Hyponatremia with

Hyponatremia is very common in hospitalized patients and is defined as a serum sodium concentration below 136 mEq/L (136 mmol/L). Clinical signs and symptoms appear at concentrations below 120 mEq/L (120 mmol/L) and typically consist of agitation, fatigue, headache, muscle cramps, and nausea. With profound hyponatremia (less than 110 mEq/L [110 mmol/L]), confusion, seizures, and coma maybe seen. Because therapy is also influenced by volume status, hyponatremia is further defined as (1) hypertonic hyponatremia (2) hypotonic hyponatremia with an increased ECF volume (3) hypotonic hyponatremia with a normal ECF volume and (4) hypotonic hyponatremia with a decreased ECF volume.16... 

Hypotonic hyponatremia with an increase in ECF is also known as dilutional hyponatremia. In this scenario, patients have an excess of total body sodium and TBW however, the excess in TBW is greater than the excess in total body sodium. Common causes include CHF, hepatic cirrhosis, and nephrotic syndrome. Treatment includes sodium and fluid restriction in conjunction with treatment of the underlying disorder—for example, salt and water restrictions are used in the setting of CHF along with loop diuretics, angiotensin-converting enzyme inhibitors, and spironolactone.15... 

In hypotonic hyponatremia with a decreased ECF volume, patients usually have a deficit of both total body sodium and TBW, but the sodium deficit exceeds the TBW deficit. Common causes include diuretic use, profuse sweating,... 

Hypoglycemia often occurs in premature children and can usually be treated by intravenous glucose. For intractable hypoglycemia an infusion of glucagon can be used. However, it can cause thrombocytopenia and hyponatremia with convulsions (11). 

An 80-year-old woman with a high baseline fluid intake developed severe hyponatremia, with loss of consciousness and seizures, after a single dose of desmopressin 0.2 mg (49). 

There have been other reports of hyponatremia with SSRIs (38,39). Hyponatremia is probably more common with SSRIs than with tricyclic antidepressants and predominantly but not exclusively affects older patients. Most reports involve fluoxetine, but this might represent greater patient exposure. All SSRIs and venlafaxine can produce this adverse effect (SEDA-23,21 SEDA-25,14). According to published reports, the median time to the onset of hyponatremia is 13 days (range 3-120) and the presentation is of inappropriate secretion of antidiuretic hormone (38). Symptoms, such as lethargy and confusion, can be non-specific, so awareness of the possibility of SSRI-induced hyponatremia, particularly in elderly people, is needed. 

Iraqi A, Baickle E. A case report of hyponatremia with citalopram use. J Am Med Directors Assoc 2004 5 64-5. 

Hyponatremia with SSRIs is well described (SEDA-27, 12) but has also been reported with other antidepressants, including the selective noradrenaline re-uptake inhibitor reboxetine. 

Masood GR, Karki SD, Patterson WR. Hyponatremia with venlafaxine. Ann Pharmacother 1998 32(1) 49-51. 

Rhabdomyolysis occurred in two men, aged 21 and 42 years, taking clozapine (198,199). The first had no risk factors, but calcium-dependent potassium efflux, normally responsible for membrane hyperpolarization and muscle refractoriness, was severely impaired in his erythrocytes. The second had marked hyponatremia, due to psychogenic polydipsia, and developed a marked rise in creatine kinase activity (62 730 U/l) after correction of hyponatremia with hyperosmolar fluids. 

Patients with sodium depletion are at risk of developing hyponatremia with aU NSAIDs. Sulindac also provoked hyponatremia in an elderly patient taking a salt-restricted diet (47). 

Chamontin B, Fille A, Salva P, Salvador M. L inhibition selective des prostaglandines existe-t-elle A propos d une hyponatremie sous sulindac. [Does selective inhibition of prostaglandins exist Apropos of hyponatremia with suhn-dac.j Presse Med 1988 17(40) 2140-1. 

Shiba S, Sugiura K, Ebata A, et al. Hyponatremia with consciousness disturbance caused by omeprazole administration. A case report and literature review. Dig Dis Sci 1996 41(8) 1615-7. 

Mennecier D, Ceppa F, Gidenne S, Vergeau B. Hyponatremia with consciousness disturbance associated with esomeprazole. Ann Pharmacother 2005 39(4) 774-5. 

In hypoosmotic hyponatremia with a normal volume status, the most common etiologies are the syndrome of inappropriate ADH (SIADH), primary polydipsia, hypothyroidism, and adrenal insufficiency (see Figure 46-2). SIADH is usually a result of ectopic or otherwise inappropriate ADH production arising from a variety of conditions (see Chapters 45 and 50) and results in excessive H2O retention. SIADH is often diagnosed when a urine osmolality that is greater than plasma osmolality (usually by more than >i00 mOsmol/kg) is observed in the setting of hyponatremia, but only when renal, adrenal, and thyroid functions are normal. Hypothyroidism impairs free H2O excretion, whereas in adrenal insufficiency, Na" is lost in preference to IC reabsorption. Finally, euvolemic hyponatremia can be... 

Elisaf M, Theodorou J, Pappas C, Siamopoulos K. Successful treatment of hyponatremia with angiotensin-converting enzyme inhibitors in patients with congestive heart failure. Cardiology 1995 86 477 80. 

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