A nurse is preparing to administer cefazolin 250 mg IM to a client. Available is cefazolin powder for injection 500 mg vial. The nurse reconstitutes the powder with 2 mL of sterile water for a concentration of 225 mg/mL. How many mL should the nurse administer? (Round the answer to the nearest tenth. Use a leading zero if it applies. Do not use a trailing zero.)
The Correct Answer and Explanation is:
To determine how many mL of the reconstituted cefazolin solution the nurse should administer, follow these steps:
- Calculate the concentration of the reconstituted solution:
- The nurse reconstituted cefazolin powder with 2 mL of sterile water to obtain a concentration of 225 mg/mL.
- Determine the required dosage:
- The prescribed dose is 250 mg of cefazolin.
- Use the concentration to find the volume needed:
- To calculate the volume needed to administer 250 mg of cefazolin, use the formula:Volume=Desired DoseConcentration\text{Volume} = \frac{\text{Desired Dose}}{\text{Concentration}}Volume=ConcentrationDesired Dose
- Plug in the values:Volume=250 mg225 mg/mL\text{Volume} = \frac{250 \text{ mg}}{225 \text{ mg/mL}}Volume=225 mg/mL250 mg
- Perform the calculation:
- Divide 250 mg by 225 mg/mL: Volume=250225≈1.111 mL\text{Volume} = \frac{250}{225} \approx 1.111 \text{ mL}Volume=225250≈1.111 mL
- Round the result:
- Round 1.111 mL to the nearest tenth: Rounded Volume=1.1 mL\text{Rounded Volume} = 1.1 \text{ mL}Rounded Volume=1.1 mL
Therefore, the nurse should administer 1.1 mL of the reconstituted cefazolin solution.
Explanation:
In this scenario, cefazolin is provided in a powdered form, requiring reconstitution before administration. The reconstitution process involves adding a specific amount of sterile water to achieve a desired concentration. In this case, 500 mg of cefazolin powder was reconstituted with 2 mL of sterile water, resulting in a concentration of 225 mg/mL. This concentration tells us that each milliliter of the solution contains 225 mg of cefazolin.
To determine how much of this solution is needed to provide a 250 mg dose, the concentration is used in a simple formula to find the volume required. By dividing the required dose by the concentration, the nurse calculates the necessary volume of solution to administer. The result is then rounded to the nearest tenth to match standard dosing practices.
This method ensures that the correct dose is administered to the client, avoiding over or under-dosing. Accurate measurement and calculation are crucial in nursing to ensure patient safety and effective treatment.