Extracorporeal therapies

Question 1

Ideal PK properties of drugs suitable for clearance by hemodialysis? Examples?

Answer 1

Low molecular weight
Low Vd (<1L/kg)
Low plasma protein binding
E.g. Baclofen

Question 2

Types of TPE?

Answer 2

1) Membrane based TPE - apheresis based on molecular size

2) Centrifugal TPE - apheresis based on molecular density. Adv - possible for other apheresis techniques e.g. RBC, WBC, platelets. Disadv - require specific machines, only available in few specialized institutions.

Question 3

Hemoperfusion (HP) - definition, indications? complications?

Answer 3

Def: direct molecular adsorption by activated charcoal, and can remove any drug or toxin with affinity to charcoal, independent of molecular weight and plasma protein binding, until saturation of the filter is reached.

Common complications: thrombocytopenia, leukopenia, hypocalcemia, hypoglycemia, hypothermia. Mostly eliminated by HP & haemodialysis (HP/HD) - combo therapy where blood is first filtered with HP and then processed through an HD filter before returning to the patient.

Question 4

TPE indications?

Answer 4

IMD
Hyperviscosity syndrome
Highly protein-bound toxins

Question 5

Anti-coagulation during TPE - methods & indications?

Answer 5

Systemic heparinization (SH) - contraindicated in hemostatic disorders (IMTP, DIC, pulmonary hemorrhage, CNS bleeding).
Regional citrate anticoagulation (RCA) - citrate-Ca complexes accumulate when administration rate > hepatic metabolism –> ionized hypoCa, metabolic alkalosis. Contraindicated for mTPE (humans). Low admin rate with hemostatic disorders (when cannot use SH).