Question 25

College comments

Syllabus topic/section: 2.1.10 Immunological and Rheumatological Intensive Care L2 topic: Plasma exchange modalities

Discussion: 

This question evaluated candidates’ understanding of therapeutic plasma exchange. A standard answer was expected to include four appropriate indications, each supported by a clear rationale, along with important complications and preventative strategies.
Most candidates successfully mentioned three or four indications; however, the rationale behind the use of TPE was not clearly articulated. Candidates who included incorrect indications or confused TPE with other extracorporeal therapies tended to score lower. No additional marks were awarded for listing more than four indications, as the question specifically requested four.

Despite clear instructions to exclude vascular access issues, some candidates included these as complications, which did not attract marks. While many candidates missed at least one of the major expected complications, several provided other relevant complications that were credited appropriately. Responses that were only wordy but lacked specific details did not gain additional marks. Complications of TPE include transfusion reactions (anaphylactoid, haemolytic, TRALI) volume overload, hypothermia and hypocalcaemia among others.
 

Interpretation

a) Indications and their rationale:

• TTP: remove autoantibodies that attack the ADAMTS13 enzyme, then replace functional ADAMTS13 with FFP
• Catastrophic antiphospholipid syndrome, GBS, myasthenia gravis: remove autoantibodies, replace with albumin
• Hyperviscosity syndrome (eg. myeloma): remove excessive blood protein to reduce blood viscosity;  replace with albumin
• Amanita phalloides poisoning: toxin is highly protein bound, remove the plasma proteins and replace with FFP to replenish clotting factors depleted by hepatic failure
• Severe hyperlipidaemia and pancreatitis: remove the excess lipid

b) Complications unrelated to vascular access:

• Due to the circuit exposure
  • Low fibrinogen and coagulopathy
  • Haemolysis and thrombocytopenia
  • Hypothermia
  • Complement activation
• Due to anticoagulation
  • Paraesthesia due to hypocalcemia (due to regional citrate anticoagulation)
  • Bleeding complications
  • HITS
• Due to the replacement fluid
  • Urticaria
  • Febrile reaction to blood products
  • Anaphylaxis
• Due to the unavoidable removal of useful blood components
  • Loss of useful drugs
  • Immunesuppression
  • Anaphylaxis
  • Hypothermia
• Due to volume loss
  • Hypotension
  • Vasovagal syncope
  • Nausea and vomiting