APHERESIS

BY EKTA JAJODIA

Apheresis is derived from a greek word meaning “to take away”

Technique in which whole blood is withdrawn – separated into its components – desired component is retained and remaining constituents are returned to donor

DEFINITION

MECHANISM OF ACTION Large-bore intravenous catheter is connected to spinning centrifuge bowl Whole blood collected from donor/ patient into the centrifuge bowl More dense elements like RBCs settle to the bottom – then WBC – Platelets – and plasma on the top

METHODOLOGY

1. Centrifugation method – separation is by density

2. Membrane filtration technique

Centrifugation method is most commonly used

TYPES OF CENTRIFUGATION METHOD

1. Intermittent flow centrifugation (IFC) –

Performed in cycles ( known as passes) Blood is collected from an individual

to prevent clotting , anticoagulant added to tubing

blood pumped into centrifuge bowl through inlet port

bowl rotates and components separated according to specific gravity

RBCs packed against outer rim of bowl(greatest density)

followed by WBCs, platelets and plasma

separated components flow from bowl through outlet port into separate collection bags

undesired components are diverted into reinfusion bag and returned to the individual

reinfusion completes one cycle

Cycles are repeated until the desired quantity of product is obtained (eg – plateletpheresis usually takes 6-8 cycles to collect a therapeutic dose)

IFC can be done – a. With 1 venepuncture (one arm procedure) –

blood is withdrawn and reinfused through the same needle

b. With 2 venepuncture (2 arm procedure) – one for phlebotomy and 1 for reinfusion

2. Continuous flow centrifugation(CFC) –

It withdraws , process and return the blood to individual simultaneously

This is in contrast to IFC procedure , which completes a cycle before beginning a new one

Always done with 2 venepuncture sites ADV- low extracorporeal blood volume is used – so useful in elderly and children

MEMBRANE FILTRATION TECHNIQUE

Blood that passes over membranes with specific pore sizes allows passage of plasma through membrane while cellular portion passes over it

Limited to only plasma collection

GUIDELINES FOR THERAPEUTIC HEMAPHERESIS BY AMERICAN

SOCIETY OF APHERESIS1. CATEGORY 1 – Efficacy demonstrated

apheresis as primary therapya. Hyperviscosityb. TTPc. GBSd. Cryoglobulinemiae. Myasthenia gravisf. CTCL

2. CATEGORY 2 – sufficient evidence to support efficacy but only on adjunctive basisa. SLEb. HUSc. RPGNd. Coagulation factor inhibitorse. Cold agglutinin hemolytic anemia

3. CATEGORY 3 - inconclusive evidence for efficacy

4. CATEGORY 4 – lack of efficacy in controlled trials

APHERESIS PROCEDURAL ELEMEMTS

1. Venous access2. Replacement fluid3. Normal constituents removed4. Anticoagulation5. Patient history and medication6. Frequency and number of procedures7. Complications

VENOUS ACCESS

Requires large bore venous catheters to sustain a flow rate of 50-100ml/min

Location – Peripheral – anticubital Central – femoral/subclavian/jugular

REPLACEMEMENT FLUID

Required in therapeutic plasmapheresis

Must be FDA approved for use with blood products – get mixed with RBCs before the return phase1.Crystalloids – 0.9% NS2.Colloids – 5% Normal serum albumin (NSA) FFP HES(hydroxy ethyl starch)

NS provides less oncotic pressure than plasma , so 2-3 times the volume removed should be replaced

Mixtures of NSA and NS has also been used

FFP is especially recommended in case of TTP

NORMAL CONSTITUENTS REMOVED

Coagulation factors – replaced in 2-3 days after exchangeMeasure PT/APTT every 2-3 days rather than daily Platelets – 25-30% loss per procedure Endogenous synthesis replaces in 2-4 days

ANTICOAGULATION

1. Citrate based – a. ACD-A(acid citrate dextrose- adenine) –MC used

b. Trisodium citrate – used with leukapheresis

2. Heparin

3. Combination of ACD-A and heparin

Citrate binds with ionised calcium and blocks calcium-dependent clotting reactions S/E – hypocalcemia – so addition of calcium with replacement solution can reduce incidence of hypocalcemia Heparin prevents conversion of prothrombin to thrombin S/E -Heparin results in systemic anticoagulation So, low amount of heparin + ACD-A is an effective anticoagulant

PATIENT HISTORY AND MEDICATION

Certain medications like antibiotic and anticoagulant are removed during aphereis – so should be given immediately after procedure

Should avoid ACE inhibitors upto 48hrs after apheresis

I II

ACE inh causes – vasodilatation

Apheresis – causes activation of bradykinin in extracorporeal circuit – potent vasodilator – profound hypotension

If ACE inh given – further hypotension

Use of apheresis technique is divided into 2 – 1. Component collection2. Therapeutic procedure

2 types of apheresis- 1. Cytapheresis (leucapheresis, plateletpheresis

and erythrocytapheresis)2. Plasmapheresis

PLATELETPHERESIS

COMPONENT COLLECTION Indication – Bleeding – secondary to thrombocytopenia or platelet dysfunction Platelet transfusion

By platelet concentrates harvested from routine whole blood donations(RDP)

By apheresis – Platelet yield is related to donor’s initial Platelet count (SDP)

Donor’s PC should be > 1.5 lakhs

If it’s the 1st donation or if 4 wks have elapsed since prior platelet donation – a PC is not reqd

If platelet donation done in <4wks – PC reqd

In apheresis product – Number of platelets (3 * 10^11 in about 300ml ) is equivalent to 6-10 random donor platelets In case of emergency can donate again after 3 days

Must not have taken NSAIDs or Aspirin within last 48 hrs

Takes about 45-90 mins Approved for 5 days storage at 20-24°C with continuous gentle agitation

At the end of storage period – the pH should be ≥ 6.2

If RBC contamination in product is negligible (<2ml) – compatibility testing not reqd

THERAPEUTIC PLATELETPHERESIS Indications - 1. For management of patients with symptomatic

thrombocythemia

2. For those who cant tolerate drug therapy like hydroxyurea and anagrelide

3. In polycythemia vera

With each procedure of TP – 50% reduction in PC

In pregnancy with thrombocythemia – drug therapy is C/I – so TP is the preferred treatment for rapid lowering of PC to prevent placental infarction and fetal death

LEUKAPHERESISCOMPONENT COLLECTION

Indication –1. Severe neutropenia2. Patients with infection unresponsive to

traditional therapy Sedimenting agents like HES allows better

separation of granulocytes from RBCs

<2% of total granulocytes in body are present in circulation – corticosteroids use in donor before collection can increase number of circulating granulocytes

Use of recombinant G-CSF and GM-CSF in donors – cause increase in collection of granulocytes(upto 1* )

Current standard dose is ≥1* 10^10

10^11

Shelf life is 24hrs at 20-24°C but s/b transfused as soon as possible

Due to large no. of lymphocytes present – must be irradiated to prevent GVHD (function of granulocytes is not affected by irradiation)

If RBC contamination >2ml – ABO compability testing reqd

THERAPEUTIC LEUCOCYTAPHERESIS Indication –1. To deplete malignant leucocytes in both acute

and chronic leukemias – to prevent/treat leucostatic syndrome wherein pulmonary/cerebral dysfunction may develop once TLC is >1 lakhs/cumm in AML or > 3 lakhs/cumm in CML

2. Leukemic phase of cutaneous T cell lymphoma (sezary syndrome)

ERYTHROCYTAPHERESISCOMPONENT COLLECTION

done in 2 ways

2 units of RBCs

In such a case, donor must wait for 16 weeks before next RBC donation

1 unit of RBC collected concurrently with plasma/platelets

Donor criteria –For females – 5’5” height ≥ 150 pounds weight hematocrit level of 40%

For males – 5’1” height ≥ 130 pounds weight hematocrit - 40%

THERAPEUTIC ERYTHROCYTAPHERESIS

Its an exchange procedure MC used in – 1. Sickle cell disease – during severe crisis such as stroke, acute chest syndrome, priapism and cholestasis

Exchanged with RBC containing ≥ 70% HbA

2. In parasitic infection – severe falciparum malaria and babesiosis – to lower parasite load

PLASMAPHERESISCOMPONENT COLLECTION

Indication – To collect immune plasma from donors with increased concentration of certain plasma immunoglobins

RBCs must be returned within 2 hrs of phlebotomy

RBC loss s/n/b > 25ml/week

Amount of blood processed at one time s/n/b >500ml – not >1000 ml in 48 hrs – and not >2000 ml in 7 day period

THERAPEUTIC PLASMAPHERESIS

Purpose is to remove offending agent in plasma causing clinical symptoms

Replacement fluid must be given

Factors removed by plasmapheresis – 1. Immune complexes (in SLE)2. AutoAbs or alloAbs (F-VIII inh)

4. Abs causing hyperviscosity (in Waldenstrom’s macroglobulinemia

5. Protein bound toxins

6. Lipoproteins

7. Platelet aggregating factors (in TTP)

IMMUNOADSORPTION Method in which a specific ligand binds to insoluble matrix in a column

Plasma is then perfused over the column

Selective removal of pathogenetic substance and return of patient’s own plasma

ADSORBENT SUBSTANCE REMOVED

APPLICATION

Charcoal Bile acids Cholestasis

A and B Ags Anti-A and Anti-B Transplantation

Anti-LDL LDL hypercholesterolemia

DNA ANA, Immune complexes

SLE

Protein A(styphylococcal)

IgG, Immune complexes ITP, HUS

PHOTOPHERESIS

FDA approved for Cutaneous T-cell lymphoma Patient is treated with drug psoralen

It binds to DNA of all nucleated cells

Leucocytapheresis done and WBCs exposed to UV-A light

this activates psoralen and prevents replication

These treated cells are then returned to patient

Also indicated in – scleroderma, RA, Acute and chronic GVHD

ADVERSE EFFECTS1. Citrate toxicity

2. Vascular access complications – sepsis, hematoma, phlebitis

3. Vasovagal reactions4. Hypovolemia5. Allergic reactions6. Air embolism7. Depletion of clotting factors8. Transfusion transmitted infections

IMPORTANT POINTS TO REMEMBER In apheresis procedure, blood is withdrawn from donor/patient – separated into components – one or more components are retained – remaining constituents combined and returned back to the individual

Apheresis by IFC – requires only one venepuncture site

Apheresis by CFC – requires 2 venepuncture site – withdrawal and return of blood occurs simultaneous

CFC has an advantage of lower extracorporeal volume

MC anticoagulant used is - ACD-A

In therapeutic plasmapheresis – replacement fluid used are – NS, NSA, HES and FFP

FFP especially in case of TTP

Granulocyte concentrates should contain a minimum of 1 * 10^10 granulocytes

Plateletpheresis products should contain a minimum of 3 * 10^11 platelets , an equivalent of 6-10 random platelet concentrates

REFERENCES

1. Modern blood banking and tranfusion practices – Denise M. Harmening

2. Recent advances in hematology

3. Various internet sources

THANK YOU