Concentrated urine (urine osmolality >300 mOsm, specific gravity >1.010).A specific gravity 1.010 suggests concentrated urine. However, a crude estimate can be obtained by looking at the urine specific gravity. The preferred way to measure this is a direct measurement of urine osmolality.Labs should always be combined with the history, medication evaluation, and physical examination. Nonetheless, laboratory tests can often point us in the correct direction.Therefore, patients have a tendency to break the rules and fall outside the boxes. Traditional diagnostic algorithms often fail, because patients frequently have multifactorial hyponatremia (especially complex ICU patients).Interpretation of labs: a note of caution This is an unusual finding, but is totally game-changing.) (Normal or increased level indicates pseudohyponatremia. Full set of serum electrolytes (including Ca/Mg/Phos) & glucose.Labs to obtain for hyponatremia of unclear etiology Renal failure can also do this, if severe.(⚠️ Hypothyroidism is often listed as a cause of hyponatremia, but this does not appear to be evidence-based.) ( 23902827)Įdematous states (hypervolemic hyponatremia).Pain or nausea (especially post-operative, or due to extreme exercise especially marathons).Neuropsychiatric disorder (virtually any).Malignancy (especially small cell lung carcinoma).Neurologic (carbamazepine, oxcarbazepine, valproate).Psychiatric (antipsychotics, SSRIs, tricyclics, MAO inhibitors).Chemotherapy (cyclophosphamide, vincristine).Vasopressin or DDAVP (these don't technically stimulate ADH release, but rather directly stimulate ADH receptors).Medications (this list is incomplete when in doubt evaluate the medication list using Medscape or Epocrates for possible causative agents).Cerebral salt wasting (possibly a form of hypoaldosteronism).Hypoaldosteronism or a drenal insufficiency (late).GI loss (vomiting, diarrhea, gastric tube drainage).Elderly patients who eat a “tea-and-toast” diet, or anorexia (low solute intake).Beer potomania (excessive beer intake with reduced solute intake). Very rapid water intake (e.g., fraternity hazing, or water loading prior to a drug screen).Psychogenic polydipsia (especially in schizophrenia).Typically occurs only when GFR solute intake.Sorbitol/glycine (used for surgical irrigation).High protein level (multiple myeloma, IVIG).Pseudohyponatremia (serum osmolality is not actually low)
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