Example 1:
A patient is to have 500ml of 5% dextrose in water, but the available strength is 100ml of 50% dextrose in water. As the nurse on duty, how would you prepare 500ml of 5% dextrose in water from 50% dextrose in water?
Desired strength = 5% Available strength = 50%
Desired volume = 500ml
Percentage solutions in drip bags... Never fun, right? The most common one we probably encounter in practice is the glucose (or dextrose) CRI. These used to absolutely baffle me until I learned this quick tip:
2.5% = 0.05ml of 50% glucose for every 1ml of fluid in the bag
5% = 0.1ml of 50% glucose for every 1ml of fluid in the bag
The complete calculation is:
Take the desired % solution you want (e.g. 5%) and divide this by the % solution of the undiluted injection (e.g. glucose is usually 50%).
Multiply this number by the volume (in ml) of fluid in your drip bag.
This gives you the total volume of drug to add to the bag.
⚠️ Remember that in order for the percentage to be accurate, 𝘵𝘦𝘤𝘩𝘯𝘪𝘤𝘢𝘭𝘭𝘺 you should remove the same volume of fluid from the bag before adding your drug. Otherwise your percentage won't be accurate. For example, if we did not remove 50ml of Hartmann's before adding out 50ml glucose, we would have 5% of 550ml, which is actually a 4.5% glucose solution! ⚠️