Knowing that there is no proven cure for autoimmune conditions might be disturbing and concerning. Symptomatic treatment includes therapeutic plasma exchange (TPE) that acts as a superhero, calming the overactive immune system that unintentionally targets the body. TPE provides the body with a reboot, resetting the immunological system.

TPE (also known as plasmapheresis) involves the patient's blood passing through an apheresis machine, which filters out or discards filtered plasma; red blood cells are then reinfused into the patient along with replacement fluid (such as albumin or plasma).  

Discover fascinating information about the process, its uses in different medical situations, and its incredible ability to improve health by continuing to read.

Introduction

TPE is the extraction and preservation of plasma while returning all cellular components to the patients. It is the most common therapeutic apheresis treatment. TPE was initially used in multiple myeloma in 1952 to regulate hyperviscosity; by the 1970s, it had developed into a therapy option for a variety of neurological conditions. 

Throughout human history, "bloodletting," or partially withholding a patient's blood for medicinal purposes, stirred interest. The process of drawing blood, separating its plasma and cellular components, and then reintroducing the cellular components to the body combined with a substitute fluid was developed in the 20th century. 

The goal is to eliminate the substance in the plasma a toxin, antibody, or aberrant protein responsible for the clinical symptoms. TPE replenishes any component or ingredient that the patient's plasma may be deficient or lacking in. A significant amount of plasma must be extracted during TPE and replaced with enough physiological fluid (fresh frozen plasma (FFP or albumin) to keep the intravascular compartment full. 

TPE's effectiveness depends on the following factors: distribution of the pathogen between intravascular and extravascular spaces that need removal, the synthesis and equilibrium rate of that substance within the compartments, and the plasma volume (PV) eliminated relative to the patient's total PV. A single volume exchange represents 65% of the initial component extracted from the intravascular space, 1.5 PV exchanges roughly correspond to 75%, and 2 PV exchanges yield around 85%. 

TPE is a valuable treatment option for rheumatologic and renal diseases, as well as neurological conditions such as Guillain-Barre syndrome (GBS), Chronic inflammatory demyelinating polyneuropathy (CIDP) and non-neurologic conditions such as hyperviscosity syndrome, thrombotic thrombocytopenic purpura (TTP), haemolytic uremic syndrome (HUS), and idiopathic thrombocytopenia.^1,2

Mechanism of TPE

Two techniques for separating plasma from blood's cellular components are:

• Centrifugation – membrane filtration plasma exchange
• Centrifugation-based plasma separation – nephrologists use a filter akin to ultrafiltration or haemofiltration using a dialysis machine

Centrifugation separation

Most of the time, continuous flow from the patient to the centrifuge occurs by centrifugal flow devices. Before centrifugation, an anticoagulant typically citrate is added. The remaining blood components are returned with the proper replacement fluid (albumin or FFP), creating an extracorporeal circuit that flows continuously.

The centrifuge is the working component; it rotates at 2000–2500 rpm to divide the anticoagulated blood's contents according to the specific gravity or density of varied blood components.

Plasma is layered close to the axis of rotation to remove nonselective plasma. A buffy coat made up of platelets, lymphocytes, monocytes, and granulocytes in that order, extending from the axis of rotation, with red blood cells forming the outermost layer, is then present.

The centrifuge's dimensions, variable speed (revolutions per minute) and dwell time the length of time the blood stays in the centrifuge all affect how well the different components of blood are separated.

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Membrane separation

Filtration through a highly permeable membrane separates the plasma from the blood's cellular constituents. This technique sieves the blood through a membrane with pores that let the plasma proteins pass through while keeping cellular components in the bloodstream, dividing the blood into its cellular and noncellular components.

Before being returned to the patient, blood obtained via central venous access is filtered using a plasma filter. Massive pores allow ultrafiltrate or effluent production that contains all of the patient's noncellular plasma components.

To prevent haemodynamic compromise, as plasma is filtered out, it is replaced simultaneously with the proper fluids in equal volume to the plasma removed

The sieving coefficient (the ratio of a particular plasma protein or solute concentration between the filtrate and the blood side of the membrane) and the plasma filtration rate determine the removal rate of specific plasma components.

Factors that affect efficiency in vivo and reduce filtering include formed element deposition, fibre clotting, protein adsorption, concentration polarisation, and the layering of rejected protein solutes on the inner surface of the membrane.^3,4

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Indications

The Apheresis Applications Committee of the American Society for Apheresis (ASFA) has classified the illnesses suitable for TPE into four groups in the table below.

Procedure and equipment

Comprehensively examining the patient and analysing their medical history are needed when customising the procedure. Patients should be well-informed with concise and easily understood information regarding the nature, purpose and possible TPE risks. Critical care specialists in the intensive care unit, nephrologists, and dialysis technicians, having undergone specialised skill-based training, commonly undertake procedures. The equipment used in the TPE method appears in the image below.

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Multiple polysulfone capillary fibres constitute hollow fibre dialysers, cylindrical shell-shaped structures. They are favoured for paediatric patients because they are gentler than parallel plate dialysers. They require a lower dosage of heparin or citrate for anticoagulation since they consume less blood volume.

Membranes with layers and ridges form parallel plate dialysers, facilitating plasma filtering depending on pressure gradients and particle size. 

Specific patient preparation is not required. Nevertheless, a local anaesthetic (2% lidocaine injection or sedation with opioids and benzodiazepines for children) works for the insertion of a central line. The patient lies in a supine position while keeping a careful eye on the vitals to monitor for signs of hypocalcemia, volume depletion, or problems from the FFP transfusion. The chart below illustrates the procedures for doing TPE with a centrifuge-based technique.⁵

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Special considerations and monitoring

For paediatric patients, there is the option to administer magnesium preventively, but the decision is physician-dependent. The draw and return tubing are primed with packed RBCs rather than regular saline if the patient weighs less than 20 kg. Blood product return rates range from 1.5 mL/kg/min to the standard adult flat rate of 70 mL/min. 

Long-term monitoring is required. Patients should be aware of the signs and symptoms of delayed transfusion responses so they can seek medical assistance as soon as possible. These reactions can occur several days after the transfusion ceases. One possible side effect of using a central venous catheter is infection reduced by using a sterile technique. Another potential problem to discuss during the initial permission process is infection associated with blood products.⁸

Complications

Following the TPE procedure, some common complications can arise:

• Citrate anticoagulation can lead to hypocalcemia or hypomagnesemia. Intravenous calcium and magnesium replenishment manages this
• Hypothermia
• Transfusion reactions: Hydrocortisone/dexamethasone, pheniramine, and epinephrine serve to treat them symptomatically
• Fluid and electrolyte imbalance
• Thrombocytopenia and hypofibrinogenemia-related bleeding diatheses
• Hypotension
• Flushing
• Gastrointestinal symptoms like nausea and vomiting⁵

FAQs

What is the survival rate of plasma exchange?

A retrospective study that included 105 patients treated with TPE in an intensive care unit (ICU) over 11 years showed survival results of 88.6% across all indications, strengthening and validating the use of TPE in treating ICU patients.⁷

Is TPE useful in the management of COVID-19?

In patients with severe COVID-19, not receiving mechanical breathing, TPE increases tissue oxygenation, efficiently removes acute phase proteins, and lowers the inflammatory response.⁶

What is the duration of the TPE process?

Depending on the amount of plasma exchange, the process can take one to three hours.¹

How do IVIg and TPE differ from one another?

Summary

TPE aids in treating several illnesses caused by immune system malfunctions like autoimmune diseases, neurological problems, and haematologic conditions. The future of TPE is full of promising opportunities. The convergence of precision medicine, ongoing technological breakthroughs, and creative replacement fluid techniques are all explored in ongoing research. Global initiatives and cooperative research are forming a shared knowledge of TPE's potential through research, and technology anticipates an even better future.