Let's say:
Your patient weighs 143 lbs. Your MD or nurse practitioner has ordered Medication "Y" at 100 micrograms per kg by Intramuscular route. Your pharmacy has sent you 20 milligrams of Medication "Y" in a vial that must be reconstituted by adding a (determined by you in looking at package options) amount of diluent to the 20 ml bottle of powered Medication "Y" to achieve concentrations of possibly: 10mg/ml, 10mg/2ml, 5mg/ml, 2mg/ml.
By "mathematics" and reading a Physician's Desk Reference (PDR) or a nursing dosage book you must:
(1) know what your patient weighs in kg
(2) convert micrograms to milligrams or vice versa
(3) be able to multiply and round correctly
(4) determine what concentration to mix
(5) ascertain if this dosage (once you figure it) falls into a safe range be administered
Possibly all this math for a single injection.
That's one med and a simple one at that. There are titrations you have to figure to a patient's conidition and IntraVenous problems can get fairly complex.
Multiply all that by 5, to 25 or 30, meds per patient and multiply by your patient load, let's say 7-10 patients per shift RN.
Yeah, the pharmacy is great and does a lot of the work for us these days (thanks:-). But the ultimate responsibility often sits with the person (nurse) who administers the med.
I'd like my nurse and the nurses caring for my family to be able to double check anything that makes him/her uncomfortable. What about in a disaster? Like Hurricane Katrina? Where were the computers and calculators during massive outages? Patients still required care.
Mathematics relate to nursing? You bet.
And we're not even getting into the critical thinking, so vital, that is fostered by working complex mathematical equations.