Potassium is the major electrolyte in the intracellular compartment and, as such, maintains ICF osmolality. Potassium works with insulin to move glucose into the cell, is controlled by the Na+/K+ pump, and plays a part in renal elimination. Potassium is essential for transmission of electrical impulses, especially in cardiac and skeletal muscle. Because of this it is extremely important to monitor a patient’s ECG if they are experiencing potassium imbalances. An ECG is also the most reliable tool for identifying potassium imbalances.
The normal range of potassium is 3.5-5 mEq/L.
Potassium levels greater than 5 mEq/L are known as hyperkalemia. This affects more than half of people with acute and chronic renal failure but is rare in patients with normal kidney function. Signs and symptoms include abdominal pain, nausea and vomiting, neuromuscular irritability (tremors and twitching), and decreased or absent urine output. ECG changes include brady dysrhythmias and tall, peaked T waves. Hyperkalemia is caused by potassium-sparing diuretics (diuretics that cause potassium to be retained), renal failure, major trauma, burns, Tumor Lysis Syndrome (secondary to chemotherapy and radiation), and acidosis. Acidosis drives potassium out of the cells in exchange for hydrogen. To treat mild hyperkalemia, restricting dietary intake of potassium may be all that is needed. Increasing fluids, either orally or by IV and stopping medications that include potassium will improve the imbalance as well. If the hyperkalemia is severe, certain medications may need to be given. A Kayexalate retention enema will cause potassium to exchange with sodium in the intestines and potassium to be excreted in the stool. IV calcium gluconate decreases the effect the extra potassium has on the heart. IV insulin and glucose or sodium bicarbonate will promote potassium uptake into the cells. Potassium-wasting diuretics with also promote excretion of potassium. With renal failure, peritoneal or hemodialysis may be needed.
Hypokalemia, or low potassium levels (<3.5 mEq/L), is common, especially in the older population. Signs and symptoms include postural hypotension, muscle cramps, weakness, polyuria, anxiety, confusion, decreased bowel sounds, and anorexia. ECG changes include tachy dysrhythmias and flattened T waves. Causes of hypokalemia are potassium-wasting diuretics (diuretics that cause potassium to be excreted, especially Lasix), gastrointestinal fluid losses, anorexia or malnourishment and hyperaldosteronism. Alkalosis also causes hypokalemia because it drives potassium into cells. The treatment of hypokalemia is to administer potassium, either orally or IV. The patient should increase their dietary intake of potassium. Click on the image below to see foods high in potassium. Oral potassium supplements can also be given. Be sure to give these with food or diluted in juice to avoid GI problems.
When potassium is given through an IV, there are some important things to know. You must ensure the patient has adequate renal function in order to excrete the potassium appropriately. The usual IV concentration of potassium is 20-40 mEq/L and is ALWAYS diluted. IV potassium is extremely irritating to the veins so should be given through a large vein. The potassium needs to be given through an IV pump so it is not delivered too fast and the patient must be on a cardiac monitor to ensure safety. Never give potassium IV push because it can cause sudden, severe hyperkalemia which can lead to cardiac arrest.
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McCarthy, M. (2011). Electrolyte imbalances [PowerPoint Slides].
White, B. (2009). Clients with electrolyte imbalances. In Black, J. M., & Hawks, J. H. (Eds). Medical-surgical nursing. Clinical management for positive outcomes, (Vol 1., 8th Ed), (pp. 151-167). St. Louis, MO: Elsevier Inc.