PHARMACY TECHNICIAN CHAPTER SEVENTEEN

Dimensional Analysis Math-based tool that combines different units (such as hours, milligrams, liters, or centimeters) to solve a specific problem Simple problems include: The number of seconds in a year The number of millimeters in a mile Complex problems include: The number of days it would take to walk 1,000 miles, given a constant rate of travel (how many miles per hour) How many gallons of water could flow through a river in 12 days, given a rate of constant rate of flow (how many gallons per minute)

How many hours are there in 6 days? 1 day = 24 hours After setting up the problem, cancel out like units and/or numbers 6 = 6 x 24 = 144 hours

Practice Ten minutes is equivalent to how many seconds? How many seconds are in 50 minutes? 1.5 days is equal to how many hours? There are how many minutes in 2.1 hours? How many seconds are in 8 hours?

Flow Duration Refers to the length of time it takes for a specific volume of liquid to drain How long an IV will be administered How long an IV bag will last before it must be changed Flow duration problems are solved with basic dimensional analysis

Example 17.6 A 1 L IV bag is being administered at a rate of 200 mL per hour. How long will this IV bag last?

Example 17.6 After setting up the problem, cancel out like units and/or numbers

Practice 500 mL of NS is being infused at 150 mL per hour. What will be the duration of the infusion? 500 mg cefazolin in 100 mL D5W is being administered at 200 mL/hr. How long will the IV last? Two 1 L bags are being infused at 250 mL/hr. How long will both bags last? 750 mL of NS is set to be administered at 150 mL per hour, starting at 11:00 a.m. At what time will the infusion be finished?

Volume Per Hour (mL/hr) Refers to calculating the amount of fluid, or solution, that will be administered to the patient intravenously per hour Unlike flow duration problems, volume-per-hour problems are solved through ratio and proportion (i.e., cross-multiplication)

Example 17.11 A patient is to receive 750 mL infused over 3 hours. What is the rate of infusion in mL per hour? Set up for ratio and proportion, then solve for the unknown

Example 17.11 (cont.) Cross-multiply 3 x X = 750 x 1 3X = 750 X = 250

Practice 1 L is being infused over 6 hours. What is the rate of infusion in mL per hour? 500 mL is being administered over 4 hours. What is the administration rate per hour? 100 mL is being infused over 30 minutes. What is the rate of infusion in mL per hour? 250 mL is being given over 100 minutes. What is the administration rate per hour?

Drug Per Hour (mg/hr) Refers to calculating the dosage, or amount of medication in milligrams, that will be administered per hour of infusion Similar to solving volume-per-hour problems Drug-per-hour problems are solved through ratio and proportion (i.e., cross-multiplication)

Example 17.16 100 mg of medication is to be administered in 500 mL of LR over 2 hours. How much drug will be administered per hour? Set up for ratio and proportion, then solve for the unknown Cross-multiply 2 x X = 100 x 1 2X = 100 X = 50

Practice 800 mg of medication in 2 L is to be infused over 4 hours. How much drug will be administered per hour? A 100 mL bag contains 75 mg of medication to be given over 30 minutes. How much drug will be administered per hour? 250,000 units of medication in 1 L is administered over 8 hours. How much drug will be administered per hour? 100 mg teniposide in 500 mL is given over 45 minutes. How much drug will be administered per hour?

Rate of IV Administration Expressed as drops per minute (gtts/min) Drip rate determines: How to calibrate the IV pump Volume of medication to be administered minute by minute Microdrip sets are calibrated to deliver 60 drops per mL

Rate of IV Administration (cont.) Macrodrip sets might be calibrated to deliver 10, 15, or 20 drops per mL Drip rate most commonly used is the microdrip, 60 gtts/mL If a problem does not indicate a specific drip rate or drop factor, the pharmacy technician should always assume 60 gtts/mL Dimensional analysis is used to solve gtts/min

Example 17-21 A 1 L bag of D5W is to be administered at a drop factor of 60 over 6 hours. What is the flow rate in gtts/min? After setting up the problem, cancel out like units and/or numbers

Example 17-21 (cont.) The infusion rate is 167 gtts/min

Practice Rx: Claforan® (cefotaxime) 500 mg/50 mL IV over 30 minutes. What is the flow rate in gtts/min? Rx: penicillin G potassium 20,000,000 units/L over 24 hours. What is the flow rate in mL/hr? Rx: antibiotic 250 mL over 2 hr. The IV administration set delivers 15 gtts/mL. What is the flow rate in gtts/min?

Total Parenteral Nutrition (TPN) Solution made to meet the body’s basic nutritional needs Also contains necessary body fluids, vitamins, and lipids In essence, everything the human body needs nutritionally Milliequivalents are used to express the concentration of electrolytes in solution TPN milliequivalent problems are solved through ratio and proportion (i.e., cross-multiplication)

Practice Na phosphate 4 mEq/mL 34mEq X MgSO4 30mEq Na acetate 2 mEq/mL Electrolyte Required Stock Vial Rx Order Volume Na phosphate 4 mEq/mL 34mEq X MgSO4 30mEq Na acetate 2 mEq/mL 10mEq KCl 40mEq Ca gluconate .0465 mEq/mL 20mEq