Hypokalemia is a low serum potassium level, which may result from a number of conditions. The normal serum potassium level ranges from 3.5 to 5.5 mEq/L; hypokalemia exists when the potassium level is less than 3.5 mEq/L.

Potassium levels normally are regulated by two mechanisms in response to variation in potassium intake. In the first mechanism, ingested potassium enters the hepatic portal circulation, which stimulates the pancreas to release insulin. The elevated levels of insulin cause the rapid transport of potassium from the extracellular space into cells. In the second mechanism, increased potassium in the circulation causes the release of renin from the renal juxtaglomerular cells; this stimulates hepatic activation of angiotensin I, which is converted to angiotension II in the lungs (Hollander-Rodriguez & Calvert, 2006).

The most common cause of hypokalemia is potassium depletion, which results from an inadequate intake or abnormal losses. Hypokalemia can also occur without actual loss of total body potassium, through processes that result in a shift from the extracellular fluid to the intracellular spaces (e.g., acidosis). In acidosis, potassium moves out of the cell in exchange for hydrogen; as the kidneys continue to excrete potassium, hypokalemia becomes evident. In metabolic acidosis, severe potassium depletion usually is seen as a result of increased bicarbonate reabsorption. Hypovolemia stimulates the rennin-angiotensin system, which leads to the secretion of aldosterone and the excretion of potassium through the kidneys (Smith, 2000).

When trauma or severe injury occurs, anabolic cellular activity increases the demand for intracellular potassium, and this can cause hypokalemia. Pseudohypokalemia can occur with leukocytosis because of an increased uptake of potassium by white blood cells after a specimen has been drawn (Smith, 2000).


Hypokalemia is an exceptionally common electrolyte abnormality in clinical practice. More than 20% of hospitalized patients have been reported to have some degree of hypokalemia (Schaefer & Wolford, 2005).

As mentioned, the most common cause of hypokalemia is potassium depletion caused by inadequate intake or abnormal losses. Although loss of electrolytes through vomiting, diarrhea, or nasogastric drainage does not cause potassium depletion, it does cause significant chloride depletion, which alters the renal signals for potassium secretion and promotes renal potassium losses (Gennari, 2002).

Increased excretion of potassium can occur through renal losses caused by diuretics, metabolic alkalosis, mineralocorticoid excess, magnesium depletion, and renal tubular acidosis.

A variety of tumors may ectopically synthesize ACTH and cause Cushing’s syndrome; this can be rapidly fatal with fast-growing tumors. The patient may complain of weakness, and hypokalemia and metabolic acidosis may be severe (Casciato, 2004).


• Inadequate dietary intake of potassium due to malnutrition or cachexia.

• Excessive loss of potassium:

• GI loss through vomiting, diarrhea, nasogastric suctioning, laxative abuse, bulimia

• Renal loss from diuretics, particularly loop and thiazide diuretics

• Metabolic acidosis

• Osmotic diuresis from uncontrolled diabetes

• Medications (penicillins can cause hypokalemia)

• Mineralocorticoid excess from primary hyperaldosteronism, glucocorticoid-responsive aldosteronism, congenital adrenal hyperplasia

• Magnesium depletion

• Renal tubular acidosis

• Excessive glucocorticoid effects (Cushing’s syndrome, exogenous steroids, ectopic adrenocorticotropic hormone production)

• Diabetic ketoacidosis (Gennari, 2002; Smith, 2000)

• Tumors that commonly cause ectopic ACTH syndrome:

• Small cell lung cancer

• Malignant thymoma

• Pancreatic cancer, especially islet cell tumors

• Bronchial carcinoids

• Tumors that uncommonly or rarely cause ectopic ACTH syndrome

• Ovarian cancer

• Thyroid cancer (except medullary)

• Colon cancer

• Prostate cancer

• Renal cancer

• Sarcomas

• Hematologic malignancies (Casciato, 2004)


The prognosis for hypokalemia depends entirely on the underlying cause. Hypokalemia caused by diarrhea has an excellent prognosis. Hypokalemia caused by a rapidly growing tumor that is producing ACTH has a poor prognosis.


1. Patients with hypokalemia usually are asymptomatic. The disorder is identified in most instances by a low serum potassium level.

2. When symptoms are present, they usually are nonspecific and related to muscular or cardiac function.

3. The patient may complain of weakness or fatigue.

4. Worsening of diabetes control and polyuria may be seen.

5. The patient may complain of palpitations.

6. Muscle cramps and pain can occur when rhabdomyolysis is caused by severe hypokalemia.

7. Vital signs usually are normal, but tachycardia and tachypnea can occur as a result of respiratory muscle weakness.

8. With severe hypokalemia, muscle weakness and flaccid paralysis may be found on the physical exam.

9. With severe hypokalemia, depressed or absent deep tendon reflexes may be found on the physical exam.

10. Alteration in mental status (depression, confusion, malaise) may be seen.

11. Dysrhythmias may be found with severe hypokalemia.

12. Laboratory tests should include electrolytes, BUN, creatinine, glucose, and magnesium levels.

13. The urine potassium level should be measured to determine whether the potassium loss is extrarenal or the result of excess renal excretion.

14. An ECG may show changes or arrhythmias. Changes associated with hypokalemia include a depressed ST segment, a flattened T wave, and the presence of a U wave.


1. The goal of treatment is to normalize the potassium level to a range of 3.5 to 5.5 mEq/L.

2. Because of the risk of hyperkalemia, intensive intravenous potassium is rarely administered or indicated (Gennari, 2002).

3. In patients with cancer, control of the underlying tumor is the most effective treatment, and hypokalemia is often difficult to treat in these patients.

4. For other causes, the primary rule is to treat the underlying cause as well.

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Oct 19, 2016 | Posted by in NURSING | Comments Off on 29. HYPOKALEMIA

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