CAUSES :
1. DECREASED INTAKE
- STARVATION
- CLAY INGESTION
2. REDISTRIBUTION INTO CELLS
A. ACID BASE
- METABOLIC ALKALOSIS
B. HORMONAL
- INSULIN
- BETA-2 ADRENERGIC AGONISTS ( ENDOGENOUS OR EXOGENOUS )
- ALPHA-ADRENERGIC ANTAGONISTS
C. ANABOLIC STATE
- VIT B12 OR FOLIC ACID ( RBC PRODUCTION )
- GRANULOCYTE-MACROPHAGE COLONY STIMULATING FACTOR ( WHITE BLOOD CELL PRODUCTION )
- TOTAL PARENTRAL NUTRITION
D. OTHER
- PSEUDOHYPOKALEMIA
- HYPOTHERMIA
- HYPOKALEMIC PERIODIC PARALYSIS
- BARIUM TOXICITY
3. INCREASED LOSS
A. NONRENAL
- GASTROINTESTINAL LOSS ( DIARRHEA )
- INTEGUMANTARY LOSS ( SWEAT )
B. RENAL
- INCREASED DISTAL FLOW: DIURETICS, OSMOTIC DIURESIS, SALT-WASTING NEPHROPATHIES
- INCREASED SECRETION OF POTASSIUM
* MINERALOCORTICOID EXCESS : PRIMARY HYPERALDOSTERONISM, SECONDARY HYPERALDOSTERONISM ( MALIGNANT HYPERTENSION, RENIN SECRETING TUMORS, RENAL ARTRY STENOSIS, HYPOVOLEMIA ) , APPARENT MINERALOCORTICOID EXCESS ( LICORICE, CHEWING TOBACCO, CARBENOXOLONE ), CONGENITAL ADRENAL HYPERPLASIA, CUSHING SYNDROME, BARTTER SYNDROME
* DISTAL DELIVERY OF NON-REABSORBED ANIONS : VOMITING, NASOGASTRIC SUCTION, PROXIMAL ( TYPE 2 ) RENAL TUBULAR ACIDOSIS, DIABETIC KETOACIDOSIS, GLUE SNIFFING( TOLUENE ABUSE ) , PENICILLIN DERIVATIVES.
* OTHER : AMPHOTERICIN B , LIDDLE SYNDROME , HYPOMAGNESEMIA
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DIFFERENTIAL DIAGNOSIS: Spurious
hypokalemia which occurs when blood with a high WBC count (> 100,000/mm3) is allowed to stand at room temperature (WBCβs extract K from plasma), thyrotoxicosis
* Serum potassium < 3.5 mEq/L (< 3.5 mmol/L)
* PLASMA ALDOSTERONE LEVELS
SPECIAL TESTS
β’ ECG - flattening or inversion of T waves, increased prominence of U waves, depression of ST segment, ventricular ectopia
β’ Work-up for etiology - excessive renal K loss is present when urinary K is in excess of 20 mEq/day in the presence of hypokalemia. In the patient with excessive renal K loss and hypertension (HTN), plasma renin and aldosterone levels should be determined to differentiate adrenal from non-adrenal causes of hyperaldosteronism.
If HTN is absent and the patient is acidotic, RTA should be considered. If HTN is absent and serum pH is normal to alkalotic, a high urine chloride (> 10 mEq/
day) (> 10 mmol/day) suggests hypokalemia secondary to diuretics or Bartter syndrome and a low urine chloride (< 10 mEq/day) (< 10 mmol/day) suggests vomiting as the probable cause.
IMAGING If there is evidence of mineralocorticoid excess (see Special Tests), proceed with CT scan of adrenal glands