IN HYPOKALEMIA, the serum potassium level drops below 3.5 mEq/liter. Because the normal range for a serum potassium level is a narrow one (3.5 to 5 mEq/liter), a slight decrease has profound consequences.
How it happens
Remember that the body can't conserve potassium; inadequate intake and excessive output of potassium upsets the balance and causes a deficiency of total body potassium. Let's take a closer look at these and other causes of potassium loss.
* Not enough intake. Very simply, a lack of potassium intake decreases the body's potassium level. That happens if a person isn't eating enough food containing potassium or is getting potassium-deficient I.V. fluids.
* Too much output. Intestinal fluids contain a lot of potassium. Thus, severe gastrointestinal fluid losses from suction, lavage, prolonged vomiting, diarrhea, or laxative abuse can deplete the body's potassium supply. Fistulas and severe diaphoresis also contribute to potassium loss.
In addition, potassium can be depleted through the kidneys. High glucose concentration in the urine causes osmotic diuresis, and potassium is lost through the urine. Potassium losses are also seen in renal tubular acidosis, magnesium depletion, Cushing's syndrome, and periods of high stress. Diuresis that occurs with a newly functioning transplanted kidney can lead to hypokalemia.
* Drugs upsetting the balance. Certain drugs also trigger potassium loss: diuretics (such as thiazide and loop diuretics), certain antibiotics (such as gentamicin, carbenicillin, and amphotericin B), laxatives (when abused), corticosteroids, insulin, cisplatin, and adrenergic agents (such as albuterol and epinephrine).
Excessive secretion of insulin, whether endogenous or exogenous, may shift circulating potassium into the cells. Potassium levels also drop when adrenergic agents, such as epinephrine or albuterol, are used to treat asthma.
* Diseases wreak havoc too. Any condition that leads to the loss of gastric acids can cause alkalosis and hypokalemia. With alkalosis, potassium ions move into the cells as hydrogen ions move out, leaving less potassium in the blood. Disorders associated with hypokalemia include hepatic disease, hyperaldosteronism, acute alcoholism, heart failure, malabsorption syndrome, nephritis, and Bartter's syndrome.
What to look for
The signs and symptoms of a low potassium level reflect how important this electrolyte is to normal body functions.
* Neuromuscular alerts. Skeletal muscle weakness, especially in the legs, is a sign of a moderate potassium loss. Weakness progresses and paresthesia develops. Leg cramps occur. Deep tendon reflexes may be decreased or absent, and the respiratory muscles could be paralyzed or weakened.
Because of potassium's effects on cell function, hypokalemia can lead to rhabdomyolysis, a breakdown of muscle fibers leading to myoglobin in the urine. As smooth muscle is affected by hypokalemia, the patient may develop anorexia, nausea, and vomiting.
* ECG alerts. The patient's pulse may be weak and irregular, and he may have orthostatic hypotension. The ECG may show a flattened T wave, a depressed ST segment, and a characteristic U wave.
Ventricular arrhythmias and cardiac arrest can result from hypokalemia. Closely watch a hypokalemic patient who's taking digitalis glycosides and a diuretic; hypokalemia can potentiate digitalis toxicity.
* Other problems. In addition, the pabent may experience intestinal problems such as decreased bowel sounds, constipation, and paralytic ileus. When hypokalemia is prolonged, the kidneys can't concentrate urine and diuresis occurs.
What tests show
The following test results help confirm the diagnosis of hypokalemia:
* serum potassium level less than 3.5 mEq/liter
* elevated pH and bicarbonate levels
* slightly elevated serum glucose level characteristic ECG changes.
How hypokalemia is treated
Treatment of hypokalemia focuses on restoring a normal potassium balance, preventing serious complications, and removing or treating the underlying causes. Treatment varies depending on the severity of the imbalance.
* Provide a high-potassium diet.
* If increased dietary potassium isn't sufficient to treat less-acute hypokalemia, provide oral potassium supplements using potassium salts, preferably potassium chloride, as ordered.
* If hypokalemia is severe or the patient can't take oral supplements, administer IN. potassium replacement therapy.
Once the serum potassium level is back to normal, the patient may get a sustained-release oral potassium supplement as well as increased dietary potassium. Patients taking diuretics may be switched to a potassium-- sparing diuretic to prevent excessive urinary potassium loss.
How you intervene
Careful monitoring and skilled interventions can help prevent hypokalemia and spare your patient complications. For patients at risk for developing hypokalemia and those who have hypokalemia already, you'll want to perform these actions:
Assess and monitor
* Monitor vital signs, especially pulse and blood pressure. Hypokalemia can cause orthostatic hypotension.
* Monitor serum potassium levels. Changes in them can lead to serious cardiac complications.
* Assess heart rate and rhythm and ECG tracings in the severely hypokalemic patient whose serum potassium level is less than 3 mEq/liter.
* Assess the patient's respiratory rate, depth, and pattern. Notify the patient's health care provider at once if respirations become shallow and rapid. Keep a manual resuscitation bag at the bedside of a severely hypokalemic patient.
* Assess for clinical evidence of hypokalemia, especially in patients getting diuretics or digitalis glycosides.
* Monitor and document fluid intake and output. Each liter of urine contains about 40 mEq of potassium. Diuresis can put the patient at risk for potassium loss.
* Check for signs of metabolic alkalosis, including irritability and paresthesia.
Give oral potassium supplements
* To prevent gastric irritation from oral potassium supplements, administer the supplements in at least 4 ounces of fluid or with food.
* Don't crush slow-release tablets; if crushed, they'll trigger a quick load of potassium into the body.
* Provide a safe environment for the patient who's weak from hypokalemia. Explain any activity restrictions.
* Check for signs of constipation. Although medication may be prescribed to combat constipation, don't use laxatives that promote potassium loss.
* Emphasize the importance of taking potassium supplements as prescribed, especially if the patient also takes digoxin or diuretics. If appropriate, teach him to recognize and report signs of digitalis toxicity, such as pulse irregularities, anorexia, nausea, and vomiting.
* Make sure he can identify the signs and symptoms of hypokalemia. 0
Source: Fluids and Electrolytes Made Incredibly Easy!, Springhouse Corp., 1997.
Copyright Springhouse Corporation Nov 2000
Provided by ProQuest Information and Learning Company. All rights Reserved