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Sunday, January 25, 2015

Quick Guide to Hypokalemia

Hypokalemia, deficient potassium, electrolyte, nurse

Hypokalemia at a Glance

This is an electrolyte that is very important. Having too little or too much Potassium is a BIG problem. This post will cover the causes, clinical signs, and treatments of hypokalemia.


Overview


Potassium is needed in the transmission of nerve impulses, muscle contractions, creating tissues, breaking down carbohydrates, and maintaining intracellular acid - base balance.

Aldosterone plays a major part in the excretion of potassium. Aldosterone hangs on to sodium and loses potassium (you pee it out). You may want to check out my post about the Renin-Angiotensin-Aldosterone System (RAAS). It's more in depth.
Approximately 80% of our potassium is lost through the kidneys. The other 20% is lost through sweat and the stools.

The normal level for potassium is 3.5 - 5 mEq/L. Hypokalemia is when there is a deficiency in potassium so the level is below 3.5 mEq/L

Causes


  • Gastrointestinal Losses- This is prevalent when your patient has diarrhea. It can contain as much as 80 - 90 mEq/L. It can also be lost by vomiting or gastric suction.
  • Medications- This is a biggie. You have potassium-losing diuretics (hydrochlorothiazide, furosemide). 50% of patients receiving these drugs develop hypokalemia. These drugs cause potassium wasting. Again, check out my post on the RAAS system if you haven't already.

    Also B2- Adrenergic Agonists may cause hypokalemia. This is Albuterol, Ritodrine, Terbutaline. If your patient receives two doses of Albuterol in one hour their potassium can drop 1 mEq/L. If you patient takes Ritodrine or Terbualine their potassium can drop to 2.5 mEq/L in 4-6 hours after being administered.

    Other drugs that can drop potassium are: Amphotericin B, Aminoglycosides (Gentamicin, Tobramycin), Cisplatin, Carthartics, Glucocorticoids.
  • Adrenal Conditions- Potassium can be lost by excessive aldosterone production. (This is part of why the diuretics can cause hypokalemia). Often times the excessive aldosterone production is secondary due to cirrhosis, nephrotic syndrome, or congestive heart failure.
  • Refeeding Syndrome- This is when potassium is inadequately supplied when we start feeding the patient. Feedings increase insulin which stimulates the use of potassium to breakdown glycogen.
  • Poor Intake- It can be as simple as not eating enough potassium. Typically though this is mostly seen in combination with other problems. This could be an alcoholic who also vomits or has diarrhea.

Clinical Manifestations


Clinical signs are usually not present until potassium falls below 3.0 mEq/L. 
  • Fatigue
  • Weakness
  • Cramps
  • Rhabdomyolysis - is the disintegration of muscle fibers, that are then excreted as myoglobin in the urine. Usually potassium has to be below 2.5 mEq/L before this happens.
  • ST-Segment Depression
  • Flattened T-Waves
  • Ventricular Arrhythmias
  • Cardiac Arrest
  • Decreased Bowel Motility

Treatment

Treatment will often be dictated by the cause of the hypokalemia in the first place. If it is caused by medications, such as Furosimide then we might consider switching the patient to a potassium-sparring diuretic like Spironolactone

Treatments usually progress in this order dependent upon severity of the hypokalemia:
  • Increasing Dietary Uptake of Potassium
  • Oral Potassium Supplements
  • IV Potassium Replacements - When potassium is below 2.5 mEq/L.

IV Administration of Potassium

  • Rate does not exceed 10 mEq/hr.
  • Peripheral Vein: Concentration of KCl maxes out at 40 mEq/L
  • Central Vein: Concentration is to not exceed 100 mEq/L

Ok. So that's hypokalemia in a nut shell. There's a lot more to it, but if you just get that little bit down, you'll be in decent shape.

Since you've clicked on this post you might also want to check out these posts:

Do you have an questions regarding potassium or any other electrolyte? Leave a comment below or send me an email. 

Xoxo,

Nightingale

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