Evidence-based guidance for hemodialysis, hemoperfusion, and therapeutic plasma exchange in the management of acute toxicoses in dogs, cats, and horses — synthesizing IRIS guidelines and peer-reviewed veterinary literature.
Three primary extracorporeal blood purification therapies (EBPT) used in veterinary toxicology, each with distinct mechanisms, circuit requirements, and indications for specific toxicoses.
Blood passes across a semipermeable dialyzer membrane against counter-current dialysate. Toxins are removed by diffusion (concentration gradient) and convection. HD in experimental dogs dates to 1913 and remains the most established EBPT modality for small animal toxicoses. Circuit volume (~104 mL) must be carefully considered in small patients.
Blood contacts activated carbon or resin cartridges directly — no dialysate is used. Toxins adsorb to the sorbent surface. Superior to HD for high-protein-bound, lipophilic, and larger molecules. Ideal for NSAID toxicities. Manual carbon HP (MCHP) reduces circuit volume to 40–50 mL, making it feasible in very small patients.
Plasma is separated from blood cells and replaced with fresh frozen plasma or albumin. Optimal for highly protein-bound toxins — NSAIDs (98–99% protein-bound) are the prototypical veterinary indication. A single TPE session reduces plasma NSAID levels by 51–85.5% in dogs. Circuit volume (~125 mL) may require blood prime in cats.
Key considerations that distinguish veterinary EBPT from human medicine, including small patient circuit management and species-specific pharmacology.
Standard machine-based EBPT platforms require ~104–125 mL priming volume. For a 3 kg cat (blood volume ~195 mL), this represents over 50% of total blood volume — potentially fatal without a blood prime. Manual carbon hemoperfusion (MCHP) reduces circuit volume to 40–50 mL, enabling safe treatment in very small patients at any facility with carbon filters and blood bank access (Haire et al., Front. Vet. Sci. 2024). Dogs: blood volume ~90 mL/kg. Cats: ~65 mL/kg. Rule of thumb: blood prime required when circuit volume exceeds ~10–15% of estimated blood volume.
EBPT recommendations for common veterinary toxicoses in dogs, cats, and horses. Based on pharmacokinetic properties and published veterinary literature.
| Toxin / Agent | Species | Category | Hemodialysis (HD) | Hemoperfusion (HP) | Plasma Exchange (TPE) | Notes |
|---|
Key physicochemical and pharmacokinetic parameters that govern EBPT efficacy. Colour coding reflects suitability for removal by each modality.
| Drug / Toxin | Mol. Weight (Da) | Protein Binding | Vol. Distribution (L/kg) | Water Solubility | Primary Clearance | Half-life (species) | HD | HP | TPE |
|---|
Select toxin and clinical parameters for modality guidance. Always consult a veterinary internist or specialist; contact ASPCA Animal Poison Control (+1 888-426-4435) for emergency guidance.
Select a toxin, species, and clinical parameters for evidence-informed modality recommendations.
Foundational clinical principles specific to extracorporeal blood purification in companion animal and large animal medicine.
EBPT provides a critical window after absorption but before irreversible organ injury. Do not wait for AKI or neurological deterioration to confirm the indication — treat the toxicokinetic risk, not just the observed signs.
Always calculate estimated blood volume (Dog: 90 mL/kg; Cat: 65 mL/kg) and compare to circuit priming volume before initiating. Consider MCHP or blood prime for patients where circuit volume exceeds ~10–15% of EBV.
Use protein binding, Vd, MW, and lipophilicity to select modality. NSAIDs → TPE or HP. Ethylene glycol, baclofen → HD. In-series HP+HD provides dual-mechanism clearance for complex cases.
Continue IV fluids, gastroprotection, antidotes (4-MP for EG; cyproheptadine for 5-HTP; ILE for lipophilic toxins), nutritional support, and pain management throughout EBPT. Do not pause supportive care for sessions.
Systemic heparin is standard; monitor ACT (target 1.5–2× baseline) or aPTT. Citrate regional anticoagulation is an option in patients with active bleeding risk. Platelet counts transiently decrease with HP — monitor closely.
Most veterinary EBPT data are retrospective case series (largest: 434 dogs, Chalifoux 2023) and case reports. No veterinary RCTs exist. IRIS 2024–2025 guidelines represent current best-practice consensus from field experts.
After EBPT, toxin redistributes from peripheral tissues back into blood. Clinically significant for lipophilic drugs (NSAIDs) and long-half-life compounds (naproxen, ~74 h in dogs). Monitor levels post-session and repeat TPE/HP if needed.
EBPT requires specialised equipment and trained staff. Establish referral relationships with veterinary dialysis centres early. Phone consultation before transport allows better triage and preparation, improving outcomes.
Veterinary and comparative literature supporting EBPT recommendations, with emphasis on publications from 2019–2025.