Therapeutic apheresis

Therapeutic apheresis is utilized to remove or manipulate specific molecules, antibodies, or cellular elements thought to be contributing to an underlying pathological process.

Relatively safe process.

Apheresis modalities include therapeutic plasma exchange, leukapheresis, extracorporeal photopheresis, thrombocytapheresis, and erythrocytapheresis.

In the process old blood and separated from the patient, a portion of which is, manipulated and the remainder return to the patient.

Procedures include therapeutic plasma exchange in which plasma is replaced with colloid or crystalloid solution, the removal and disposal of plasma solutes, Known as plasmapheresis and white blood cells, leuko-pheresis or platelets thrombocytapheresis.

In extracorporeal photopheresis the white cells removed are manipulated prior to be reinfused into the patient.

Majority of apheresis procedures are by centrifugation and require withdrawal of blood flow at 50-150 mls per minute.

Peripheral antecubital veins can be cannulated and will accommodate blood flow rates at 80 mL/min. and is an adequate technique for centrifugation.

For sequential, discontinuous exchange cycles a 1 lumen catheter is sufficient, whereas for continuous processing 2 lumens are needed.

For apheresis of less than 2 weeks duration a non-tunneled semirigid polyethylene catheter is utilized, and for longer term duration management by tunneled central venous catheters are pref2242ed over a non-tunneled catheter to decrease infection risk.

Tunnelled catheters for long-term use are usually made of silicone and are flexible, biocompatible, and have the least thrombogenicity.

Central venous catheter sites are usually in the internal jugular vein.

Central venous catheter access is not always required, and peripheral venous access alone may be an acceptable technique for apheresis.

Central venous access is associated with a high complication rates including: Infection 2-28%, thrombosis 0.2-11 %, hemorrhage 2-14%, venous stenosis 10-26% with internal jugular catheters and up to 42% with subclavian vein catheters (Allon M).

The incidence of total adverse events associated with all vascular access is as low as 1-2%.

Peripheral veins are commonly used in Europe and Australia, whereas central venous catheters are most common vascular access types used for therapeutic apheresis in North America, South America and Asia.

Apheresis procedures utilize centrifuges to separate blood components into layers within a rapidly rotating separation changes based on relative density.

The most dense layer is red blood cells, and the least dense is plasma.

Intermediate layers consist of platelet-rich plasma, lymphocytes, and granulocytes.

Red blood cells, plasma, or cells of intermediate density can be removed from anticoagulated blood during the procedure, and the fluid portion returned back to the patient along with anticoagulant, crystalloid and colloid solutions.

Membrane filtration systems can separate and collect plasma utilizing membranes permeable to high molecular weight proteins but not cellular elements.

Overall incidence of adverse events with TA is 5-12%.

Patients may experience hypersensitivity reactions due to plasma or blood product replacement fluid with manifestations ranging from urticaria to anaphylaxis.

Patients may experience hypocalcemia due to citrate anticoagulants with paresthesias, nausea, vomiting, lightheadedness and twitching.

TA may be associated with hypovolemia due to fluid shifting or vasovagal reaction with hypotension, headache, and muscle cramps.

Rare, but serious adverse events may require int2242uption or abandonment of the procedure is 0.8% of cases.

TA associated fatality can occur in less than 0.5% of cases due to cardiovascular manifestations such as arrhythmia, ischemia, pulmonary edema, pulmonary embolus, respiratory arrest tetany, seizures, and stroke.

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