Basic IV Drip Rates

TOPICS COVERED

1. IV fluids

2. IV drip factors

3. Choosing infusion set tubing

4. Infusion pumps

5. Labeling IVs

6. Calculating basic IV drip rates: milliliters over a number of hours, milliliters per hour (mL/hour), and drops per minute (gtt/minute)

7. Determining hours an IV will run

8. Assessment

9. Adding medications to continuous IVs

10. Intermittent piggyback drip rates

11. Enteral feeding

12. Recording IV intake

Administration of parenteral fluids and medications by the IV (intravenous) route is common medical practice and is a specialty within nursing and health care. Texts such as Plumer’s Principles and Practice of Intravenous Therapy (Lippincott Williams & Wilkins, 2006) present detailed and extensive information. This chapter presents basic knowledge—types of fluids, equipment, calculation of drip rates, and recording intake. Chapter 7 presents rules and calculations for special types of IV orders.

Types of IV Fluids

IV fluids are packaged in sterile plastic bags or glass bottles. It is essential to choose the correct IV fluid to avoid serious fluid and electrolyte imbalance that may occur from infusing the wrong solution. Physicians and healthcare providers order IV fluids and the IV flow rate.

If you have any doubt about the correct IV solution, always double-check with another healthcare professional.

Common abbreviations for IV fluids are listed in Table 6-1.

FIGURE 6-1Drip chambers for macrodrip and microdrip IV tubing.

Kinds of IV Drip Factors

IV fluids are administered through infusion sets. These consist of plastic tubing attached at one end to the IV bag and at the other end to a needle or catheter inserted into a blood vessel. The top of the infusion set contains a chamber. Sets with a small needle in the chamber are called microdrip because their drops are small. To deliver 1 mL of fluid to the patient/client, 60 drops drip in the drip chamber (60 gtt = 1 mL). All microdrip sets deliver 60 gtt/mL.

Infusion sets without a small needle in the chamber are called macrodrip (Fig. 6-1). Drops per milliliter differ according to the manufacturer. For example, Baxter-Travenol macrodrip sets deliver 10 gtt/mL, so 10 drops drip in the drip chamber (10 gtt = 1 mL); Abbott sets deliver 15 gtt/mL, so 15 drops drip in the drip chamber (15 gtt = 1 mL). The package label states the drops per milliliter (gtt/mL). Sometimes the drop factor is also stated on the top part of the chamber. To calculate IV drip rates, you must know this information.

The tubing for these sets includes a roller clamp (Fig. 6-2A) that you can open or close to regulate the drip rate; use a watch or a clock with a second hand to count the number of drops per minute in the chamber (Fig. 6-2B).

FIGURE 6-2(A) Roller clamp (B) Timing the IV drip rate. (© B. Proud.) (With permission From Taylor, C., Lillis, C., & LeMone, P. [2004]. Photo atlas of medication administration. Philadelphia, PA: Lippincott Williams & Wilkins, p. 46.)

FIGURE 6-3Dial-a-Flow device. (Copyright 2010 L. Farmer Photography)

FIGURE 6-4IV rate is programmed into the infusion pump in milliliters per hour. (With permission from Craven, R., and Himle, C. (2007) Fundamentals of nursing (5th ed). Philadelphia, PA: Lippincott Williams and Wilkins, p. 576.)

The Dial-a-Flow device (sometimes referred to as Dial-a-Flo) is an extension IV tubing that attaches to the primary IV tubing (Fig. 6-3). It is calibrated in milliliters per hour; you “dial” the rate, and the device regulates the flow. The roller clamp must be open all the way. Usually, these devices are not used with an infusion pump. The rate is still an approximate amount, and changes in the patient/client position can affect the flow rate.

Infusion Pumps

Electric infusion pumps also deliver IV fluid. Some are easy to operate; others are more elaborate. You must enter two pieces of information: the total number of milliliters to be infused and the number of milliliters per hour. Pumps used in specialty units also allow you to input the name of the medication, the concentration of the medication, the amount of fluid, and the patient/client’s weight. The infusion rate is set in milliliters per hour, and the pump automatically calculates the dose in milligrams, micrograms etc. There are several manufacturers of IV pumps; some pumps use regular IV tubing, while other pumps use tubing specific to that IV pump. All IV pumps allow you to program the primary IV rate, volume to be infused, secondary IV rate, and total volume that has infused over a period of time. The pump can also calculate the dosage based on weight. Figure 6-4 shows the face of an infusion pump with IV tubing connected.

The tubing factor for an IV infusion pump is 60 gtt/mL; however, the rate is stated and programmed as milliliters per hour.

Labeling IVs

Every IV must be labeled so that any professional can check both the fluid that is infusing and the drip rate. A typical order includes the following information:

• Patient/client name, room, bed number, date, and time

• Order: 500 mL D5W½NS. Rate: 50 mL/hr.

EXAMPLE

Calculating Basic IV Drip Rates

Routine IV orders specify the number of milliliters of fluid and the duration of administration:

EXAMPLE

As mentioned previously, an infusion pump is set in milliliters per hour, so your dosage calculations are in milliliters per hour as well. IV tubing sets infuse at drops per minute, and the infusion rate depends on the drip rate of the tubing used. Although many institutions only use infusion pumps occasionally you will need to calculate and infuse IV fluid using the drip rate calculation.

RULE SOLVING IV CALCULATIONS WITH MICRO- AND MACRODRIP TUBING

The terms drop factor, drip factor, gtt factor, and tubing drip factor are all used to explain how many drops per milliliter the tubing delivers. In this text, we will use tubing factor or TF to mean all of these terms.

Calculation

For example, the order is to infuse 120 mL of IV fluid over 60 minutes with a tubing factor of 10 drops per milliliter. The calculation is:

For dimensional analysis, you set up the equation as such:

In this example:

Cancel “mL.” Reduce the fraction. Solve.

Explanation

TF: the tubing drip factor—either microdrip (60 gtt = 1 mL) or macrodrip. Depending on the manufacturer, macrodrip could be 10 gtt = 1 mL, 15 gtt = 1 mL, or 20 gtt = 1 mL.

minutes: the number of minutes, specified in every IV order. If the order reads “hour,” then you convert to minutes by multiplying by 60 (60 minutes = 1 hour).

gtt/minute: the drip factor, calculated to deliver an even flow of fluid over a specified time. To regulate the drip rate, use a second hand on a watch or a clock. If the drip rate is calculated to be 20 gtt/minute, open the clamp and regulate the drip until you reach that amount. Usually, you break this amount down into seconds rather than counting for a full minute. For this example, 20 gtt/minute becomes approximately 5 gtt every 15 seconds (20 gtt divided by 60 = 0.33 gtt every second. multiply 0.33 times 15 = approximately 5 gtt every 15 seconds).

The problems requiring calculation in this text will supply the tubing (or drip) factor. When you’re working in the clinical area, you must read the package label of the IV tubing to identify the drops per milliliter.

Solving IV Calculations Using an Infusion Pump

Infusion pumps are always calculated in milliliters per hour. Here’s how to calculate the example from above, infusing 120 mL of IV fluid over 60 minutes:

The calculation looks like this:

Note that 60 minutes was changed to 1 hour (60 minutes = 1 hour).

After calculating, connect the IV fluids to the infusion pump with the appropriate tubing, set the pump at 120 mL/hour, set the volume for infusion—120 mL, and start the infusion.

Explanation

mL: The physician or healthcare provider will indicate the number of milliliters to be infused in the order.

hours: The number of hours to run depends on the way the order is written. For example:

Alternate Way

Here’s a formula you can use to calculate what rate to set on the infusion pump:

Since the tubing factor is always 60 gtt/mL with infusion pumps, for the calculation “infuse 120 mL of IV fluid over 60 minutes using an infusion pump,” the formula looks like this:

Drip rates are rounded to the nearest whole number unless using an infusion pump that can infuse in tenths or hundredths (i.e., 8.25 mL/hour). Usually, these infusion pumps are used in a specialty setting such as critical care or pediatrics.

Choosing the Infusion Set

Experience will enable you to judge which IV tubing to use. In clinical settings, the guidelines below will help you make your choice. An electric infusion pump poses no problem, because it will deliver the amount programmed. Specialized pumps in neonatal and intensive care units can deliver 1 mL/hour and even less. Specialized syringe pumps also can deliver less than 1 mL/hour.

When an IV pump is not available, consider these guidelines:

Use microdrip when

• the IV is to be administered over a long period

• a small amount of fluid is to be infused

• the macrodrops per minute are too few (Without an infusion pump, IV fluids flow by gravity. Blood flowing in the vein exerts a pressure. If the IV is too slow, the pressure of the blood in the vein may back up into the tubing, where it may clot and cause the IV to stop infusing.)

Use macrodrip when

• the order specifies a large amount of fluid over a short time

• the microdrips per minute are too many, and counting the drip rate becomes to difficult

EXAMPLE

EXAMPLE

EXAMPLE

Determining Hours an IV Will Run

Knowing how to calculate approximately how long an IV will last helps you to know when to prepare the next IV, or to be aware if the IV is infusing too fast or too slow.

EXAMPLE

EXAMPLE

EXAMPLE

Assessment

Many factors may interfere with the drip rate. When you are not using an infusion pump, gravity will cause the IV to vary from its starting rate; you will need to observe and assess the infusion and IV site frequently. You’ll need to monitor other conditions as well. As the amount of fluid decreases in the IV bag, pressure changes occur—and they, too, may affect the rate. The patient/client’s movements can kink the tube and shut off the flow; they can change the position of the needle or catheter in the vein. The needle can become lodged against the side of the blood vessel, thereby altering the flow, or it may be forced out of the vessel, allowing fluid to enter the tissues (infiltration). (Signs of possible infiltration are swelling, pain, coolness, or pallor at the insertion site. If you notice any of these signs, discontinue the IV and start a new one at another insertion site.)

Infusion pumps have an alarm system that beeps to alert you when the rate cannot be maintained or when the infusion is nearly finished. Be sure to check the infusion pump frequently, and know how to troubleshoot the various alarms.

Adding Medications to IVs

When a continuous IV order includes a medication, generally this medication arrives already premixed in the infusion bag or the pharmacist adds it on site. In some institutions, you, the nurse, add the medication to the IV and determine the rate of flow. If the task falls to you, first calculate how much of the medication to add to the IV fluids and then calculate the drip rate.

EXAMPLE

EXAMPLE

FIGURE 6-5A Buretrol is an IV delivery system with tubing and a chamber that can hold 150 mL delivered as microdrip (1 mL = 60 drops). (This device is sometimes referred to as a Volutrol.) The top of the Buretrol has a port so that a reservoir of fluid can be added. The Buretrol is a volume control because no more than 150 mL can be infused at one time.

Medications for Intermittent IV Administration

Some IV medications are administered not continuously but only intermittently, such as every 4, 6, or 8 hours. This route is termed intravenous piggyback or (IVPB) (Fig. 6-6). The term admixture refers to the premixed IVPB.

Most of these drugs are prepared in powder form. The manufacturer specifies the type and amount of diluent needed to reconstitute the drug; later, you, the nurse, connect the IVPB (containing the reconstituted drug) by IV tubing to the main IV line. Some IVPB medications come premixed from the manufacturer. For other medications, the institutional pharmacy may reconstitute and prepare IVPB solutions in a sterile environment using a laminar flow hood. This procedure saves nursing time, because when you are ready to administer the drugs, they have already been prepared, labeled, and screened for incompatibilities. Nevertheless, the nurse still bears considerable responsibility: You must check the diluent and volume. You must also check the dose and the expiration date of the reconstituted solution; note whether the IVPB should be refrigerated before use or whether it can remain at room temperature until hung. Finally, you must calculate the drip rate and record this information on the IVPB label before hanging the bag.

FIGURE 6-6A primary IV line (right) and an IVPB (or secondary) line (left). Fluid flows continuously through the primary line into the patient/client’s vein. At timed intervals, medication placed in an IVPB is attached by tubing to the primary IV for delivery to the patient/client. The primary fluid is lowered and the IVPB fluid flows. After the IVPB has infused, the primary fluid begins infusing again. An IV infusion pump may also be used, where medication in the IVPB is infused through the pump.

The physician or healthcare provider may write a detailed order, such as “Vancomycin 0.5 g IVPB in 100 mL D5W over 1 hour.” More often, however, the physician or healthcare provider writes only the drug, route, and time interval, relying on you to research the manufacturer’s directions for the amount and type of diluent and the time for the infusion to run (e.g., Order: cefazolin 1 g IVPB q6h).

Explanation

To solve IVPB problems, you use a calculation much like the one you used for the IV:

mL: The label or the package insert will state the type and amount of diluent.

TF: The tubing for IVPB is referred to as a secondary administration set and has a macrodrip factor. It is shorter than main line IV tubing. In the clinical setting, check the label for the tubing drip factor.

Minutes: The manufacturer may or may not indicate the number of minutes needed for the IVPB medication to be infused. When the number is not given, follow this general rule for adults: allow 30 minutes for every 50 mL of solution.

EXAMPLE

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