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Palestine Polytechnic University

Biomedical Engineering

"Apheresis"

Prepared by:

Nabhan Ebia

Presented to:

Dr. Ramzi Al-Qwasmih

4\1\2011

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Blood Components

Blood is a complex mixture of plasma (the liquid component),

white blood cells, red blood cells, and platelets as shown in figure 1.

Plasma is 90 percent water and constitutes about 55 percent of blood

volume. Plasma can be fractionated or separated into

derivatives/products. These include albumin (the chief protein

constituent), fibrinogen (responsible in part, for the clotting of blood),

globulins (including antibodies), and other clotting factors.

Red cells contain hemoglobin, an iron-containing protein that

carries oxygen throughout the body and gives blood its red color. Donors

must have a hemoglobin level of 13.3 gm/dl to donate automated double

red cells. The percentage of blood volume composed of red cells is called

hematocrit.

Figure 1 Blood Components

Platelets are vital to life because they help prevent massive blood

loss by helping your blood to clot. Because they are sticky cells, they need

to be in constant motion after they are donated or they will clump and

cannot be transfused.

Plasma is the liquid portion of the blood that carries platelets, red

cells and proteins throughout the body. Plasma is made up of 90 percent

water and is more than 55 percent of your total blood volume.

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Introduction to Apheresis

Apheresis is a medical technology in which the blood of a donor &

patient is passed through an Apheresis Machine that separates out one

particular constituent and returns the remainder to the circulation, so the

apheresis is a device in which the whole blood from a patient or donor is

removed. The components of whole blood are separated within the cell

separator. One or more of the separated portions are then withdrawn and

the remaining components are retransfused into the patient or the donor.

The Apheresis Machine should have facility for all blood component

collection including peripheral blood stem cells with both single &

double access platelet pheresis & also therapeutic plasmapheresis red cell

pheresis.

Figure 2 Apheresis

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Principle of Operation

The overall operation of the device (as shown in figure 3) is the

blood is removed from a vein and mixed with a substance called citrate to

stop it clotting while in the blood collection set. It is then processed in the

collection set to separate the red blood cells from the plasma and

platelets. The components that are required are kept in the collection set

and the red blood cells are returned to the donor. This process allows 2-3

times the usual volume of plasma and up to 12 times the usual number of

platelets to be removed at a single donation, without making the donor

anaemic.

Figure 3 Principle of Apheresis

Types of Apheresis

There are two types of apheresis:

1- Donor apheresis:

In this type of ahresis the erythrocytes, platelets, and plasma are

collected .

The basic steps in apheresis are:

1) the separation f blood components

2) the removal of the desired component(s) using an online automated

system.

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The ability of various techniques and equipment to carry out these

basic steps determines collection efficiency and product purity.

Separation can be accomplished by filtration, centrifugation, or a

combination of both. Filtration takes advantage of differences in particle

size to separate blood plasma from the cellular elements. Centrifugation

uses differences in specific gravity to separate and isolate blood

components.

Centrifugation

In a tube of blood that has reached equilibrium after the application

of centrifugal force, mature red cells (the most dense component) would

be located at the bottom, and plasma (the least dense component) would

have risen to the top. In between, in order of decreasing density, would be

neocytes (young red cells), granulocytes, mononuclear cells, and

platelets. The granulocyte fraction contains neutrophils, basophils, and

eosinophils. The mononuclear cell fraction contains lymphocytes,

monocytes, peripheral blood progenitor cells, and, in some leukemic

patients, blast cells. Unfortunately, a perfectly clean separation of these

components is not usually achieved in apheresis instruments. Instead,

there is some mixing; for example, small amounts of platelets and red

cells may be mixed in with the white blood cells (WBCs).

In the apheresis field, centrifugal separators are classified as

intermittent flow or continuous flow. In intermittent flow devices (also

called discontinuous or semicontinuous flow), blood is processed in

discrete batches. Separation can occur until the separation container is

filled with the most dense component; then the container must be emptied

before the next batch is processed. This is in contrast to continuous flow

devices, in which low-, high-, and intermediate- density fractions can all

be removed in an ongoing manner so that the separation container need

not be emptied until the end of the procedure.( see figure4)

Figure 4 Centrifuging

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Filtration

Filtration or the use of membrane separators isolates blood

components on the basis of differences in particle size. Usually, plasma is

separated from the cellular elements. For example, the effective filter

pore size may be 0.6 micron, whereas the diameter of the platelet, the

smallest cellular element, is 2 to 3 microns. As whole blood flows by the

membrane surface under pressure, plasma passes through the pores and is

collected while the cellular elements are retained for return to the donor

or patient.

Most membrane separators used in apheresis today are composed

of a bundle of parallel, single, hollow fiber filters confined in a plastic

cylinder. Each fiber resembles a straw with many holes in its walls.

Whole blood under pressure enters at one end; as it flows through the

hollow fibers, plasma is squeezed out the walls and a more concentrated

cell suspension exits at the other end. In the most common layout, blood

enters through a bottom port, cells exit from a top port, and plasma is

withdrawn from a side port. An additional side port is usually provided to

monitor pressure.

2- Therapeutic apheresis:

Blood is removed via a compatible blood pump capable of

monitoring pressures and detecting air and sent through the Plasmaflo

filter fibers, which separates whole blood from plasma. The holes in the

wall of the filter fibers are too small to allow blood cells to pass through,

so the plasma is 'sieved out' and removed by the PlasmaPro dual track

pump for discard. Simultaneously, replacement fluid is infused into the

blood circuit by the PlasmaPro and the whole blood is returned to the

patient. A typical set-up for membrane TPE is shown to the right.( see

figure5)

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Figure 5 Theraputic Apheresis

In this type of ahresis the the basic functions are: Plasma exchange

(TPE), Selective apheresis

Cytaphersis, Erythrocytapheresis, Leucapheresis

Thrombocytapheresis, and Extracorporeal photopheresis.

It is the process of withdrawing blood from a patient, removing a

specific component and subsequently rein fusing the remaining

components to treat or palliate a disease. Therapeutic Apheresis consists

of the following procedures:

1. Plasma Exchange – The removal of plasma (the liquid portion of

the blood) from a patient and replacement with a solution mixed into the

cellular portion of the blood. The replacement solution may be plasma,

5% albumin, normal saline or lactated Ringer’s solution.

2. Red Cell Exchange – The removal of a predetermined volume of

red blood cells and transfusion of allergenic red blood cells with

reinfusion of the patient’s other blood components.

3. Cytapheresis – The removal of platelets and/or white blood cells

for therapeutic reasons.

Depending on the patient’s disease, Therapeutic Apheresis may be

performed as often as daily when prescribed by the ordering physician.

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Apheresis techniques:

Depending on the substance that is being removed, different

processes are employed in apheresis. If separation by Density is required,

centrifugation is the most common method. Other methods involve

absorption onto beads coated with an absorbent material and filtration.

The centrifugation method can be divided into two basic

categories:

1- Intermittent-flow centrifugation (IFC):

The centrifugation process itself has four variables that can be controlled

to selectively remove desired components. The first is spin speed and

bowl diameter, the second is "sit time" in centrifuge, the third is solutes

added, and the fourth is not as easily controllable: plasma volume and

cellular content of the donor. The end product in most cases is the classic

sedimented blood sample with the RBC's at the bottom, the "buffy coat"

of platelets and WBC's (lymphocytes/granulocytes (PMN's, basophils,

eosinophils/monocytes) in the middle and the plasma on top

The machine is a tripod filter progam-control auto centrifugal

machine that unloads from the bottom with scrapers. It operates

intermittently. The program can be set according to the demands. The

machine can finish automatically feeding, separating, dewatering,

unloading and other process with hydraulic system, electric control

system. It can carry out close or distance operation. The machine adopts

unloading at low speed with narrow scrapers. It iswidely used in

separating suspension whose grain size is 0.05-0.15mm, it is also suitable

for separating materials whose heat sensitivity is strong. its crystal is not

broken and the operator may not be near. The machine has advantages,

such as high automation, large treatment volume, good separating result,

steady running, xonvenient operation and others, (see figure6).

The governor motor drives the tumbler to rotate at middle speed.

The feeding valve opens and the materials enter the tumbler through the

feeding pipes. The materials are spread even on the tumbler wall. When

the materials reach the preset volume, the feeding stops. The tumbler

rises to high speed. The liquid passes through the filter cloth and

discharges from thd tumbler wall holes under the function of the

centrifugal force. The solid remains in the tumbler. When the rotational

speed reduces to low speed, the scrapers rotate over and over again to

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scrape the solid down from the tumbler wall and discharge it from the

bottom of the machine.

Figure 6 IFC

2- Continuous-flow centrifugation (CFC):

Continuous flow centrifugation (CFC) historically required two

venipunctures as the "continuous" means the blood is collected, spun, and

returned simultaneously. Newer systems can use a single venipuncture.

The main advantage of this system is the low extracorporeal volume

(calculated by volume of the apheresis chamber, the donor's hematocrit,

and total blood volume of the donor) used in the procedure, which may be

advantageous in the elderly and for children.

It is uniquely designed for processing very large sample volumes.-

typically, from bioreactors and fermentors-in just a single run. With its

high speed, autoclavable continuous flow rotor, the Centrifuge Stratus is

ideal for harvesting bacterial cultures, yeast, algae, human and animal

cell. With a sediment capacity of up to 400 ml and a flow rate of 36L per

hour, the Centrifuge Stratus can easily accommodate up to 50L

bioreactors or fermentors. As a result, compared with batch processing,

time savings of up to 80% can be achieved (see figure 7).

It is designed for quick filterless separation of filler from binder

solution or other mixtures containing sediments (cement, soil, clay), in

suspension. As no filter is required, there is no dispersion of material so

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that the highest accuracy is assured. The solution is poured into the top

funnel and falls into the rotating test container dia. 70x200 mm. Because

of the centrifugal effect, the liquid rises vertically leaving the filler and

mineral particles inside the beaker. The centrifuge is supplied complete

with aluminum beaker, two sieves 0,149 mm. and 0,074 mm. mesh

respectively. The rotation speed is 11500 rpm, with automatic ramp and

preset speed control.

Figure 7 CFC

The Possible Problems Or Risks Of Apheresis Donation:

Some of the minor problems seen occasionally in normal donations

may also occur from time to time with apheresis donations. Many of

these relate to the use of a needle to puncture the vein of the donor and

include pain, bruising, infection or minor damage to the nerves in the

skin. Dizziness and fainting can also occur occasionally. These potential

problems are no more common, and some may be less common with

apheresis donations, than with ordinary whole blood donations.

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• Apheresis donations take longer than normal donations and usually

require:

• 1-2 hours for platelet apheresis

• 35-45 minutes for plasmapheresis.

• Tingling in the fingers and around the mouth can occur when the red

blood cells are returned to the donor. This is due to the infusion of citrate

(which is mixed with the blood in the collection set to prevent clotting)

with the red blood cells. Citrate is used as a fuel by the body and is

rapidly removed from the blood stream, making this a very brief

phenomenon. It can generally be overcome by slowing the rate of return

of the red blood cells or by having a drink containing calcium.

• Despite the use of citrate, it is possible that the blood may clot while out

of the body, preventing its return. However, this is very uncommon and

the volume of blood that can be lost in this way is no more than that of a

normal whole blood donation.

• Rare theoretical risks include the possibility that air might be introduced

into the donor’s blood stream but modern apheresis machines include

alarms to prevent this and donors are monitored very closely during the

procedure.

• All the tubing, needles, and bowls used in this process are sterile and

disposable. A new blood collection set is used for each donation,

avoiding any problems of contamination.

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References

1- Peter Flanagan "APHERESIS DONOR."

2- Frank Corbin; Herbert M. Cullis; "Development of Apheresis

Instrumentation".

3- http://www3.interscience.wiley.com/journal/113467388/abstract

last visit on 1\1\2011.

4- http://en.wikipedia.org/wiki/Apheresis. last visit on 1\1\2011.