Potassium Repletion Calculator Mdcalc

Potassium Repletion Formula:

\[ \text{Repletion (mEq)} = (\text{Desired K} - \text{Current K}) \times \text{TBW} \times \text{Distribution Factor} \]

Current Potassium (Current K):

mEq/L

Desired Potassium (Desired K):

mEq/L

Weight:

Gender:

Distribution Factor:

(typically 0.4)

Potassium Repletion Needed:

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1. What is Potassium Repletion Calculation?

The potassium repletion calculation estimates the amount of potassium (in milliequivalents) needed to correct hypokalemia. It accounts for total body water, the current potassium deficit, and the distribution of potassium between intracellular and extracellular spaces.

2. How Does the Calculator Work?

The calculator uses the potassium repletion formula:

\[ \text{Repletion (mEq)} = (\text{Desired K} - \text{Current K}) \times \text{TBW} \times \text{Distribution Factor} \]

Where:

\( \text{Desired K} \) — Target serum potassium (mEq/L)
\( \text{Current K} \) — Current serum potassium (mEq/L)
\( \text{TBW} \) — Total body water (0.6 × weight for men, 0.5 × weight for women, in kg)
\( \text{Distribution Factor} \) — Typically 0.4 (dimensionless)

Explanation: The equation estimates the potassium deficit by accounting for the volume of distribution of potassium in the body and the desired correction.

3. Importance of Potassium Repletion

Details: Accurate potassium repletion is crucial for treating hypokalemia while avoiding overcorrection which can lead to dangerous hyperkalemia. The calculation helps guide appropriate potassium supplementation.

4. Using the Calculator

Tips: Enter current and desired potassium levels in mEq/L, weight in kg, select gender, and distribution factor (typically 0.4). All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why use different TBW factors for men and women?
A: Men typically have a higher percentage of body water (about 60% of body weight) compared to women (about 50%) due to differences in body composition.

Q2: What is a typical distribution factor?
A: The distribution factor is typically 0.4, representing that only about 40% of administered potassium remains in the extracellular space where it can be measured.

Q3: How often should potassium levels be rechecked?
A: Potassium levels should be rechecked 2-4 hours after repletion, especially in patients with renal impairment or those receiving large doses.

Q4: Are there limitations to this calculation?
A: This is an estimate. Actual requirements may vary based on acid-base status, renal function, and ongoing losses. Clinical judgment is essential.

Q5: What's the maximum safe IV potassium infusion rate?
A: Typically 10-20 mEq/hour for peripheral lines, up to 40 mEq/hour via central line with cardiac monitoring in severe cases.