Fun Fizzyology Facts When One Banana May Not be Enough!

02/01/2017

Blog post by SimGHOSTS member Kim Baily

Healthcare Facts for Simulation Technology Specialists: The Fun "Fizzyology" of Electrolytes

This is the fourth post in a series designed to help sim techs without a medical background understand some basic physiology (or those who need a refresher). Simulation technicians can help create fidelity in simulation by understanding the physiology and/or pathophysiology behind each scenario. Missing data or typical equipment can confuse learners and leave them guessing about their next action. The appropriate cues from lab reports, IV therapy, 12 lead EKG, patient complaints, catheter placements and moulage can help guide learners.

Although potassium ions are found both inside cells and in fluids surrounding cells the concentration inside the cells is much higher (141-150 mEq/L inside and 3- 5mEq/L outside). Please see previous posts for details. Small changes in blood plasma concentrations of potassium can have dramatic effects on cardiac and neurological function. The body does not store potassium and a daily intake of 40- 80 mEq is needed. However, even when a patient is not eating, potassium levels fall quite slowly as cells that break down to produce energy release potassium into plasma. Foods rich in potassium include fruits, vegetables, meats and nuts.

This post will discuss low potassium levels. A low potassium level is known as hypokalemia – less than 3.5mEq/L.

The most common causes of hypokalemia are:

  • Loss of fluid from GI tract. Internationally diarrhea is the most common cause of hypokalemia.
  • Diuretics – drugs that cause water to be eliminate from the kidneys – e.g. Lasix a loop diuretic. Note there are a few diuretics that “spare” potassium e.g. spironolactone, amiloride and triamterene.
  • Some steroids e.g. corticosteroids which cause sodium retention and potassium excretion (hence the fluid retention, weight gain and classic “moon face” seen with prolonged steroid treatment.)
  • Beta stimulants such as epinephrine can cause transient hypokalemia.
  • Alkalotic serum pH > 7.4. As the body attempts to bring pH to normal levels H+ ions move out of cells in exchange for potassium resulting in a hypokalemia. (Note: hypokalemia may contribute to the development of metabolic alkalosis).

Hypokalemia can cause bradycardia or paroxysmal tachycardia, premature ventricular contractions (PVCs). These changes are rare in patients unless there is underlying cardiac disease. NOTE: for patients taking digitalis, hypokalemia is more serious because the toxic effects of digitalis are more likely when potassium levels are low. The ECG in a client with hypokalemia has prominent U waves and the T waves are flat with eventual ST depression. Other symptoms of hypokalemia may include anorexia, muscle weakness, decreased bowel sounds and abdominal distention. Ileus and lethargy are key symptoms of hypokalemia in newborns. Flaccid paralysis may also develop. The symptoms listed may be found with other disorders so the learners should take a thorough history and analyze labs.

Hypokalemia Treatment:

Potassium may be given three different ways: IV, oral or by increasing potassium in the diet with K+ rich foods.

  • Potassium may be ordered in mEq, % solutions or as mg. Care needs to be taken not to make a med error when administering potassium.
  • Oral preparations come in liquids, pills, capsules and elixirs. These preparations can cause stomach upset so should not be given on an empty stomach. The pills are often huge and some patients have difficult swallowing these “horse pills”! Salt substitutes often contain as much as 50mEq of potassium per teaspoon. The dose of routine oral supplements depends to some extend on the amount of potassium in the diet.
  • IV. Sometimes IV medicines are given all at once – this is known as IV push. NOTE: Potassium is NEVER given IV push. Usually pharmacy mixes IV potassium.
    • Potassium is always mixed with a new bag of IV fluid – this ensures an accurate concentration of ion.
    • Typically no more than 40mEq of potassium is added to a liter bag and the potassium is infused at a maximum rate of 10mEq per hour (note some authorities say 20mEq/h may be given). If the order reads 10mEq/h and the concentration of potassium in the bag is 40 mEq/L, what would be the flow rate of the IV be in mL/h?
    • Potassium is extremely irritating to veins and may cause a burning sensation. Ideally a central line should be used because a larger blood volume will dilute the potassium ions.
    • Urine output must be adequate (>30mL/h in adults, 4ml/h in newborns, 1-2mL/kg in older children) or hyperkalemia may result. Urine output should be checked during administration.
  • Signs and Symptoms of Digoxin Toxicity.
    • Bradycardia – the pulse is always checked before digoxin is administered. If below 60 the dose is held and the provider notified.
    • Nausea, vomiting, diarrhea, headaches, visual disturbances such as blurred vision or seeing halos around bright objects.

A hypokalemia scenario can be set a many learner levels. Hypokalemia makes a wonderful basis for many learning objectives; however, the labs and ECG are key in providing learners with the correct cues.