Background:
Hyponatremia is a commonly identified electrolyte abnormality. In general, the lower is the serum sodium, the greater is the likelihood of serious sequelae. Published data on profound hyponatremia is lacking. The goal of this study is to describe the initial symptoms, etiology, and outcome in patients presenting with severely depressed serum sodium.
Methods:
The computerized laboratory records of a large integrated health system were searched from January 1, 1995, through November 30, 2007, for adults with a serum sodium below 110 mEq/L Persons who developed hyponatremia while inpatients and those with a serum glucose greater than 400 mg/dL were excluded. Medical records were reviewed for demographics, symptoms at presentation, medications, chronic conditions, length of stay, survival to discharge, and neurologic outcome. The tracking of medications was limited to those linked to hyponatremia in the literature. Discharge summaries were reviewed for the presumptive cause of the hyponatremia. Online records of the Social Security Administration were queried for deaths 6 and 12 months after discharge.
Results:
One hundred and sixty‐seven patients were found who met the criteria. This represented .04% of the hospitalizations during the study period. The average age of patients was 65.7 years, and 66% were female. Racial breakdown was 47% white, 42% African American, and 11% other. Average length of stay was 9.7 days. Presenting symptoms included mental status changes (40%), nausea and vomiting (30%), and generalized weakness (30%). Hypertension affected 63% of the patients, followed by chronic obstructive lung disease (19%) and congestive heart failure (16%). The most common suspect medications were thiazide diuretics (34%), loop diuretics (22%), and neuroleptics (18%). Few patients suffered permanent neurologic injury, with 94% of those discharged at their baseline mental state. No cases of central pontine myelinolysis occurred. There was a wide range of postulated etiologies including SIADH (22%), volume contraction (13%), and polydipsia (11%). Many discharge summaries (37%) did not list an etiology for the hyponatremia. Overall mortality was 7% during the index admission and was 24% and 31% at 6 and 12 months, respectively. Most patients died with a normal serum sodium from what appeared to be underlying disease.
Conclusions:
Profound hyponatremia in adult outpatients is extremely rare. Most cases present with vague generalized symptoms, and patients often suffer from multiple comorbidities. SIADH appears to be the most common etiology, although many times physicians may not list a specific cause. Our experience reveals lower rates of mortality and morbidity because of low serum sodium than previously reported in the literature. Although profound hyponatremia should be aggressively managed, overall prognosis seems to be influenced more by the underlying disease.
Author Disclosure:
G. Buran, none.