#Euvolemic Hyponatremia, moderate and likely chronic, etiology unknown
DDx of euvolemic hyponatremia: SIADH, Endocrinopathies, Psychogenic (primary) polydipsia, Low solute (“tea & toast” or “beer protomania”), Reset Osmostat.
ABCs – pt stable. No severe symptoms like seizures, obtundation, coma, and respiratory arrest.
Pert +/- hx:
No hx of CHF, Cirrhosis, nephrotic syndrome, or advanced renal failure which are common causes of hypervolemic hyponatremia.
No hx indicating renal losses or extra-renal losses as one would see in hypovolemic hyponatremia.
Hx review for common causes of euvolemic hyponatremia shows: No hx of polydipsia, excessive alcohol intake (beer potomania unlikely) or Low solute:“tea & toast”. No common SIADH causes such as malignancy, pulmonary disease, intracranial process, and drugs like antipsychotics, antidepressants, chemotherapy, etc. No hyperglycemia or history of mannitol or sorbitol use or recent administration of radiocontrast media.
Pert +/- PE: Volume status is euvolemic (Based on PE, evaluating of vital signs, orthostatic vitals, and evaluating for JVP, skin turgor, the status of mucous membranes, peripheral edema, BUN, Cr. Uric acid not drawn).
Pert +/- Labs:
Pert +/- Imaging/Studies:
Tx: Free water restriction.
F/u Serum Osmolality, Serum Sodium (in CMP); Urine Osmolality, Urine Sodium; Urine creatinine. All five labs must be drawn at the same time. This evaluates for SIADH.
F/u AM Cortisol, TSH, and free T4 to evaluate for endocrinopathies (hypothyroidism and glucocorticoid deficiency which can mimic SIADH)
Urinalysis; CXR
F/u daily BMP
F/u to calculate FENa
NPO for now.
D/C meds that could contribute to hyponatremia (diuretics, NSAIDs, TCAs, antipsychotics, antiepileptics, SSRIs, theophylline, amiodarone)