Your are preparing to give potassium chloride 30 meq in 1000 ml of normal saline over 10 hours. The medication label reads 40 meq per 20 ml. how many milliliters of potassium chloride do you need to administer the correct dose ?

Appeared in: NORCET 1 - 2020

Explanation

The question requires calculating the volume of a liquid medication needed to deliver a specific dose.
The standard formula for dosage calculation is: (Dose ordered / Dose on hand) × Quantity.
Plugging in the values from the question: (30 mEq / 40 mEq) × 20 mL.
The calculation simplifies to 0.75 × 20 mL, which equals 15 mL.
The total volume of the IV fluid (1000 mL) and the total infusion time (10 hours) are distractors for this specific calculation problem, which only asks for the volume of medication to add.

Option A: This volume would provide only 20 mEq of potassium chloride (10 mL × (40 mEq / 20 mL)), which is an underdose compared to the 30 mEq ordered.
Option B: This volume contains the full 40 mEq from the vial, which is 10 mEq more than the ordered dose of 30 mEq, resulting in an overdose.
Option D: This volume would provide 100 mEq of potassium chloride (50 mL × 2 mEq/mL), which is a massive and potentially lethal overdose.

Visual 1: Infographic - A visual breakdown of the dosage calculation formula (D/H × Q) with the values from the question (30 mEq, 40 mEq, 20 mL) clearly labeled to show how the answer is derived.
Visual 2: Image - A picture of a potassium chloride vial next to a syringe drawing up 15 mL of the solution, reinforcing the practical application of the calculation.

Clinical Relevance

Nursing practice connection: Knowing Medication Dosage Calculation helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Accurate dosage calculation is a fundamental and critical nursing skill to prevent medication errors, especially with high-alert drugs like potassium chloride.
Potassium chloride must ALWAYS be diluted and administered via an infusion pump. It should never be given as an IV push, as this can cause immediate cardiac arrest.
Before administering potassium, the nurse must verify adequate renal function (urine output of at least 30 mL/hr) to prevent life-threatening hyperkalemia.

How to Approach the Question

First, identify the 'Dose Ordered' (Desired) from the problem: 30 mEq.
Next, identify the 'Dose on Hand' (Have) and its corresponding 'Quantity' (Volume) from the medication label: 40 mEq in 20 mL.
Recognize that other information, like the total IV fluid volume (1000 mL) and infusion time (10 hours), are distractors for the specific question being asked (how many mL to draw up).
Apply the standard dosage calculation formula: (Desired / Have) × Quantity.
Substitute the values into the formula: (30 / 40) × 20.
Calculate the result (15 mL) and always double-check your math, preferably with another registered nurse, as this is a high-alert medication.

Concept Tested & Keywords

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Practise the full NORCET 1 - 2020

Attempt every question from this paper in a timed mock, then review the full solution for each one.