# Haemoperfusion Basics > Haemoperfusion for Dialysis Technology: charcoal cartridge adsorption, protein-bound poison indications, priming, anticoagulation and complications. - Canonical URL: https://prepelephant.com/topics/allied/dialysis-technology/haemoperfusion-basics - Exam / course: Allied Health · Subject: Dialysis Technology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Haemoperfusion Basics", PrepElephant, https://prepelephant.com/topics/allied/dialysis-technology/haemoperfusion-basics ## Direct answer Haemoperfusion passes blood directly over an adsorbent cartridge of activated charcoal or resin, letting poisons that are tightly protein-bound or too large for a dialyser stick to the sorbent instead. It is the modality of choice for severe carbamazepine, phenytoin, phenobarbitone, theophylline and paraquat poisoning, where plasma concentrations and clinical severity justify extracorporeal removal; sometimes it runs in series with haemodialysis to add small-solute clearance. The technique needs higher heparin than dialysis (adsorbents consume clotting factors and platelets), cartridges saturate within about 2-3 hours, and the watchlist is hypotension, thrombocytopenia, hypocalcaemia and charcoal embolism from a ruptured cartridge. ## What you must remember - **Principle:** adsorption onto a large sorbent surface — no membrane, no dialysate; the cartridge is the treatment. - **Target poisons (protein-bound, large Vd or poorly dialysable):** carbamazepine (about 70-80 per cent protein-bound), phenytoin (about 90 per cent), phenobarbitone, theophylline, paraquat, amanita mushroom toxin, some sedatives — whereas lithium, methanol and ethylene glycol belong to haemodialysis, not charcoal. - **Not removed usefully:** small water-soluble solutes (urea, potassium, alcohols) — pairing with dialysis covers both classes in mixed poisoning. - **Setup:** cartridge primed with saline per insert (usually 1-2 litres, gently, to wash microfines), blood flow 150-250 mL/min, session 2-3 hours until saturation, repeated as levels dictate. - **Anticoagulation is heavier than HD:** typically an initial heparin bolus around 2000-3000 units with a continuous infusion, because the sorbent surface is strongly prothrombotic — per unit protocol. - **Complications:** thrombocytopenia (platelets adhere to charcoal), hypotension at initiation, hypocalcaemia, hypoglycaemia (rare), leucopenia, and pulmonary charcoal emboli if the cartridge membrane ruptures — filter integrity is checked by visible fines in the venous line. - **Declining indications:** modern antidotes and lipid emulsion have narrowed its role, but theophylline and carbamazepine crises still reach Indian ICUs, and examination boards still love the modality logic. ## Routing a poisoned patient Three overdoses arrive in one week. The first is lithium — small ion, no protein binding, total body water distribution: charcoal cannot adsorb it meaningfully and the answer is haemodialysis, ideally early, with flow high enough to clear a toxin that re-equilibrates from cells. The second is carbamazepine — 75 per cent bound to albumin, so the dialyser sees only the free quarter, but the charcoal cartridge binds the drug from both fractions as equilibrium shifts: this is the haemoperfusion case, run at 200 mL/min for three hours, watching for a seizure-free but hypotensive hour one and a platelet count that dips by the next morning. The third is an unknown mixed sedative-plus-alcohol ingestion — here the pragmatic Indian solution is a cartridge in series with a dialyser: the dialyser clears the alcohol and acidosis, the charcoal picks up the protein-bound sedative, one vascular access, one session. The recurring decision rule is worth memorising as a sentence: dialyse what dissolves, perfuse what binds. Before committing, confirm severity criteria — rising or very high drug level, deteriorating consciousness, refractory seizures or arrhythmia, and failing native clearance — because no poison qualifies for a fistula-sized procedure just on the basis of the name. ## Where students slip The classical MCQ swaps the modalities: methanol or lithium assigned to haemoperfusion, carbamazepine or theophylline assigned to plain dialysis — both wrong, and both common distractor options. The second slip is forgetting the biology of the cartridge: it adsorbs platelets and clotting factors, so bleeding risk and platelet count are monitored, and heparin dosing runs higher than a dialysis session, not lower. Third is duration logic: the cartridge saturates by about 2-3 hours, so extending the session adds nothing — you change the cartridge or stop; and levels rebound after stopping as tissue drug re-equilibrates, which is why repeat sessions are planned rather than one heroic run. ## Frequently asked questions ### Which poisons are best removed by haemoperfusion rather than haemodialysis? Heavily protein-bound or large drugs — carbamazepine, phenytoin, phenobarbitone, theophylline and paraquat — adsorb well to charcoal, unlike small water-soluble toxins such as lithium and methanol. ### Why does haemoperfusion require more anticoagulation than haemodialysis? The sorbent surface activates platelets and consumes clotting factors, demanding higher heparin dosing with platelet and bleeding surveillance. ### How long does a haemoperfusion cartridge function usefully? About 2-3 hours before saturation, after which the cartridge is changed or the session ends; drug levels often rebound and repeat sessions are scheduled. ### What are the complications of haemoperfusion? Thrombocytopenia, hypotension at initiation, transient hypocalcaemia and leucopenia, and rare pulmonary charcoal embolism if the cartridge ruptures. ### Why combine haemoperfusion with haemodialysis in mixed poisoning? Running the cartridge in series with a dialyser clears protein-bound drugs by adsorption and small water-soluble toxins by diffusion in a single session through one access.