The major aim of this study was to assess the outcome of severe hyponatremia and characterize factors influencing outcome in hospitalized patients with this disorder. This study suggests that severe hyponatremia is associated with high mortality. It is unclear if this association derives from hyponatremia per se, or the associated comorbidity in these subjects.
Demographic and Clinical Characteristics of Study Patients
We found severe hyponatremia in 168 patients out of a total of 5994 patients with a diagnosis of hyponatremia at our facility over the study period, yielding an incidence of approximately 2.8%. Tables 1 and 2 summarize the demographic and clinical features of these patients.
Study Setting
This study was done at Grady Memorial Hospital, a large tertiary teaching hospital , that serves a mostly urban population of city of Atlanta and the surrounding counties of Dekalb and Fulton.
Hyponatremia is the most common electrolyte disorder in clinical medicine. Severe hyponatremia, defined as a serum sodium concentration of less than 115 mmol/L, may be associated with substantial morbidity and increased mortality. However, considerable controversy surrounds the optimal therapy for severe hyponatremia, as both an overly rapid correction rate and slow correction may be associated with neurologic injury and death. Ayus et al. proposed an hourly correction rate of 1.3mmol/L, using 5% saline with generic furosemide, while avoiding correction to normonatremic or hyperna-tremic levels at 48 hours, or a correction of no greater than 25mmol/L in the first 48 hours. Sterns and his coworkers, on the other hand, suggest that patients with severe chronic hyponatremia are more likely to avoid neurologic complications when hyponatremia was corrected slowly. Furthermore, it appears that chronic hyponatremia is not an entirely benign condition, as a recent report has shown that chronic symptomatic hyponatremia in post-menopausal women can be associated with major morbidity and mortality.
The treatment is based on the etiology of the hypernatremia and the estimated rapidity of development. Hypernatremic patients may have low, high or normal total body sodium (Drug Depakote used in the UK and U.S. for the treatment of the manic episodes of bipolar disorder). Hypovolemic hypernatremia is a much more common entity. These patients may have evidence of ECF volume depletion and have sustained water losses that are greater than the sodium (Canadian Cozaar helps the kidneys to eliminate extra sodium and fluids) losses. On the other hand, hypernatremic patients may have evidence of ECF expansion. These are invariably patients who have received excessive amounts of hypertonic NaCl or sodium bicarbonate. This variety of hypervolemic hypernatremia is rather infrequent. Most patients with hypernatremia secondary to water loss appear clinically euvolemic with near-normal total-body sodium (Fosamax tabletes is taken for the prevention or treatment of osteoporosis in postmenopausal women and men) status on physical examination. Hypernatremia usually occurs only in those who have no access to water. The renal losses of water that lead to euvolemic hypernatremia are a consequence of a defect in vasopressin production or release, or a failure of the collecting duct to respond to vasopressin.
Hypernatremia is not uncommon at the extremes of age and is particularly prevalent among the elderly. A serum sodium (Canadian Coumadin is in a class of drugs known as anticoagulants) level of 150 meq/1 or greater should be considered clinically significant. The prevalence of hypernatremia in the elderly has been reported to be about 1% in both hospitalized patients and in residents of long-term care facilities. Since the percentage of body water falls with age, equal volumes of fluid loss in older individuals may represent more severe dehydration than in younger individuals. In healthy older men compared to younger controls, there are deficits in both the intensity and threshold of the thirst response, compared to younger controls. As mentioned earlier, the ability of the elderly to conserve water is also impaired. In the elderly, hypernatremia carries a high risk of morbidity and mortality ranging from 40-60%. Although mortality rate was highest in those with a rapid onset and those with serum sodium level >160 meq/L, a slow correction of serum sodium (Depakote drug affects chemicals in the body that may be involved in causing seizures) over a 72-hour period was reported to improve recovery of mental functions. Several common causes of hypernatremia in the elderly are shown (Table 4).
Treatment is dependent upon the pathogenesis of the hyponatremia and the severity of symptoms. Patients with hypotension should initially be treated with normal saline to replenish the intravascular volume. Patients should then be reassessed and if symptoms of hyponatremia persist following normalization of blood pressure, hypertonic saline should be given. Furthermore, the change in serum sodium (Drug Cozaar helps the kidneys to eliminate extra sodium and fluids) concentration in response to treatment needs to be followed closely. The rate of rise of serum sodium should not exceed 0.3-0.4 mmol/hr (7-10 meq/24 hours), since correction at a rate greater than 0.5 mmol/hr has been associated with severe neurologic complications, including osmotic demyelination syndrome. Care must also be taken not to induce fluid overload and pulmonary vascular congestion. The administration of normal saline at 75 ml/hr should raise serum sodium (Fosamax medication is taken for the prevention or treatment of osteoporosis in postmenopausal women and men) by approximately 0.3-0.4 mmol/hr. If there is any concern of heart disease, a lesser rate of about 50 ml/hr is advisable. The serum sodium level should be repeated as necessary, regulated as dictated by the clinical situation with adjustment of the fluid rate as required. In sodium depletion, the quantity of sodium required to increase the serum sodium concentration by a given amount can be estimated more precisely by multiplying the desired change in serum sodium by the total body water (e.g., 8 mmol/liter change in a 60-kg person over 24 hours is 8 mmol/liter x 36 liters = 288 mmol = approximately 1.9 liter normal saline or 560 ml 3% NaCl). It should be noted that symptoms related to hyponatremia occur disproportionately throughout the population. Both aging and male gender appear to confer protection against the development of hyponatremia-associated seizures, permanent brain damage and/or mortality, although the reasons) for this is unclear. In asymptomatic patients with no evidence of volume depletion, as in SIADH, correction of the underlying problem and restriction of free water intake to 1 liter per day is usually sufficient to normalize the serum sodium (The active ingredient in Emulgel 50gm is the non-steroidal anti-inflammatory diclofenac sodium 1% w/w).