Potassium is essential for proper muscle function, including both skeletal and smooth muscle. It helps the muscles contract and relaxes, impacting movement, digestion, and much more!

Potassium is essential in regulating fluid balance within the body. Potassium has the same tonicity as sodium, drawing water with it wherever it goes. Potassium is essential in the movement of fluid across cell membranes.

Probably one of potassium’s most essential functions, it helps the cardiac system function! The heart uses conductive tissue, which uses potassium to help transmit its signal for every heartbeat – just like it uses calcium, magnesium, and sodium as well!

Studies show that high-potassium diets can help improve insulin sensitivity and reduce the risk of type 2 diabetes.

Just like our heart, the nervous system is ALL about conducting electricity and “action potentials,” but on a much more complex level. Potassium helps our nerve cells communicate with each other.

This is a catch-all, but the sodium-potassium pump is essential for the proper function of almost every cell in our body. That’s how vital potassium is and how hypokalemia can affect our patient’s health!

The kidneys play a crucial role in regulating potassium levels. These filter out excess potassium and retain more potassium when levels are low.

Several hormones impact potassium levels, primarily Aldosterone and Insulin.

Aldosterone, produced by the adrenal glands, is a signal that tells the kidneys to retain more sodium and potassium.

Insulin, which is produced by the pancreas, helps to promote the uptake of potassium into the cells.

The body’s acidity can also affect potassium levels, with acidosis causing potassium to move out of the cells into the bloodstream and interstitial spaces.

Dietary potassium intake is essential in helping the body maintain adequate potassium levels; however not as important as you might think since the body is good at keeping extra potassium if dietary intake is inadequate. 

Certain medications and conditions can shift potassium into the cells, which can cause low potassium levels. This includes Insulin, inhalers like albuterol, and alkalosis.

A common cause of hypokalemia is when it is lost from the GI system. This is usually from either excessive vomiting, diarrhea, or tube drainage.

There isn’t a ton of potassium in the emesis, but excessive vomiting leads to increased potassium wasting in the urine.

This is when potassium is lost in the urine and is often caused by diuretics like LOOP diuretics (Lasix) or increased mineralocorticoid activity (like hyperaldosteronism, crushing’s syndrome, etc.).

Often, this is not the only cause, as the body is pretty good about compensating for inadequate dietary intake.

Muscle weakness is one of the most common symptoms of hypokalemia, which can affect the legs, arms, chest muscles, or any muscle in the body. The patient may have trouble walking, taking the stairs, or lifting objects. This usually only occurs if levels drop below 2.5 mEq/L.

Severe hypokalemia can lead to muscle cramps and even a buildup of myoglobin, leading to rhabdomyolysis. This can be damaging to the kidneys. Hypokalemia also leads to decreased perfusion of the muscles during exercise, which can worsen rhabdo.

A generally non-specific symptom, but patients with low potassium often experience fatigue.

Hypokalemia can cause ileus and constipation and lead to abdominal distention, nausea, and vomiting. The patient may have diarrhea which may contribute to the hypokalemia, but can also have constipation from hypokalemia.

Hypokalemia can cause numbness and tingling in the hands or feet.

Low potassium can cause the kidneys to produce more urine, leading to increased urination.

This is usually only in severe cases with severe muscle fatigue of the respiratory muscles, and the patient may even need to be intubated.

Abnormalities such as premature beats (PAC, PVC), Afib, sinus bradycardia, or even VTACH or VFIB or asystole/PEA.

• HR: May be fast or low depending on cardiac arrhythmias present
• BP: Largely unaffected, but hypokalemia can increase the risk of hypertension
• Respirations: usually normal, but may be decreased in severe cases that cause paralysis
• SPO2: Usually normal unless respiratory failure
• Temp: Normal

• Signs of muscle weakness, such as difficulty walking or moving
• Signs of fatigue or lethargy

• Listen for irregular heart rhythm, which may be caused by ectopy or arrhythmia from the hypokalemia

• Muscle tenderness may be from hypokalemia.
• Edema or ascites, which may indicate underlying kidney or liver failure that can cause hypokalemia
• Abdominal tenderness, which can indicate GI issues that may be leading to hypokalemia

Identifying and addressing the underlying causes of hypokalemia is critical before correcting the potassium. The potassium may not be low but has shifted into the cells from something like alkalosis, hypothermia, and certain medications.

Low magnesium can cause potassium wasting in the kidneys. This means the magnesium level should be evaluated in all patients with hypokalemia and replaced first (assuming the patient is stable).

We need to replace potassium, and a large amount of potassium can be absorbed by the GI system. How much is ordered will depend on the severity of the hypokalemia.

• Mild to moderate hypokalemia = 10-20mEq of potassium given 2-4x/day
• severe hypokalemia or severe symptoms = Doses up to 40mEq 3-4x/day in ADDITION to IV potassium

You are limited in how fast you can infuse potassium through the IV to prevent arrhythmias and IV site irritation. Rates can be faster in a central line and slower in a peripheral IV line.

• Mild to Moderate hypokalemia: typically not needed, and PO is fine, but if the patient is NPO, then IV can be given. Through a peripheral line, 10mEq “K-riders” are usually ordered, and you can expect the potassium to increase by ~0.1 mEq per K-rider.
• Severe hypokalemia: In extreme cases, can give 20mEq every 2-3 hours

Potassium levels will be redrawn and assessed depending on the severity and what the Provider orders. Generally, mild hypokalemia is often only rechecked on the next lab draw (usually by the following day). Severe hypokalemia being replaced is recommended to be checked every 2-4 hours (usually in the ICU).

As we’ve discussed, low potassium levels can impact cardiac rhythms, and whenever a patient’s getting IV replacement of potassium or magnesium, they should be on a cardiac monitor to monitor for cardiac ectopy or arrhythmias.

Severe hypokalemia can cause respiratory failure, so monitoring their breathing, lung sounds, respiratory rate, and pulse ox is essential.

Monitoring for phlebitis and thrombophlebitis at the insertion site is essential, as IV potassium often burns.