Hypotonic	Isotonic (290 mOs)	Hypertonic
2.5% dextrose in water (2.5% DW)	5% dextrose in water (D5W or 5DW)	10% dextrose in water or (10DW)
0.45% NaCl (sodium chloride) solution (0.45NS, ½ NS, or ½-strength NS)	Normal saline (NS) solution (0.9% NaCl solution)	5DW in 0.45% NaCl solution or D5W in ½ NS
	Lactated Ringer’s solution (L/R, R/L, or LRS)	D5LR or D5RLS solution

Additives such as vitamins, minerals, potassium chloride (KCl), and many other medications may be ordered for inclusion in these solutions. Figure 9-1 shows labels of selected isotonic solutions.

FIGURE 9-1 Labels of isotonic solutions. A, 5% dextrose. B, 0.9% sodium chloride. C, Lactated Ringer’s solution.

Q: Ask Yourself

1. Which type of solution most closely approximates the tonicity of plasma—hypotonic, isotonic, or hypertonic? Refer to “Osmolarity” in the Essential Vocabulary.

_______________________________________

2. How does the percentage of solute in hypotonic and hypertonic solutions differ from that in isotonic solutions? (Give a brief answer and refer to Essential Vocabulary if necessary.)

_______________________________________

A: My Answer

FAQ

Why is ½ NS labeled 0 45% rather than 0 5% NaCl?

ANSWER

Because it contains half the NaCl content of NS solution. NS solution contains 0.9%, not 1%, NaCl.

All IV solutions and medications must be checked for compatibility using a current drug reference before being administered. When in doubt, the nurse should consult the pharmacy. In some large agencies, the pharmacy has an IV telephone “hotline.”

Q: Ask Yourself

1. What are five types of equipment needed for all IV infusions?

____________________________________________

A: My Answer

Intravenous Solution Volume

Volumes of solution per IV container are usually 500 or 1000 mL but can vary from less than 50 to more than 1000 mL. Some medicated solutions are provided in 100- and 250-mL containers. Volumes of 500 and 1000 mL are among the most frequently encountered for maintenance and continuous solutions.

If the order calls for a liter, the nurse selects a 1000-mL container. Often, the order for a continuous IV infusion states only the name of the solution and the flow rate per hour. The nurse selects the volume for the infusion that will last a reasonable amount of time.

A superscript o may be seen on orders to designate hour (e.g., q8^o). Do not use this notation. The o may be mistaken for a zero.

Intravenous Solution Orders for Milliliters per Hour

One calculation needed for all infusions so that flow rate can be monitored is a determination of the number of milliliters per hour (mL per hr).

The following are two typical orders for a continuous IV infusion:

Order	Meaning
1000 mL 5DW at 125 mL per hr	1 Liter of 5% dextrose in water to flow at a rate of 125 mL per hour until further notice
1 liter L/R solution q8h	1000 mL of lactated Ringer’s solution every 8 hours

• Identify the ordered flow rate in mL per hr and any special instructions.

• Determine how long the IV solution will last.

The calculations are usually very basic.

• If the prescriber orders D5W at 125 mL per hr, the nurse administers a continuous flow rate of 125 mL per hr until the order is discontinued or changed.

The equipment may vary and require further calculations, but the essential rate in mL per hr must be known.

• If the prescriber orders 1 L D5W q8h, the flow rate is derived with a simple calculation:

mLhr:1000ml8hr=125mL per hr

• Milliliters and hours are both desired in the answer. This distinguishes hours from minutes or other time frames that may be ordered. The initial entry in the equation setup is the matched units in the numerator (milliliters). Hours (hr) must be entered in a denominator.

• Round flow rates to the nearest whole number.

Q: Ask Yourself

1. What is the one calculation that is needed for all infusion rates?

____________________________________________

A: My Answer

Determining Infusion Durations

• If the order states 1 L q8h, it is obvious that the IV infusion will require replacement in 8 hours. If the order states only the mL per hour, a simple calculation is required.

EXAMPLES

If the order states mL per hr such as 120 mL per hr, and a liter (1000 mL) will be supplied:

1. Determine the hours of duration first (total mL ÷ mL per hr)

2. Convert any remainder of hours to minutes using a conversion factor: 60 minutes = 1 hr (60 × hr = minutes).

Total expected duration of 1000 mL flowing at 120 mL per hr = 8 hr and 18 min.

CLINICAL RELEVANCE

Calculating the duration of an infusion helps the nurse to know when to prepare the subsequent infusion (i.e., before the current one runs dry) or when to discontinue the infusion. If an infusion runs dry, the site coagulates and the patient needs to have a new site established. This is very unpleasant for the patient and takes time that could be better spent on other nursing priorities.

Communication

After the nurse identifies the patient, she or he briefly explains the purpose for administering the IV solution: “Mr. Smith, your doctor has ordered some fluids and (name) medications in your vein to help your (state the condition).” It is better to say “help” than “prevent.” Accentuate the positive. “Have you had an IV before? How did it go?” or “How did you do with them?” “Do you have any allergies to these medications or any other medications? What kind of reaction did you have?” Listen carefully to the patient’s responses to these questions.

Calculating simple milliliter per hour (mL per hr) orders

Experienced nurses calculate simple orders, such as 1 L q8h, by converting 1 L to 1000 mL and performing simple division, 1000 mL ÷ 8 (total volume of the container divided by hours), yields a flow rate of 125 mL per hr.

When the question is, How many mL per hr, think of per as a division line: total milliliters÷total hours=mLhr

Always double check your answers.

Check agency policy pertaining to IV solution, tubing, and needle replacement. Some solutions need to be changed every 24 hours, others every 48 hours. TJC regulations present replacement guidelines. The contents of solution are factors in the policies. The product label may indicate an expiration date.

Q: Ask Yourself

1. What are the abbreviations for three commonly ordered isotonic IV solutions?

____________________________________________

A: My Answer

With all patient communications, it pays to stop, look, and listen and respond accordingly.

If you are comfortable with multiplication and division skills, use a calculator for multiplication and long division.

RAPID PRACTICE 9-3 Flow Rates and Infusion Times for Intravenous Solutions

Estimated completion time: 15-20 minutes Answers on page 536

Directions: Using the flow rate supplied, fill in the abbreviations for the solution ordered, the flow rate in mL/hr, the nearest whole number, and the infusion time in hours and minutes, if applicable. Use a calculator for long division and multiplication.

Order	Abbreviation(s) for Solution	Flow Rate (mL per hr)	Infusion Time, Hours (and Minutes, If Applicable)
1. Infuse 500 mL normal saline over 6 h	__________	__________	__________
2. 1000 mL 5% dextrose in water at 125 mL per hr	__________	__________	__________
3. 1 L lactated Ringer’s q10h	__________	__________	__________
4. 250 mL half-strength normal saline q4h	__________	__________	__________
5. 500 mL 5% dextrose in lactated Ringer’s @40mL per hr	__________	__________	__________

FAQ

How do I know which size, in milliliters, of IV bag to select?

ANSWER

There are three criteria:

• Infusion time

• Flow rate ordered

• Solutions available or supplied

The commonly available solutions are packaged in amounts of 250, 500, and 1000 mL. Smaller amounts, including medicated solutions, are also supplied by the pharmacy. If the infusion is to last 8 hours and the flow rate is 100 mL/hr, 800 mL would be the minimum needed. The closest amount that can be selected would be a 1000 mL bag. If the solution is to infuse at 50 mL per hr continuously, most nurses will select a bag that contains at least enough to last for an 8- or 12-hour shift: 50 mL × 8 = 400 mL, or 50 mL × 12 = 600 mL. The nurse would probably select a 500 or 1000 mL bag even for the 50 mL per 8 hr order, assuming that the IV infusion would be reordered.

Intravenous Flow Rate Entries for Electronic Infusion Devices

When electronic controllers or pumps are used for IV infusion, the nurse must enter the ordered flow rate on the digital device. The LED screen displays the number of milliliters being infused per hour, the total number of milliliters that have been infused, and various other information, depending on the sophistication of the device (Figure 9-2).

FIGURE 9-2 Dual-channel electronic infusion pump. (From Kee JL, Marshall SM: *Clinical calculations: with applications to general and specialty areas,* ed. 6, St. Louis, 2009, Saunders.)

For an order of 1000 mL q8h, the nurse would set up the equipment and enter a flow rate of 125 mL per hr.

It is preferable to administer medicated solutions through EIDs. Critical care units do not usually use gravity infusions.

Gravity Infusions

Some agencies use simple gravity devices with manual rate controllers for temporary emergency purposes, for administering unmedicated solutions or less powerful medicated solutions, and for maintenance unmedicated IV therapy (Figure 9-3).

FIGURE 9-3 A, Gravity flow intravenous infusion equipment. (A, Modified from Clayton BD, Stock YN, Hicon001-9780323069045un RD: *Basic pharmacology for nurses,* ed. 15, St. Louis, 2010, Mosby. B, From Lilley LL, Harrington S, Snyder JS: *Pharmacology and the nursing process,* ed. 6, St. Louis, 2011, Mosby. From Rick Brady, Riva, MD.)

Outpatient centers, emergency vehicles, outpatient recovery units, home-care settings, rehabilitation units, and long-term care units are examples of places where gravity devices may be encountered.

Gravity infusions are hung on a pole approximately 36 inches above heart level of the patient. The flow rate is dependent on the flow rate control clamp adjustment, positioning of the solution, tubing patency, and the patient’s position.

Intravenous Administration Sets

Intravenous tubing provides the connection between the IV solution and the patient. The nurse selects the tubing needed based on the order and the infusion equipment provided by the agency.

The physician does not specify the equipment. Some tubing administration sets may be used interchangeably on infusion pumps and gravity devices. The tubing label describes the use. The containers are available in supply stations. The tubing is supplied in various widths to accommodate various flow rates and solution viscosities.

There are several types of specialized IV tubing. The main types include

• Primary (main) tubing for “main” and “maintenance” IV lines, EIDs, and gravity infusion devices (see Figure 9-3, B)

• Secondary, shorter tubing that connects to the primary tubing at a port to permit additional intermittent solutions to be added (piggybacked) without having to create a new injection site (see Figure 9-3, B)

• Blood administration sets with special filters and a Y connector for NS solution to prime the lines before and flush after blood transfusion or to use if the blood needs to be stopped or removed for any reason

• Extension tubings that are used when more length is needed (e.g., for ambulation)

A needle adapter with a cap, tubing, a clamp to stop and start flow, a drip chamber, and an insertion spike are included in the administration sets.

Selection of Gravity Infusion Administration Sets

For gravity devices, the nurse selects the calibration of tubing needed based on the equipment available, the flow rate ordered, and the contents of the IV solution. The DF is available on the tubing administration set. Figure 9-4, A illustrates a DF of 10 (10 drops per mL).

FIGURE 9-4 A, DF 10. B, DF 15. C, DF 20. D, DF 60. (From Gray Morris D: *Calculate with confidence,* ed. 5, St. Louis, 2010, Mosby.)

Macrodrip (large-diameter) tubing, with a DF of 10, 15, or 20, is selected for unmedicated solutions, solutions requiring faster flow rates, and solutions that have less powerful medications (Figure 9-5, A).

FIGURE 9-5 Contrast the macrodrip chamber **(A)** with the microdrip chamber **(B)**. (Modified from Clayton BD, Stock YN: *Basic pharmacology for nurses,* ed. 15, St. Louis, 2010, Mosby.)

Microdrip tubing (also known as pediatric tubing) has a DF of 60 and nicon001-9780323069045w tubing that delivers tiny drops from a needle-like projection to achieve 60 drops/mL. Because of the projection, microdrip sets can be recognized at a glance without having to go to a supply room to check the DF (Figure 9-5, B).

Check agency policy for administration set selection protocols.

Agency policies must be checked for regulations pertaining to choice of IV equipment. If a solution is medicated, it may be required to be on a volumetric pump.

Calculating Flow Rates for Gravity Infusion Devices

The flow rate for simple gravity devices that consist of only an IV solution and tubing is derived from the number of mL per hr ordered and is delivered in drops per minute. The drop-per-minute rate is calculated by the nurse. The nurse adjusts the flow rate with a hand-operated slide pinch or roller clamp (Figure 9-6).

FIGURE 9-6 Nurse adjusting flow of IV infusion. (From Perry AG, Potter PA: *Clinical nursing skills and techniques,* ed. 7, St. Louis, 2010, Mosby.)

To convert mL per hr to drops per minute, identify the following factors:

1. Number of mL per hr ordered

2. Calibration (DF, or drops per milliliter) of the selected tubing administration set, stated on the administration set package: 10, 15, 20, or 60.

When the drop-per-minute count is correct, the flow rate will deliver an approximate equivalent of the number of mL per hr ordered.

The nurse needs to assess IV sites and flow rates during each visit to the bedside and/or every hour or more often. Check agency policies.

Some agencies provide a flow rate control device for gravity infusions, such as the one shown in Figure 9-7. The Dial-a-Flo device is an example of an in-line apparatus that can be added to a gravity infusion set so that the number of mL per hr can be set on the dial and the number of drops per minute does not have to be calculated.

FIGURE 9-7 Dial-a-Flo® extension set with pre-pierced Y-site. (From Hospira, Inc., Lake Forest, IL.)

Check calibrations on gravity flow rate devices. Dial-a-Flo provides a range from 5 to 250 mL per hr.

Calculation of gravity infusion rates

The key to accurate calculation of flow rates for gravity devices is to understand the underlying process. Once the method described in this section is thoroughly understood, faster methods will become apparent.

EXAMPLES

Ordered: IV D5W 1000 mL at 100 mL per hr or 1 L D5W q10h. How many drops per minute will the nurse set on the gravity infusion set?

• Identify the mL per hour to be infused: 100 mL per hr

• Identify the DF from the IV administration set.

Note that 10 drops per mL ÷ 100 mL per hr ordered = 1000 drops per hr. The nurse cannot count the drops for an hour to see if the rate is correct. The nurse wants to know the count for 1 minute that would result in the desired number of drops per hour.

• Enter the data in a DA equation along with an hr to min conversion.

All the data can be entered in one equation (when the number of mL per hr is known) to obtain the number of drops per minute. Examine the example that follows.

Calculation of Gravity Infusion Rates Using DA

EXAMPLES

Ordered: IV D5W 1000 mL at 100 mL per hr

Drop factor (DF): 10 (10 drops per mL)

(The DF is found on the tubing administration set.)

The nurse will set the flow rate for how many drops per minute (min)?

The final equation will be written like this:

Analysis: We need a rate, drops and time in the answer. Once again, the selected Starting Factor, the conversion factor of 10 drops in 1 mL, was the factor containing the desired answer units. The rate and time factor was 100 mL per hr. The only time available was hour so we used it and then converted hours to minutes. The rest of the factors were entered so that they could be canceled sequentially starting with mL. Drops has to be in a numerator and minutes has to appear in a denominator.

Evaluation: Only the desired answer units remain. Our estimate of about 1/6 of 100 is supported by the answer (Math check: 100 ÷ ÷ 6 = 16 2/3 rounded to 17 drops per minute). The equation is balanced. Note that once again, cancellation makes the math simple.

Note the 1000 mL in the order was not needed. Rate, drops, and time were already selected. If we had also added the 1000 mL somewhere in the equation, mL would have appeared 3 times and could not have been canceled. The answer would have been 17,000 mL drops per minute; however, 60 drops per minute is about as fast as the nurse can count.

Be aware that some orders still use the outdated abbreviation “gtt” for drops.

FAQ

What is the advantage of a Dial-a-Flo type rate control device (Figure 9-7, p. 275) over gravity infusion sets?

ANSWER

The nurse does not have to calculate drops per minute. The Dial-a-Flo device takes care of that step when the precise mL per hr from the order is entered. (These devices are not always supplied.)

RAPID PRACTICE 9-4 Calculating Flow Rates for Gravity Infusions Using DA Equations

Estimated completion time: 15 minutes Answers on page 536

Directions: Examine the example on p. 276 and the example in problem 1. For problems 2-5, identify the number of mL per hr and the drop factor. Calculate the flow rates to the nearest whole drop per minute for the ordered solutions. Evaluate the equation. Use a calculator for long division and multiplication.

Remember that the DF is in drops per 1 mL. The DF and the number of mL per hr ordered must be entered in the equation.