MOFFITT ENDOCRINE REPORT PEARLS 1/25/17: Hyponatremia and the DDAVP Clamp!

Thanks to Sam for presenting the case of a middle-aged man found down with hyponatremia and hypoglycemia that resolved with IV fluids and other supportive measures. Sam taught us a bit about preventing overcorrection of hyponatremia with DDAVP (affectionately known as the “DDAVP clamp”)! Pearls below:

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Top Pearls:

  1. Hypertonic saline is the tx of choice for acute hyponatremia and chronic symptomatic hyponatremia.
  2. DDAVP “clamp” may be used for severe chronic symptomatic hyponatremia (co-administration of hypertonic saline and desmopressin) to prevent overcorrection.
  3. Do not use DDAVP in psychotic patients, edematous patients, or chronic SIADH.

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For those who want more info:

Hyponatremia is acute if it is known to have occurred within 48 hours. If >48 hours or unknown, it is chronic.

The recommended correction is no more than 8 mEq/L/day. This applies to both acute and chronic hyponatremia, although the risk of demyelination is less with acute hyponatremia.

*Pearl: Thanks Lauren for letting us know that the term “central pontine myelinolysis” has been replaced with “osmotic demyelination” since it occurs outside the pons as well!

Most cases of osmotic demyelination occur in severe hyponatremia (Na <120) when the rate of correction was more than 10-12 mEq/L in 24 hours.

Therapy regimens:

Emergency therapy = hypertonic saline bolus, 50-100 mL over 10-15 mins. Indicated in patients with severe symptoms (seizures, obtundation) and acute symptomatic hyponatremia (even mild symptoms!).

Non-emergency therapy = hypertonic saline infusion, 15-30 mL/hour. Indicated in patients with severe hyponatremia (Na <120) with mild symptoms, and acute asymptomatic hyponatremia.

What about isotonic saline? Primarily used for correction in mild hypovolemic hyponatremia (Na >120) with minimal or no symptoms. Make sure to look for causes that might be better treated with free water restriction or disease-directed therapy (e.g. steroids for adrenal insufficiency).

Sam Miller taught us about the “DDAVP clamp”: co-administration of hypertonic saline and DDAVP to prevent overly rapid correction of sodium levels. It can be considered in severe chronic hyponatremia but less in acute hyponatremia since the risks of overcorrection in that setting are lower.

The “clamp” regimen is a slow infusion of hypertonic saline (15-30 mL/hour) in combination with desmopressin (1-2 mcg IV/subQ) every 8 hours for 24-48 hours.

If DDAVP is used, it is important to restrict subsequent free water intake to avoid worsening hyponatremia. It also should not be used in psychotic patients, edematous patients, or chronic SIADH.

 

Evernote: https://www.evernote.com/shard/s272/sh/ca60a8d7-2b3e-4f3d-8234-aec159efa952/2abaddf286c93406f203e374eaa8215b

Have a great day everyone!

Sammy

 

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