Efficacy of sustained low-efficiency dialysis in the treatment of salicylate toxicity

Bryce Lund1, Steven A. Seifert1 and Michael Mayersohn2

1 University of Nebraska Medical Center, Omaha, NE 68198 and 2 College of Pharmacy, University of Arizona, Tucson, AZ 85721, USA

Correspondence and offprint requests to: Bryce Lund, MD, University of Nebraska Medical Center, 983040 Nebraska Medical Center, Omaha, NE 68198-3040, USA. Email: blund{at}unmc.edu

Keywords: haemodialysis; overdose; salicylate; sustained low-efficiency dialysis



   Introduction
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 Introduction
 Case
 Discussion
 References
 
Sustained low-efficiency dialysis (SLED) has been used for acute renal replacement therapy [1]. It has not been evaluated in the management of salicylate toxicity or the toxicity of any agent, however. We present a case of severe salicylate toxicity initially managed with haemodialysis and then with SLED. The efficacy of SLED is compared with that found in the literature for haemodialysis and continuous therapies.



   Case
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 Introduction
 Case
 Discussion
 References
 
The patient was a 24-year-old male evaluated at a referring hospital 14 h after the ingestion of one hundred 325 mg salicylate pills (32 500 mg total dose). The serum salicylate concentration at that time was 110 mg/dl. He was transferred to our institution for dialysis.

On arrival he had been treated with intravenous bicarbonate and oral charcoal. He was afebrile with a pulse of 145 b.p.m., blood pressure was 98/62 mmHg and respirations were 35/min. He was alert and oriented but anxious, tremulous and diaphoretic. ECG demonstrated sinus tachycardia and chest X-ray was normal. Blood gases were determined at presentation with pH 7.44, pCO2 20 mmHg, and PO2 86 mmHg. Pertinent laboratory data included: haemoglobin 17.3 g/dl, sodium 136 mmol/l, potassium 4.9 mmol/l, chloride 94 mmol/l, bicarbonate 13 mmol/l, anion gap 29 mmol/l, BUN 35 mg/dl, creatinine 2.9 mg/dl, glucose 161 mg/dl, calcium 11.1 mg/dl, phosphorus 9.9 mg/dl and INR 2.2.

Serum salicylate concentration on arrival was 92.3 mg/dl (~20 h post-ingestion). The patient was in oliguric acute renal failure at this time, suggesting that any change in serum salicylate was from redistribution or activated charcoal. The next salicylate concentration was drawn when beginning haemodialysis and was 68 mg/dl. Because of a suspected laboratory error, an extrapolated value of 84 mg/dl was used for kinetic modelling. Haemodialysis was performed for 4 h using a Baxter PSN 210 filter with blood flow of 300 ml/min and dialysate flow of 500 ml/min. After completion of this 4 h treatment, the salicylate level was redrawn and the patient continued on SLED with the same filter and blood flow was changed to 200 ml/min with dialysate flow of 200 ml/min. The salicylate level was drawn every 4 h on SLED. He remained on SLED for 12 h, at which time the salicylate level decreased to 16 mg/dl. The salicylate level was 15 mg/dl 4 h after cessation of SLED. Figure 1 chronologically lists salicylate levels and mode of dialysis.



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Fig. 1. Log of serum salicylate concentration vs time. The concentration at initiation of haemodialysis (open circle) is extrapolated from previous values.

 
Urine was collected for 24 h from the initiation of haemodialysis. This included the 4 h of haemodialysis, 12 h of SLED and the remaining 8 h with no intervention. During this time, the patient produced 872 ml of urine. This collection contained 800 µg/ml, or 698 mg of salicylate eliminated via the urine. This is 2.1% of the total ingested dose estimated at 32 500 mg.

Endogenous renal clearance of salicylate was estimated to be 1.7 ml/min. The relative clearance of SLED to haemodialysis was 0.84, based on half-life estimates.



   Discussion
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 Introduction
 Case
 Discussion
 References
 
Wrathall et al. [2] reported their experience with management of salicylate toxicity with continuous veno-venous haemodiafiltration (CVVHDF). They achieved a 77–84% reduction with 11 h of CVVHDF. This is similar to our 70% reduction with 12 h of SLED. Liao et al. [3] performed a kinetic comparison between continuous veno-venous haemofiltration (CVVH), SLED and haemodialysis. The solute clearance in CVVH was 8 and 60% higher than SLED and intermittent haemodialysis, respectively.

SLED is similar to true continuous therapies in terms of salicylate clearance. The advantages of SLED include fewer complications, no specialized equipment and decreased nursing requirements [1]. The optimum role for SLED in the management of toxicities merits further study.

Conflict of interest statement. None declared.



   References
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 Introduction
 Case
 Discussion
 References
 

  1. Marshall MR, Golper TA, Shaver MJ, Alam MG, Chatoth DK. Sustained low-efficiency dialysis for critically ill patients requireing renal replacement therapy. Kidney Int 2001; 60: 1629[ISI]
  2. Wrathall G, Sinclair R, Moore A et al. Three case reports of the use of haemodiafiltration in the treatment of salicylate overdose. Hum Exp Toxicol 2001; 20: 491–495[CrossRef][ISI][Medline]
  3. Liao Z, Zhang W, Hary PA et al. Kinetic comparison of different acute dialysis therapies. Artif Organs 2003; 27: 802–807[CrossRef][ISI][Medline]
Received for publication: 27. 1.05
Accepted in revised form: 2. 3.05





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