Plastic blood bag system including a bag having a generally longitudinal
seal extending from the top of the bag and between two blood bag
ports downwardly to at least the lower half of the bag but not to
the bottom of the bag, thereby leaving the sole passageway within
the bag and between two ports located in the lower half of the bag.
1. A method of separating a blood product into useful components
comprising the sequential steps of
(a) introducing the blood product into a blood bag having at least
two ports at the top of the bag and a longitudinal seal extending
downwardly from the top of the bag and between the two ports to
at least the lower half of the bag, wherien a channel is formed
on one side of the longitudinal seal;
(b) centrifuging the blood to separate the blood into an upper
less dense portion and a lower more dense portion, and;
(c) expressing the more dense portion out of the bag from the lower
portion of the bag via the channel and a port with which the channel
2. The method of claim 1 wherein the blood product is whole blood,
the less dense portion is plasma and the more dense portion is red
3. The method of claim 1 wherien the expression of the red blood
cells is monitored using electronic monitoring means.
4. A method of preparing platelets from whole blood comprising
the sequential steps of
(a) introducing whole blood into a blood bag having at least two
ports at the top of the bag and a longitudinal seal extending downwardly
for the top of the bag and between the ports to the lower half of
the bag, wherein a channel is formed on one side of the longitudinal
(b) centrifuging the bag and its whole blood contents to form a
lower more dense portion of red blood cells, an upper less dense
portion of plasma and an intermediate buffy coat portion comprising
platelets and while blood cells;
(c) expressing the plasma portion out of the bag via one of the
ports at the top of the bag and on one side of the longitudinal
seal and expressing the red blood cell portion out of the bag via
the channel on the other side of the longitudinal seal and a port
with which the channel communicates;
(d) then subjecting the remaining buffy coat portion to conditions
sufficient to separate platelets from the buffy coat portion.
5. The method of claim 4 wherein the buffy coat portion of step
(d) is expressed from the bag into another bag connected via tubing
to the top of the bag having the longitudinal seal.
6. The method of claim 5 wherein the other bag is elongated, having
a length to width ratio of at least 2 to 1 and adapted to facilitate
separation of platelets from the buffy coat portion when the elongated
bag containing the buffy coat portion is centrifuged under conditions
sufficient to encourage separation of the platelets from the buffy
7. The method of claim 6 wherein the elongated bag has attached
thereto via tubing yet another bag suitable for storage of platelets.
8. The method of claim 7 wherein the bag suitable for storage of
9. The method of claim 8 wherein the bag suitable for storage of
platelets comprises a bag made from a plastic film having a relatively
high gas transmissivity.
10. The method of claim 8 wherein the bag suitable for storage
of platelets includes a platelet storage solution.
U.S. patent application Ser. No. 07/493024 filed Mar. 13 1990
in the names of R. A. Carmen et al and entitled, "Blood Separation
BACKGROUND OF THE INVENTION
This disclosure is concerned generally with the collection and
separation of whole blood into useful components and specifically
with a plastic blood bag system which permits a more dense centrifuged
component in the lower part of the bag to be expressed to and out
of the top of the bag.
2. Prior Art
Whole blood is commonly separated into its major components of
less dense plasma and more dense red blood cells (RBCs) by first
drawing the whole blood into a plastic bag known as a donor or primary
bag. The bag contents are then centrifuged under controlled conditions
to result in a lower, more dense portion of packed RBCs and an upper
less dense plasma portion, which may be rich in platelets (platelet
rich plasma or PRP).
The donor bag is typically connected via blood bag ports by plastic
tubing to one or more satellite bags to form a "closed"
system into which separated blood components (e.g., the PRP or RBCs)
may be expressed by external manipulation and valves for further
processing or use.
The above system for separating blood into its major components
has remained generally unchanged since the 1950's when plastic blood
bags were introduced commercially on a large scale.
In recent times, efforts have focused on preparing very specific
"components" from whole blood (or fractionated plasma)
so that if a patient needs a certain component (e.g., coagulation
factors, albumin, platelets, ISG, RBCs, etc.), only that specific
component can be administered. Although the system of this disclosure
may be used to prepare other blood products, it is especially useful
for preparing platelets.
The classical method of preparing platelet transfusion products
from whole blood consists of an initial centrifugation of whole
blood in a plastic blood bag at relatively low centrifugal force
to separate most of the PRP from the red cells. The PRP is then
commonly expressed into an attached satellite blood bag. This is
followed by centrifugation of the PRP in the satellite bag at relatively
high centrifugal force. This results in a lower sediment of platelets
and an upper platelet poor plasma (PPP). The sedimented platelets
are in the form of a pellet or "button" which is resuspended
in a small volume of the PPP donor plasma (50-60 ml) to give the
platelet concentrate (PC).
With good technique, about 2/3 of the platelets in a whole blood
collection unit (about 450 ml.+-.10%) are recovered in the platelet
concentrate. This is equivalent to about 8.times.10.sup.10 platelets
per concentrate. However, achieving this yield of platelets requires
strict attention to centrifugation protocols, frequent calibration
of the centrifuges, and operator diligence. The fact that the minimum
standard for platelet yield is only 5.5.times.10.sup.10 per concentrate
attests to the operator-dependent nature of this procedure.
Recently, some transfusion services in Europe have begun to investigate
and in some cases employ an alternate method of platelet preparation,
specifically preparation from the "buffy coat" of centrifuged
whole blood. In this procedure the initial centrifugation of whole
blood is performed at relatively high centrifugal force to form
three portions: an upper layer of relatively cell-free plasma, an
intermediate "buffy coat" layer containing platelets and
leukocytes, and a lower layer of red cells.
The intermediate buffy coat is separated and mixed with either
a small volume of plasma (50-60 ml) or a synthetic medium. The mixture
is then centrifuged at low centrifugal force to separate platelet
concentrate (upper layer) from leukocytes (WBCs) and residual red
cells. Data suggest that platelets prepared in this fashion are
of improved quality, presumably because platelet activation that
would otherwise occur during the pelleting step of the PRP centrifugation
method is avoided.
The original work on buffy coat platelets was done at the Dutch
Red Cross. Referred to as the Amsterdam method, it employed a standard
quadruple multiple plastic bag system. After centrifugation of blood
and removal of plasma from the main bag, the buffy coat layer was
transferred to an empty connected satellite bag and then processed
to platelet concentrate. Using this method, Pietersz et al (Vox
Sang 1985; 49:81-85) found a mean of 7.2.times.10.sup.10 platelets
per concentrate; the volume of blood collected in this study was
about 500 Ml. Kretschmer et al (Infusionstherapie 1988; 15:232-239)
found a mean of 6.3.times.10.sup.10 platelets per concentrate from
450 ml blood collections.
The Amsterdam method, while apparently giving respectable platelet
yields, was cumbersome and labor-intensive. The buffy coat transfer
step required the operator to massage the bag to prevent hang-up
of the "sticky" buffy coat layer. These manipulations
might influence platelet function and release of granulocyte enzymes.
There was also no way to control the volume of buffy coat removed.
Other efforts to improve blood separation procedures or at least
make it less burdensome are known. For example, U.S. Pat. No. 3911918
to Turner discloses a blood bag having an hour glass shape. That
bag has a top portion for plasma, a bottom portion for RBCs and
a middle portion for platelets and white blood cells. The hour glass
shape is said to help position clamping or sealing devices at the
juncture of the separated components after whole blood in the bag
is centrifuged. This system has not been used on any significant
commercial scale to date. See also U.S. Pat. No. 4857190 to S.
Wada and B. Kuhlemann showing a blood bag having a continuous but
smaller receptacle adapted to help collect and define the interface
of a centrifuged component.
In U.S. Pat. No. 4608178 to A. S. Johansson and C. F. Hogman
there is disclosed a "top/bottom" bag in which the upper
and lower portions of separated blood components can be simultaneously
expressed from a specially designed bag which leaves behind in the
bag the intermediate portion known as buffy coat. The expression
of that system is controlled by a pressure plate on the bag and
sensors which monitor the position of the intermediate layer such
that it remains in the bag while the upper plasma is expressed from
a top part and the lower red blood cells are expressed from a bottom
part in the bag. Hence, the name top/bottom bag. The sensors in
that system assure the simultaneous expression of the top and bottom
The above described systems are fairly recent and it is not clear
yet whether those systems will in time replace existing blood separation
systems based on the use of a relatively simple unmodified donor
However, the systems do offer new ways to separate WBCs from platelets
or to prepare platelets (contained in the intermediate or buffy
coat portion). The patent to Johansson and Hogman show how to do
this in a semi-automated manner. Hence, it potentially represents
a semi-automated way to prepare platelets.
In an effort to overcome problems associated with the Amsterdam
method, Johansson and Hogman (see above-cited patent) developed
the bag system with the top and bottom drainage of the primary bag
and a sensor device which allowed partially automated blood separation.
Kretschmer et al, cited above, used that type of system to prepare
platelet concentrates from buffy coats and found a mean of 6.7.times.10.sup.10
platelets per unit.
In co-pending patent application Ser. No. 07/493024 filed in the
names of R. A. Carmen et al, there is disclosed another system for
removing the lower contents of a blood bag in a relatively simple
way. That system uses a tubular member which extends from an upper
port into the interior of the bag, terminating just above the bag
bottom. When pressure is applied to the bag, the lower contents
of the bag exit through the tubular member and the top of the bag.
Although the above system has been found useful and may be a practical
alternative to the top-bottom bag, we have now found what may be
an even more practical alternative which uses a novel blood bag
construction that offers surprising manufacturing and use advantages.
Details of the system are described below.
SUMMARY OF INVENTION
Our blood separation system comprises a main plastic blood bag
(a primary bag or a donor bag) in which separated components can
be expressed from the top of the bag and in an order chosen by the
The system includes a main or donor bag having a generally longitudinal
seal extending from the top of the bag and between two blood bag
ports downwardly to at least the lower half of the bag but not to
the bottom of the bag, thereby leaving an internal passageway between
the two ports that is located in the lower half of the bag.
In one use, whole blood (or a component to be separated) is introduced
into the bag through one port via conventional methods. The whole
blood is then centrifuged to form a lighter portion and a more dense
portion. If desired, the denser portion can then be removed from
the lower part of the bag before removal of the upper less dense
component by applying pressure (which can be manual or automated)
to the bag to push substantially all of the denser component through
the internal passageway to one side of the longitudinal seal and
out of the bag through the port communicating with that side of
the longitudinal seal. That port must, of course, be opened for
In preferred embodiments, the longitudinal seal is relatively narrow
(e.g. <5 mm wide), generally parallel and close to one side edge
of the bag, and terminates at its lower portion within the lower
50% (preferably within the lower 10%) of the bag length. In very
preferred embodiments, the volume of the side through which the
more dense component exits the bag is less than 10% of the total
bag volume. The system may be used with electronic monitoring means
(see below) to provide semi-automated blood separation.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a plan view of one preferred blood bag separation system.
FIG. 2 is a plan view of a plastic bag illustrating one embodiment
of the main bag of the invention.
FIG. 3 is a cross sectional view of the bag in FIG. 1 taken through
lines 2--2 of FIG. 2.
Our preferred system for the separation of blood components comprises
a main donor bag having optical sensor-activated clamps or valves
associated with conventional tubings communicating with each of
the outlet ports of the bag. The outlet port for the more dense
component communicates with the internal passageway toward the bottom
of the bag interior. In preferred embodiments, the longitudinal
seal is, on average, within about 7 mm of the edge seal at one side
of the bag (in a flattened, empty bag). The longitudinal seal also
preferably extends to within about 7 mm of the seal at the interior
bottom of the bag. Preferably, the bag is made using simple, conventional
seals for the top, bottom, side and longitudinal seals. When the
bag is filled with fluid (and balloons out), the resulting passageway
toward the bag bottom will have an average diameter of less than
about 7 mm.
One preferred system is a "triple" blood bag consisting
of a primary or donor bag and two satellite bags pre-connected to
the primary bag by conventional PVC blood bag tubing and fittings.
The bags themselves may be made from conventional PVC plastic film
used to make blood bags (e.g., PVC plasticized with plasticizer
such as DEHP, TOTM, citrate esters and the like) or from other acceptable
plastic materials (e.g. polyolefins). The primary bag is made using
conventional techniques but is modified in that the blood collection
bag has the longitudinal seal extending from between two top ports
toward the bottom of the bag as shown generally as seal 3f in FIGS.
1 and 2. The bags and tubing are essentially transparent.
FIG. 1 shows one example of our system (a "closed" triple
multiple blood bag system) used in conjunction with electronic fluid
monitoring means. The main difference between the system of FIG.
1 and that of co-pending patent application Ser. No. 07/493024
is in the middle bag, shown in more detail in FIGS. 2 and 3.
FIG. 2 shows the main bag 3 (the center bag) of FIG. 1 in more
detail. As can be seen in FIG. 2 the bag 3 has a generally conventional
appearance except for a longitudinal seal line 3f which extends
from the top of the bag (and between at least 2 ports, 17a and 27a)
downwardly to a position in the lower half of the bag but not to
the bag bottom. By not quite extending to the bottom of the bag,
a passageway 3d remains between the bulk of the bag interior 3g
and a "channel" 3e running along side and generally parallel
to the left side of the bag. The only "closed" communication
between the upper ports 17a and 27a on either side of the longitudinal
seal 3f is passageway 3d. In preferred embodiments passageway 3d
and the width of the channel 3e should be as small as possible but
large enough to permit non-turbulent and unobstructed flow of the
lower bag contents out via tubing 17 when pressure is applied to
the bag (after centrifugation of the whole blood or other blood
FIG. 3 illustrates a cross sectional view taken through lines 2--2
of FIG. 2 and shows the relatively small size and volume of the
channel 3e compared to the remaining bag volume 3g.
After collection of whole blood via conventional needle assembly
3c and phlebotomy tubing 3a into a donor bag 3 such as that shown
in FIG. 1 the blood is centrifuged at relatively high centrifugal
force to form upper plasma component 9 intermediate buffy coat
component 13 and lower red cell component 11. The bag 3 is then
placed in a simple, conventional pressure-separator device (blood
bag expresser) consisting of a moving spring-loaded expresser plate
and a fixed plate.
In one very preferred embodiment, the separation system includes
two on-off tubing clamps, 19 and 31 one on tubing 17 and one on
tubing 27 activated by a sensor such as a photocell shown generally
as box 16. The lower RBCs pass through port 17 while the upper plasma
passes through port 27. Other ports (not shown) may be added as
needed to the donor bag in place or in addition to bag access port
15. Passage of the bag contents through the attached tubings may
be controlled using conventional frangible valves 3h (see FIG. 2).
An example (preferred) of one such frangible valve is described
in detail in U.S. Pat. No. 4586928 to B. Barnes et al.
At the start of the plasma expression, the valve 3h communicating
with tubing 27 is open and the corresponding valve 3h for tubing
17 is closed. Plasma is expressed into bag 35 by pressure on bag
3 until red cells (in the buffy coat 13) are first seen or detected
in tubing 27 by a photocell sensor positioned on the tubing 16
at which time clamp 31 on tubing 27 closes in response to an electrical
signal on wire line 25 from the sensor and the clamp 19 on tubing
17 opens in response to a signal on similar line 25. Red cells are
then expressed via passage way 3d through the top of bag 3 into,
for example, a second satellite bag 21 containing a conventional
red cell preservation solution such as AS-3 or the like (not shown).
The expression continues until only a volume of about 50 to 60 ml
(the buffy coat 13) remains in bag 3. This volume may be set, if
desired, by a simple stop (not shown) between the expresser plate
and the back plate against which the bag 3 is pressed in an otherwise
conventional blood bag expresser. Optical sensors may be positioned
at convenient places along lines 27 or 17 as needed to activate
valves 31 and 19.
For test purposes, whole blood was collected into a bag containing
a conventional anticoagulant and or preservative solution (CP2D/AS-3),
then transferred into the "channel bag" of this disclosure.
See bag 3 of FIG. 1. In practical use, however, the whole blood
would be collected directly into the donor bag 3 via phlebotomy
needle assembly 3a.
The blood unit was then centrifuged at about 3000Xg (2977Xg) for
9 minutes. Using a manual plasma expressor the upper plasma was
expressed via tubing 17 into an empty bag 35. Red cells were then
expressed through passageway 3d (see FIG. 2) and the "channel"
(see 3e of FIG. 2) into additive bag 21. Expression of plasma was
stopped when red cell layer was about 1 cm from the top of the bag.
Expression of red cells was stopped when the pressure plate of plasma
expressor reached a predetermined mark. At this point about 60 g
of buffy coat (BC) remained in primary bag 3. About 60 g of plasma
from bag 35 was expressed back to the BC in bag 3.
The BC in bag 3 was incubated overnight on a platelet agitator
(to break up platelet aggregates) at about 22.degree. C. The next
morning the BC was transferred into another separation bag. An elongated
separating bag as shown in U.S. Pat. No. 4892537 to R. Carmen
et al for neocyte separations was used. This bag can be connected
directly via tubing to an added port at the top of bag 3 for a truly
closed system. The reconstituted BC (about 60 g BC in 60 g plasma)
was centrifuged at 454Xg for 7 minutes. The top layer of platelet
concentrate was then expressed into an attached TOTM plasticized
PVC blood bag (see U.S. Pat. No. 4280497 to Warner et al) for
Platelet counts were performed on all fractions using either an
electronic cell counter (plasma and platelet concentrate) or a manual
method. Data are summarized in the table below.
TABLE ______________________________________ Platelets from Buffy
Coat Data on Channel Bag (n = 9) Platelets Platelets % of Whole
Leukocytes Fraction No. .times. 10.sup.10 Blood No. .times. 10.sup.8
______________________________________ Whole blood 13.6 .+-. 4.2
100 Plasma 1.4 .+-. 0.6 10.3 Red Cells 0.3 .+-. 0.4 2.2 12.4 .+-.
7.7 Platelet Concentrate 8.1 .+-. 2.4 59.5 0.2 .+-. 0.2 Residual
Buffy Coat 3.0 .+-. 1.2 22.1 ______________________________________
The main bag of this disclosure provides manufacturing advantages
since it can be made using conventional blood bag manufacturing
methods. For example, many conventional blood bags are made by simply
sealing the edges (perimeter) of two sheets of plasticized PVC film.
The seal can be accomplished using conventional heat or radio frequency
(RF) plastic sealing devices. Chemical solvent sealing, though possible,
is less preferred because of possible seal failure or breakage.
The longitudinal seal for the preferred bag of this disclosure
was made using an RF sealing device and this method of sealing is
preferred for bags made from plasticized PVC. Bags made from other
plastics (e.g., polyolefins) could be sealed, for example, using
a simple heat seal.
We are unaware of the use of longitudinal seals in any blood bag
system which are made to facilitate removal of the lower contents
of a blood bag through the top of the bag. In U.S. Pat. No. 4619650
to L. Wisdom, however, a blood bag with a different type of longitudinal
seal is shown. Although the central longitudinal seal of that bag
appears to leave a passageway between two halves of the bag at the
top (not the bottom) that bag would not allow the lower contents
of the bag to be removed from the top of the bag as in the present
system. More over, the purpose of the seal in that bag is to provide
a line along which the bag can be torn open for the efficient removal
(via machine) of frozen plasma.
Although the plasma bags of that patent do not disclose or suggest
the present invention, the various ways to make blood bags taught
in that patent and the blood bag patents cited above are incorporated
into this disclosure by reference to those patents.
The main bag of this disclosure may be used for a gross separation
of whole blood into plasma (PRP) and RBCs or, preferably, a finer
separation of a blood component (e.g., the separation of platelets
from the buffy coat portion of blood) as described above.
The sequence of component removal may be varied to suit a particular
need or the availability (or non-availability) of expressors (machines
designed to press a bag to squeeze out a given component).
For example, in our platelet preparation steps using the main bag
of this disclosure, we now prefer to express the less dense plasma
portion from the top of the bag first (before the RBCs are expressed).
This is done to reduce the chance of inadvertently getting some
of the platelets (in the buffy coat) into the channel from where
it would be difficult to recover those platelets. By thus expressing
the upper plasma (platelet poor plasma) first, the adjoining buffy
coat is kept as far away from the channel entrance (passageway)
Thus, in our preferred method, we first express the plasma from
the main bag. This leaves only the upper buffy coat and the lower
RBCs in the bag. It should be understood that the upper buffy coat
will contain some residual RBCs but, in general, there is a clearly
visible interface between the buffy coat portion and the lower RBCs.
Since the volume of buffy coat portion in a typical unit of blood
is about 50-60 ml, and since this amount is typically reconstituted
with an equal amount of plasma (60 ml), this total volume (120 ml
or about 120 g) can be used to determine how much of the RBCs should
be expressed to leave behind only the buffy coat portion. For example,
we have found that when a conventional blood bag expressor is used
(either a V-expressor or a two-parallel plate expressor) the expressor
can be marked to show a distance that the expressor plates should
be apart to result in a remaining volume of about 120 ml (or about
120 g). After the position of the mark (can be a simple pencil mark)
is set with about 120 ml of a fluid (e.g., water) the mark can then
be used as a guide for future expressions of the red blood cells.
In a preferred method for preparing platelets from whole blood,
a 50--50 mixture of buffy coat and plasma is made by transferring
about 60 ml (or about 60 g) of plasma from the plasma collection
bag back to the main bag. This mixture is then incubated overnight
at room temperature with gentle agitation to break up platelet aggregates.
Incubation can be in the original main bag (with the longitudinal
seal) or in another bag to which it is expressed, preferably under
closed conditions. Ideally any such other bag is preconnected via
tubing to the main valve and includes an externally manipulated
valve to control timing of the transfer.
We have found that the elongated bag of U.S. Pat. No. 4892537
to R. A. Carmen et al provides especially good platelet from buffy
coat separations. That bag has a length to width ration of at least
2 to 1 and a tapering and portion that expands to form a funnel-like
guide for directing a separated component from the bag after centrifugation.
In our application, the less dense platelets form the top portion
after centrifugation of the buffy coat in the elongated bag. Those
platelets are then expressed out for storage into yet another preconnected
bag, preferably a bag suitable for such storage (e.g., a polyolefin
bag or a plasticized PVC bag, either having been made from plastic
having a relatively high gas transmissivity, helpful for platelet
One such PVC bag is the TOTM plasticized bag of U.S. Pat. No. 4280497
to W. Warner et al. The bag described in that patent had wall thicknesses
in the range of about 0.01 to 0.20. The walls had a CO.sub.2 transmission
of at last about 4000 ml/meter.sup.2 /day and an O.sup.2 transmission
of at least about 600 ml/meter.sup.2 /day. These rates would be
considered relatively high gas transmissivity as the expression
is used here.
Given the above disclosure it is thought variations will now occur
to those skilled in the art. Accordingly, the above examples should
be construed as illustrative and the scope of the invention disclosed
herein should be limited only by the following claims.