A nurse is preparing to administer lorazepam 50 mcg/kg IM to a client who weighs 176 lb. Available is lorazepam 4 mg/mL. How many mL should the nurse administer? (Round the answer to the nearest whole number. Use a leading zero if it applies. Do not use a trailing zero.)
The Correct answer and Explanation is:
To calculate the amount of lorazepam to administer, we need to follow these steps:
- Convert the weight from pounds to kilograms:
The client weighs 176 lb. To convert pounds to kilograms, we use the conversion factor:1 lb=0.453592 kg1 \text{ lb} = 0.453592 \text{ kg}1 lb=0.453592 kgThus,176 lb×0.453592 kg/lb≈79.832 kg176 \text{ lb} \times 0.453592 \text{ kg/lb} \approx 79.832 \text{ kg}176 lb×0.453592 kg/lb≈79.832 kgFor practical purposes, we can round this to 79.8 kg. - Calculate the total dosage in micrograms:
The prescribed dose is 50 mcg/kg. Therefore, the total dosage for the client is:50 mcg/kg×79.8 kg=3990 mcg50 \text{ mcg/kg} \times 79.8 \text{ kg} = 3990 \text{ mcg}50 mcg/kg×79.8 kg=3990 mcg - Convert micrograms to milligrams:
Since 1 mg = 1000 mcg, we convert:3990 mcg÷1000=3.99 mg3990 \text{ mcg} \div 1000 = 3.99 \text{ mg}3990 mcg÷1000=3.99 mg - Determine how many mL of lorazepam to administer:
The available concentration of lorazepam is 4 mg/mL. To find the volume in mL to administer, we use the formula:Volume (mL)=Dosage (mg)Concentration (mg/mL)\text{Volume (mL)} = \frac{\text{Dosage (mg)}}{\text{Concentration (mg/mL)}}Volume (mL)=Concentration (mg/mL)Dosage (mg)Substituting the values:Volume (mL)=3.99 mg4 mg/mL≈0.9975 mL\text{Volume (mL)} = \frac{3.99 \text{ mg}}{4 \text{ mg/mL}} \approx 0.9975 \text{ mL}Volume (mL)=4 mg/mL3.99 mg≈0.9975 mL - Round to the nearest whole number:
Rounding 0.9975 mL gives us 1 mL.
Conclusion
The nurse should administer 1 mL of lorazepam. This calculation ensures that the patient receives the correct dosage based on their weight and the available medication concentration. Administering the precise dose is crucial in preventing both under-treatment and potential overdose, particularly with medications like lorazepam, which is used for anxiety and sedation. Always confirm calculations and dosages, especially with medications that have a narrow therapeutic range.