Symptom Finder - Hyperkalemia
HYPERKALEMIA
When confronted with a laboratory report of an unexpected elevated potassium level, the first thing to do in most cases is to repeat the test. The increased potassium may be due to hemolyzed blood or excessively tight tourniquet used to draw the blood. If these causes can be ruled out, one can recall most of the causes by thinking of the physiologic mechanisms of excretion and regulation.
1. Excretion: Acute renal failure causes retention of potassium. This may be caused by drugs, heavy metals, transfusion, shock, dehydration, glomerulonephritis, or obstructive uropathy.
2. Regulation: The exchange of potassium and hydrogen ions for sodium in the distal tubule is regulated by the hormone aldosterone. Consequently, in Addison disease this mechanism is partially shut down causing the retention of potassium. Various diuretics such as triamterene and the spironolactones may do the same thing. Metabolic acidosis, especially diabetic acidosis, may be associated with hyperkalemia because the potassium moves out of the cell in exchange for hydrogen ions to buffer the acidosis.
Approach to the Diagnosis
Most helpful in the diagnosis will be laboratory tests to rule out renal failure and Addison disease. Thus a CBC, urinalysis, chemistry panel, renal function tests, plasma cortisol, 24-hour urine aldosterone level, and serial electrolytes may be necessary. As a precaution, it may be wise to hold all but critical drugs until the diagnosis is certain.
Other Useful Tests
1. Corticotropin stimulation test (Addison disease)
2. Cystoscopy and retrograde pyelography (obstructive uropathy)
3. CT scan of abdomen (renal disease, neoplasm)
4. Renal biopsy (renal disease)
5. Nephrology consult
6. Endocrinology consult
7. Plasma renin level (Addison disease)
When confronted with a laboratory report of an unexpected elevated potassium level, the first thing to do in most cases is to repeat the test. The increased potassium may be due to hemolyzed blood or excessively tight tourniquet used to draw the blood. If these causes can be ruled out, one can recall most of the causes by thinking of the physiologic mechanisms of excretion and regulation.
1. Excretion: Acute renal failure causes retention of potassium. This may be caused by drugs, heavy metals, transfusion, shock, dehydration, glomerulonephritis, or obstructive uropathy.
2. Regulation: The exchange of potassium and hydrogen ions for sodium in the distal tubule is regulated by the hormone aldosterone. Consequently, in Addison disease this mechanism is partially shut down causing the retention of potassium. Various diuretics such as triamterene and the spironolactones may do the same thing. Metabolic acidosis, especially diabetic acidosis, may be associated with hyperkalemia because the potassium moves out of the cell in exchange for hydrogen ions to buffer the acidosis.
Approach to the Diagnosis
Most helpful in the diagnosis will be laboratory tests to rule out renal failure and Addison disease. Thus a CBC, urinalysis, chemistry panel, renal function tests, plasma cortisol, 24-hour urine aldosterone level, and serial electrolytes may be necessary. As a precaution, it may be wise to hold all but critical drugs until the diagnosis is certain.
Other Useful Tests
1. Corticotropin stimulation test (Addison disease)
2. Cystoscopy and retrograde pyelography (obstructive uropathy)
3. CT scan of abdomen (renal disease, neoplasm)
4. Renal biopsy (renal disease)
5. Nephrology consult
6. Endocrinology consult
7. Plasma renin level (Addison disease)