Question

Sodium nitroprusside is ordered at 0.3 mcg/kg/min for a 220-lb patient. A vial containing 50 mg of sodium nitroprusside in 2 mL is diluted to 250 mL with NSI and ordered to run at 14 mL/h. Is this run rate correct? If not, what should be the correct infusion rate? The correct answer is no, and 9 mL/h. Please show how this problem is solved.

Answer 1

Ans. # Step 1: Given, weight of the patient = 220 lb = 99.7903 kg

# Prescribed flow rate = (0.3 mcg kg^-1 min^-1) x 99.7903 kg = 29.93709 mcg min^-1

                                                = 29.93709 x (0.001 mg/ mcg) x min^-1

                                                = 0.02993709 mg min^-1

                                                = 1.7962254 mg Hr^-1

# Step 2: Total drug, 50.0 mg is diluted to a final volume to 250 mL.

So,

            [Drug] in diluted soln., = (50 mg) / 250 mL = 0.20 mg mL^-1

# Step 3: Required run rate = Prescribed flow rate / [Drug]

                                                = 1.7962254 mg Hr^-1 / 0.20 mg mL^-1

                                                = 8.98 mL Hr^-1

# Result: No, the specified run rate 14.0 mL Hr^-1 is higher than the actual run rate, 8.98 mL Hr^-1.