Dosage Help

D

Dextrose

Mass for Mass :Given an amount of mass per tablet, how many tablets do you require? Ordered/Have = Y (tablets required)

Ex: Metroprolol (Lopressor), 25 mg PO, is ordered. Metropolol is available as 50 mg tablets. How many tablets would the nurse administer? Ordered/Have = Y (Tablets Required) 25 mg/50 mg = 0.5 tablets

Volume/Time - IV Drop Rate Questions: Given a certain amount of liquid, a time period, and a drop factor (gtts/mL), what is the necessary IV flow rate in gtts/min? Measurement used when IV is regulated manually. Because it is not possible to give a patient a fraction of a drop, it is typical to round answers for these problems up or down to the nearest whole number. Volume (mL)/Time (min) x Drop Factor (gtts/mL) = Y (Flow Rate in gtts/min)

Example: Calculate the IV flow rate for 1200 mL of NS to be infused in 6 hours. The infusion set is calibrated for a drop factor of 15 gtts/mL. Volume (mL)/Time (min) x Drop Factor (gtts/mL) = Y (Flow Rate in gtts/min) Convert 6 hours to minutes. min ← hr ( x by 60 ) 6 hr x 60 = 360 min 1200 mL/360 min x 15 gtts/mL = 50 gtts/min

Amount in IV Fluid Questions: Given a volume of IV fluid and a dosage expressed in percent, what is the mass of a particular dosage? Concentration %/100 x Volume (mL) = Y (Dosage Amount in g)

Example: Calculate the amount of dextrose in 1000 mL D5W. Concentration %/100 x Volume (mL) = Y (Dosage Amount in g) 5%/100 x 1000 mL = 50 g

Volume/Time - IV mL Rate Questions: Given a certain amount of liquid and a time period, what is the necessary IV flow rate in mL/hr? Measurement used when IV regulated electronically by infusion pump. Volume (mL)/Time (hr) = Y (Flow Rate in mL/hr)

Example: Infuse 250 mL over the next 120 minutes by infusion pump. Volume (mL)/Time (hr) = Y (Flow Rate in mL/hr) Convert 120 minutes to hours. min → hr ( ÷ by 60 ) 120 min ÷ 60 = 2 hr 250 mL/2 hr = 125 mL/hr

Mass/Liquid For Liquid Questions: Given an amount of mass per liquid, how much liquid do you require? Ordered/Have x Volume Per Have = Y (Liquid Required)

Example: Phenytoin (Dilantin), 0.1 g PO, is ordered to be given through a nasogastric tube. Phenytoin is available as 30 mg / 5 mL. How much would the nurse administer? Ordered/Have x Volume Per Have = Y (Liquid Required) Convert 0.1 g to mg. mcg ← mg ← g ← kg ( x by 1,000 ) 0.1 g x 1,000 = 100 mg 100 mg/30 mg x 5 mL = 16.7 mL

RL or LR

Lactated Ringer's

Flow Rate

Measure of the flow of liquid from an IV. Usually measured in gtts/minute (how many drops are released every minute) or in mL/hour (how many mL flow through each hour). gtts/minute is used for manually regulating an IV while mL/hour is used when utilizing an electronic IV regulator.

NS

Normal Saline (0.9% NaCl)

Drop Factor

Number of drops per volume of IV fluid. Varies depending on the tubing used. Usually measured in gtts/mL

S

Saline

W

Water

gtts

drops