Calculation of Medications Used Intravenously

Published on 02/03/2015 by admin

Filed under Basic Science

Last modified 22/04/2025

Print this page

rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 0 (0 votes)

This article have been viewed 6294 times

Chapter 12

Calculation of Medications Used Intravenously

Objectives

• Interpret orders for volume of medications to be administered as intravenous (IV) fluids

• Calculate dosages of IV solutes in IV fluids including those expressed as percentages

• Calculate IV flow rates in drops per minute (gtts/min)

• Calculate time needed to infuse an ordered volume of IV fluids

Key Words

Tech Note

The medications found in this chapter are capitalized because that is how IV medications are designated when used for IV medication therapy.

Pretest

Answer the following problems to determine your level of ability in calculating medication orders for IV administration of fluids. In final answers round to the nearest drop or nearest milliliter (if less than one, round to the nearest tenth). Measurements for total volume in containers (such as liters) should be rounded to the nearest hundredth. Weight measurements should be carried to the nearest hundredth as appropriate unless otherwise stated. Time measurements should be to the closest minute or hour as indicated. Show your work. When adding volumes of medication to fluids, the volume of medication(s) added should be included when calculating the total volume of fluids.

image 1 A physician orders a continuous infusion of 1000 mL D-5-W with 20 mEq KCl/L q8h.

image 2 A physician orders 500 mL D-5-1/2 NS q8h as a continuous infusion to be administered to a patient. The physician wants the pharmacy technician to calculate the total amount of DEXTROSE and SODIUM CHLORIDE the patient will receive.

 3. A physician orders 1 L of D-5-NS to be infused over 8 hours.

image 4 A physician orders 3000 mL LACTATED RINGER’S solution to infuse over 16 hours. The drop factor is 10 gtts/mL.

image 5 A physician orders ANCEF 1g in 100 mL D-5-W IVPB to be infused over 1 hour.

6. A container of fluids contains 550 mL, and the drop rate for the infusion set is 20 gtts/mL.

image 7 A physician orders 1500 mL 0.45% NaCl IV over 24 hours. The drop factor on the infusion set is 20 gtts/mL.

image 8 A physician orders 1000 mL of D-10-W to be administered over 6 hours. The infusion set supplies 10 gtts/mL.

9.image A physician orders LACTATED RINGER’S solution to be administered with a 20 gtts/min infusion set. The physician wants the pharmacy to decide the amount of fluid that should be necessary over a 24-hour period if the medication is administered at 2 mL/min.

10.image A physician orders D-5-NS q24h. The drop factor is 20 gtts/mL, and the flow rate is 50 mL/hr.

11.image An order is given for a patient to receive D-5-NS as a continuous infusion until further orders. The drop factor is 20 gtts/mL, and the flow rate is 40 mL/hr.

12.image How many grams of DEXTROSE are in the fluids for the label shown? ____________________

13.image How many grams of SODIUM CHLORIDE are in the fluids shown in the following label? ____________________

image

14.image One L of D-5-NS is to infuse at 8 mL/min, and the drop factor is 20 gtts/mL.

image 15 A physician orders KEFZOL 1 g IVPB; the KEFZOL is to be mixed in 100 mL D-5-W to infuse over 1 hour. The drop factor is 50 gtts/mL.

16.image Three L of D-10-W are to infuse over a 24-hour period.

17.image A liter of D-5-NS is infusing at the rate of 45 gtts/min. The drop factor is 15 gtts/mL.

image 18 A physician orders PEPCID (FAMOTIDINE) 20 mg IVPB q12h. The medication is available in 10 mg/mL vials. The medication is to be added to 100 mL LACTATED RINGER’S solution and is to infuse over 30 minutes.

image 19 A physician orders AMPHOTERICIN B 40 mg IV in 500 mL of D-5-W daily to be infused over 12 hours. After reconstitution, the medication contains 50 mg/10 mL. The drop factor is 25 gtts/mL.

image 20 A physician orders AMPICILLIN 2 g IVPB. After mixing in 500 mL of D-5-1/2 NS, it will be administered over 2 hours using a drop factor of 10 gtts/mL. The available medication is AMPICILLIN 1 g vials to be reconstituted with 2.5 mL NS in each vial.

Introduction

The definition of intravenous is to administer a medication and/or fluid directly into a vein. All medications administered intravenously must be in liquid form and must be sterile. IV fluids may be given in large volumes for continuous infusion in such basic fluids in 1000 mL amounts as sterile water or normal saline with dextrose added to meet caloric needs. Medications, such as electrolytes or antibiotics, may also be added to these containers to supply drugs or nutritional needs over a period of time. The physician’s order will include the type and total fluid volume to be administered over a total period of time. In other cases, medications may be added to small volumes of fluids for administration on an intermittent basis either through an injection port in the tubing or a secondary line called IV piggyback (IVPB).

Intravenous medication prescriptions (intermittent, IVPB) specify the drug (solute), the dose to be given, and frequency of dosing but do not commonly state infusion rate or infusion time. The pharmacy determines the solvent, solvent volume, and time to be infused while the physician’s order provides the solute to be added. This information from both the physician’s order and the determinations made by the pharmacy is the information to be included on the label added to the parenteral fluid container for the specific person.

Fluids may be given as replacements for electrolytes or lost fluids such as with patients who have dehydration. Maintenance therapy provides the nutrients necessary to meet the daily needs for water, electrolytes, and glucose. With a deficit of fluids and electrolytes over a period of time, usually 48 hours, replacement therapy may be necessary to meet the fluid and electrolyte needs of the person. Finally, restorative therapy is a day-by-day restoration of vital fluids and electrolytes. With this therapy, the types of fluids being lost are those that are replaced. Often, several different types of fluids will be ordered for the patient on the same day.

Fluids may also be ordered as a means for transporting medications needing rapid absorption in the body. With the addition of drugs, the infusion is used as prophylaxis or therapeutically for disease processes.

Intravenous solutions are available in 50-mL to 1000-mL containers (commonly in flexible plastic bags) with each containing solutes and solvents prescribed for the patient’s specific needs. The reason for therapy dictates the type of fluid and rate of infusion ordered. Fluids given to keep a vein open are given slowly, whereas replacement fluids are usually given at a rate that will provide the necessary fluids while preventing an overload on the vascular system. The rate of flow depends on the patient’s physical condition. Most IV fluids are found in percentages of solutes (solids) in the total volume of solvent (solution) such as D-5-W, which is 5% dextrose in water. As learned in Chapter 11, this means that 5 g of dextrose are dissolved in every 100 mL of sterile water, or 50 g of dextrose are found in 1000 mL of water. While most IV fluids are infused by pump today, it is still important to be conscious of selecting the correct fluids for the IV infusion and ensuring an infusion is administered at the prescribed rate.

This chapter will focus on how to determine flow rates in drops per minute and determining the infusion time. You may need to determine the total time necessary for an amount of fluid to be administered as ordered, or you may need to calculate the flow rate when a total time of administration has been specified in the physician’s order.

Persons allowed to prepare and administer IV fluids are regulated by state law and the regulations of the facility where the fluids are to be administered. In some states, technicians may prepare the IV fluids for infusion, whereas in others this preparation must be done by the pharmacist. As a pharmacy technician, you must always be cognizant of the laws of your state of practice and regulations of the place of employment.

Pharmacy technicians who work in retail pharmacy may find that they do not use this chapter often, because IV infusion preparation is rarely performed in a community pharmacy. On the other hand, IV fluids are often used in the hospital setting. Understanding the calculations related to IV infusions is important for the hospital pharmacy technician but is also necessary for the retail pharmacy technician, who might one day practice in the hospital setting.

Interpreting Amounts of Solutes in Intravenous Fluids

To provide patients with continuous medications or for fluid replacement over a period of time, IV fluids are often administered to them rather than requiring them to undergo repeated injections by other parenteral routes. The medications found in fluids may be standard medications found in prepared IV fluids, such as dextrose or sodium chloride, or they may be added in the pharmacy to fill the physician’s orders, such as antibiotics or electrolyte replacements. In some instances medications may be prepared by manufacturers as commonly seen with premixed IV piggyback solutions containing antibiotics found in routinely used volumes such as 50-mL containers. The health care professional must have the ability to read the physician’s order and select the correct fluids and additives for the patient’s needs. Remember that once the fluids have been injected into the vein, the medications cannot be retrieved because the medication circulates throughout the body instantaneously. Therefore it is imperative for patient safety that the correct fluids with the correct additives (medications) are used at a safe flow rate depending on the patient’s physical condition and the medication being administered. Calculations for IV medications are performed using either ratio and proportion, formula (Dose desired/Dose on hand × Quantity = Dose to be given), or dimensional analysis, depending on method of choice.

In most cases the physician will use common abbreviations for ordering IV fluids. These are shown in Table 12-1. Notice fluids are labeled with a percentage of solute in the container of fluids or the amount of solute found in the solvent. D-5-W indicates that 5% dextrose is available in the solvent (sterile water). Remember that percentage is based on 100. So if the percentage is shown in 100 mL of solution, the 5% indicates that 5 g of dextrose is found in 100 mL of fluid. However, if the 5% is shown in 500 mL of a solvent such as water, then the total weight of the solute must be calculated. The easiest method for calculating the weight of solute is ratio and proportion (Known solute : Known volume :: Desired-to-know solute : Desired-to-know volume). To review percentage and ratio and proportion, see Chapter 2.

TABLE 12.1

Abbreviations for Common Intravenous Solutions

ABBREVIATION SOLUTION
NS Normal saline; 0.9% sodium chloride
image Half-normal saline; 0.45% sodium chloride; or image strength normal saline
D-5-W or 5% D/W Dextrose 5% in water
D-5-LR Dextrose 5% in lactated Ringer’s
RL or LR Ringer’s lactate solution or lactated Ringer’s
D-5-NS Dextrose 5% in 0.9% sodium chloride; dextrose 5% in normal saline
D-5-image Dextrose 5% in image normal saline or 0.45% sodium chloride
D-2.5-imaget 2.5% dextrose in 0.45% sodium chloride
D-2image-W image dextrose in water

image

Tech Note

Remember that when interpreting fluid solutes, 1 mL of water has a weight of 1 gram.

Example 12-1

A physician orders 500 mL 5% D/W to be given to a patient. What is the metric weight (in grams) of the dextrose in this bag of fluids? Remember, 5% means that 5 g (solute) of dextrose is found in 100 mL of water (solvent).

image

< ?xml:namespace prefix = "mml" />5 g:100::x:500

image

100x=5 g×500or2500

image
image

x=25 g of DEXTROSE in 500 mL of the above fluids

image

In some cases it is necessary to calculate the amount of medication a patient has received when the entire amount of ordered fluids is not infused.

Example 12-2

A 1000-mL container of D-5-W contains 80 mEq KCl. The patient has received 650 mL of the fluids when it is discontinued. How many mEq KCl has the patient received?

KnownUnknown80 mEq:1000 mL::x:650 mL

image
image

1000x=650×80 mEqor52,000 mEq

image
image

x=52 mEq of KCl were received by the patient

image

Practice Problems A

Calculate the solute volume found in the IV fluids. Use the method of choice for the calculations. Round answers to the nearest tenth. In some cases, the answer must be shown in hundredths; these will be noted with an asterisk. Supply answers in metric weight such as grams, unless otherwise noted. Show all of your work.

 1. What is the weight of SODIUM CHLORIDE in these fluids? ____________________

image

 2. What is the weight of DEXTROSE in these fluids? ____________________

image

 3. image A 50-mL IVPB contains PENICILLIN 1.5 million units. The patient has received 35 mL of the medication.

 4. What is the weight in grams of SODIUM CHLORIDE in the fluids shown in the following illustration? ____________________

image

 5. *What is the weight of SODIUM CHLORIDE in grams found in the fluids shown below? ____________________

image

 6. image A physician orders PENICILLIN G POTASSIUM 2.4 million units to be added to 1 L NS. You have on hand a vial of this medication that has been reconstituted to 1,000,000 units/mL.

 7. image One liter of D-5-NS contains the POTASSIUM CHLORIDE as shown on the following label using the entire vial. The vein infiltrates after 900 mL have been infused.

image

 8. A physician orders FUROSEMIDE 100 mg in 200-mL NS. The patient receives 150 mL of the medication. Available medication is FUROSEMIDE 10 mg/mL.

 9. image A physician orders FENTANYL CITRATE 50 mcg to be added to D-5-W 500 mL. The medication is available as 10 mcg/mL.

10. A physician orders 1 L of DEXTROSE 3% to be administered over 6 hours.

11. image A physician desires that a patient receive LIDOCAINE 150 mg in D-5-W 200 mL IVPB. The available medication is 1% LIDOCAINE for injection.

12. image A physician orders AMPICILLIN 2000 mcg/kg IV stat for a patient who weighs 165 lb. The medication is to be added to 50 mL of D-5-W to infuse for 20 minutes. The AMPICILLIN is reconstituted to 250 mg/5 mL.

13. image A physician orders METHYLPREDNISOLONE 125 mg IV in D-5-W 100 mL to run for an hour for a patient with asthma. The medication comes in a vial containing 250 mg/5 mL.

14. image A 50 mL container of D-10-NS contains PENICILLIN 1.5 million units. These fluids are to be infused over 30 minutes.

15. image A physician orders AMINOPHYLLINE as a loading dose of 5 mg/kg to be administered IVPB over 1 hour for a patient who weighs 154 lb. The available medication is AMINOPHYLLINE 250 mg/10 mL.

16. image A physician orders OXYTOCIN 2 units added to 1 L of D-5-W. The available medication is OXYTOCIN 10 units/mL.

17. A physician orders MAGNESIUM SULFATE 10 g to be added to LACTATED RINGER’S solution 1 L. The available medication is 50% MAGNESIUM SULFATE.

18. A physician orders 1 L of D-10-image to infuse over 10 hours.

19. image A physician orders ERYTHROMYCIN 500 mg in 100 mL of NS for IVPB stat. The vial of medication contains 1 g of ERYTHROMYCIN to be diluted with 10 mL of sterile water and added to 100 mL NS.

20. image A physician orders regular INSULIN 150 units to be added to 50 mL of NORMAL SALINE.

Calculating Intravenous Flow Rates in Drops Per Minute

In some medical instances fluids are infused without added medications, whereas in other circumstances medications are added for prophylactic or therapeutic reasons. The rate of administration varies depending on the patient’s condition and the medications/fluids to be administered. The physician’s order may state the number of milliliters per minute or per hour at which the fluids are to infuse, whereas in other circumstances the physician may state an amount of time for fluid infusion.

This section covers calculation of the drops or milliliters per minute (called flow rate). An IV infusion set (or equipment) includes the sealed container of sterile fluids and tubing connected to the needle for insertion into the vein for administration of the fluids. Equipment for IV infusions includes tubing for carrying fluid from the container to the person (Figure 12-1). The packaging for the tubing provides information on the number of drops per milliliter to be supplied. The rate of flow or the infusion rate in drops per minute is adjusted by the clamp on the tubing and the size of the drop from the drip chamber or the drop factor or by the use of infusion pump that calculates drops/minute based on the size of the drop.

image
FIGURE 12-1 A, Primary infusion set showing drip chamber, tubing, and roller clamp. B, Primary infusion set for IVPB additions. C, IVPB being added to a primary line.

For patient safety, the person preparing the fluids must ensure that the proper infusion set has been chosen to fill the physician’s order. The size of the drop depends on the way the manufacturer designs the drop orifice. The larger the diameter of the drop orifice into the drip chamber, the larger the drop entering the chamber providing fewer drops in 1 mL. Conversely, the smaller the opening into the drip chamber, the smaller the drops providing more drops per milliliter. The person preparing the fluids must be aware of the number of drops per milliliter (gtts/mL) or the drop factor to be used to complete a drop/minute (gtt/min) rate.

image Tech Alert

The number of drops per milliliter for the infusion set is found on the box. Tubing is not interchangeable. This information is essential for proper fluid administration time and calculation of IV flow rates.

The most common drop factors for IV fluids are 10, 15, 20, and 60 gtts/mL (Figure 12-2, A). Drop factors that deliver fewer and larger drops per milliliter such as 10, 15, or 20 gtts/mL are called macrodrip infusion sets. Macrodrip sets are used when large volumes of fluids must be administered or if fluids must be administered at a rapid rate. Tubing that delivers 60 drops per milliliter is called a microdrip infusion set. These sets are used for slower delivery of fluids such as at rates of 50 mL per hour (see Figure 12-2, B).

image
FIGURE 12-2 Infusion sets for administration of IV fluids. A, Macrodrip set shows 10 gtts/mL. B, Microdrip set shows 60 gtts/mL.

The rate of infusion for IV fluids must be calculated to complete the physician’s order, which provides type and amount of fluids and usually a desired infusion rate or infusion time. The proper infusion set must be chosen to supply the fluids as ordered. Therefore, the four factors to be considered with administration are as follows:

Using the previous information, the formula for calculating the flow rate of IV fluids is as follows:

Flow rate=Amount of fluid×Calibration on administration setTime for infusion

image

OR

Flow rate=mL ordered×gtts/mLminutes for infusion

image

image Tech Alert

1 L of fluids is considered to be 1000 mL.

Tech Note

Be sure that all conversions within the formula are made before final calculations, such as hours to minutes or liters to milliliters.

Example 12-3

A physician orders 1.5 L of LACTATED RINGER’S solution to be infused over 8 hours. The infusion administration set reads 20 gtts/mL.

Tech Note

In the following example calculation, 1.5 L has been converted to 1500 mL.

Flow rate=1500mL×20 gtts/mL8 hr×60 min/hr

image

Flow rate=1500mL1×20gttsmL8 hr 1×60 min1 hr}Fractional units

image
image

Flow rate=1500×20 gtts8×60 min

image
image

Flow rate=62.5 gtts/minor63 gtts/min

image

Hint: Return to Chapter 2 if you need to review the rules for rounding decimals.

If it is easier for you to complete the infusion rate in two steps, the following two steps may be used.

Example 12-4

A physician orders 1.5 L of LACTATED RINGER’S solution to be infused over 8 hours. The infusion administration set reads 20 gtts/mL.

Step 1 :mL/hr=Total volume of fluids(TV)Total time in hours(TTH)mL/hr=1500(TV)8 h(TTH)mL/hr=187.5or188 milliliters per hour should be administered

image
image

If dimensional analysis is the preferred means of calculating dosage, see Example 12-5.

Example 12-5

A physician orders 1.5 L of LACTATED RINGER’S solution to be infused over 8 hours. The infusion administration set reads 20 gtts/mL.

Tech Note

The following abbreviations will be used in the following formula:

The necessary information for dimensional analysis with the preceding example is as follows:

DF×CFV×DV×DT×CFT=FR(flow rate in gtts/min)

image

20 gtts(DF)1 mL×1000 mL(CFV)1 L×1.5 L(DV)Dose×Dose8 hr×1 hr(CFT)60 min=x(FR in gtts/min)

image
image

20 gtts×1000×1.5×11×1×8×60min=x(FR)

image

30,000 gtts480 min=x(FR)

image
image

FR=62.5or63 gtts/min should be administered

image

Tech Note

Remember that with dimensional analysis, you are completing the entire problem in one step.

Practice Problems B

Use the method that is most comfortable to calculate the flow rate in drops per minute of the following problems. Round all answers for medication weight/volume to the nearest tenth and for drops per minute to the nearest whole number. With this set of practice problems, the total volume of fluids for infusion is that given in the problem.

 1. A physician orders 2 L of LACTATED RINGER’S solution over 12 hr. The drop factor is 20 gtts/mL.

 2. A physician orders D-5-W 100 mL IV over 2 hours. The drop factor is 50 gtts/mL.

 3. A physician orders 250 mL D-5-NS to be administered over 16 hours to keep a vein open. The drop factor is 60 gtts/mL.

 4. A physician orders 1000 mL D-10-1/2NS to be administered over 12 hours. The drop factor is 10 gtts/mL.

 5. A physician orders 150 mL of D-5-NS to be infused in 40 minutes. The drip factor is 15 gtts/mL.

 6. image A physician orders a piggyback infusion containing AMPICILLIN 250 mg in 75 mL of NORMAL SALINE. The medication is to infuse over 1 hour using an infusion set labeled as 50 gtts/mL.

 7. image A physician orders OXYTOCIN 10 units in 500 mL of NS to be infused over 30 minutes. The drop factor is 20 gtts/mL.

 8. image A physician orders ZANTAC 50 mg in 100 mL NS to infuse over 15 minutes. The drop factor is 15 gtts/mL.

 9. image A physician orders METHYLPREDNISOLONE SODIUM SUCCINATE 500 mg in 150 mL NS to infuse over 2 hr. The drop factor is 20 gtts/mL.

10. image A physician orders NAFCILLIN 1 g to be added to 100 mL D-5-W to run for 1 hour. The drop factor is 15 gtts/mL.

11. image A physician orders NOVOLIN R 60 units to infuse in 500 mL NS over image hours. The drop factor is 15 gtts/mL.

12. image A physician orders TOBRAMYCIN 1 mg/kg in LR 50 mL IVPB to run for 50 minutes. The patient weighs 178 lb. The drop factor is 10 gtts/mL.

13. image A physician orders CONJUGATED ESTROGENS 25 mg to be added to 50 mL D-2 1/2-W to run for 15 minutes. The drop factor is 15 gtts/mL.

14. image A physician orders LIDOCAINE 300 mcg/kg IV for a heart patient who weighs 190 lb. The medication available is 4% LIDOCAINE solution.

15. image A physician orders 2000 mL of 1/2 NS to run for 16 hours. The drop factor is 50 gtts/mL.

16. image A physician orders GENTAMICIN 0.02 g to be added to 50 mL NS for infusion over 45 minutes. The drop factor is 20 gtts/mL.

17. image A physician orders FAMOTIDINE 20 mg in NS IV q12h to run over 25 minutes. The medication is available as FAMOTIDINE 10 mg/mL and a premixed IVPB of 20 mg/50 mL 0.9% NaCl.

18. image A physician orders CEFAZOLIN 1 g q4h to be mixed in 50 mL LACTATED RINGER’S solution and infused over 50 minutes. The medication available for reconstitution for this order is CEFAZOLIN 250 mg/vial.

19. image A physician orders KETOROLAC 60 mg/day total dose IVPB to be divided and administered q6h over a 20-minute infusion time.

20. image A physician orders CLEOCIN 1.8 g/d to be administered in divided doses q8h to run over 45 minutes. CLEOCIN is available in vials of 300, 600, and 900 mg.

Calculating Intravenous Infusion Times

In some instances the physician will provide an order for the amount of fluids to be infused and the milliliters per hour without providing the specific infusion time. The problem then becomes a decision on how long it will take for each volume of fluids to be infused using the rate ordered by the physician. As the pharmacy technician, you have a responsibility to be sure fluids are available at the necessary time for infusion and for the next dose as ordered. Therefore when the time is not designated for the fluids, but the amount of fluid is designated, the necessary calculation may include deciding how long the ordered fluids will infuse when the infusion rate and/or drop factor is provided.

Tech Note

Remember that flow rate is indicated as drops/minute.

Example 12-6

A physician orders 1000 mL D-5-NS to be administered at 20 gtts/min. The drop factor is 15 gtts/mL. What is the infusion time for these fluids?

Using the formula shown in the previous section and substituting information into the formula, the calculation can be made:

Flow rate=mL ordered×gtts/mL(drop factor)Minutes for infusion(TM) 

image

Flow rate=20 gtts/min

image

mL ordered=1000 mL

image

gtts/mL=15 gtts/mL

image

With these numbers, the equation would appear as follows:

20 gtts/min=1000 mL×15 gtts/mLx

image

20 gtts/min x=1000 mL×15 gtts/mL

image
image

20(min) x=15,000

image

x=15,00020 min

image
image

x=750 minutesor12.5 hours(750 min%60 min/hr)

image

Tech Note

Remember that when you cross the “=” sign while completing calculations, multiplication on the left side of the equation becomes division on the right side of the equation and vice versa.

Example 12-7

A physician orders 1000 mL D-5-NS to be administered at 20 gtts/min. The drop factor is 15 gtts/mL. What is the total infusion time for the ordered fluids (using dimensional analysis)?

DF ×CFV×DV×FR=DT

image

Again, use substitution and complete the equation.

15 gtts(DF)1 mL×1000 mL(CFV)1000 mL×1000 mL(DV)Dose×Dose20 gtts/min(FR)=DT

image
image

15×1×10001×1×20min=DT

image

15,00020min=DT

image
image

15002min=DT

image

DT=750 minutes,then,convert minutes to hours=12.5 hours(750%60 min/hr)

image

Practice Problems C

Use either the formula method or dimensional analysis, whichever is more comfortable for you, to complete the following problems. Round time to the units of hours and minutes as indicated. Round drops to the nearest whole drop in the final answer. Drug weights/volumes and kilograms of body weight should be rounded to the nearest tenth, unless marked with an asterisk, and then round to the nearest hundredth. If asking for total hours, use tenths of hours; if asking for hours/minutes make the needed conversion. Show your work.

 1. image A physician orders 500 mL D-5-NS to be infused at 15 gtts/min. The drop factor is 10 gtts/mL.

 2. image A physician orders 2500 mL D-5-image NS to be infused at 30 gtts/min. The drop factor is 10 gtts/mL.

 3. image A physician orders AMIKIN 1 g in 100 mL D-5-W to infuse at 25 gtts/min using an infusion set calibrated to 60 gtts/mL.

 4. image A physician orders MANNITOL 75 g IV for renal failure. The solution is provided in D-5-NS 50 mL. The infusion rate is 20 gtts/min with a drop factor of 50 gtts/mL.

 5. image A physician orders LR 250 mL to be infused at 50 gtts/min. The infusion set reads 10 gtts/mL.

 6. image A physician orders 2 L of D-5-W to be infused at 25 gtts/min. The infusion set is 10 gtts/mL.

 7. image A physician orders GENTAMICIN 1.5 mg/kg/dose to be given q8h IVPB in 150 mL NS for a patient who weighs 148 lb. The infusion is to be infused at 25 gtts/min. The drop factor is 20 gtts/mL.

 8. image A physician orders OXACILLIN 12 g/day given in divided doses q3h IVPB.

image

 9. image A physician orders the solution shown in the following illustration to be administered at 30 gtts/min using a drop factor of 50 gtts/mL.

image

10. image A physician orders CEFOPERAZONE 2 g IV in LR 75 mL to be infused at 10 gtts/min. The drop factor is 25 gtts/mL.

image

11. image A physician orders CEFTAZIDIME 750 mg IV in D-5-W 50 mL q12h for a severe case of pelvic inflammatory disease. The drop factor is 20 gtts/mL, and the fluids are to run at 2.5 mL/min. Using the following label, reconstitute the medication and prepare the fluids for infusion.

12. image A patient is to receive D-5-1/2 NS × 1.5 L at the rate of 100 gtts/min using an administration set of 10 gtts/mL.

13. image A physician orders AMPICILLIN 250 mg IVPB to be infused in 50 mL NS at 30 gtts/min. The drop factor is 10 gtts/mL.

14. image A physician orders AMINOPHYLLINE 750 mg IVPB to be added to 100 mL of fluids for a patient with severe asthma. The medication is available as AMINOPHYLLINE 500 mg/25 mL. The administration set is 60 gtts/mL, and the rate of infusion is 10 gtts/min.

15. image A physician orders ERYTHROMYCIN 200 mg IVPB in 250 mL D-5-W. The medication is available as 400 mg/5 mL after reconstitution. The drop factor is 30 gtts/mL, and the rate of infusion is 20 gtts/min.

16. image A physician orders 1000 mL LR + 20 mEq KCl per liter × 2 L. The drop factor is 10 gtts/mL. The infusion rate is 15 gtts/min.

17. A physician orders AMPHOTERICIN B 40 mg IVPB to be administered in D-5-W 250 mL to be infused at a rate of 20 gtts/min with a drop factor of 60 gtts/mL.

image

18. A physician orders VANCOCIN 1 g in 100 mL D-5-W. The drop factor is 20 gtts/mL, and the infusion rate is 1.5 mL/min.

image

19. image A physician orders 150 mL D-5-W for a young child who is dehydrated. The drop factor is 60 gtts/mL, and the infusion rate is 0.5 mL/min.

20. image A physician orders HEPARIN SODIUM 3500 units to be added to 100 mL of NS for IV infusion. The drop factor is 60 gtts/mL, and the infusion rate is 20 gtts/min.

image

Review

Physicians order IV therapy for several reasons—maintenance, replacement, and restorative therapy. In some cases medications such as electrolytes and antibiotics may be added to the container of fluids for infusion over a period of time; such medications may be given by intermittent infusion over a short period of time (e.g., most by IVPB) or may be infused over long periods of time (e.g., continuous infusions or continuous IV fluid orders). To ensure that medications are supplied and infused as ordered by the physician, the pharmacy is responsible for providing the medications and fluids for the order. In some cases, the pharmacy may assist in providing the needed tubing with the correct drop factor for accurate administration.

After the correct fluids have been selected, as the pharmacy technician, you may be responsible for ensuring adequate amounts of fluids have been provided for the desired length of time. Furthermore, you may be asked to calculate the amount of time that a container of fluids will need for infusion, the necessary volume of fluids, or rate of infusion per minute or hour to provide the medication as ordered for the ordered time or the amount of medication that has been infused over a given period of time. Patient safety is ensured when the fluids are those ordered by the physician and are calculated for the correct infusion rate using formulas provided in this chapter. Because of the rapidity of administration of medications through an IV route, the pharmacy must take care with these calculations. As the pharmacy technician, you must be sure the correct fluids are chosen, along with the correct administration supplies. Rechecking calculations always enhances patient safety with intravenous medications.

Posttest

Before taking the Posttest, retake the Pretest to check your understanding of the materials presented in this chapter.

Calculate the following situations using the method most comfortable for you. Round to the nearest whole number for hours/minutes as appropriate. Round to the nearest tenth for weight/volume. If the question is marked with an asterisk, the answer should be rounded to the nearest hundredth. Round drops to whole numbers. Interpret each order for IV fluids and medications. Show your calculations.

image 1 A physician orders KEFUROX 1.5 g in D-5-NS 100 mL to be infused over 1 hr as IVPB. The drop factor is 20 gtts/mL. Use the following label for your calculation.

image

image image 2 A physician orders FUROSEMIDE 60 mg to be infused in D-5-W 500 mL. The drop factor is 20 gtts/mL, and the drop rate is 60 gtts/min. Use the following label for your calculations.

image

image 3 A physician orders HUMULIN R 60 units added to D-2.5-image NS 100 mL as an IVPB. The drop factor is 60 gtts/mL. The physician wants the INSULIN to infuse at 2.5 units/hr. Use the following label for your calculations.

image

image 4 A physician orders AMPICILLIN SODIUM 1 g to be added to LACTATED RINGER’S solution 100 mL. The drop factor is 60 gtts/mL. The medication must be given over a 2-hour time. Use the following label for calculations.

image

image 5 A physician orders NITROGLYCERIN IV 50 mg in D-5-W 250 mL to be infused at the rate of 50 mcg/min. The drop factor is 60 gtts/mL.

 6. A physician orders D-5-NS 3000 mL to be infused over 24 hours. The drop factor is 15 gtts/mL.

image

image 7 A physician orders AMIKIN 5 mg/kg q8h in 100 mL of fluids IVPB. The patient weighs 176 lb. The drop factor is 20 gtts/mL. The time of infusion is 2 hours.

 8.image What is the time in minutes for infusion of the fluids shown in the following label if the drip rate is 3 mL/min, and the drop factor is 20 gtts/mL? ____________________

image

 9image A physician orders 500 mL D-5-LR to be infused over 12 hours. The drop factor for the infusion set is 60 gtts/mL.

10.image A physician orders D-2.5 image 1000 mL for a child who is dehydrated. The physician wants the patient to receive 90 mL the first hour and the remainder over 12 hours. The drop factor is 60 gtts/mL.

image 11 A physician orders ROCEPHIN 25 mg/kg IVPB to run in 100 mL NS over 1 hour to be given q 12 h. The patient weighs 176 lb. The drop factor is 15 gtts/mL. The available medication is 2 g/vial.

image 12 A physician orders potassium chloride 30 mEq to be added to D-5-W 150 mL IVPB and infuse over image hours. The drip factor is 20 gtts/mL.

image

13.image A physician orders DOXYCYCLINE 150 mg IVPB in LR 85 mL to be administered over image hours. The medication is available as DOXYCYCLINE 100 mg/10 mL. The drop factor is 20 gtts/mL.

14.image A physician orders RETROVIR (ZIDOVUDINE) 2 mg/kg IVPB to be administered to a patient who weighs 167 lb. The medication is to be infused in D-5-W 100 mL over a period of 1 hour. The drop factor is 15 gtts/mL. The order is to be repeated q4h × 24 hours.

image

image 15 A physician orders AMPICILLIN 500 mg q6h in D-5-NS 50 mL to infuse over 15 min. The medication is available as shown in the following illustration. The drop factor for the infusion is 20 gtts/mL.

image

image 16 A physician orders HEPARIN SODIUM 20,000 units in NS 500 mL to run over 24 hours. The administration set is 60 gtts/mL. The medication available is shown on the following labels.

image
image

image 17 A physician orders EPINEPHRINE 6 mg added to D-5-W 500 mL to be infused at 10 mL/hr. The drop factor is 60 gtts/mL.

image 18 A physician orders LIDOCAINE 100 mg in D-5-W 250 mL to be infused over an hour. The lidocaine is available in 10 mg/mL. The drop factor is 40 gtts/mL.

image 19 A physician orders EPINEPHRINE 50 mcg/min to be administered from fluids that contain epinephrine 5 mg in D-5-LR 500 mL. The drop factor is 20 gtts/mL.

image 20 A physician orders AMPHOTERICIN B 200 mg IVPB to be added to D-5-W 500 mL to infuse over 6 hours. The medication is available in a 100-mg/20-mL vial. The drop factor is 15 gtts/mL.

Review of Rules

Interpreting the Amounts of Solutes in Intravenous Fluids

Calculating Intravenous Flow Rates in Drops per Minute

• Tubing used for the IV infusion set provides information for the number of drops per milliliter to be supplied to the patient.

• The drop factor is found on the packaging for the infusion set and may be either microdrops or macrodrops.

• To calculate the flow rate, consider the following factors:

• The flow rate of IV fluids may be calculated using the following formula:

Flow rate=Amount of fluid(mL)×Calibration on administration set(gtts/mL)Time for infusion(min)

image

    OR

Flow rate=mL ordered×gtts/mLminutes for infusion

image

• This calculation may also be accomplished using two steps:

    Step 1:

mL/hr=Total volume of fluids(TV)Total time in hours(TTH)

image

    Step 2:

gtts/min=Drop factor(gtts/60 min)Time in minutes(TM)×Total volume(mL)

image

• If dimensional analysis is used, the formula is based on the following: DF = Drip factor; CFV = Conversion factor volume; DV = Dose volume; DT = Dose time; CFT = Conversion factor time; FR = Flow rate in gtts/min.

DF×CFV×DV×DT×CFT=FR

image

Share this:

Related posts:

Conversion of Clinical Measurements of Numbers, Time, and Temperature Assessment of Mathematical Calculation Skills Needed for Pharmacy Technicians Reconstitution of Powders or Crystals into Liquid Medications Interpretation of Medication Labels and Orders Interpreting Physicians’ Orders for Dosages Calculation of Medications for Special Populations Based on Body Weight and Patient Age