A nurse is preparing to administer chlorpromazine 0.55 mg/kg IM to a child who weighs 66 lb. Available is chlorpromazine 25 mg/ml. for injection. 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 calculate the volume of chlorpromazine to administer, follow these steps:
- Convert the child’s weight from pounds to kilograms:
- 1 pound = 0.4536 kilograms.
- Weight in kilograms = 66 pounds × 0.4536 kg/pound.
- Weight in kilograms = 29.94 kg (rounded to two decimal places).
- Determine the total dose of chlorpromazine required:
- Dose required = 0.55 mg/kg.
- Total dose = Weight in kg × Dose required per kg.
- Total dose = 29.94 kg × 0.55 mg/kg.
- Total dose = 16.467 mg (rounded to three decimal places).
- Calculate the volume of chlorpromazine to administer:
- Concentration of chlorpromazine available = 25 mg/mL.
- Volume (mL) = Total dose (mg) / Concentration (mg/mL).
- Volume (mL) = 16.467 mg / 25 mg/mL.
- Volume (mL) = 0.6587 mL.
- Round the volume to the nearest tenth:
- 0.6587 mL rounded to the nearest tenth is 0.7 mL.
So, the nurse should administer 0.7 mL of chlorpromazine.
Explanation
To ensure accurate medication administration, it is crucial to convert units and calculate dosages based on the patient’s weight. The first step is to convert the child’s weight from pounds to kilograms, as most medication dosages are calculated based on the metric system. This conversion ensures that the dosage calculations are aligned with the standard units used for medication administration.
Once the weight is converted, the total dose of the medication required can be calculated by multiplying the weight by the dosage per kilogram. This calculation gives the exact amount of medication needed in milligrams. To find out how much volume to administer, this amount is divided by the concentration of the medication available, which is provided in mg/mL.
Finally, rounding to the nearest tenth is standard practice for practical administration, ensuring the dose is both accurate and easy to measure. Proper rounding minimizes errors in dosing, which is critical for patient safety and effective treatment.