Snapshot A 44-year-old woman with a recent diagnosis of small cell lung cancer presents to the emergency room with her partner. She had reported some nausea and feelings of malaise yesterday. Today, she continued to feel unwell, and reported feeling lethargic and weak. She is oriented to person and place but not to time. On physical exam, she is noted to have normal skin turgor and no edema. Laboratory testing reveals hyponatremia and decreased serum osmolality. Introduction Clinical definition syndrome of inappropriate antidiuretic hormone (SIADH) is characterized by excessive free water retention and impaired water excretion, leading to dilutional hyponatremia Epidemiology demographics common in hospitalized patients, particularly those on mechanical ventilation risk factors older age malignancy pulmonary disease pneumonia tuberculosis etiology ectopic production small cell carcinoma of the lung central nervous system disorders infection e.g., encephalitis and meningitis malignancy stroke trauma drugs cyclophosphamide nonsteroidal anti-inflammatory drugs carbamazepine selective serotonin reuptake inhibitors (SSRIs) Pathogenesis impaired water excretion due to ↑ ADH may be due to increased production of ADH may be due to enhanced effects of ADH due to medications may be due to overdose of desmopressin Presentation Symptoms depends on level of hyponatremia mild symptoms (sodium usually 125-130 mEq/L) nausea and malaise moderate symptoms (115-125 mEq/L) headaches lethargy weakness severe symptoms (< 120 mEq/L) seizures coma respiratory arrest Physical exam euvolemic fluid status absence of edema normal skin turgor Studies Serum labs ↓ serum osmolality (< 275 mOsm/kg) ↓ serum sodium (< 135 mEq/L) ↓ serum uric acid (< 4 mg/dL) adrenal and thyroid function are normal Urine studies urine osmolality > serum osmolality ↑ urine osmolality (> 100 mOsm/kg) ↑ urine sodium (40 mEq/L) Differential Other causes of euvolemic hyponatremia hypothyroidism psychogenic polydipsia distinguishing factor ↑ urine osmolality on water deprivation test thiazide-diuretic use certain diets e.g., "tea and toast" (low solute diet) and beer potomania Treatment Management approach sodium management is dependent on symptom severity duration of hyponatremia (acute vs chronic) chronic hyponatremia must be corrected slowly to prevent osmotic demyelination syndrome (central pontine myelinolysis) correct underlying cause when possible Medical fluid restriction indication mild or moderate symptoms asymptomatic cases intravenous hypertonic (3%) saline indication chronic hyponatremia severe symptoms acute hyponatremia all cases salt tablets indication adjuvant therapy in patients who are asymptomatic ADH receptor antagonists indication not routinely used medications demeclocycline vaptans (tolvaptan or conivaptan) Complications Osmotic demyelination syndrome (central pontine myelinolysis) caused by rapid correction of chronic hyponatremia
QUESTIONS 1 of 5 1 2 3 4 5 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.EC.15.75) A 57-year-old female presents to the emergency department with complaints of nausea, muscle aches, and confusion that presented and worsened over the past several days. On further probing, she also reports a nagging cough with shortness of breath and a 10-lb. weight loss over the last 3 months. She does not have a primary care doctor and denies having regular check ups. She reports smoking 1 pack of cigarettes per day and denies any alcohol consumption. Her medical history is significant for hypertension, a 30 pack year smoking history, and anxiety. Vital signs are as follows: T 37.2 C, HR 86, BP 137/86, RR 14, and SpO2 96%. Physical examination shows normal skin turgor, moist mucus membranes, and no peripheral edema. A CT scan is performed to investigate the patient's cough in Figure A. Lab work is performed in the ED and the findings are below.Na: 128 mEq/LPlasma osmolality: 260 mOsm/kgUrine osmolality: 300 mOsm/kgUrine Na: 47 mEq/LWhich of the following is most likely also found in this patient? QID: 106822 FIGURES: A Type & Select Correct Answer 1 History of increased consumption of fluids 6% (3/50) 2 Increased urine glucose 0% (0/50) 3 Kidney unresponsive to antidiuretic hormone 2% (1/50) 4 Increased antidiuretic hormone 78% (39/50) 5 Decreased antidiuretic hormone 14% (7/50) M 2 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic (M1.EC.13.79) A 48-year-old female presents to the emergency room with mental status changes. Laboratory analysis of the patient's serum shows:Na 122 mEq/LK 3.9 mEq/LHCO3 24 mEq/LBUN 21 mg/dLCr 0.9 mg/dLCa 8.5 mg/dLGlu 105 mg/dLUrinalysis shows:Osmolality 334 mOsm/kgNa 45 mEq/LGlu 0 mg/dL Which of the following is the most likely diagnosis? QID: 100380 Type & Select Correct Answer 1 Aspirin overdose 12% (13/109) 2 Diarrhea 4% (4/109) 3 Diabetes insipidus 36% (39/109) 4 Primary polydipsia 17% (18/109) 5 Lung cancer 27% (29/109) M 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK
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