Why IV potassium needs extra care
Potassium controls nerve signals and muscle contraction, most importantly in the heart. Too much or too little can cause dangerous heart rhythms.
Low potassium can be treated by mouth or by IV. The concentrate and concentrated bag labels say IV potassium chloride is for clients who cannot take potassium by mouth.
The biggest danger is speed: IV potassium given too fast can stop the heart.
Normal range and low potassium
The Open RN Fundamentals textbook gives a normal serum potassium of 3.5 to 5.1 mEq/L. At work, use the range on your facility’s lab report. Above the range is hyperkalemia; below it is hypokalemia.
Causes of low potassium include vomiting, diarrhea, some diuretics and a low-potassium diet. Signs include weakness, lethargy (low energy, sleepiness), a weak “thready” pulse and abnormal heart rhythms. The concentrate label adds that low potassium upsets nerve and muscle function and can stop the bowel from moving (ileus).
Never IV push
The most important rule: never give potassium by IV push or bolus. A dose pushed by syringe into a vein can stop the heart at once.
It comes in two main forms:
- Concentrate vials (for example 2 mEq per mL). The concentrate must be diluted in a larger bag of IV fluid and mixed well. Injected straight into a vein, it may kill the client at once.
- Premixed bags. Standard bags often hold 20 or 40 mEq of potassium chloride per liter of IV fluid. There are also highly concentrated premixed bags (10 to 40 mEq in 50 or 100 mL). These are only for clients who must limit how much fluid they receive.
Rate, pump and monitoring
Give IV potassium slowly, at a controlled rate, on an infusion pump. The highly concentrated bag label allows these bags only through a calibrated infusion device. The standard bag label warns against giving it by hand without an infusion device.
Rate limits from the concentrate label:
| Client’s serum potassium | Maximum rate | Other limits |
|---|---|---|
| Above 2.5 mEq/L | 10 mEq per hour | Up to 40 mEq/L; no more than 200 mEq in 24 hours |
| Below 2 mEq/L with ECG changes or muscle paralysis (urgent) | Up to 40 mEq per hour, very cautiously | Continuous cardiac monitoring is essential; up to 400 mEq in 24 hours |
The highly concentrated bag label gives the same rates. 10 mEq per hour is the most cautious limit here. Use it whenever potassium is above 2.5 mEq/L. If an order runs faster than the label or facility policy allows, do not start it. Contact the prescriber to clarify it first.
Two concentrations that seem to disagree. The concentrate label allows up to 40 mEq/L, but the highly concentrated bags are 100 to 400 mEq/L. They are a different product with strict conditions:
- the client is on continuous cardiac monitoring, with frequent serum potassium checks
- a central line is recommended when possible, and the 300 and 400 mEq/L strengths go only through a central line
So a bag stronger than 40 mEq/L is not automatically an error. Check that the product, line and monitoring match the label. If not, hold it and call the prescriber.
For other clients, the concentrate label recommends cardiac monitoring with heart disease, especially with kidney disease. It says serial ECGs should guide potassium therapy, especially with digitalis (digoxin). Follow facility policy.
Check the kidneys first
About 80 to 90% of the potassium we take in leaves the body in urine. If the kidneys are failing, potassium builds up and can reach life-threatening levels.
- The concentrate and concentrated bag labels list hyperkalemia and renal failure as contraindications.
- The standard premixed label says to avoid it in severe kidney impairment, and lists acute dehydration as a risk for high potassium.
- So check urine output and kidney function before you start. Report very low urine output or kidney failure to the prescriber first.
Take extra care if the client also takes a drug that raises potassium: a potassium-sparing diuretic such as spironolactone, an ACE inhibitor, an ARB, cyclosporine or tacrolimus.
Watch the IV site
Potassium solutions can hurt veins. The labels list pain at the site, vein irritation, phlebitis, venous thrombosis and extravasation.
Check the site often. Signs of infiltration include pain, swelling, redness, cool or tight skin, leaking fluid, a change in flow, or frequent pump alarms. If fluid has leaked into the tissue, stop the infusion and follow agency policy. When an irritating solution leaks (extravasation), the skin may also burn or blister, and tissue can die (necrosis).
Signs of too much potassium
Watch for hyperkalemia during and after the infusion:
- muscle weakness, tingling or numbness in the hands and feet (paresthesia), loss of reflexes, and in severe cases paralysis, including of the breathing muscles
- confusion or irritability
- cramping or diarrhea (potassium solutions can also cause nausea, vomiting and belly pain)
- low blood pressure
- heart rhythm problems: a slow, fast or irregular heartbeat, heart block, ventricular tachycardia or fibrillation, and cardiac arrest
- ECG changes: first peaked T waves and a longer PR interval; at higher levels the P wave disappears, the QRS widens and asystole can follow
Hyperkalemia may also cause no symptoms and show only in the blood test or ECG. An ECG change that may come from high potassium is an emergency.
If you suspect hyperkalemia, stop the infusion right away, assess the client and notify the primary health care provider.