Note: Descriptions are shown in the official language in which they were submitted.
METHOD AND CONTAINER FOR STORING PLATELETS
Technical Field
_
The present invention relates Jo the storage of blood
components. More particularly, the present invention relates
to the storage of platelets in concentrated form.
Background An_
The use of blood components instead of whole blood is
now widely accepted. Blood may be collected and processed
under sterile conditions to obtain various blood components as
may be desired, such as packed red culls, plasma, platelets and
cryoprecipitate, for example. The individual components may
then be stored for a limited period of time and then utile Ed
as desired. For example, platelet concentrates may be used in
the Truman of thrombocytopenia. Since platelets are
generally stored for a period a time before use, effective
storage techniques are needed.
Generally preferred storage conditions for platelet
concentrates include storage in medical grade polyvinyl
chloride (PVC) bags at about 22C. Several available storage
bags for platelets contain polyvinyl chloride materials which
are heat stabilized with epoxidized vegetable oils. Typical
epoxidized vegetable oils which are used as heat stabilizers
for PUKE include epoxidized soybean oil and epoxid kid linseed
oil. For example, such platelet storage bags are disclosed in
US. Pun No. 4,280,497 to Warner et at. A unit of platelet
--2--
concentrate (the amount of platelet concentrate obtained from a
unit of blood) would have at least 0.55 x 1011 viable
platelets according to the American Association of Blood
Banks. Generally, a unit of platelets will contain from about
0.55 x 1011 to about 1.5 x 1011 platelet cells. Thus, the
amount of platelet cells obtained from a unit of blood can vary
widely. As used herein, unless otherwise specified, a unit of
platelet cells contains from about 0.55 x 1011 to about 1.5 x
1011. The absolute number of platelet cells present in a
unit of normal human blood can be as high as about 2.0 x
1011. Currently available platelet cell harvesting
techniques generally permit harvesting about 80%, or in some
cases, about 90X, of the total number of platelets present in
whole blood. It is anticipated that in the future, improved
harvesting techniques may become available and such improved
techniques will not affect the spirit or scope of the present
invention and appended claims.
The number of platelets present in a container
markedly affects the storage characteristics of the platelets.
Since the number of platelets collected from a unit of blood
generally varies between about 0.55 x 1011 and 1.5 x 1011,
it would be highly desirable to by able to provide a container
and method for storing platelets which optimize storage
conditions for this particular number or number range of
platelet cells or some other number or number range of platelet
cells in order to maximize the storage time and viability of
the stored platelet cells
-3-
Disclosure of the Invention
In accordance with one aspect of the present
invention, it has been discovered that certain types ox storage
conditions are more conducive to platelet viability over
storage periods of up to at least five days. More
specifically, it has been discovered that improved platelet
viability results when platelet cells are stored in a container
which has a carbon dioxide gas permeability transfer rate
through the container within a certain range relative to the
number of platelet cells stored therein. Platelet viability of
the stored cells diminishes when the carbon dioxide
permeability transfer rate is not within the specified range.
thus, it has been discovered that either too little or too much
carbon dioxide gas transfer through the container is
deleterious to the viability of stored platelets.
Generally, to optimize platelet storage and to
maintain an acceptable level of platelet viability, the
container should be such thaw the following range is satisfied:
110 R 360
wherein R = (C)x(Pco?)x(SA) (1)
(FT)x(number of platelet cells to be
stored in the container x 10 11)
and wherein R is in units of (nanomoles C02)x(min. x
owe platelet cells-cm H9CO2);
C represents a unit conversion constant of 2.S8 x
10-4 in units ox (nanomoles-sec)/(cc-min);
Pco2 represents the C02 gas permeability constant
for the container material in units of
banner [ (Cm3)(Cm) lo-lo]
"
(Sec)tCm')tCmHgcO2)
SPA represents the total surface area of the container
in square centimeters; and
FIT represents the thickness of the container material
in centimeters.
Preferably, the container should meet the R value
requirements for any number of platelet cells between 0.55 x
1011 and 1.5 x 1011. Preferably the number of platelet
cells to be stored therein will be greater than about 0.75 x
loll
In accordance with another aspect of the invention an
improved platelet storage container for maintaining a unit of
platelets at an acceptable level of viability is provided
wherein the gas transfer rate (GTR) of the container satisfies
the following range: 85 GTR 180
. (C)x(Pco USA (2)
wherein GTR = --- 2
FIT
and wherein GTR is in units of (nanomoles)/(min.-cm
H9co2) '
and C, Pro SPA and FIT are the same variables as in
equation (1).
In accordance with another aspect of the invention, a
method of storing platelet cells is provided and includes
containing the platelet cells in a container wherein the
following range is satisfied: 110 R 360
wherein R = (C)x(Pco2)x(SA)
(FT)x(number of platelet cells to be
stored in the container x 10~
~27~32
R, C, Pro SPA and FIT being the sap variables as in equation
(1) and generally, more than about 0.75 x 10 platelet cells
are stored therein.
In accordance with still another aspect of the
invention, a method of storing a unit of platelet cells is
provided and includes containing the unit of platelet cells in
a container wherein the following range is satisfied:
GUT 180
wherein GTR = USA
FIT
the variables being as previously defined with respect to
equations (1) and (2).
In accordance with another aspect of the invention, a
container suitable for storing platelets and having a
concentrate of platelet cells stored therein is provided and
includes a container which satisfies the following range:
110 R 360
whereon R = (c)x(pco2)x(sA)
(FT)x(number of platelet cells to be
stored in the container x 10 11)
the variables being as previously defined. Preferably, the
container will have at least about 0.75 x 1011 platelet cells
stored therein.
In accordance with another aspect of the invention, a
container having a concentrated unit of viable platelet cells
stored therein which is suitable for intravenous use is
provided and includes a container which satisfies the range:
GTR 180
or I
--6--
I ) )
the variables being as previously defined.
In each of the foregoing embodiments, the number of
platelet cells to be stored in the container can be set forth
as a number range so that an optimum storage container with a
specific GTR is provided for the number range of platelet cells
that will be encountered. Thus, optimized containers for
storing a unit of platelet cells are provided.
In accordance with still another aspect of the
invention, a method is provided for manufacturing a platelet
storage container of the proper size, volume and thickness for
storing a given number or range of platelet cells under
improved conditions so that an acceptable level of platelet
viability is maintained during storage. In accordance with the
method, a platelet Syria container is manufactured for
containing a number or number range of platelet cells in which
the hollowing range is satisfied: 110 R 360,
2Q wherein R = _ (C)xlPco2)xlSA3
Fox (number of platelet cells to be
stored in the container x 10~
the variables being as previously defined. Preferably, the
number of platelet cells to be stored in the container will be
greater than about 0.75 x 1011.
Usually, the container will be constructed of a
flexible polymer film material of a suitable type. Suitable
types of polymers include plasticized polyvinyl chloride
compositions, polyethylene materials and polyolefin materials.
-pa-
Other important aspects of -this invention
are as follows:
A platelet storage container for storing from
about 1.30 x 1011 to about 3.5 x 1011 platelets at an
acceptable level of viability for a period of time comprising a
container constructed of material wherein the container is
within the range 200 GTR 420,
wherein GTR = (C)x(Pco2)x(s~)
o and wherein GTR is in units of nanomoles C02/min.-Cm
kiwi;
C represents the constant 2.68 x 10
nanomoles-sec./cc-min.;
Pco2 represents the C02 gas permeability constant
15 . for the material in units of
banner [ (Cm3)(Cm) lo-lo]
Succumb )(CmHgc02)
SPA represents the total surface area of the container
in square centimeters; and
FIT represents the thickness of the material in
centimeters.
The platelet storage container referred to
hereinabove wherein the container is for storing frock about
3.5 x 1.0 -to about 9.4 x 10 platelets and the container
is within the range of 538 GTR 1130.
or I
..~,
-6b-
A platelet storage container for storing more
than 1.30 x 1011 platelets at an acceptable level of
viability for a period of time comprising a container
constructed of material wherein the container is within the
range, per platelet cell stored therein, of So x 10 lo TRY
3.3 x 10 9.
wherein GTR = FIT
and wherein GTR is in units of nanomoles C02/min.-cm
lo H9co2;
C represents the constant 2.68 x 10-4
nanomoles-sec./cc-min.;
Pco2 represents the C02 gas permeability constant
for the material in units of
banner _(Cm3~(Cm) lo-lo]
Succumb )(CmHgc02)
SPA represents the total surface area of the container
in square centimeters; and
FIT represents the thickness of the material in
centimeters-
I.'
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I
BRIEF DESCRIPTION OF TOE DRAWING
The present invention can be more completely
understood by reference to the following Detailed Description
and the accompanying drawing in which:
Fig. 1 is a plan view of a platelet storage container
in accordance with the invention.
DETAILED DESCRIPTION
Referring to Fig. 1, there is illustrated a platelet
storage container in accordance with the present invention
which is a platelet storage bag loo Platelet storage bag 10
may be of conventional construction, with the exception of the
type of materials of which it is made and the size and
thickness of the container. As illustrated, platelet storage
bag 10 includes an inlet port 14 to which is connected a length
of flexible tubing 16 to a donor bag (not shown), for example.
Alternately, tubing 16 may communicate with the
interior of another container snot Sheehan Also, as
illustrated, the container includes a number of normally
sealed, selectively operable access ports 12.
I As previously discussed, the container satisfies the
range 110 R 360. Preferably, R is greater than 120 and
even more preferably R is greater than 140. Most preferably,
R is greater than 160~ Preferably, R is less than 270 and most
preferably, R is less than 210. For storing a unit of
platelets in accordance with the methods and containers of the
invention, the gas transfer rate, ~'GTR", as previously
discussed, is within the range 85 GTR 180. Preferably GTR
is within the range 100 GTR 170 and more preferably 120
GTR 170. The most preferred range for GTR for storing a unit
of platelet cells is from about 160 to about 170.
I
In accordance with the invention, a platelet storage
container can be provided which is optimized for storing a
number of platelet cells within a given range. A container is
provided such that the GTR of the container preferably provides
an R value within the range of 110 R 360 and more
preferably 120 R 270 for the entire range of platelet cells
which may be stored in the container. For example, if an
optimum platelet container is desired for storage of a unit of
platelet concentrate, which generally may contain from about
0.5 x 1011 to about 1.5 x 10~1 platelet cells, a container
having a GTR of 165 would have an R of 110 when 1.5 x 10
platelets are stored therein and an R of 330 when 0.5 x 1011
platelets are stored wherein. If the container was optimized
for a narrower range of platelet cells, such as from 0.7~ x
owe to 1.25 x 10113 an R value could be provided within
the more preferred R range of 120 R 270. For example
storage of platelet cells in a container having a GTR of
between about 150 and 180 would always result in an R value in
the range of 120 R 240 when from 0.75 x 1011 to 1.25 x
1011 platelet cells are stored therein. Thus, the invention
allows platelet storage containers to be optimized for storage
of a wide range of platelet cells, such as the range
encountered when units of platelet concentrate are obtained
from units of blood.
Platelet storage bag 10 may be constructed of a
material of a suitable type. For example, polymer material
such as a plasticized polyvinyl chloride resin compositions,
polyethylene material and polyolefin material may be used.
Such materials may be plasticized and heat stabilized as
desired by any suitable material or materials known to those
skilled in the art, as long as the resulting material is
suitable for storing platelets and the value of R or TRY is
- 9 -
within the desired range. Other types of materiels, polymers
or non polymers, may be used, as long as the requirements for
gas transfer are provided. Thus, combinations of materials
could be used and materials having various thickness could also
be used, as long as the overall gas transfer requirements are
met. For example, a container could have a very thick,
relatively non-porous portion or portions with other portions
of the container being relatively porous, as long as the
overall gas transfer requirements are met. Thus, the invention
is not limited to containers of a certain material or design or
to materials having a uniform thickness. Polymers and polymer
films are generally useful in practicing the invention.
For example, one preferred type of polyvinyl chloride
composition includes PVC resin, an effective amount of
it tri-(2-ethylhexyl) trimellitate to plasticize the PVC, less
than about one percent by weight of the total composition of
the heat stabilization system and optionally an effective
amount of an anti block agent.
As will be appreciated, the amount of plasticizer can
be chosen such that the desired degree of flexibility is
obtained. Compositions containing a relatively low quantity of
plasticizer may be harder and less flexible than desired and
those with a relatively high quantity of plasticizer may be
softer and more flexible than desired. Generally, do the
amount of plastic ken is increased, mixing becomes more
difficult and plasticizer leaching will be increased and as
the amount of plasticizer decreases, gas permeability generally
decreases, which may not be desirable for platelet storage.
Generally, an effective amount of plasticizer for this type of
.. . . . . . . . . .. . . . . , . . , .. , ,, . , . .. . .
I
10-
composition will be from about 25 to 90 parts per 100 parts
resin by weight. Preferably, the amount of plasticizer is from
about 63 to 85 parts per 100 parts rosin by weight and most
preferably about 74 parts.
The heat stabilization system should generally be
present in an amount greater than about 0.15 percent by weight
of the total composition and is preferably present in an amount
of between about 0.26 and 0.35 parts per 100 parts resin by
weight. Generally, as the amount of heat stabilizer is
increased, increased leaching occurs and hazing may also result
if the amount of heat stabilizer is high enough.
Generally, when utilized, the anti block agent will be
present in an amount sufficient to provide the desired
anti block effect, or stated otherwise, to prevent adhesion of
films made from the composition. The amount of anti block agent
will usually be from about 0.2 to about 0.6 parts per 100 parts
resin by weight and preferably about 0.4 parts. Again,
generally as the amount of wax increases, increased leaching
also results. Thus, the preferred amount of ankiblock agent is
generally the minimum amount which will prevent adhesion of
films made prom the composition.
An especially preferred composition is, per 100 parts
of PVC resin, 74 parts of tri(2-ethylhexyl) trimelli~ate, 0.3
parts of a calcium Stewart and zinc Stewart heat stabilizer
sold by the trade designation "SHEA P" by the Inter stab
Company and about 0.4 parts of a wax anti block agent sold under
the trade designation "Acrawax C" by Glyco Chemicals, Inc.
Such a composition has a Pco2 at 25C of about 49 bar.
The ingredients of a composition can generally be
suitably mixed by a blender, for example. A composition can be
formed into sheets by conventional methods such as by
calendaring or by extrusion to a desired thickness. A mixing
:~22~'~3~
screw type apparatus may be used in extruding the material.
Generally, the materials are processed under suitable
conditions so that unacceptable heat degradation or color
change of the material does not occur. The type and amount of
5 heat stabilizer will affect the processing conditions to which
the composition may be subjected without the occurrence of
significant degradation or color change. For example, a PUKE
composition without calcium Stewart is more likely to
undesirably darken during processing than a PVC composition
lo containing calcium Stewart and zinc Stewart.
The polyvinyl chloride resin can be any suitable
type. Those types of PVC resins which relatively easily absorb
the plasticizer are preferred. Especially suitable resins are
those known as "blotter" resins. One such preferred resin is
marketed by the BY Goodrich Chemical Co. under the trade
designation "GOON 80X80." Another preferred resin is marketed
by the Weaker Co. under the trade mark "YINNOL H70DF".
The plasticizer which may be utilized,
trit2-ethylhexyl) trimellitate, is commercially available. One
zap source is the Hatch Chemical Corp. marketing the plasticizer
under the trade mark "~ATCOL 200".
As previously discussed, the heat stabile ration system
may be calcium Stewart, zinc Stewart or mixtures thereof.
More generally, the heat stabilization system can be at least
on salt of C10 to C26 saturated fatty acids. A 1:,1 weight
ratio of zinc stearate/calcium Stewart is preferred. A
suitable commercial source of the zinc stearate/calcium
Stewart combination is the Inter stab Company which markets
such a heat stabilizer under the trade designation "SHOP".
"CZ-ll-P" formulation may also contain minor amounts of calcium
palpitate, zinc palpitate and C18 fatty acids.
'7~3~
~12-
The anti block agent which may be present generally may
be any material that provides the desired anti block effect
without an undesired degree of leaching and which is not
otherwise objectionable. Preferred anti block agents are low
viscosity, high melting point waxes, such as wax marketed under
the trade designation "Acrawax C" by Glycol Chemicals, Inc.
High viscosity oils may also be utilized. In general, oils
will leach to a greater degree than waxes. Mixtures of
anti block agents may also be used. Reference is made to-
Canadian Patent Application Serial No. 434,993 filed August
19, 1983 for a more complete description of such PVC
compositions. Other PUKE compositions may contain an epoxidized
vegetable oil or oils which function as a heat stabilizer.
Such compositions are disclosed in US. Patent No. 4,280,497 to
Warner et at. and reference is made thereto for further
descriptions thereof. However it should be kept in mind that
the scope and spirit of the present invention is not limited to
particular materials or compositions.
Generally, the thickness of the polymer material will
be between about 0.01 centimeter and 0.05 centimeter.
Other platelet storage materials may be used including
those previously described and other which are known to those
skilled in the art.
The present invention can be further understood by
reference to the following example.
Example
A study was conducted with various types of platelet
storage bats to demonstrate the effect of "R" and "GTR" on
platelet viability during storage for three and five days. The
effect on platelet viability was determined by the pi of the
. _ . . . .
I
-13-
stored platelets since it is generally recognized that pi is
the best indication of eventual in viva platelet survival and
function after infusion. Generally it is desired that the pi
of stored platelets remain in the pi range of from about 6.5 to
about 7.2 during storage.
The following types of materials and storage bags were
utilized:
. .. . _ .. .. .. . . . . . .. .. .
-14-
Material A
Type: Polyolefin
Pco2 a 25C: 58 bar
Bag Yolume/Surface Area:
300 ml/365 cam
1000 ml/644 cm2
Thickness:
300 ml bag. 0.03 cm
1000 ml bag: 0.045 cm
Metro at B
Type: Polyvinyl chloride
Pco2 at 25~C: 4g bar
Bag Volume/Surface Area:
300 ml/280 cm2
600 ml/39B cm2
Thy ckness:
300 ml bag: 0.015 cm
600 ml bag: 0.015 cm
Material C
Type: Polyvinyl chloride
- Pco2 at 25~C 30 bar
Bag Volume/Surface Area:
300 ml/280 cm2
Thickness:
0.038 cm
.
-15-
Platelet concentrate was obtained from single units of
blood or from a continuous centrifugation system in which blood
was continuously withdrawn, centrifuged to remove platelets and
returned to the donor. The platelets were stored at ambient
temperature and the following results were obtained after
storage for about three and five days:
. . .
-16-
Three and Five Day Sty a
# Platelet pi pi
Cells Bag wafter (after
Material (x10 11) Size R GTR 3 days) 5 days)
C 4.66 2000ml 45 208 5.88
C 1.29 300ml 46 59 5.76 5.79
C 4.40 2000ml 47 208 5.98
C 1.24 300ml 48 59 5.67 5.67
C 4.13 2000ml 50 208 6.09
C 3.86 2000ml 54 208 5.84
A 4.13 lamely 54 223 5.92 5.75
C 1.01 300ml 59 59 5.70 5.64
A 3.62 1000ml 62 223 6.24 5.89
C 3.35 2000ml 62 208 6.11
A 3.58 1000ml 62 223 6.24 5.92
A 3.18 1000ml 70 223 6.10 6.18
C 0.76 300ml 78 59 6.08 5.62
C 0.74 300ml 80 59 5.95 5.67
B 1.15 300ml 84 97 6.19 5.63
0 0.59 300ml 100 59 6.04 5.72
B 0.86 300lnl 113 97 6.57 6.69
C 0.51 300ml 116 59 6.70 6.38
B 1.00 600ml 137 137 7.05 6.94
B 0.69 300ml 140 97 7.11 6.89
C 0.42 300ml 141 59 7.30 7.23
B 0.62 300ml 156 97 7.12 6.88
B 0.81 600ml 170 137 7.07 go
A 1.00 300ml 189 189 7~10 6.96
B 0.50 300ml 193 97 7.26 6.84
B 0067 600ml 206 137 7.06 6.92
-17-
Three and Five Day Storage
# Platelet pi pi
Cells Bag (after (after
Material (lo 11) Size R GTR 3 days) 5 days
A 0.85 300ml 227 189 7.42 7.26
A 0.65 300ml 291 189 7.45 7.36
A 0.55 300ml 344 189 7.29 7.23
A 0.46 300ml 411 - 189 7.65 7.80
A 0.42 300ml 450 189 7.91 7.91
10 A 0.17 300ml 1,112 189 7.71 8.03
I
-18-
Thus, the foregoing results indicate the critical nature of the
R and GTR parameters. Platelets stored under conditions such
that R was with the range 110 R 360 exhibited a relatively
uniform pi which was generally with the range of from 6.5 to
7.2 after 3 and 5 days of storage. Platelets stored under
conditions such that R was not within the range 110 R 360
exhibited more pi instability and pi values that were generally
significantly higher or lower than the range of from 6.5 to
7.2. Platelet units between about 0.5 and 1.5 x 1011
platelet cells) stored under conditions such that GTR was
within the range 85 GTR 180 for 3 and 5 days also exhibited
a relatively uniform pi which was generally 6.5 and 7.2. Units
not stored within that GTR range generally exhibited pi values
outside of the range of 6.5 Jo 7.2.
While the invention has been described with respect to
preferred embodiments, it is understood that the invention is
capable of changes, modifications and alterations as fall within
the scope of the appended claims.
