To the Editor,

Indications for renal and extra-renal clearance techniques as treatment for acute poisoning have decreased in recent years, given the increased efficiency of general support measures and the fact that a better understanding of toxin kinetics has shown such methods to be truly useful. With this in mind, we thought that readers of Nefrología might be interested in our comments on a case published recently by Ruiz-Zorrilla et al on acetylsalicylic acid poisoning.1

Although the authors cited above state that the patient was treated with urinary acidification (Spanish version), we do not believe that this was really the case, since that treatment does not currently play any part in resolving cases of poisoning. The treatment which was in fact indicated was alkalisation of urine to reduce tubular reabsorption of acetylsalicylic acid.2 On the other hand, the reported decrease in the serum concentrations of salicylates coinciding with haemodialysis should not be considered a result of the treatment’s effectiveness. The foolproof way of demonstrating the results of these techniques is to measure the amount which is actually extracted. This is performed by using the system’s clearance of the toxin and periodically measuring the afferent and efferent salicylate concentrations, which are then compared to the body’s total toxin content. It is also necessary to point out that a patient with a serum salicylate concentration of 65.68mg/dl is not considered to absolutely require haemodialysis treatment due to poisoning, which most texts define as levels greater than 80-100mg/dl.3,4

Lastly, upon reviewing the treatment of this case of poisoning we were surprised to find no references to the use of activated charcoal. This treatment method, which cleanses the digestive tract, has nearly completely replaced gastric lavage and is fully indicated for cases of salicylate poisoning.5

We believe it necessary to stress that indications for renal and extrarenal clearance in acute poisoning depend on an evaluation of the toxin characteristics, patient's clinical situation, laboratory findings, serum toxin concentration, and the absence of other alternatives that are less costly and which may also be more effective. In the case at hand, it is very likely that the patient would also have responded well to alkaline diuresis, with early administration of activated charcoal and no haemodialysis.

Conflicts of interest

The authors affirm that they have no conflicts of interest related to the content of this article.