5% solution

we do a lot of calculations in medicine. maybe that's why maths is an entry requirement to med school.
for example, patients are prescribed dextrose 5% as an intravenous drip. what this contains is 5g of dextrose (aka sugar) in 100mls of solution. this equals 5000mg in 100mls, or 50mg per ml.

similarly, normal saline or 0.9% saline contains 0.9g of sodium chloride (aka salt) in 100mls of solution, which equals to 900mg sodium chloride in 100mls, or 9mg per ml.

so, 5% of any medication equals to 50mg of that medication in 1ml of solution.

yesterday, i prescribed a 0.5% of a local anaesthetic to a patient to be given in the ward. the solution is prepared & labelled as 5mg per ml from the manufacturer. so this nurse called up the pharmacy & asked if they could prepare a 0.5% solution for the ward. the pharmacy assistant said they couldn't do it & asked the nurse to do it herself. feeling lost, she reverted to me on my instruction, saying the local anaesthetic only came in 5mg per ml preparation & not 0.5%.

if you go by the previous example, 5% solution is the same as 50mg per ml, so 0.5% is the same as 5mg per ml. which means, the nurse should have just used the solution as prepared.

this is a basic calculation which everyone prescribing, preparing & dispensing medication should be familiar with. fortunately or unfortunately, the responsibility of giving the right dose to the patient falls squarely on the doctors' shoulder.

don't you think an A in maths should be a compulsory requirement for entry into med school & a strong credit for nursing & pharmacy school?

after all, you don't want to to be on the receiving end of a 10-time higher dose of medication, right?