If your patient’s potassium level on labs is 3 mEq/L, it’s basically saying 3 mEq K+ is present in every liter of their blood. Knowing that an adult has roughtly 5 liters of blood, does it mean to get your patient from 3 mEq/L to 4 mEq/L we just need to give (4 – 3 ) X 5 = 5 mEq KCL ? Not that simple ! the admistered potassium distributes not only to blood, but also quickly spreads to tissue fluid and most of it ends up making it’s way to inside the trillions of cells in our body. So 5 meq wouldn’t cut it ! In other words when the blood concentration is low, the actual “Total-body potassium deficit” is a much higher number.
Read on for how to dose potassium chloride for hypokalemia:
STEP 1 : Decide goal Potassium level
Usually 4.0 is a good goal, in cases of renal failure, I lower goal to 3.5-3.6
STEP 2: Decide TOTAL KCL amount to be given ( Total-body potassium deficit ):
Instead of scratching heads about the technicals of potassium body distribution and complex formulas – just remember this clinically practical trick to use:
To get an adult patient’s potassium concentration from 2 mEq/l to 3 mEq/L, we need to give roughly a total of 200 mEq in KCL ( or indicates a 20 mEq total-body potassium deficit per 0.1 mEq/L desired increase in blood concentration ) . And to get from 3 mEq/L to 4 mEq/L, its an additional 100 mEq total KCL dose needed ( or indicates a 10 mEq total body deficit per 0.1 mEq/L increase desired from 3 mEq to 4 mEq )
These are conservative values I use, so that you don’t overdo it – since hyperkalemia is more dangerous than hypokalemia !!
Examples:
- K = 3.2 mEq/L . To get to a goal of 4.0 mEq/L, that would be 0.8 more or 8 increments of 0.1 more. Total-body deficit (or total dose needed) would be 8 increments X 10 = 80 meq KCL
- K = 2.8 mEq.L. To get to of 4.0 mEq/L: From 2.8 to 3.0 is (2 increments of 0.1) X 20 = 40 meq and from 3 to 4 is an additional 100, giving us a total dose needed of 140 mEq KCL
STEP 3: Decide on Oral (PO) v/s Intravenous (IV) administration:
Prefer PO when possible, but IV KCL is done if patient is strictly NPO, is very nauseous or if potassium is less than 2.5 or has ongoing Insulin drip that risks continuously dropping potassium levels more while the drip is running
STEP 4: Decide dosing plan & frequency:
If giving PO, doses usually are done 40 meq at a time or less, KCL is very irritating to the GI tract and and causes nausea. Also, since they are bigger pills, giving 4 pills of 10 mEq each might be easier for people with swallowing difficulies and elderly patients.
So in our example # 2 above, for a total dose 140 mEq, I would do 40 mEq KCL PO every 6-8 hours X 3 doses, then 20 mEq KCL 6-8 hours later. Recheck level after last dose is done
Pro-Tip: PO KCL on a empty stomach is a bad idea , coz ….puke !! Always give along with a snack or meal.
If Giving IV , 10 mEq an hour max via peripheral vein or 20 mEq an hour max via a central vein line using a controlled infusion pump. Never ever order a IV push for KCL, that carries a high risk of stopping then heart ! 🙁
