Therapeutic Apheresis

Therapeutic Apheresis

Inside the black box

• Apheresis is a process by which blood being removed from a subject is continuously speparated into component parts, usually to allow a desired component(s) to be retained while the remainder is returned to the subject

• Plasmapheresis from greek apairesos or Roman aphairesis meaning to take away by force

History of Apheresis

History

• Earliest continuous flow centrifugation device was hand cranked cream separator in 1877 by Dr. Carl Gustav Patrik De Laval

• Applications of flow centrifugation in:– Petroleum industry (separate impurities)– Nuclear fuels (separate uranium isotopes)– Waste management (separate solid and liquid

wastes)

History

• Plasmapheresis (removal of plasma with return of RBC) first performed 1914 John Abel at Johns Hopkins University in a dog in context of artificial kidney research

History

• Developed manual plasmapheresis where blood drawn from donor (vein then kept open by IV saline)

• Centrifuge blood in blood bank

• RBC then reinfused with saline

• Plasma stored for use

• Major method of collecting source plasma from paid donors until early 1980’s

History

• 1959 Skoog and Adams used manual plasmapheresis in patient with Waldenstrom’s to reduce serum viscosity

• Followed by use in treatment of Rh sensitized pregnant women to prevent hemolytic disease of newborn with variable outcomes

History

• Earliest work in early 1950’s by Dr. Edwin Cohn at Harvard– Devised fractionation scheme for plasma and

important in providing albumin for WWII– Developed the Cohn centrifuge in response to

need for cellular components that might be needed in event of nuclear war

– Blood into conical centrifugal separation chamber

History

• 1962 IBM engineer son dx with CML• Together with Dr. Emil Freireich and IBM

developed NCI-IBM (2990) at National Cancer Institute

• Initially process 11L of blood from CML patients for leukopheresis

• 1964 studies on CLL patient leukopheresis• 1969 1st automated plasma exchange

procedures

Principle of Operation

Principle of Operation

• Blood reaching equilibrium after application of centrifugal force:

Plasma (1.025-1.029 specific gravity)

Platelet (1.040)

Mononuclear (lymph, mono, PBSC,blast) (1.070)

Granulocyte (neut, baso, eos) (1.087)

Neocyte RBC

RBC (1.093-1.096)

Principle of Operation

• Intermittent flow– Blood processed in discrete batches– Separation until container filled with dense

component (RBC)– Needs to empty before next batch

• Continuous flow– All fractions can be removed in ongoing

manner • Do not need to empty container until end of

procedure

Principle of Operation

Gambro Spectra:

• Continuous automated centrifugal separator

Inlet PumpACD pump

Waste bagPlasma collect bag

Plasma pump

Centrifuge channel

272ml ECV52ml RBC ECV

Physiology of Apheresis

Effectiveness of TPE depends on:• Volume of plasma removed relative to total

plasma volume• Distribution of substance to be removed

– Between intra and extravascular compartments

• Speed at which the substance equilibrates between compartments

• Rate at which substance is synthesized

• Mathematical models used to predict TPE outcome assume the intravascular plasma volume is a closed compartment

• Also assumes that steady state between synthesis and catabolism is not altered during TPE

• The equation that describes the removal of a substance in PLEX is:

Y = Y0e-x

Y = final concentrationY0 = initial concentratione = base of natural logarithms (2.718…..)X = number of times patient’s total plasma volume

is exchanged

• Assumes no equilibration with extravascular stores

• Assumes no further substance is produced

• Predicts 37% of substance remains at end of 1 plasma volume exchange

• 22% remaining after 1.5 PV exchange

• 14% remaining after 2.0 PV exchange

Metabolic Characteristics of Plasma Proteins

Protein Concentration in plasma (mg/mL)

% intravascular Change in catabolism with decrease conc.

Molecular weight

(kDa)

IgG 12.1 45 Decrease 150

IgA 2.6 42 Constant 160

IgM 0.9 76 Constant 950

IgD 02.6.02 75 Increase 175

IgE 0.0001 41 Increase 190

Albumin 42 40 Decrease 66

Fibrinogen 2-4 80 Constant 340

C3 1.5 53 240

A2 macroglobulin

100 constant 820

Normal Immunoglobulins

One plasma volume exchange:• IgG drops to 34% of baseline• IgA drops to 39% of baseline• IgM drops to 31% of baseline• Varying reports as to time to recovery of Ig• Ranges from 3 days to 5 weeks to full recovery

– Variation due to different methods of calculating recovery, some patients on immunosuppressive medications

Paraproteins

• Removal of paraproteins (ie myeloma) is 50% of predicted– Some cases can have greater removal than predicted

(see last 2 reasons)

• Due to:– Increase in plasma volume (up to 1.5x greater,

especially if IgG >40g/L)– Some myeloma patients have higher proportion of

IgG in intravascular space (56-85%)– As remove paraprotein in TPE, plasma volume

progressively decreases

Complement and Immune Complexes

• C3 has equal distribution between intra/extravascular space

• Decrease to 37% of baseline with 1 plasma volume exchange

• Recovery to 90% at 24 hours and 100% at 48 hours

• Similar results for circulating immune complexes

Coagulant Proteins

Fibrinogen:

• Decrease to 25% of pretreatment with single exchange of 1 PV

• Decrease to 10-30% of pretreatment with consecutive daily 1 PV exchange

• recover to 100% of pretreatment levels by 2-3 days

Coagulant Proteins

Prothrombin:• Decreased to 30% of baselineFactor VII & factor VIII:• Decreased to 45-50% of baselineFactor IX:• Decreased to 60% of baselineFactor V, X, XI:• Decrease to 38% of baselineAntithrombin:• Activity to 40%, Ag to 70%

• Recovery to 85-100% of baseline within 24 hours

• Elevation of PTT, PT, TT post exchange

• PTT,TT returned to normal 4 hours post exchange

• PT returned to normal 24 hours post exchange

• While decreases in coagulation proteins, large studies have not shown increased bleeding risks in patients undergoing repeat exchanges

• Concern if preexisting hemostatic risk:– Currently bleeding, surgical procedure within

last 24 hours, preexisting coagulopathy

Electrolytes

• Potassium decrease (minimal)(0.25meq/L with albumin and up to 0.7meq/L with FFP

• No change in sodium and glucose

• Bicarbonate decrease 6meq/L and chloride increase 4meq/L with albumin and this reverses with FFP (more citrate in FFP)

Other plasma proteins and molecules

• LDL cholesterol, ALP, ALT decrease to 37% after 1 PV exchange

• AST, LDH,amylase, CK, ferritin, transferrin decrease to 47% after 1 PV exchange

• ALT, AST, amylase 100% recovery in 48hrs

• LDH, ALP,CK 60% recovery in 48hrs• LDL cholesterol 44% recovery in 48hrs

CBC

RBC:• Up to 12% decrease in Hb immediately

after 1 PV exchange• Recovery to 100% within 24 hours• Felt to be due to expansion of plasma

volume with albumin more than FFPWBC:• Some have shown increase in neutrophils

(up to 2x109/L), while others have not

CBC

Platelets:• 15-50% reductions have been seen post

1PV exchange• With 5-10 repeated exchanges platelets

may drop to 20-25% pretreatment levels• Recover to 70-85% by 24 hours and 100%

by 72-96 hours• Platelets may fall by smaller amount if

baseline platelets <150

Removal of Autoantibodies

• Monoclonal immunoglobulins

• Paraproteins

• Polyclonal autoantibodies

• Antibodies in immune complexes

• IgG 45% intravascular• 1.25 plasma volume exchange removes 32% of

total body IgG• Reequilibration between intra/extravascular

compartments may be complete by 24 hours• To deplete total body IgG by 85% requires 5

exchanges of 1.25 plasma volumes on alternate day schedule

• 21 day resynthesis half life

• IgM 75% intravascular

• Faster rate of synthesis than IgG at 5-6 day resynthesis half life

• To reduce to 85% requires 3-4 exchanges of 1.25 plasma volumes

Hyperviscosity Syndrome

• Concentration of paraprotein at which patients develop clinical hyperviscosity is variable

• For IgM, reduction of serum viscosity may occur with removal of 0.5 plasma volume

Drug Removal

• Can remove:– ASA, tobramycin, dilantin, vancomycin, propranolol

• May reduce plasma levels of enzymes that metabolize drugs

• May reduce plasma levels of proteins that bind and transport drugs

• Depends on distribution of drug between intra/extravascular space, half life of drug in circulation, timing of administration of drug, protein bound status, not lipid or tissue bound

• 1% of prednisone removed• IVIG mainly removed as remains intravascularly• Ideally give medications after exchange

TBV calculations

• Calculate TBV by Nadler’s formula

• For male: (0.006012xht3) / (14.6xwt) + 604 = TBV(ml)

• For female: (0.005835xht3) / (15xwt) +183 = TBV (ml)– Will overestimate obese patient blood volume

and underestimate muscular patient blood volume

TBV calculations

• Other methods:• Gilcher’s Rule of 5’s:

BLOOD VOLU ME (ml/kg) of

Body wt

Fat Thin Normal Muscular

Male 60 65 70 75

Female 55 60 65 70

Infant /

child

- - 80/70 -

• Extracorporeal blood volume limited to 15% of TBV– To limit hypovolemia– Can prime with RBC if extracorporeal RBC volume is

more than 15% of RBC volume– Intraprocedure hematocrit:

(RCV-extracorporeal RCV)/TBV x100– If this is <24%, the PLEX may not be tolerated– Acute onset anemia less tolerated on exchange

Replacement Fluid

• Need replacement fluid to exert oncotic pressure to replace removed plasma– 5% albumin exerts oncotic pressure resulting

in slight reequilibration of fluid into intravascular space at end of PLEX

– FFP– Pentastarch

Volume Replacement

• Up to 2/3 of anticoagulant volume may be retained in removed plasma– Don’t have to replace this whole volume

• Hypovolemic exchanges– Potential for hypotension even if volume

overloaded at start of exchange– PLEX modulates intravascular volume only

• Unlike hemoperfusion or hemodialysis

Anticoagulant

• Citrate

• Chelates calcium and block calcium dependent clotting factor reactions– Ensures extracorporeal blood remains in fluid

state– Minimize activation of platelets and clotting

factors

Anticoagulant

• 40% plasma calcium bound to albumin• 47% free plasma calcium

– Target of chelation by citrate– Will decrease with little decrease in total

calcium

• 13% complexed to citrate/phosphate/lactate

• Ionized calcium decrease 0.1mmol/L for each 0.5-0.6 nmol/L rise in plasma citrate

Anticoagulant

• Dilution, redistribution, removal, metabolism and excretion of infused citrate are factors protecting against severe hypocalcemia

• Much of infused citrate is discarded with separated plasma

• Usually 23-33% reduction in ionized calcium• Most rapid decrease in 1st 15 mins• Serum citrate levels return to normal 4 hours

post exchange

Anticoagulant

• Citrate infusions 65-95mg/kg/hour are safe• >100mg/kg/hr lead to increased side

effects• Hypomagnesemia can worsen symptoms• Duration of procedure increases risk of

symptoms• 5% albumin can bind ionized calcium and

contribute (more than FFP which contains citrate)

Anticoagulant

Variables affecting symptoms:

• Absolute amount of calcium

• Rate of decrease

• Serum pH

• Decrease in Mg, K, Na

• sedatives

Anticoagulant

• Oral, acral paresthesia• Nausea and vomiting• Lightheadedness• Shivering, twitching, tremors• Worsening of myasthenia gravis during exchange• Muscle cramping• Tetany• QT prolongation• May cause metabolic alkalosis if renal disease and using

FFP

Vascular Access

• Blood flow rates for adults ~60-150 ml/min

• For small children may be down to 10ml/min

• Flow rate depends on:– Vascular access– Ability to tolerate citrate (related to TBV)

Vascular Access

• Peripheral veins when possible

• Draw site:– 16-18 G steel needle allows flows up to

120ml/min– Antecubital fossa

• Medial cubital, cephalic, basilic

– Disorders of autonomic nervous system have poor vascular tone, peripheral neuropathies; may be unable to maintain good flow rates

Vascular Access

• High Hct or hyperviscous patients may need 16 G

• 18 G can be used for normal viscosity or Hct to get flow up to 110 ml/min

• Soft plastic IV will colapse

Vascular Access

• Return lines:

• 17-18 G for >80ml/min

• 19 G for < 70 ml/min

• Can be used in other arm veins

• If use same arm, return line should be above (downstream) from draw line to decrease recirculation

Vascular Access

• Central lines:• Large bore allows faster flow rates up to

150ml/min• Less concern re: loss of site or vasospasm• Increased concern re: infection and/or

thrombosis• Need hard plastic hemodialysis type line• Red port: shorter draw line• Blue port: longer return line

Complications

AABB survey (1999):• 3429 therapeutic apheresis procedures • 6.8% of 1st time procedures• 4.2% of repeat procedures

– 1.6% transfusion reactions (in plasma)– 1.2% citrate related nausea/vomiting/paresthesia– 1.0% hypotension– 0.5% vasovagal event– 0.5% diaphoresis and pallor

Complications

AABB survey (contd):– 0.4% tachycardia– 0.3% respiratory distress– 0.2% tetany/seizure– 0.2% chills or rigors

• Other registry data; Canadian, Swedish demonstrate roughly same event rates

• Rates of events decreased from 80’s to 90’s due to improvement in technical issues

• Severe events ~0.3%

Complications

Mortality rates:• French registry: 1-2/10,000• Swedish registry: 0/14,000• American data: 3/10,000

– 60% cardiac or respiratory– Mainly in FFP replacement– Anaphylaxis– Spesis– PE– Line related– Risks increase in FFP exchanges

Complications

Rare events:– Allergic reactions due to ethylene oxide used

in sterilization of apheresis kit– Hemolysis in tubing– Air embolism– Circuit clotting

Indications

AABB / ASFA Guidelines

Category I:• Considered primary or standard therapy usually

on basis of controlled trialsCategory II:• Supportive or adjunctive to other therapyCategory III:• Insufficient data to determine effectiveness;

results of clinical trials may be conflicting or uncontroled anecdotal reports of efficacy

Category IV:• do not respond to apheresis therapy

Renal and Metabolic

• Antiglomerular basement membrane (Goodpastures)

• Rapidly progressive GN

• HUS• Renal tx:

– Rejection– Sensitization– Recurrent FSGS

I

IIIII

IVIIIIII

Renal and Metabolic

• Heart transplant rejection

• Acute hepatic failure• Familial

hypercholesterolemia• Overdose/poisoning• Phytanic Acid storage

disease• Lupus Nephritis

III

IIII (adsorption)II (PLEX)IIII

IV

Autoimmune and Rheumatic

• Cryoglobulinemia• ITP• Raynaud• Vasculitis• Autoimmune

hemolytic anemia• Rheumatoid Arthritis

II

II (adsorption)

III

III

III

II (adsorption)

IV (PLEX)

Autoimmune and Rheumatic

• Scleroderma• SLE• Bullous pemphigoid• Pemphigus Vulgaris

III

III

NR (AABB) /II (ASFA)

II

Hematologic

• ABO mismatched BMT

• PCV• Leuko/thrombocytosis• TTP• Post transfusion

purpura• Sickle Cell• Myleoma

(hyperviscosity)

I (RBC removal marrow)

IIIII

III

Hematologic

• Myeloma (ARF)• Coagulation factor

inhibitors• Aplastic anemia• Pure RBC aplasia• Cutaneous T cell

lymphoma• HDN• PLT alloimmunization

IIII

IIIIIII (photopheresis)

IIIIII

Hematologic

• Malaria• babesiosis

III

III

Neurologic

• Acute/chronic inflamatory demylinating polyradiculoneuropath

• Lambert-Eaton myasthenia

• Multiple Sclerosis• Myasthenia Gravis

I

II

III

I

Neurologic

• Acute CNS inflammatory demylinating

• Paraneoplastic neurologic syndrome

• Demylinating polyneuropathy IgG and IgA

• Sydenham chorea

II

III

I

II

Neurologic

• Polyneuropathy with IgM

• Cryoglobulinemia with polyneuropathy

• Myeloma with polyneuropathy

• POEMS• AL amyloidosis

II

II

III

III

IV

Neurologic

• Polymyositis• Dermatomyositis• Inclusion body

myositis• Rasmussen’s

encephalitis• Stiff man syndrome• PANDAS• ALS

IIIIIIIII

III

IIIIIIV