Question

Heparin is a drug frequently used to prevent blood clots from forming in an IV catheter. The typical dose of heparin to prevent clotting in the IV catheter of a newborn infant is 1 ml of 10 units/ml heparin.

A. One unit of heparin is roughly 0.002 mg. How many mg of heparin should be used to prevent clotting in a typical newborn IV catheter? Show your work.

B. Using the value obtained in part A, convert the concentration of 10 units/ml heparin to moles/liter (molar, M). For the type of heparin used to prevent clotting, the formula weight is approximately 5000 g/mol. Show your work.

C. Several years ago, heparin solutions of different concentrations were sold in vials with similar packaging that could be easily confused (see image). This confusion resulted in several widely publicized cases, some fatal, of heparin overdose in newborns. If the person giving the heparin only has access to the 10,000 units/ml concentration heparin solution, how much saline solution would this person need to mix with 0.3 ml of the 10,000 units/ml heparin solution to yield a 10 units/ml solution for use in a newborn? Show your work.

Answer 1

QUESTION - A

One unit of heparin is 0.002mg

1 unit heparin = 0.002mg

Given that, typical dose of heparin to prevent clotting in the IV catheter of a newborn infant is 1 ml of 10 units/ml heparin.

ie, in 1ml --- 10 units of heparin is present

We have to calculate how many mg of heparin should be used to prevent clotting

ie, in 10units howmany mg heparin present = 10 x 0.002 = 0.02mg of heparin

Dose of heparin to prevent clotting = 0.02mg heparin

QUESTION - B

We have found that there is 0.02mg heparin.

Formula weight of heparin = 5000g/mol

• ie, 5000g in 1 moles
• 1g = (1/5000) moles
• 0.02mg = 2 x 10^-5 g

Therefore in 2 x 10^-5 g = ( 2 x 10^-5 ) x ( 1 / 5000) = 4 x 10^-9 moles

• ie, in 0.02mg --- 4 x 10^-9 moles

in the question, it was given that 0.02mg in 1ml

ie, 2 x 10^-5 g in 10^-3 L

We have already found that there is 4 x 10^-9 mol in 2 x 10^-5 g

Therefore in 1 ml --- there will be 4 x 10^-9 moles of heparin

• ie, 10^-3 L has 4 x 10^-9 moles
• so in 1 L there will be --- (4 x 10^-9 ) / ( 10^-3 ) = 4 x 10^-6 moles

Therefore the concertration of heparin in moles / L = 4 x 10^-6 moles / L

QUESTION - C

We need heparin solution to be 10 units/ml

• ie, 10 units in 1ml
• 1unit in --- (1/10)ml

We have only 10000units/ml concentration heparin solution.

Out of which 0.3ml solution is taken

• So, 1ml in 10000units
• 0.3ml in --- 10000 x 0.3 = 3000units

We have to yield a 10 units/ml solution from 0.3ml of 10000unit/ml heparin solution

So in the final solution, we will be having only 3000 units of heparin

So by equating,

• 1unit --- 1/10ml
• 3000 unit --- (1/10) x 3000 ml = 300ml

This 300ml is the total volume of the solution

We have to find the volume of saline solution to be mixed with 0.3ml of given solution

Total volume = 300ml

So volume of saline = 300 - 0.3 ml = 299.7 ml of saline