When serum potassium is less than 3.5, the condition hypokalemia is suggested. There can be many causes of hypokalemia, and it is important to find out why potassium levels are low, not assuming it is merely a low potassium intake.
Causes
Nutritional: Poor potassium intake, IV fluids low in potassium (if hospitalized), anorexia, a high carbohydrate diet.
GI Loss: Diarrhea, vomiting, malabsorbtion, intestinal fistula, ureterosigmoidostomy, laxative/enema use.
Renal Loss: Renal tubular acidosis, chronic renal disease, Fanconi’s syndrome, Barter’s Syndrome, Liddle’s Syndrome, Gentamicin, Amphotericin, Carbenicillin or diuretic use.
Endocrine: Insulin therapy, glucose therapy, diabetic ketoacidosis, GI drainage, hyperaldosteronism, congenital adrenal hyperplasia, hypokalemic periodic paralysis, exogenous mineralocorticoids, Adrenal adenomas, Leukemia (pseudohypokalemia).
Alkalosis is associated with low potassium also. Potassium is necessary for proper nerve conduction, and cardiac arrhythmia is the most serious consequence of this condition.
The clinical signs of hypokalemia include weakness, silent distention of the abdomen, dyspnea, cardiac arrhythmia, and EKG changes. Serum potassium levels are usually low, but may be normal in spite of intracellular depletion (as is common in diabetic ketoacidosis). Many of the causes are renal; these may be divided into those associated with hypertension (secondary to hyperaldosteronism and hyperreninism) versus normotensive causes which affect tubular function. Symptoms start to appear when serum potassium drops below 3.0. These symptoms include: hyperglycemia, carbohydrate intolerance, sodium retention and edema, hyposthenia causing polyuria and polydipsia, and neuromuscular signs such as weakness, paralysis, intestinal ileus, autonomic insufficiency with orthostatic hypotension, lethargy and confusion. Cardiac arrhythmias may also develop.
Conventional treatment
If the potassium is less than 3, or symptoms are present, the patient should be placed on a cardiac monitor during treatment. Urine output should be measured to make sure that urine is produced, and that potassium will not accumulate to toxic levels. Unlike treatment of hyponatremia, potassium replacement is not a matter of calculating a correction based on serum potassium levels, since these are a poor reflection of the overwhelming proportion of potassium that is intracellular. Except for emergency management, potassium replacement should proceed slowly to allow equilibration. Large intravenous loads of potassium should be avoided. Potassium can be given by mouth, using 3 mEq/kg/day in addition to maintenance requirements. The citrate salt is more palatable than the chloride salt.
The approximate total body potassium is 55 meq/kg. When serum potassium (K+) is decreased by 1 meq/dl: there is an approximate 350 meq K+ deficit. When serum potassium is less than 2 meq/dl: there is an approximate 1000 meq K+ deficit.