Treatment of Hyponatremic Encephalopathy

Treatment of Hyponatremic Encephalopathy

Correspondence LETTERS TO THE EDITOR Treatment of Hyponatremic Encephalopathy To the Editor: In the March issue of AJKD, Ayus et al1 describe their ex...

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Correspondence LETTERS TO THE EDITOR Treatment of Hyponatremic Encephalopathy To the Editor: In the March issue of AJKD, Ayus et al1 describe their experience treating hyponatremic encephalopathy with 500 mL of 3% sodium chloride solution over 6 hours. This provocative report raises at least 2 important questions. First, the authors point out that “symptoms of hyponatremic encephalopathy are largely related to cerebral edema” and therefore this condition “constitutes a medical emergency.”1(p435) Given this context, why do the investigators support a slow infusion (83 mL/h) rather than the recently recommended bolus therapy of 100 to 150 mL of 3% sodium chloride solution given over 10 to 20 minutes (up to 3 doses or until serum sodium concentration has increased by 5 mEq/L), which can prevent brain herniation and stop seizure activity quickly?2,3 Second, why did the authors’ continuous hypertonic saline solution protocol not include an adjustment for body weight, as has been recommended for bolus therapy?2,3 Because all patients received the same “uniform treatment protocol,” a 50-kg patient would be expected to have had twice the increase in serum sodium concentration as would a 100-kg patient (assuming similar percentages of water weight). Thus, applying this protocol without considering a patient’s total-body water risks overcorrection in small people, who are found frequently among patients with diuretic-induced hyponatremia,4 and undercorrection in very large ones, as may have occurred in 2 of the authors’ cases.

treatment, and why did we not adjust the volume administered for weight. Our treatment protocol was initiated in 1996, well before repeated-bolus hypertonic saline solution became an accepted therapy.3 Bolus therapy was incorporated into guidelines for the treatment of exercise-associated hyponatremia in 2007,4 and the 2014 European guidelines currently recommend a variation of our approach.5 Even so, the superiority of bolus therapy versus continuous infusion has never been demonstrated. What our series demonstrates is that as much as 500 mL of 3% sodium chloride solution can be given safely and effectively through a peripheral intravenous line in a non–intensive care unit setting to treat hyponatremic encephalopathy.2 This is very similar to the 450 mL that would result from 3 repeated boluses of 150 mL of 3% sodium chloride solution given over 1 hour as per the European guidelines.4 On the second point, Dr Spital is correct that the response to 3% sodium chloride solution will vary by patient size. We used a uniform rather than weight-based dose for simplicity because most of these patients were critically ill and we thought that obtaining an accurate weight at the time of presentation could be challenging. For similar reasons, current recommendations for repeated-bolus therapy are not based on patient weight.4-6 Use of 500 mL of 3% sodium solution is sufficient to increase the serum sodium level by 5 mEq/L in a 100-kg individual, and although administration of 500 mL could increase serum sodium level by as much as 10 mEq/L in a 50-kg patient, we consider this as within the acceptable limits of safe correction for severe hyponatremic encephalopathy, as our study demonstrates. Juan Carlos Ayus, MD1 Michael L. Moritz, MD2 1 Renal Consultants of Houston, Houston, Texas 2 University of Pittsburgh School of Medicine Pittsburgh, Pennsylvania

Aaron Spital, MD Mt. Sinai St. Luke’s Roosevelt Hospital, New York, New York

Acknowledgements Financial Disclosure: The author declares that he has no relevant financial interests.

References 1. Ayus JC, Caputo D, Bazerque F, et al. Treatment of hyponatremic encephalopathy with a 3% sodium chloride protocol: a case series. Am J Kidney Dis. 2015;65(3):435-442. 2. Spasovski G, Vanholder R, Allolio B, et al. Clinical practice guidelines on diagnosis and treatment of hyponatremia. Nephrol Dial Transplant. 2014;29(suppl 2):ii1-ii39. 3. Sterns RH. Disorders of plasma sodium—causes, consequences, and correction. N Engl J Med. 2015;372(1):55-65. 4. Hix JK, Silver S, Sterns RH. Diuretic-associated hyponatremia. Semin Nephrol. 2011;31(6):553-566. Ó 2015 by the National Kidney Foundation, Inc. http://dx.doi.org/10.1053/j.ajkd.2015.04.052

In Reply to ‘Treatment of Hyponatremic Encephalopathy’ We appreciate the comments of Dr Spital1 regarding our case series reporting our experience2 with a uniform treatment protocol of 500 mL of 3% sodium chloride solution over 6 hours for hyponatremic encephalopathy. Dr Spital raised 2 important concerns: why did we not use bolus therapy for

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Acknowledgements Financial Disclosure: Drs Moritz and Ayus have received consulting fees from Otsuka Pharmaceuticals.

References 1. Spital A. Treatment of hyponatremic encephalopathy. Am J Kidney Dis. 2015;66(3):540. 2. Ayus JC, Caputo D, Bazerque F, Heguilen R, Gonzalez CD, Moritz ML. Treatment of hyponatremic encephalopathy with a 3% sodium chloride protocol: a case series. Am J Kidney Dis. 2015;65(3):435-442. 3. Ayus JC, Arieff A, Moritz ML. Hyponatremia in marathon runners. N Engl J Med. 2005;353(4):427-428. 4. Hew-Butler T, Ayus JC, Kipps C, et al. Statement of the Second International Exercise-Associated Hyponatremia Consensus Development Conference, New Zealand, 2007. Clin J Sport Med. 2008;18(2):111-121. 5. Spasovski G, Vanholder R, Allolio B, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrol Dial Transplant. 2014;29(suppl 2):i1-i39. 6. Moritz ML, Ayus JC. 100 cc 3% sodium chloride bolus: a novel treatment for hyponatremic encephalopathy. Metab Brain Dis. 2010;25(1):91-96. Ó 2015 by the National Kidney Foundation, Inc. http://dx.doi.org/10.1053/j.ajkd.2015.05.026

Am J Kidney Dis. 2015;66(3):540-544