapidly to 30–37°C.
All frozen components should be transported in a manner to maintain their frozen state.
This can be achieved with a suitable quantity of dry or wet ice in well-insulated containers or
standard shipping cartons lined with insulating material such as plastic air bubble packaging
or dry packaging fragments. If possible, they should have been placed in cardboard boxes
before freezing to protect bags from developing small cracks. The transit time for blood and
blood components should not normally exceed 24 h. At no point should ice be allowed to
come into direct contact with red cell units in the liquid state, as the red cells nearest to the ice
might freeze and haemolyse. Appropriate materials and packing arrangements are therefore
necessary. In boxes shipped long distances or at high environmental temperatures, the
volume of ice should at least equal to that of the blood component. In an insulated container,
the temperature can be considered to be in the 2–10°C range as long as unmelted ice is still
present on arrival at destination.
Medical Laboratory Technology: Volume 1
Cryoprecipitate
Cryoprecipitate is the cold insoluble portion of plasma remaining after FFP has been
thawed between 1–6°C. It is a white powdery substance, which is rich in factor VIII and
von Willebrand factor. It transfused in patients with Haemophilia A and von Willebrand’s
disease. The plasma must be frozen solid within 8 h of blood collection and within 30 min
of separation from red cells. The plasma is then thawed slowly at below 4°C. In order to get
the maximum yield of factor VIII in the cryoprecipitate from a blood unit, it is important to
adhere strictly to the standard procedures for the collection, storage and processing of the
component.
The following procedure for the preparation of cryoprecipitate is recommended:
1. Collect blood in a collection unit with two integrally aached transfer containers.
2. Centrifuge the blood between 1–6°C at 5000 G for 5 min.
3. Separate the plasma from the RBCs within 8 h of phlebotomy. Collect at least 200 mL
(206 g) of cell-free plasma for processing into cryoprecipitate.
4. Place the plasma at 18°C or colder within 6 h of phlebotomy. The plasma should be
frozen solid within 1 h of the time freezing was started. Fast freezing by the use of blast
freezers that maintains temperatures of 65°C or lower or use of dry ice (or ethanol-dry
ice), freezes the plasma in about 15 min.
Note Protect the plasma containers with an over wrap. The frozen plasma is used for
cryoprecipitate preparation, when needed. This frozen plasma for cryoprecipitate
preparation can be stored for up to 12 months at 18°C or lower (preferably 30°C or lower).
5. For preparing cryoprecipitate from the frozen plasma, allow the plasma to thaw at
1–6°C by placing the bag in a refrigerator set at 4°C temperatures.
6. When the plasma has a semi-solid consistency, centrifuge the unit at 1–6 °C at 5000G
for 5 min. Hang the bag in an inverted position and allow the supernatant plasma to
ow rapidly in the transfer bag, leaving the cryoprecipitate adhering to sides of the
primary bag. Ten to 15 mL of supernatant plasma may be left in the bag to re-suspend
the cryoprecipitate after thawing. Separate promptly to prevent the cryoprecipitate
from re-dissolving and owing out of the bag; then refreeze immediately.
7. Alternatively, place the thawing plasma in plasma expresser when approximately onetenth of the contents are still frozen. With the bag in an upright position, allow the
supernatant plasma to ow slowly into the transfer bag, using the ice crystals at the top
as a lter. The cryoprecipitate paste adheres to the sides of the bag or to the ice. Seal the
bag when about 90% of the cryoprecipitate-poor plasma has been removed and refreeze
the cryoprecipitate immediately.
Collection and Processing of Blood for Transfusion
8. Store the cryoprecipitate at 18°C or lower for up to 12 months from the date of blood
collection. Losses in potency can be reduced by storage at 30°C, if available.
417
autotranSfuSion
In case of autotransfusion (patient receives his/her own red cells), blood is collected ahead
of surgery, concentrated red cells are prepared from the whole blood and a cryoprotective
agent (like glycerol) is added prior to freezing. The cryoprotective agent allows the red cells
to freeze without bursting (haemolysis). The cryoprotective agent is removed by repeated
washing before the red cells are transfused to its own owner. As intraoperative cell salvage,
acute normovolaemic haemodilution, and other autologous red cell techniques are employed
in the operative suites (in addition to rapid availability of allogeneic blood components),
preoperative autologous donation is becoming a less favourable transfusion strategy.
plaSmaphereSiS
Plasmapheresis is a procedure by which whole blood is withdrawn from a donor, prevented
from coagulating immediately upon withdrawal and separated into its components. As part
of the procedure, the separated erythrocytes are returned to donors by intravenous infusion.
Each plasmapheresis procedure must be carefully supervised by a physician and no donor
may be subjected to such a procedure without his/her full consent in writing.
tranSportation of Blood
Whole blood and red cells must always be stored at a temperature between 1–6°C. The
anticoagulant/ preservative solution in the blood bag contains nutrients for the blood during
storage and stops the blood from cloing. The red cells can only carry and deliver oxygen if
they remain viable; that is, if they retain the same properties as they have during their normal
circulation in the body. The most important substances in maintaining the viability of red
cells are glucose and adenosine triphosphate (ATP). It is essential to maintain an equilibrium
between ATP, 2,3 Diphosphoglycerate (2,3 DPG), glucose and pH. One of the most commonly
used anticoagulant/preservatives is citrate phosphate dextrose with adenine (CPDA-1). The
dextrose and adenine help the red cells to maintain ATP during storage, and the citrate is the
anticoagulant which stops the blood from cloing. Refrigeration also retards the growth of
micro-organisms. The lower limit of 1°C is also very important. This is because red cells are
very sensitive to freezing. If they are allowed to freeze, the red cell membranes rapture and
the cells are haemolysed. The transfusion of haemolysed blood can be fatal. Before issuing
the blood for transfusion, the technician must see the transparent blood bag very carefully
for any kind of contamination and haemolysis. In case of contamination, the plasma will be
turbid.
Points to Remember
The following general observations must be kept in mind:
• Label the container THIS WAY UP with an arrow.
• Ice should be placed above the blood because cool air moves downwards. Cubed wet ice
may be beer than chipped or broken ice for long distance shipments of blood because
it melts more slowly. Ice packs can be used at –5°C or below.
• The recommended storage conditions must be maintained when blood is moved
from one location to another, including from a mobile or satellite collection site to the
laboratory, from the blood bank to a dierent facility (to a hospital or clinic or another
blood bank) and from the blood bank to hospital wards or operating rooms.