Patient safety depends on RNs being able to administer correct medication amounts.
Registered nurses, or RNs, use math daily to control IV flow rates, set medicine dosages and convert measurements when necessary. The math requirements rarely exceed junior high school algebra and usually involves ratios, proportions or conversions. Medication calculation mistakes can lead to injury or death for patients, so it's important for nurses to master their math skills while in nursing school.
Measurements
RNs need to be proficient in both the metric and American measurement systems. The metric system measures distance in meters, volume in liters and mass in grams. Metric scales up in multiples of 10, with the prefix "centi" standing for hundreds and "milli" for thousands. The American system, also called the household system, measures distance in feet, volume in fluid ounces and mass in pounds. A basic understanding of the old apothecary system is also necessary, as it may show up sometimes, especially with older patients describing their medications. The apothecary system uses pounds, ounces and scruples from the classic Roman weight system, as well as the drachm, barley and grain from Greek measurements.
Conversions
RNs need to be able to accurately and quickly convert measurements from one system to another. A prescription may be given in grams, and the RN may need to calculate how much liquid medication the patient requires. Some other possible conversions are changing oz. to mL, grain to mg, and oz. to gram. RNs memorize all the different conversion formulas in nursing school.
Dosages
RNs are responsible for dosage calculation for their patients. A prescription may be given by weight, and the RN may have to convert the patient's weight to kg and then multiply by the dosage per kg to calculate an appropriate dosage. A medication for 50 mg may be ordered, and the pharmacy only has 100 mg / 2 mL available. A patient may require 50 mg of a medication, and you only have access to 10 mg tablets. The ability to correctly calculate dosages is essential to the patient's health.
IV Flow Rates
Some medicines are administered by syringe or intravenous drips (IV). Syringe calibrations can be used by RNs to calculate the amount of medicine to administer through an IV. A RN may be told to administer 300 mL of a medication over 120 minutes by infusion pump and needs to calculate the appropriate flow rate in mL/hr. A more difficult scenario may require calculating an IV flow rate for 300 mL of a medicine over 180 minutes given a drop factor of 20 gtts/mL. ("Gtts" means drops per minute.)
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