A technical reference covering the principles of blood component separation, centrifugal and membrane-based instrumentation, anticoagulation strategies, and vascular access protocols — designed for apheresis practitioners and trainees.
The dominant technology for therapeutic apheresis. Exploits density differences between blood components using continuous or discontinuous flow centrifugation. Enables selective removal of plasma, RBCs, platelets, or leukocytes.
Uses hollow-fiber membranes with defined pore sizes to separate plasma from cellular components. Employed in membrane plasma separation (MPS) and double-filtration plasmapheresis (DFPP). Less common in the U.S. but widely used in Asia and Europe.
Prevents clotting within the extracorporeal circuit. Citrate-based anticoagulation (ACD-A) is standard for most therapeutic procedures. Heparin is used as an alternative or adjunct. Proper management prevents both thrombotic and hemorrhagic complications.
Adequate vascular access is a prerequisite for all apheresis procedures. Access route selection depends on procedure type, patient anatomy, urgency, and duration of therapy. Peripheral veins, central venous catheters, and arteriovenous fistulas are all utilized.
Centrifugal apheresis exploits the principle that blood components separate by density when subjected to centrifugal force. Denser components (RBCs, density ~1.09 g/mL) sediment to the outer wall of the centrifuge bowl, while less dense components (plasma, density ~1.025 g/mL) accumulate at the inner wall. Platelets and leukocytes occupy intermediate positions based on their respective densities.
Blood is simultaneously drawn from and returned to the patient through a dual-lumen catheter or two separate venipunctures. The centrifuge bowl spins continuously, allowing real-time separation and collection. Requires smaller extracorporeal volume (typically 200–300 mL). Preferred for most therapeutic procedures due to hemodynamic stability.
Blood is drawn into a separation chamber, centrifuged, the target component is removed, and the remainder is returned to the patient — in cycles. Requires only a single venous access site. Larger extracorporeal volume per cycle (250–500 mL). More commonly used for platelet and granulocyte donation. Less hemodynamically favorable for critically ill patients.
In the centrifuge bowl, blood components layer in order of density from outer to inner wall: RBCs → granulocytes → monocytes → lymphocytes → platelets → plasma. The "buffy coat" interface between RBCs and plasma contains the white cell and platelet layers. Precise control of the interface position allows selective collection of any component.
A specialized centrifugal technique used in extracorporeal photopheresis (ECP). The Therakos® CELLEX® system uses counterflow centrifugation (elutriation) to enrich a mononuclear cell (MNC) fraction from the buffy coat. The MNC-enriched product is then photoactivated with 8-MOP and UVA light before reinfusion.
| Parameter | Definition | Typical Range | Clinical Significance |
|---|---|---|---|
| Inlet Flow Rate | Rate at which blood is drawn from the patient into the circuit | 40–150 mL/min (therapeutic); up to 200 mL/min (donor) | Higher rates shorten procedure time but increase hemodynamic stress; limited by vascular access |
| Centrifuge Speed (RPM) | Rotational speed of the separation chamber | Device-specific; typically 1,500–3,500 RPM | Determines separation efficiency; set automatically by most modern devices based on procedure type |
| Plasma Volume Processed | Total volume of plasma removed and replaced during TPE | 1.0–1.5× calculated plasma volume per session | Determines efficiency of target molecule removal; >1.5× provides diminishing returns with increased depletion of beneficial proteins |
| Extracorporeal Volume (ECV) | Total blood volume in the circuit at any given time | 150–350 mL (adult); must be <15% TBV in pediatrics | Larger ECV → greater hemodynamic impact; critical safety parameter in pediatrics and small adults |
| Collection Efficiency (CE) | Percentage of target component in inlet blood that is collected | CE1 (single pass): 60–80% for platelets; CE2 (double pass): higher | Determines yield per procedure; affected by hematocrit, platelet count, and device settings |
| Fraction of Cells Remaining (FCR) | Proportion of target RBCs remaining post-exchange (RBC exchange) | Target FCR ≤30% for sickle cell acute stroke prevention | Determines post-procedure HbS%; FCR = (1 − exchange efficiency)^n for n exchange volumes |
Membrane-based plasma separation uses hollow-fiber filters with defined pore sizes to separate plasma from cellular blood components. The primary membrane (pore size 0.2–0.6 µm) allows plasma to pass while retaining cells. A secondary membrane or adsorption column may further fractionate the separated plasma.
| Technique | Mechanism | Applications | Advantages / Limitations |
|---|---|---|---|
| Membrane Plasma Separation (MPS) | Primary hollow-fiber membrane (0.2–0.6 µm pore) separates plasma from cells; separated plasma is discarded and replaced with albumin/FFP | Equivalent to centrifugal TPE for most indications; widely used in Europe and Asia | Advantages: Single-needle access possible; no centrifuge required. Limitations: Transmembrane pressure must be monitored; membrane fouling with high-viscosity plasma (e.g., cryoglobulinemia) |
| Double-Filtration Plasmapheresis (DFPP) | Primary membrane separates plasma; secondary membrane (smaller pore, 0.02–0.04 µm) selectively retains large molecules (IgM, IgG, immune complexes) while returning albumin to patient | Hyperviscosity syndrome (Waldenström's); cryoglobulinemia; familial hypercholesterolemia | Advantages: Reduces albumin loss; allows selective removal of large molecules. Limitations: More complex setup; secondary membrane requires monitoring; not widely available in U.S. |
| Selective Adsorption (Immunoadsorption) | Separated plasma is passed over a column containing a specific ligand (Protein A, anti-IgG antibody, dextran sulfate) that selectively binds the target molecule; plasma is then returned to patient | Anti-GBM disease; dilated cardiomyopathy (anti-β1-AR antibodies); ABO-incompatible transplant desensitization; LDL apheresis | Advantages: Highly selective; minimal albumin depletion; columns may be regenerated for multiple uses. Limitations: Expensive; limited availability; requires specialized columns |
| LDL Apheresis | Dextran sulfate cellulose adsorption or heparin-induced extracorporeal LDL precipitation (HELP) selectively removes LDL, Lp(a), and VLDL from separated plasma | Homozygous familial hypercholesterolemia (HoFH); refractory heterozygous FH; elevated Lp(a) with progressive cardiovascular disease | Advantages: Highly selective for atherogenic lipoproteins; preserves HDL. Limitations: Requires biweekly treatments; expensive; limited to specialized centers |
Anticoagulation prevents clotting within the extracorporeal circuit. The choice of anticoagulant depends on the procedure type, patient clinical status, bleeding risk, and replacement fluid used. Citrate-based anticoagulation is the standard for most therapeutic apheresis procedures.
Trisodium citrate chelates ionized calcium (Ca²⁺) in the extracorporeal circuit, preventing activation of calcium-dependent coagulation factors (II, V, VIII, X, XI, XIII) and platelet activation. ACD-A (Anticoagulant Citrate Dextrose Solution, Formula A) is the most commonly used formulation. The citrate is metabolized by the liver to bicarbonate after return to the patient, making it essentially non-systemic at standard doses. The ratio of ACD-A to whole blood (inlet ratio) is typically 1:10 to 1:16 depending on the procedure and device.
| Parameter | Standard Setting | Adjustment Rationale |
|---|---|---|
| ACD-A:Blood Inlet Ratio | 1:12 to 1:16 (typical for TPE) | Increase ratio (more citrate) if clotting occurs in circuit; decrease if symptomatic hypocalcemia develops |
| Calcium Supplementation | Oral calcium carbonate 500–1000 mg before and during procedure; IV calcium gluconate 1–2 g for symptomatic hypocalcemia | FFP replacement → higher citrate load → more aggressive calcium supplementation required; pediatric patients require weight-based dosing |
| Monitoring | Ionized calcium (iCa²⁺) if symptomatic; clinical monitoring for paresthesias, tetany, ECG changes | Target iCa²⁺ ≥0.9 mmol/L during procedure; <0.6 mmol/L → cardiac risk |
| Hepatic Impairment | Reduce citrate dose; increase monitoring frequency | Impaired citrate metabolism → systemic hypocalcemia risk; consider heparin-based anticoagulation |
| Aspect | Details |
|---|---|
| Mechanism | Potentiates antithrombin III, inhibiting thrombin (IIa) and Factor Xa; prevents fibrin formation within the circuit |
| Typical Dosing | Initial bolus: 50–100 units/kg IV; maintenance: 1,000–2,000 units/hour infused into circuit; target ACT 200–250 seconds or aPTT 1.5–2× baseline |
| Indications | Patients with citrate intolerance (severe hepatic failure); procedures where systemic anticoagulation is desired; LDL apheresis (some protocols) |
| Contraindications | Active bleeding; HIT (heparin-induced thrombocytopenia) — use argatroban or bivalirudin instead; recent surgery (<72 hours) |
| Reversal | Protamine sulfate 1 mg per 100 units heparin administered; use with caution (risk of hypotension and anaphylaxis) |
Citrate toxicity results from systemic hypocalcemia when citrate metabolism is overwhelmed (high citrate load, hepatic impairment, hypothermia). Mild symptoms (Grade 1): perioral paresthesias, tingling in fingers/toes, metallic taste — slow infusion rate, administer oral calcium. Moderate symptoms (Grade 2): muscle cramps, tetany, nausea — IV calcium gluconate 1 g over 10 minutes; may continue procedure. Severe symptoms (Grade 3): carpopedal spasm, laryngospasm, ECG changes (prolonged QT) — stop procedure; IV calcium gluconate; cardiac monitoring; physician notification.
In therapeutic plasma exchange, the removed plasma must be replaced with an appropriate fluid to maintain oncotic pressure and intravascular volume. Replacement fluid selection significantly impacts both efficacy and adverse event risk.
| Replacement Fluid | Composition | Preferred Indications | Advantages | Limitations |
|---|---|---|---|---|
| 5% Albumin | Human albumin 50 g/L in saline; oncotically equivalent to plasma | Most TPE indications (TTP, AIDP, MG, etc.); preferred when coagulation factors not needed | Lower allergic reaction risk than FFP; no infectious disease transmission risk; no citrate load; no ABO compatibility required | Depletes coagulation factors and immunoglobulins; fibrinogen may drop below hemostatic threshold after multiple sessions; more expensive than FFP |
| Fresh Frozen Plasma (FFP) | All plasma proteins including coagulation factors, immunoglobulins, complement; ABO-compatible required | TTP (first-line — provides ADAMTS13); anti-GBM disease; Goodpasture syndrome; coagulopathic patients; pediatric patients with bleeding risk | Replaces ADAMTS13 in TTP; maintains coagulation factor levels; contains all plasma proteins | Higher allergic/anaphylactic reaction risk; citrate load (hypocalcemia risk); requires ABO compatibility; infectious disease transmission risk (low but present); transfusion-related lung injury (TRALI) risk |
| Solvent-Detergent FFP (SD-FFP) | Pooled, pathogen-inactivated plasma; same protein composition as FFP but reduced viral transmission risk | Patients with prior severe FFP reactions; high-risk settings; TTP when standard FFP not tolerated | Pathogen-inactivated (enveloped viruses); reduced allergic reaction risk vs. standard FFP; consistent protein levels | Reduced Protein S levels (thrombotic risk in some patients); more expensive than standard FFP; limited availability |
| Combination (Albumin + FFP) | Typically 70–80% albumin + 20–30% FFP | Patients requiring some coagulation factor replacement but not full FFP; multiple consecutive sessions | Balances coagulation factor maintenance with reduced allergic reaction risk; reduces citrate load vs. 100% FFP | More complex to administer; requires ABO-compatible FFP component |
Adequate vascular access is a fundamental prerequisite for all apheresis procedures. The minimum required blood flow rate for most therapeutic apheresis procedures is 40–60 mL/min, though 80–100 mL/min is preferred for efficient procedures. Access route selection must balance flow requirements, patient anatomy, procedure duration, and complication risk.
Preferred for: Short-term or single-session procedures; patients with adequate antecubital veins; discontinuous flow procedures (single-needle). Requirements: Minimum 16–18 gauge needle; vein diameter ≥3–4 mm; adequate flow rate achievable (≥40 mL/min). Limitations: Vein collapse at high flow rates; not suitable for long-term therapy; infiltration risk. Assessment: Apply tourniquet; assess vein prominence, compressibility, and straightness; warm compresses if needed.
Preferred for: Acute/urgent procedures; inadequate peripheral access; ICU patients; procedures requiring high flow rates (>80 mL/min). Common sites: Internal jugular (preferred — lower infection and thrombosis risk than femoral); femoral (rapid access in emergencies); subclavian (higher pneumothorax risk). Catheter specifications: 11–13 Fr dual-lumen apheresis catheter; minimum 20 cm length for IJ/subclavian; 24 cm for femoral. Complications: Infection, thrombosis, pneumothorax (subclavian), arterial puncture, air embolism.
Preferred for: Chronic/recurring apheresis therapy (e.g., weekly ECP for CTCL; ongoing TPE for chronic conditions); patients requiring >6 sessions. Advantages: Reduced infection risk vs. temporary CVC (subcutaneous tunnel creates barrier); patient comfort; reliable long-term access. Specifications: 12–14 Fr dual-lumen tunneled catheter; Dacron cuff promotes tissue ingrowth. Maintenance: Heparin lock between sessions; sterile dressing changes; regular assessment for infection/thrombosis.
Preferred for: Patients on chronic hemodialysis with existing AVF/AVG; long-term apheresis in dialysis patients. Advantages: High flow rates achievable; durable long-term access; no catheter-related infection risk. Limitations: Requires mature fistula (typically >6 weeks post-creation); requires trained staff for cannulation; risk of fistula damage with repeated needling; not appropriate for patients without pre-existing AVF/AVG.
Preferred for: Patients requiring intermittent apheresis (e.g., monthly LDL apheresis); patients who refuse external catheter. Advantages: Fully subcutaneous; no external components between sessions; lower infection risk than tunneled CVC. Limitations: Requires Huber needle access for each session; maximum flow rates may be lower than tunneled CVC; not suitable for procedures requiring very high flow rates (>100 mL/min); port needle dislodgement risk during procedure.
Catheter malfunction (most common): Poor flow → check patient position, catheter kinking, fibrin sheath formation; attempt catheter reversal (use arterial port as venous return); if persistent, notify physician for thrombolytic instillation (tPA 1–2 mg/lumen). Air embolism: Immediately clamp all lines; place patient in left lateral Trendelenburg position; 100% O₂; physician notification; CPR if cardiac arrest. Catheter-related bloodstream infection (CRBSI): Fever, rigors, erythema at exit site → blood cultures from catheter and peripheral vein; empiric antibiotics; consider catheter removal if unstable or fungal infection suspected.
Several apheresis platforms are in clinical use in the United States. Each platform has specific capabilities, disposable set requirements, and operational parameters. Staff must be trained and competency-assessed on each device used in their program. The following represents a general overview; practitioners should consult manufacturer Instructions for Use (IFU) for device-specific guidance.
| Platform Category | Technology | Primary Therapeutic Applications | Key Operational Features |
|---|---|---|---|
| Continuous Flow Centrifuge — Therapeutic | Continuous centrifugal separation; dual-lumen access; automated replacement fluid management | TPE, RBC exchange, leukocytapheresis, plateletpheresis, ECP (with photoactivation unit) | Automated plasma volume calculation; real-time pressure monitoring; citrate anticoagulation with automated ACD-A pump; blood warmer integration |
| Continuous Flow Centrifuge — Donor/Collection | Continuous centrifugal separation optimized for component collection efficiency | Plateletpheresis, plasmapheresis, granulocytapheresis, HPC collection (mobilized peripheral blood) | High collection efficiency; optimized for healthy donors; automated component yield calculation; CD34+ cell counting integration (some platforms) |
| Membrane Plasma Separator | Hollow-fiber membrane primary separation; optional secondary membrane or adsorption column | TPE (membrane), DFPP, immunoadsorption, LDL apheresis | Transmembrane pressure monitoring; single-needle access option; secondary column integration for selective apheresis |
| ECP Photoactivation System | Integrated buffy coat collection + 8-MOP addition + UVA photoactivation + reinfusion | CTCL (Sézary syndrome, mycosis fungoides); GvHD; solid organ transplant rejection | Automated Uvadex® (8-MOP) dosing; UVA light delivery system; closed system to minimize contamination; integrated with centrifuge platform |
All apheresis equipment must undergo Installation Qualification (IQ), Operational Qualification (OQ), and Performance Qualification (PQ) before clinical use. IQ verifies correct installation; OQ verifies the device operates within manufacturer specifications; PQ verifies the device performs as expected in the clinical setting using representative procedures. Preventive maintenance must follow manufacturer schedules, and all maintenance must be documented. Loaner or replacement equipment must be re-qualified before clinical use.
Clinical Disclaimer: This page is intended for educational and informational purposes only. Technology specifications, machine parameters, and procedural protocols described here are general summaries and may not reflect the most current device software, institutional configurations, or manufacturer updates. Always consult current manufacturer documentation, institutional SOPs, and qualified apheresis specialists before clinical application. This content does not constitute medical advice and is not a substitute for professional clinical judgment.