Tuesday, May 22, 2012

Mild Hyponatremia: new risk of memory changes, gait disturbances and death



Mild Hyponatremia: new risk of memory changes, gait disturbances and death


Hyponatremia: Hyponatremia is defined as a lower than normal serum sodium concentration using routine laboratory testing of serum electrolytes. Although chronic hyponatremia below 120 mEq almost universally prompts medical investigation, milder forms are usually overlooked or disregarded as being of little clinical significance. Recently, mild-moderate hyponatremia (i.e., a serum sodium concentration >125-135 mEq/L) has been associated with distinct symptoms as well as with increased mortality after hospitalization.

What causes hyponatremia? Many conditions are associated with chronic hyponatremia, the single most common electrolyte abnormality. These include inflammation in the brain or lung, cancers, thyroid disease, kidney disease, heart failure, and several categories of medications such as oral hypoglycemics (used in patents with diabetes mellitus), narcotics, diuretics, and antidepressants, particularly those agents referred to as selective serotonin receptor inhibitors (SSRI agents).

What are the consequences of mild hyponatremia? Recent epidemiologic evidence associates mild hyponatremia (average 131 mEq/L) with impairment of short-term memory as well as an abnormal gait. While both deficits are concerning, the risk of fall is significant (more than double compared to patients with a normal serum sodium), especially in the elder population at greatest risk for hip and femoral fractures.

Standard of Care: Serum sodium should be evaluated in all patients receiving routine laboratory testing for serum electrolytes, glucose and kidney function. The finding of a serum sodium concentration below 135 mEq/L should prompt inquiry for associated changes in short-term memory, as well as an evaluation of gait. If either are implied, a search for the cause of hyponatremia is important in normalizing these parameters, thereby potentially reducing the risk of short-term memory loss, the likelihood of falling due to an unsteady gait, and decreasing the risk of mortality, particularly in patients with underlying chronic disease conditions.

References:

1. Hufschmidt A, Shabarin V, Zimmer T. Drug-induced confusional states: the usual suspects? Acta Neurol Scand. 2009;120(6):436-8.
2. Sandhu HS, Gilles E, DeVita MV, Panagopoulos G, Michelis MF. Hyponatremia associated with large-bone fracture in elderly patients. Int Urol Nephrol. 2009;41(3):733-7.
3. Waikar SS, Mount DB, Curhan GC. Mortality after hospitalization with mild, moderate, and severe hyponatremia. Am J Med. 2009;122(9):857-65.

About this Expert:

The Nephrologist Expert who wrote this article is an Associate Professor of Medicine and an attending physician in the Renal Section. His interests include education of medical students and house staff, basic research on the cellular mechanisms of ischemic acute renal failure and the care of patients with both general medical and renal diseases. This Expert is the senior author of numerous publications in the area of the cellular stress response to acute renal ischemia and has been a Principal Investigator for the National Institutes of Health for almost 20 years. He also received several awards for excellence in teaching from medical students, house staff and colleagues. Most recently, he was a finalist for the Metcalf Teaching Award for full-time faculty and received the Grant V. Rodkey award from the Medical Society for significant contributions to medical student education and mentoring. This expert has been involved in the care of complex internal medicine and nephrology patients for more than 25 years in both private practice and university hospital settings.

This medical malpractice article was written by an expert witness working with American Medical Experts, LLC (AME). AME is the nation’s leading source of medical experts for case review and testimony; AME also offers the lowest flat rate fees on Complete Case Reviews ($695) and Expert Witness Reports ($995). For more information, call 888-678-EXPERTS (888-678-3973) or visit AmericanMedicalExperts.com.

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