Question

Nitroprusside has been ordered at 0.5 - 7 mcg/kg/min to maintain a mean systolic blood pressure of 100 mm Hg for your 5'4" patient who weighs 125 lb. The available solution contains 50 mg nitroprusside in 250 mL.

A. Calculate the minimum flow rate in mL/hr. Include units with your answer.

B. Use a proportion, based on the minimum dose and rate, to calculate the maximum flow rate in mL/hr. Include units with your answer.

C After several minutes, the physician adjusts the dose to 1.5 mcg/kg/min.  Use a proportion, based on the minimum dose and rate, to calculate the rate administered in mL/hr.   Include units with your answer

D. After several minutes, the physician adjusts the dose to 3 mcg/kg/min.  Use a proportion, based on the minimum dose and rate, to calculate the rate administered in mL/hr.   Include units with your answer.

E.   The patient finally stabilizes when given a rate of 65 mL/hr.  Use a proportion, based on the minimum dose and rate, to calculate the dose administered in mcg/kg/min.   Include units with your answer.

Answer 1

Given,

Weight = 125lb = 56.699kg = 56.7kg.

Height = 5'4" = 162.56cm.

Nitroprusside has been ordered at 0.5 - 7 mcg/kg/min.

The available solution contains 50 mg nitroprusside in 250 mL.

i,e 250ml contains 50mg.

1ml contains 50/250 = 0.2mg.

In mcg = 0.2 x 1000 = 200mcg.   (1mg = 1000mcg)

Answer A

Given minimum dose is 0.5mcg/kg/min.

i.e, 0.5 x 56.7 mcg/min = 28.35mcg/min.

1mcg present in 1/200 ml.

so, 28.35mcg present in, 28.35/200 ml = 0.14175ml in one minute.

0.14175ml 1/60 hr. ( 1hr = 60min)

Therefore in 1 hr, 0.14175 x 60 ml = 8.505ml.

Therefore the minimum flow rate is = 8.505ml/hr.

Answer B

The propotion between maximum and minimum dose is = 7/0.5 = 14.

i,e The maximum dose of nitroprusside is 14 times that of minimum dose.

Therefore the maximum flow rate is 14 times that of minimum flow rate, = 14 x 8.505ml/hr

=119.07ml/hr.

Answer C

After several minutes, the physician adjusts the dose to 1.5 mcg/kg/min.

The propotion between the present dose and the minimum dose = 1.5/0.5 = 3.

i,e The present rate is 3 times that of minimum rate.

Therefore the present flow rate is 3 times that of minimum flow rate = 3 x 8.505ml/hr = 25.515ml/hr.

Answer D

After several minutes, the physician adjusts the dose to 3 mcg/kg/min.

The propotion between present dose and minimum dose = 3/0.5 = 6.

i,e The present dose is 6 times that of minimum dose.

Therefore the present flow rate is 6 times that of minimum flow rate = 6 x 8.505ml/hr = 51.03ml/hr.

Answer E

Here the rate is given as 65ml/hr.

The minimum flow rate is 8.505ml/hr.

Therefore the propotion is = 65/8.505 = 7.64.

i,e The present rate is 7.64 times that of minimum rate.

Therefore the present dose is 7.64 times that of minimum dose = 7.64 x 0.5mcg/kg/min = 3.82mcg/kg/min.