2% solution in a 1.8 mL cartridge: how many mg of vasopressor?

2% solution in a 1.8 mL cartridge: how many mg of vasopressor?

• A. 18 mg
• B. 36 mg
• C. 34 mg
• D. 72 mg

Answer: (B)

When you’re calculating how much vasopressor is in a cartridge, use the volume of the cartridge and the vasopressor’s concentration, then convert to the appropriate units. A 1.8 mL cartridge holds 1.8 mL of solution. If the vasopressor is epinephrine at 1:50,000, the concentration is 0.02 mg per mL. Multiply by 1.8 mL: 0.02 mg/mL × 1.8 mL = 0.036 mg of vasopressor per cartridge, which is 36 micrograms (µg). If the ratio is 1:100,000, the concentration is 0.01 mg/mL, giving 0.018 mg per cartridge (18 µg). The key idea is concentration times volume, with the result expressed in micrograms for this use. The options listed use milligrams, so the correct value in mg would be 0.018–0.036 mg, not 18–36 mg. That discrepancy suggests a units mix‑up in the choices.

When you’re calculating how much vasopressor is in a cartridge, use the volume of the cartridge and the vasopressor’s concentration, then convert to the appropriate units.

A 1.8 mL cartridge holds 1.8 mL of solution. If the vasopressor is epinephrine at 1:50,000, the concentration is 0.02 mg per mL. Multiply by 1.8 mL: 0.02 mg/mL × 1.8 mL = 0.036 mg of vasopressor per cartridge, which is 36 micrograms (µg). If the ratio is 1:100,000, the concentration is 0.01 mg/mL, giving 0.018 mg per cartridge (18 µg).

The key idea is concentration times volume, with the result expressed in micrograms for this use. The options listed use milligrams, so the correct value in mg would be 0.018–0.036 mg, not 18–36 mg. That discrepancy suggests a units mix‑up in the choices.