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    This is Jeffrey Berns, Editor-in-Chief of Medscape Nephrology. I would like to call to your attention an outstanding, although rather voluminous, clinical practice guideline[1] on the diagnosis and treatment of hyponatremia. It’s out as a supplement to Nephrology, Dialysis, and Transplantation. It is mostly a European and Canadian guideline that was written by the Hyponatraemia Guideline Development Group, and it is very well worth reading. It is an outstanding description of virtually everything that you would want to know about hyponatremia. I would like to make a couple of important points from the paper. Of course, I can’t cover the whole thing; it’s about 40 pages, and the authors make several important points.

    First, they make the contention that although we sometimes see people in the hospital or in various settings who we say have “asymptomatic hyponatremia,” the vast majority of patients who have significant hyponatremia, although appearing to be asymptomatic, really are not and probably have subtle clinical abnormalities. These may be gait disturbances, a tendency to fall, decreased ability to concentrate, cognitive defects, and so forth. We are all aware of the association between hyponatremia and death, but on the more mild end of the spectrum, there are a variety of abnormalities that we are not able to detect regularly in people who have mild to moderate hyponatremia in terms of the serum sodium concentration. So the authors make the contention that there is really not such a thing as truly asymptomatic hyponatremia other than perhaps in people with minimal hyponatremia.

    They also remind us that despite common opinion, pseudohyponatremia, the laboratory abnormality due to severe hyperlipidemia or hyperproteinemia, still does exist because laboratories measure serum sodium concentration on diluted venous samples. They go through an extensive differential diagnosis and interpretation of urine osmolality and urine sodium concentration. They talk about the difference between syndrome of inappropriate antidiuretic hormone (SIADH) and so-called cerebral salt wasting. They also give some very specific guidelines about initial and subsequent treatment of hyponatremia. For instance, in the acutely symptomatic patient with severe hyponatremia, they recommend that the initial response be to give 150 mL over 20 minutes of 3% hypertonic saline, which should then be repeated at least once or perhaps more, with careful monitoring of the serum sodium concentration until symptoms resolve and the serum sodium concentration comes up by 5 mmol/L or more. They give specific guidelines about how rapidly to correct the serum sodium concentration. Of course, there has been a lot of debate and discussion about this over the years. Their recommendation is no more than 10 mmol/L in the first 24 hours and no more than 8 mmol/L subsequently over each next 24-hour period until the serum sodium comes up to about 130 mmol/L.

    They make some interesting comments and observations about treatment. They recommend against the use of demeclocycline in every circumstance, as far as I can tell. They also recommend against the use of vasopressin receptor antagonists, or vaptans, also in any circumstance. They point out that there has not been significant evidence to suggest that vaptans improve mortality or other important outcomes other than just raising the serum sodium concentration. Apparently there are some reports from manufacturers about neurologic sequelae associated with the use of these drugs, although there have not been specific cases of osmotic demyelination syndrome. There have also been reports of some liver dysfunction with high-dose vaptans in the setting of polycystic kidney disease. So the recommendations very clearly do not include the use of demeclocycline or vaptans.

    Again, this is very well worth reading. It is a thorough, comprehensive, very well-evidenced and referenced review of the clinical practice guideline on the diagnosis and treatment of hyponatremia in Nephrology, Dialysis, and Transplantation. The first author is Spasovski. It is very well worth reading.

    Jeffrey Berns, Editor-in-Chief of Medscape Nephrology, from the Perelman School of Medicine at the University of Pennsylvania in Philadelphia.

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