Three case reports of the use of haemodiafiltration in the treatment of salicylate overdose

Aspirin (acetylsalicylic acid) is widely available without prescription. Although self-poisoning is rare, if severe it may be life threatening. Haemodialysis has been recommended in severe cases when salicylate levels exceed 7.3 mmol l-1. We describe three cases of severe salicylate poisoning, which were treated with continuous veno-venous haemodiafiltration (CVVHDF). All patients survived. The first case had already undergone haemodialysis before transfer to the ICU, where CVVHDF was commenced because salicylism persisted at 3 mmol l-1. A small reduction in serum salicylate was noted. In the second case, serum salicylate decreased from 8.5 to 3.5 mmol l-1 after 3 h of CVVHDF even though only minimal urine was produced. Our third case is a chronic overdose in whom serum salicylate decreased from 6.2 to 4 mmol l-1 after 4 h and to 1.4 mmol l-1 after a further 7 h. No bicarbonate was administered to this patient and elimination can only be attributed to CVVHDF and urinary clearance, which is known to be slow. We discuss the pathogenesis of severe salicylate toxicity and postulate that CVVHDF, which is widely used in the intensive care setting, may be a useful therapy in severely poisoned patients who are unstable and cannot undergo haemodialysis or in situations where haemodialysis is unavailable.