Drug Calculation PDF

4 Drug Calculation Preparing and Giving Drugs LEARNING OUTCOMES 1. Apply the appropriate formula to accurately calculate drug dosages. 2. Select the correct equipment to prepare and give parenteral drugs, including insulin. 3. Explain the different types of parenteral drug delivery. 4. Identify ana...

4 Drug Calculation Preparing and Giving Drugs LEARNING OUTCOMES 1. Apply the appropriate formula to accurately calculate drug dosages. 2. Select the correct equipment to prepare and give parenteral drugs, including insulin. 3. Explain the different types of parenteral drug delivery. 4. Identify anatomic landmarks used for giving parenteral drugs. 5. Apply the correct formula for calculating intravenous flow rates for infusions. 6. Correctly apply Clark's rule used to accurately calculate drug dosages for children. 7. Explain the principles and procedures to safely and accurately give drugs by the enteral, parenteral, and percutaneous routes. KEY TERMS ampules (ĂM-pūls, p. 46) Small, breakable glass containers that contain one dose of drug for intramuscular or intravenous injection. aseptic technique (ā-SĔP-sĭs, p. 41) Manipulation that does not contaminate the sterility of the drug and drug delivery system. body surface area (BSA) (p. 38) The total tissue area (including height and weight) of a patient's body. buccal route (p. 57) A drug that is given by being applied to or held in the cheek. The drug diffuses through the oral mucosa directly into the bloodstream. capsule (CĂP-sūl, p. 41) Gelatin container that holds powder or liquid drug. Clark's rule (p. 38) A method for determining pediatric drug dosage calculated by ratio and proportion, based on the child's body weight. drop factor (p. 39) The number of drops per milliliter of fluid. flow rate (p. 39) The rate at which intravenous fluids are given. intradermal injections (ĭn-tră-DĔR-măl ĭn-JĔK-shănz, p. 47) Injections that are given into the dermis, just below the epidermis, most often used for allergy testing and tuberculosis testing. 88 intramuscular (IM) route (ĭn-tră-MŬS-kū-lăr, p. 49) Injections that deposit drugs past the dermis and subcutaneous tissue, deep into the muscle mass. intravenous (IV) route (ĭn-tră-VĒN-ěs, p. 39) The administration of drugs directly into the bloodstream. Mix-o-Vial (MĬKS Ō VĪ-ăl, p. 46) A two compartment vial that contains a sterile solution in one compartment and the powdered drug in the second compartment, separated by a rubber stopper. The solution and drug powder are mixed together immediately before use. nasogastric (NG) tube (nā-zō-GĂS-trĭk, p. 42) An enteral route of drug administration and oral feeding that bypasses the mouth by use of a tube going through the nose and esophagus into the stomach. nomogram (NŌM-Ō-grăm, p. 38) A chart that displays the relationships between two different types of data so that complex calculations are not necessary. parenteral route (pě-RĔN-těr-ăl, p. 43) Administration of a drug by injection directly into the dermal, subcutaneous, or intramuscular tissue; epidurally into cerebral spinal fluid; or through intravenous injection into the bloodstream. percutaneous route (pěr-kū-TĀ-nē-ŭs, p. 56) Administration of a drug through topical (skin), sublingual (under the tongue), buccal (against the cheek), or inhalation (breathing) methods. piggyback infusion (ĭn-FŪ-zhŭ n, p. 52) A second or secondary intravenous fluid bag or bottle containing drugs or solution that is connected to the main IV line rather than directly to the patient. subcutaneous injections (sŭb-kū-TĀ-nē-ěs, p. 48) Injections that place no more than 2 mL of drug solution into the loose connective tissue between the dermis of the skin and muscle layer. sublingual route (sŭb-LĬNG-wĕl, p. 57) Application of a drug to the mucous membranes under the tongue. tablet (TĂB-lĕts, p. 41) Dried, powdered drugs compressed into small shapes. topical route (TŎP-ĭ-kăl, p. 56) Drugs applied directly to the area of the skin requiring treatment; most common forms are creams, lotions, and ointments. transdermal (trăn(t)s-DĔR-măl, p. 56) Drugs applied to the skin for absorption into the bloodstream. vial (VĪ-ăl, p. 45) Small, single or multiple dose glass drug container. Z-track technique (p. 51) A type of IM injection technique used to prevent tracking (leakage) of the medication into the subcutaneous tissue (underneath the skin). In this chapter, we give an overview of basic principles of drug administration. Major sections are divided into dosage calculations, drugs given by the enteral route, drugs given parenterally, and drugs given percutaneously. Calculating Drug Dosages 89 Giving the correct dose of a drug is one of the most important responsibilities of the licensed practical or vocational nurse (LPN/VN) to ensure patient safety. Many drugs are now prepackaged with the correct dosage already prepared for the patient (known as “unit dose” drugs); however, you will need to understand how to accurately calculate the correct drug dosage using basic math formulas. Sometimes the drug dose the healthcare provider orders is not what is available. You then will need to use a mathematical formula to figure out how much to give to the patient. Even a small error in dosage can have severe consequences for the patient. These number relationships form important building blocks for accurate drug dosage. The metric system is used to convert from one unit of measure to another. For example, the metric system is used in the calculation of drug dosages, the conversion of Fahrenheit to Celsius while taking temperatures, and the conversion of pounds to kilograms when weighing patients. In the following section, we provide a brief review of essential information to master in calculating drug dosages. If you need a review of basic mathematics associated with drug calculations, read this section carefully and then use the Student Study Guide or Evolve resources to practice fractions, percentages, proportions, and ratios. Fraction Method When you are using fractions to compute drug dosages, write an equation consisting of two fractions. First, set up a fraction showing the number of units to be given over x—the unknown number of tablets or milliliters using what you want to give over what you have on hand. For example, if the healthcare provider's order states, “ibuprofen 600 mg,” you would write . On the other side of the equation, write a fraction showing the drug dosage as listed on the drug to be given over the number of tablets or milliliters to be given. The ibuprofen bottle label states, “200 mg per tablet,” so the second fraction is . The equation then reads: Note that the same units of measure are in both numerators and the same units of measure are in both denominators. Now solve for x: 90 Ratio and Proportion Method A fraction uses a division line to describe the mathematical relationship between two numbers; for example, or . Proportions describe the relationship between two sets of numbers. For example, , so when you multiply across the diagonal, 1 × 4 equals 2 × 2. In using the ratio method, first write the amount of the drug to be given and the quantity of the dosage (x) as a ratio. Using the previous example, this is 600 mg: x tablets. Next, complete the equation by forming a second ratio consisting of the number of units of the drug in the dosage form and the quantity of that dosage form as taken from the bottle. Again, using the previous example, the second ratio is 200 mg: 1 tablet. Expressed as a proportion, this is: Solving for x determines the dosage: Using this method provides the answer of a dosage of 3 tablets, which is correct. Dimensional Analysis Method Dimensional analysis is a technique used in a select number of LPN/VN programs instead of using ratio and proportion to solve dosage problems. Dimensional analysis is a method of comparing and equating different physical aspects and quantities by using simple algebraic rules together with known conversion factors (called equivalency ratios). However, it does require additional steps. Dimensional analysis is often used to convert from one set of measurement units to another set of units by using conversion factors in such a way that unwanted units are canceled out. A person comfortable with this method of calculation can always account for these units. A simple example of this method is how many pounds (lb) are in 20 kilograms 91 (kg) of a given substance? One kilogram is equivalent to 2.2 lb (in medical measurement), so the conversion factor from kilograms to pounds is 2.2 pounds per kilogram (2.2 lb/kg). So multiply the 20 kg by the conversion factor, 20 kg × 2.2 lb/kg, or expressed as the following equation: Now cancel out the kg because this unit is in both the numerator and the denominator. As you can see, the kilogram unit is canceled out through simple algebra. What about going the other way? How many kilograms are in 315 lbs? Flip the conversion factor over, so 1 kg/2.2 lb, and multiply the weight in pounds by the new conversion factor, 315 lb × 1 kg/2.2 lb, which results in 143.2 kg. The equation would look like this: Once again, the weight unit (this time the pounds unit) was factored out. These two simple examples highlight how this method could be used for longer problems and how it allows the nurse using it to keep track of the units involved. Here is a dosage example: A patient who weighs 220 lb is prescribed a dose of drug at 12.5 mg/kg body weight. The concentration of the drug solution on hand is 125 mg/mL, and the patient wants to take the drug orally, by teaspoon. How many teaspoons of drug solution will the patient need to take per dose? Use the following dimensional analysis steps for the conversions and accounting: Step 1: 1 kg = 2.2 lb, so the weight conversion ratio is 1 kg/2.2 lb; the patient weighs 100 kg, so 220 lb × 1 kg/2.2 lb or Step 2: The weight (amount) of drug needed based on body mass is 92 12.5 mg/kg × 100 kg = 1250 mg or Step 3: 1 tsp = 5 mL, so the volumetric conversion ratio is 5 mL/tsp. The concentration in teaspoons is now 125 mg/mL × 5 mL/tsp = 625 mg/tsp or Step 4: The final dose in teaspoons is 1250 mg divided by 625 mg/tsp = 2 tsp, or Steps 1 and 3 were conversions in which dimensional analysis was explicitly used. Steps 2 and 4 were simple calculations, but using dimensional analysis to solve for them allows for a higher degree of accountability and understanding of the units involved. Memory Jogger Steps to Solving Drug Dosage Calculations 1. Change dosages to the same unit of measurement if they are different. 2. Set up your equation as what dose is ordered (want) over what dose you have on hand (have). 3. Calculate the dosage, using fractions or ratios and proportions. 4. If preferred, use dimensional analysis to solve the problem. 5. Check your answer for correctness. Ask yourself, “Does this make sense knowing the dosage range for the drug?” Drug Calculation Using Units Insulin is an example of a parenteral drug that is not given by milligrams (mg), but by units (u). Great accuracy is important in preparing and giving insulin, because the quantity given is very small, and even minor variations in dosage may result in severe consequences in the patient. The preparation and calculation of insulin in insulin dosages is unique in the 93 following three ways: 1. There are many kinds of insulin, available in short- and long-acting forms. All types of insulin come in a standardized measure called a unit. Insulin is available in 10-mL vials and in a specific strength (concentrations): U-100 (100 units per 1 mL of solution) (Fig. 4.1). U-100 vial. FIG. 4.1 2. Insulin should be drawn up in a special insulin syringe that is marked or calibrated in units (Fig. 4.2). FIG. 4.2 U-100 syringe. 3. The insulin order, the insulin bottle, and the insulin as drawn up should always be rechecked by another nurse for maximum accuracy. To draw up a dose of U-100 insulin, use the corresponding 100-unit syringe. Next, draw up the number of units ordered. For example, the order reads: “48 units NPH insulin U-100 1 hour before breakfast.” Using a U-100 syringe, you would draw up 94 48 units of NPH insulin. Occasionally an order will be written by the healthcare provider for two different types of insulin. In some cases, both types of insulin may be given at the same time in the same syringe. Usually, one type of insulin is cloudy and one type is clear. Some insulins cannot be mixed at all. For example, never mix Lantus or Levemir insulin with any other insulin preparation. Be sure to check with your healthcare provider, pharmacist, or diabetes educator before mixing. Chapter 17 has complete information on the processes used to give insulin. Be certain that you are using the correct type of insulin. Top Tip for Safety • Insulin is a high-alert drug that can cause serious harm to a patient if given at too high or too low a dose, or if it is not given to a patient for whom it was prescribed. • You must be very accurate in these calculations. A small error makes a big change in insulin dosage. Use the correct syringe, the correct insulin, and the correct dose. Check your calculations, insulin type, and dose with another nurse or licensed healthcare professional. Calculating Drug Dosages for Infants and Children Recently, much attention has been given to drug administration errors that can lead to patient harm (see Chapter 2). This is especially true in the pediatric setting, where drug errors by both healthcare professionals and parents occur more frequently and have the potential for greater harm. Pharmaceutical companies list the recommended dosages of their drugs for a child or infant, and these dosages are much smaller than the recommended adult dosage. Although children's dosages were once frequently calculated, there remain only a few drugs that require the nurse to determine how much to give a child. In past years, several general rules were developed to calculate these special reduced dosages for infants and children. The Joint Commission, a nonprofit agency that credentials and certifies healthcare organizations, now recommends that all dosages for children be weight-based, usually in kilograms. One of the most widely accepted methods for determining a child's dosage based on the child's body weight is Clark's rule. This rule is used to calculate drug doses for children aged 2 to 17 years. Just as for adult drug dosage calculations, ratios and proportions may be used to calculate the pediatric value. Assuming that an average adult weighs 150 lbs and we know the adult dosage, it follows that if we know the child's weight, we can calculate the child's dosage. The formula for calculating pediatric drug doses based on Clark's rule is as follows: 95 Although you, as a nurse, should be familiar with the fact that there is a need to adjust adult drug dosages for use in children, the healthcare provider would be responsible for calculating the pediatric child dose using Clark's rule when ordering the drug. Another way to calculate drug dosages in the pediatric patient uses body surface area (BSA), or total tissue area (including height and weight), of the child. This is the most accurate method for determining pediatric dosages. The reason for using the BSA is that children have a greater surface area than adults in relation to their weight. For drugs that require careful dosage, charts known as nomograms are used to calculate the BSA in square meters. Nomograms (BSA charts) are constructed from height and weight data. Even with the use of standardized charts, the calculated dosages are more accurate for children than for very young infants. When giving drugs to infants or children, an important nursing responsibility is to doublecheck the original order and confirm the correct dose was calculated before giving the drug. Most healthcare organizations require any dose calculations for this population to be double-checked by two individual nurses to prevent drug errors that can have severe consequences to the pediatric patient. Your agency pharmacist is also an invaluable resource for any questions or concerns that arise regarding infant or child drug dosage and administration. Calculations for IV Infusions Drugs can also be given through the intravenous (IV) route, which deposits the drug directly into the bloodstream. Drugs delivered in this manner are directly infused into the circulatory system though a vein. IV therapy can be used to correct dehydration in a patient or to give drugs directly and immediately into the bloodstream. Some drugs cannot be taken by mouth or by subcutaneous or intramuscular (IM) injection into the skin because of issues with drug absorption. However, because IV fluids and drugs enter the bloodstream directly, the potential for adverse events such as fluid overload or an adverse drug reaction is a concern. Adverse drug reactions are unintended responses associated with the use of a drug in a patient. These can range from mild allergic reactions to severe problems resulting in tissue damage or death. An IV fluid administration order has several components: • the specific IV fluid to be infused • the amount (volume) of fluid to be infused • the duration of the time the IV fluid should be infused • the rate (how fast) the IV fluid should be infused The flow rate of an IV fluid refers to how fast the IV fluid infuses. The flow rate tells how many milliliters are given to the patient in an hour. The diameter of the IV tubing determines the flow rate of the IV. IV tubing with a larger diameter will permit larger drops into the vein and more fluid into the body. The number of drops used to make a milliliter (mL) of IV fluid is called the drop factor. Regulating the IV infusion rate is a common nursing responsibility. Some 96 institutions have automatic infusion pumps that make flow rate calculations easy. Each nurse will learn to use the equipment available at their place of employment. However, all nurses must learn to calculate infusion rates without relying on equipment, in case of power or equipment failures or when working in agencies where no automatic pumps are available. A complete IV infusion order specifies not only the type of solution and the volume to be infused (usually 500 or 1000 mL), but also the length of time over which the total volume of IV is to be infused. IV infusions that contain drugs need to have the flow rate calculated to determine how fast the drug will be infused. You can consult with the pharmacist or healthcare provider if the IV order is not clear, or not complete, or if you are infusing a high-alert drug, such as heparin, and wish to verify your calculations. You must be familiar with two mathematical procedures regarding IV infusions: • calculating the flow rates for IV fluid administration, and • calculating total administration time for IV fluid. To calculate the flow rate for IV fluid administration, you must understand two concepts: the flow rate and the drop factor. The rate at which IV fluids are given is the flow rate, and this is measured in drops per minute. The drop factor is the number of drops per milliliter of liquid and is determined by the size of the drops. The drop factor is different for different manufacturers of IV infusion equipment, and it must be checked by reading it on the infusion set itself. Regular infusion sets (macrodrip) generally range between 10 and 15 drops/mL. Other infusion sets are supplied in microdrops that are generally 60 drops/mL, which are most commonly used with pediatric patients or in skilled nursing or home care settings. Calculating IV Flow Rate Once you know the drop factor for the equipment being used, you can calculate the flow rate by using the following formula: Occasionally, you may see an order for an IV fluid to “keep vein open” (KVO) or “to keep open” (TKO). This stand-alone order does not meet the criteria for safe drug administration. A flow rate must be specified, or the institution may have a specific policy that addresses the flow rate for a KVO order. For example, a KVO IV order may equal 20 drops/min in one institution, but 25 drops/min at another institution. Either way the flow rate must be clearly established by a healthcare provider order or institution policy. Calculating IV Administration Time The order reads: “1000 mL normal saline (NS) to be given over 5 hours.” The drop 97 factor is 15. To calculate the flow rate, use: Calculating Total Infusion Time Calculating the total administration time for IV fluid depends on calculating the total number of drops to be infused. Using this information, plus the drop factor, you can easily determine the total infusion time by using the following formula: To calculate the total infusion time: 1. Determine the total number of drops ordered. The total number of drops to be infused comes from the healthcare provider's order for the total amount of fluid to be infused. This amount of fluid to be infused is multiplied by the drop factor (read from the infusion set) to determine the total number of drops. 2. Determine the number of minutes the IV is to flow. The number of drops per minute is multiplied by the drop factor to give the number of drops infused in 1 hour. This will give the number of hours and minutes for the total infusion. For example, the order reads: “1000 mL D5W to be given at 50 drops/min with a drop factor of 10 drops/mL.” Thus: Factors That Influence IV Flow Rates 98 Many other factors influence the flow rate of an infusion, such as the age, size, and condition of the patient, as well as the size of the patient's veins. Other factors may be changed or altered to assist in infusion of IV fluids, such as the size of the needle, the needle's position in the vein, the height of the IV pole or pump, and the positioning of the patient. If the fluid does not infuse at the calculated rate, the entire IV system should be carefully checked from the IV solution all the way down to the IV catheter insertion site for any of the following: level of fluid in the IV set drip chamber, air in the tubing that obstructs flow, patency of the IV, or signs of IV infiltration (e.g., redness or swelling of the area). Flow Rates for Infants and Children Infants and small children are very sensitive to extra amounts, or volumes, of fluids. Smaller total amounts of IV fluids are often ordered, and the infusions are given in very small drops to prevent accidental fluid overload and ensure patient safety. Usually 60 microdrops/mL is the drop factor for infants. As with adults, the drop factor must be determined from the infusion setup. For calculating the flow rates in infants, the same formula is used, but the microdrop drop factor must be used for the formula. An example of a microdrip calculation formula is: For example, if the IV infusion order reads: “Give 50 mL D5W [5% dextrose in water] IV in 4 hours.” The drop factor is 60 microdrops/mL. Thus: Modifications to the IV flow rate or IV drug dosage for an infant or child are strictly controlled and are ordered only by the healthcare provider. Memory Jogger • The drop factor for infusions depends on the type of equipment and must be read from the IV set label. • The flow rate is calculated by using the following formula: 99 • IV administration time is calculated using the following formula: • The total infusion time depends on the total number of drops to be infused, the amount of fluid to be infused, and the number of minutes the IV is to flow. General Principles of Drug Administration The process of oral drug administration involves several steps and safety measures to ensure you have correctly adhered to the 9 Rights of Drug Administration (see Chapter 1 for details on this topic), the nursing process, and your institution policy. In general, you are responsible for knowing the drug you are giving, the reason the drug is being given, side effects that can be expected, and the adverse effects for which the patient should be monitored. You must also know any specific allergies your patient may have, and how these may relate to drugs ordered. Some drugs have specific limits on when and if they can be safely given. For example, you would not give a drug for hypertension (high blood pressure) if the patient's blood pressure was below a certain point. The healthcare provider may include these types of limits in the original order, or you may use your nursing judgement to “hold” giving a certain drug until you clarify the order with the prescriber. The following steps are a general guide for giving drugs to your patient: • Follow the 9 Rights of Drug Administration. • Minimize interruptions and distractions while preparing drugs (see Chapter 2). • Wash your hands to avoid contamination of the drugs. • Assemble necessary equipment, such as medication cups, and water for swallowing drugs. • Follow the written drug order. Compare drug order with the written order, medication administration record (MAR), and the drug label. Be careful of look-alike and sound-alike drug names, as this is a significant source of drug error! • Accurately identify the patient before giving any drugs by checking the patient's wristband and by asking the patient his or her name and date of birth. For bar-coded drug administration systems, scan the patient's wristband to confirm that the correct drug, dose, and 100 route is given to the correct patient. • Do not unwrap or remove the drug from the container until you are with the patient. • Follow aseptic technique for oral drugs by not touching the drug or the inside of the drug container. Pour the oral liquid or pills into the appropriate medication cup. Hold liquid drugs at eye level to avoid errors. • Follow sterile technique when handling needles and syringes for giving subcutaneous, IM, or IV drugs. Dispose of needles and syringes properly immediately after giving the drug. • Follow the institution procedure for proper documentation (charting) after giving the drug, or if the patient refuses the drug. Enteral Drugs Enteral drugs are given directly into the gastrointestinal (GI tract) extending from the mouth through the anus. Enteral drugs can be given by the oral (PO), nasogastric (NG), or rectal route. Giving Oral Drugs The most common way of giving drugs is by the oral route. Oral drugs come in several different forms, and each form serves a specific purpose. For example, different forms of oral drugs can either increase absorption, delay absorption, or reduce irritation to the stomach. Some oral drugs can come in tablet or capsule form, but patients may still call this type of drug form a “pill,” which is an outdated term for health professionals. Tablets may be covered with a special coating that resists the acidic pH of the stomach, but will dissolve in the alkaline pH of the intestine. Advantages of oral preparations are: • Oral drugs are convenient, economical, and noninvasive. • There is a variety of short- or long-acting formulations, and some have enteric coating to protect the stomach. The major disadvantages of oral preparations are: 101 • They cannot be given to patients who are nauseated, vomiting, or who are unconscious. • Oral drugs cannot be given to patients who cannot swallow. • Older adult patients may need additional time to swallow oral tablets or capsules. • Some drugs become ineffective when mixed with the acid and enzymes in the stomach and intestines. • The drug onset of action may vary because the drug absorption in the GI tract is unpredictable. Safety Alert! You are responsible for the following aspects of patient safety: • You have the responsibility to ensure that patients safely take the drug(s) given to them. Do not leave drugs at the bedside for patients to take later. • Never give a drug poured or prepared by another nurse or healthcare provider to a patient. You may only give drugs that you have prepared. Giving Oral Tablets or Capsules Tablets and capsules are different forms of oral drugs. A tablet is made up of dried, powdered drugs that have been compressed into small shapes, whereas a capsule is gelatin container that holds powder or liquid drug. Before you give oral drugs, you must make sure the patient can safely swallow any drug given. If the patient is unable to swallow the drug as ordered, notify the healthcare provider who ordered the drug. Be sure you have followed all the steps in the correct procedure for drug administration (see earlier) and have a glass of water ready for the patient. If the drug is in the form of a lozenge, it is meant to be sucked, not swallowed. All oral drugs are brought to the patient's bedside unwrapped, or in the original container, and can be placed in a paper soufflé cup using aseptic technique before giving the drug. Do not crush tablets or break capsules without checking with the pharmacist. Many drugs have special coatings that are essential for proper absorption. If they are broken, cut, crushed, or chewed, drug absorption can be so rapid that adverse effects are more likely. If a patient has difficulty swallowing the drug, have him or her take a few sips of water before placing the drug in the back of the mouth, then follow with more water. Help patients keep their heads forward while swallowing, as they do when they eat. It is generally not helpful to tilt the head backward. You are responsible for making sure the patient takes all drugs safely, and on schedule. Do not leave drugs at the patient's bedside to be taken later, or ask another 102 person to give them for you. Giving Liquid-Form Oral Drugs Liquids or solutions often must be shaken before they are poured to ensure the drug is evenly distributed throughout the liquid. Check to make sure the lid on the bottle is tightly closed before shaking. Take the lid off the bottle and place the lid upside down (outer surface down) on a flat surface. This protects the inside of the lid from dirt or contamination. When pouring liquids from a bottle into a plastic medication cup, hold the bottle so the label is against the hand. This prevents the drug from running down onto the label so that it cannot be read. Hold the medication cup at eye level to read the proper dose (Fig. 4.3). Read the level at the lowest point in the medication cup. The drug could also be drawn up from the bottle or medication cup with a syringe or a medicine dropper (Fig. 4.4). These methods are useful in helping you to be accurate when a small dose is ordered or when giving drugs to infants or small children. The syringe or medicine dropper is placed halfway back in the baby's mouth, between the cheek and gums, and slowly emptied, giving the baby time to swallow it. The drug in the syringe or medicine dropper can be emptied into a nipple for an infant to suck the dose (see Fig. 4.4). Wipe any extra drug from the bottle top and replace the lid quickly to avoid contamination. Do not dilute a liquid drug unless ordered to do so by the prescriber. FIG. 4.3 Checking the drug dose in a medication cup. (From Potter AG, Perry P: Clinical nursing skills and techniques, ed 7, St. Louis, 2009, Mosby.) 103 FIG. 4.4 Oral drug delivery for infant or child. Lifespan Considerations Older Adults: Giving Drugs Allow extra time when giving drugs to older adult patients. These individuals often are slower to take a drug, in swallowing drugs and water, and in understanding the answers provided to questions about their drugs. Giving Drugs by Nasogastric or Percutaneous Endoscopic Gastrostomy Tube Patients who cannot swallow, are nauseated, or who have bowel obstruction may be able to take drugs through an NG or percutaneous endoscopic gastrostomy (PEG) tube. A nasogastric (NG) tube is an enteral route of drug administration and oral feeding that bypasses the mouth by use of a tube going through the nose and esophagus into the stomach. The tubing and a clamp allow the nurse to easily give drugs in this way. The PEG tube is similar, but instead of going through the nose it is placed by surgical endoscopy directly through the abdomen wall and into the stomach. As with any other oral drug administration, check with the pharmacist before crushing tablets or opening capsules. Some tablets may be crushed, mixed with 50 mL of water, and given through the NG or PEG tube. Others drugs cannot, 104 and a liquid formulation must be ordered. It is important to know that some drugs are not compatible with feeding formulas (phenytoin [Dilantin]) or are degraded more quickly after crushing, making them less effective (enteric-coated pantoprazole). Sustained-release drugs are meant to be delivered over a period of time, so crushing this type of tablet can release the drug too quickly, resulting in increased drug blood levels and toxicity. Top Tip for Safety Do not open, cut, crush, or allow a patient to chew a sustained-release drug because these actions can release the drug too quickly and result in toxicity. Follow the general procedure for preparing for drug administration. Double-check the prescriber's order to make sure you are giving the drug by the correct route, because all nonliquid drugs will need to be crushed or capsules opened to give drugs through NG or PEG tubes. Wash your hands and use gloves as needed following the agency's policy/procedure during this procedure. Place the patient in an upright position. For NG tube drug administration, check that the NG tube is in the stomach. Aspirate (remove) some stomach contents with a syringe and test the pH of the stomach contents. If the pH is 0 to 5, then the tube is most likely in the stomach. Auscultation over the area of the stomach and listening for a whooshing sound is no longer considered a reliable way to test NG tube placement. The process for giving a drug through a PEG tube is very similar to that for the NG tube. In addition to the tubing, the PEG has a gastrostomy feeding button (a small, flexible silicone device that has a mushroom-shaped dome at one end and two small wings at the other end) that can be used to close the tube between uses. Irrigate this button with sterile water or normal saline after the drug has been given and clean the area according to institution policy. In general, avoid crushing all tablets or capsules together; drugs should not be mixed together for administration through an NG or PEG tube. Each drug should be given separately because of possible incompatibilities, tube blockage, or changes in the pharmacodynamics of the drugs. Crushing enteric-coated drugs breaks them into small pieces that, when mixed with water, can result in clogging the tube. Always rinse the tube with sterile water or sodium chloride before and after giving the drug(s). Top Tip for Safety • Do not give sustained-release (long-acting), chewable, or enteric-coated capsules through an NG or PEG tube. • If you are unsure if a drug can be given through an NG or PEG tube, ask the pharmacist. Patients Who Are Receiving Enteral Feedings 105 For patients receiving enteral feedings, once tube placement is checked, the residual (amount) of stomach contents must also be checked. Drug administration may be held if the residual amount of feeding exceeds the standards set by the institution. Clamp the NG tube and attach a bulb syringe. Next, pour the drug mixed with water into the syringe, unclamp the NG tube, and let the drug run in by gravity. Add 50 mL of sterile water or normal saline according to the institution's policy to flush and clean out the tubing when all the drug has passed through the tube. Clamp the feeding tube for 30 minutes before and after drug administration to minimize interactions with the feeding formula, making sure to rinse the feeding tube well with sterile water or normal saline. Patients With Nasogastric Tube to Suction If suction is attached to the NG tube, disconnect it and clamp the suction tube shut for 30 minutes before drug administration. Attach a bulb syringe, pour the drug mixed with sterile water or normal saline into the syringe, unclamp the NG tube, and let the drug run in by gravity. Add 50 mL of sterile water or normal saline according to the institution's policy to flush and clean out the tubing when all of the drug has passed through the tube, making sure to rinse the feeding tube well with sterile water or normal saline. Keep the feeding tube clamped for 30 minutes before and after drug administration to minimize interactions with the feeding formula. The tube remains clamped for at least 30 minutes before the suction tube is reattached so that there is time for the drug to be absorbed. For additional information on this procedure, refer to your nursing fundamentals textbook. Parenteral Drugs General Principles Giving drugs by the parenteral route refers to any drug given by intradermal, subcutaneous, IM, or IV route. Drugs are given parenterally for the following reasons: • The patient cannot take an oral drug. • The patient needs a drug that can act quickly. • The drug needed may be destroyed by gastric enzymes. • A steady blood level of the drug is needed. • The drug is not available in an oral form. For example, patients with severe, life-threatening infections may need IV antibiotics, or a patient may receive continuous IV heparin for anticoagulation. IV drugs are injected directly into the bloodstream, and they act quickly, whereas drugs given by IM or subcutaneous injection require time for the drug to reach the bloodstream, so the onset of action is slower than for drugs given IV. Some IV drugs are effective for only a short time, requiring frequent doses. If an overdose of an IV 106 drug is accidentally infused, the consequences to the patient can be very serious, because the effects are almost instantaneous. Once injected, the drug cannot be withdrawn, so accurate administration of the correct drug and dose is essential. When giving subcutaneous or IM drugs, you must accurately locate the appropriate injection site to avoid pain or tissue damage. Aseptic (sterile) technique must be followed to prevent infection. Potential exposure to blood or body fluids can occur when giving parenteral drugs. Therefore the Centers for Disease Control and Prevention (CDC) issued standard precautions that include the wearing of gloves when there is risk to exposure to blood, body fluids, broken skin, or mucous membranes to prevent disease transmission. Therefore always wear gloves when giving any parenteral drugs. When giving parenteral drugs, it is important that you do not recap needles and that you dispose of them properly in a designated “sharps” container to prevent needlestick injury. Usually these containers are present within a patient's room or in other patient care areas. Many hospitals and clinics now use needleless systems, retractable needles, or needles with a plastic safeguard to protect healthcare workers from needlestick injuries. Needle-free syringes dispense the drug using a highpressurized air cartridge, although only a few drugs are available for delivery using this system. The needleless syringe is disposable anywhere because it does not come in contact with the skin and is a one-time use component of the device (Fig. 4.5). FIG. 4.5 Needleless syringe system. (© Baxter Healthcare Corp., Deerfield, IL.) 107 Syringes Syringes come in a variety of sizes and are made up of three main parts. The tip is the portion that holds the needle. The needle screws onto the tip or fits tightly so it does not fall off. The barrel is the container for the drug. The calibrations are printed numbers on the barrel, and they indicate the amount or volume of drug in milliliters (mL), units, or cubic centimeters (cc) (Fig. 4.6). FIG. 4.6 Comparison of different types of syringes. The plunger is the inner portion that fits into the barrel of the syringe. When the plunger is pushed into the barrel, the drug is forced out through the needle. Needles The needle is made up of the hub, which attaches to the syringe; the shaft, which is the hollow part through which the drug passes; and the pointed or beveled tip, which pierces the skin (Fig. 4.7). The longer the pointed tip of the needle, the more easily the needle enters the skin. The diameter of the needle is called the gauge. The larger the number of the gauge, the smaller the hole (e.g., a 25-gauge needle is smaller than a 17-gauge needle). Thick solutions require larger diameters for injection. The needle gauge is written on the needle hub and on the package. Needles also come in varying lengths. Generally, the smaller the needle (larger the gauge), the shorter the needle. The smallest needles are used for intradermal or subcutaneous injections because they do not need to go very far into the skin and do not enter other tissues. Filter needles are also available for use when a drug is drawn from an ampule to prevent uptake of glass shards and risk of injection. 108 FIG. 4.7 Parts of the needle and various needle gauges. The sizes of the needle and syringe are determined by how viscous (thick) the drug is and by the amount to be injected. For example, blood is very thick and requires a 15- to 18-gauge needle. Sometimes when the volume is very small and the dosage must be very accurate (as with heparin or insulin), a small-gauge needle (such as a 27-gauge) is used so that no drug is lost. If more than 3 mL of drug is to be given IM, the drug must be divided and given in two injections so that a large pool of drug does not form in the tissue, which would irritate the tissue. A general guide for choosing the best syringe and needle size is presented in Table 4.1. Various needleless syringes are also used because it removes the risks associated with both reuse and disposal of needles. Table 4.1 Suggested Guide for Selecting Syringe and Needles ROUTE GAUGE (G) LENGTH (INCHES) VOLUME TO BE INJECTED (mL) Intradermal Subcutaneous Intramuscular Intravenous 25–27 25–27 20–22 15–22 3/8–1/2 1/2–1 1–2 1/2–2 0.01–0.1 0.5–2 0.5–2 Unlimited Procedure for Preparing and Giving Parenteral Drugs The basic procedure for preparing and giving parenteral drugs is similar to that for oral drugs (Box 4.1). The type of parenteral injection and the specific drug to be given require the selection of the appropriate equipment and injection techniques. Inspect all syringe and needle packages to ensure they are sealed and the sterilization date has not expired. Any drug with a questionable seal that has changes in color or appearance or is expired is to be returned promptly to the pharmacy unused. 109 Box 4.1 Giving Parenteral Drugs Step One: Preparation Check the drug order as written for the patient, allergies, and the time to be given. Wash hands well to avoid contaminating the drug and equipment. Assemble all the necessary equipment (needles, syringes, alcohol swabs, and drug ordered). Make certain the equipment is sterile and not expired. Compare the drug order with the drug label. Check for the right patient, drug, route, dosage, and time to be given. Attach the needle to the syringe, keeping the needle covered with a cap. Open the drug vial or ampule, cleansing the top of the drug container as appropriate. Insert the needle into the drug container and fill the syringe with the proper amount of drug. Remove any air bubbles. Do not mix more than one drug in a syringe unless they are compatible. Replace the needle for a new sterile needle after the drug has been drawn up through a rubber stopper, multidose vial, or glass ampule. Step Two: Giving the Drug Accurately identify the patient per institution policy. Explain what drug is being given and answer any of the patient's questions. Examine previous injection sites for signs of necrosis, infection, or swelling. Examine the site to be injected. Put on gloves. Clean the skin with alcohol. Follow the specific procedure for intradermal, subcutaneous, or IM injection. Dispose of the syringe per institution procedure and then wash your hands. Document the drug was given as ordered per institution policy. Check the patient, noting the response or adverse effects that must be recorded and reported. Top Tip for Safety • Check all equipment and drugs to ensure they are correct, sterile, and not expired before preparing the drug. • Always wear gloves when giving parenteral drugs to avoid exposure to blood and body fluids. • Clean the skin from the center outward, using a circular motion to minimize risk for infection. 110 • Do not recap needles! Recapping needles can result in needlestick injury and disease exposure. Preparation of Parenteral Drugs Parenteral drugs are supplied in a variety of different forms. A vial is a small, singleor multiple-dose glass or plastic container of a drug. The top of the glass container is fitted with a rubber diaphragm and a small aluminum lid. To draw up drugs from a vial, the metal lid is removed, and the rubber diaphragm is cleansed with alcohol. An amount of air equal to the amount of solution to be withdrawn is injected with a syringe into the vial to assist the withdrawal of the drug (Fig. 4.8). Needles are always inserted into the vial bevel up so you can inspect the needle as it goes into the rubber stopper. The vial may contain a solution, or it may contain a powder to which a liquid diluent is added to make a solution. Read the label carefully to determine the type and amount of diluent that is required. Roll the vial carefully to make certain all of the powder is dissolved in the liquid. If the powder does not completely dissolve, do not give the drug and notify the pharmacy. FIG. 4.8 (A) Example of a vial. (B) Remove the metal lid and cleanse the diaphragm with an alcohol wipe. (C) Pull into the syringe an amount of air equal to the amount of solution to be withdrawn. (D) Insert the needle with the bevel up and inject the air into the space above the solution. (E) Withdraw the drug. (F) Move the needle downward to allow the needle to continue to fill. Ampules. Ampules contain one dose of a drug in a small, breakable glass container. The narrow neck of the base usually has a line (score) or ring around it, indicating a weakened area where the top can be broken off. All of the drug can be shifted to the bottom of the ampule by flicking the top lightly with a finger. Grasp the top above 111 the scored or ringed area with a small gauze pad and pull down quickly on the glass top, breaking the ampule at the level of the line, or scored area, allowing insertion of the needle into the ampule to draw up the drug (Fig. 4.9). A filter needle is used to draw up the drug to prevent any glass shards from being drawn up into the syringe. FIG. 4.9 (A) Examples of scored and ringed ampules. (B) Shift drug from the top to the bottom portion of the ampule by flicking the top lightly with a finger. (C) Wrap a gauze pad around the neck of the ampule and use a snapping motion to break off the top of the ampule along prescored line at the neck. Always break away from the body by bending the top toward you. (D) Insert the filter needle into the ampule and draw up the drug. Mix-o-Vials. Parenteral drugs may come in a two-compartment vial called a Mix-o-Vial. The top compartment contains a sterile solution; the bottom compartment contains the drug powder. A rubber stopper separates the two areas. Pressure on the rubber plunger of the top compartment forces the stopper to fall below into the bottom compartment, letting in a solution that dissolves the powder. Roll the vial gently between your palms to help dissolve the powder. When the powder is dissolved, insert the needle of the syringe to withdraw the solution (Fig. 4.10). 112 FIG. 4.10 Example of a Mix-o-Vial. (A) Remove the protective sterile cap from the Mix-oVial. (B) Push the rubber plunger on the top compartment; this will force the rubber stopper into the bottom compartment and let the solution dissolve the powder. The solution is mixed by gently rolling the container. (C) The needle is inserted through the top rubber diaphragm into the solution. (D) The required dose is withdrawn into the syringe. Multiple-dose vials. Any multiple-dose vial or newly mixed (reconstituted) powdered solution must be clearly labeled with the date, time, drug concentration and expiration time, and your initials. Once you withdraw a drug dose from a multiple-dose vial, change the needle before injecting the drug into the patient. Forcing the needle through the rubber stopper makes it dull and causes pain when injected into skin. Mixing two parenteral drugs. Occasionally, two drugs are ordered that may be given in the same syringe. For example, two compatible drugs are often given together as preoperative sedation before surgery. Two types of insulin (regular and NPH) may be ordered to be given together. In contrast, many antibiotics must be given in separate syringes because they precipitate (form solid particles) or become inactive if mixed together. Memory Jogger It is important when mixing two drugs in one syringe to remember: • The compatibility of the two drugs must be known; check with an up-to-date drug resource or your pharmacist. • Air must be injected into both vials before any drug is withdrawn (to avoid accidental injection of a drug already in the syringe into the second vial). Prefilled syringes or cartridges. Prefilled syringes and cartridges packaged this way are a convenient and reliable way of giving parenteral drugs. For patients, the advantages are ease of preparing and injecting drugs at home. Many opioids (narcotics) and emergency drugs (epinephrine) come in prefilled syringes and cartridges. These drug cartridges may be quickly slipped into a plastic holder and screwed into place (Fig. 4.11). The drug 113 may then be quickly and accurately given. FIG. 4.11 (A) Example of a syringe and prefilled sterile cartridge with needle. (B) Assembling the syringe-needle system. (C) The cartridge slides into the syringe barrel, turns, and locks at the needle end. The plunger then screws into the cartridge end. (D) Expel excess drug to obtain accurate dose. (From Potter PA, Perry AG: Fundamentals of nursing, ed 7, St. Louis, 2008, Elsevier.) Giving Intradermal Drugs Intradermal injections are used for several purposes, such as for allergy sensitivity testing, tuberculosis exposure testing, and some vaccinations. Intradermal injections consist of a drug injection into the intradermal space between the upper two layers of the skin—the epidermis and the dermis (Fig. 4.12). Injections are made into the inner aspect of the forearm, the scapular area of the back, and the upper chest, if these areas are reasonably hairless. The blood supply to this area of the skin is less than that in other areas, so there is very slow absorption from the intradermal layer. Usually just a small volume is injected, producing a small bump like a mosquito bite, called a bleb. Once the drug has been injected, instruct the patient not to wear tight clothing over the area. 114 FIG. 4.12 Anatomy of skin showing placement for intradermal injections. For intradermal injections, choose a needle that is both small (25-gauge) and short (3/8 inch). Wash your hands and don gloves. Cleanse the skin before giving the injection. Once you draw up the drug, insert the needle firmly at a 15-degree angle, with the bevel of the needle pointing upward. Do not aspirate (pull back) the syringe plunger before giving the drug. Inject the drug and then quickly remove the needle. The small bleb should be seen on the skin at the point where the drug was injected into the intradermal space. After giving the injection, check the patient's skin for sensitivity or an allergic reaction to the injection. You may see an immediate reaction, or reactions may take hours to several days to develop. Tuberculin tests are given intradermally and are checked for reactivity in 48 to 72 hours after the injection. Making a circle mark around the injection site with a pen as soon as the drug is given can help you identify the site of the injection and the size of the reaction. Document any reaction noted and notify the healthcare provider. Giving Subcutaneous Drugs Subcutaneous injections are given into the tissue between the dermis of the skin and the muscle layer (Fig. 4.13). There will be a slow but long duration of drug action because less blood is normally supplied to this area. Heparin and insulin are the drugs most frequently given by subcutaneous injection. See Chapters 14 and 17 for detailed information on these drugs. The drug volume given in a subcutaneous injection is usually between 0.5 and 1 mL per injection. When giving subcutaneous drugs daily over a long time period, you will need to rotate the injection sites to avoid irritating the tissue or causing changes in the tissue with repeated injections in the same area. FIG. 4.13 Anatomy of skin showing placement for subcutaneous injections. Subcutaneous injections require a small syringe and needle. Usually a 25- or 27gauge needle with a 3/8-inch needle length is used. Subcutaneous injections may be given in the upper arms, upper back, scapular region, anterior thighs, and abdomen. 115 Before giving the injection, wash your hands and don gloves, then cleanse the appropriate skin area with alcohol. To give a subcutaneous injection, insert the needle bevel up into the skin at a 45-degree angle. Do not aspirate before giving the drug to prevent bruising and other tissue damage. Inject the drug and remove the needle. Once the needle is removed, apply slight pressure to prevent bleeding. Apply additional or pressure of longer duration if the patient is at risk for bleeding. Document the injection site (location) and any skin or other reactions to the injection. Top Tip for Safety Do not aspirate before giving a drug subcutaneously to prevent bruising and other tissue damage. If a patient is to continue subcutaneous drug administration for any length of time at home, teach the patient about the drug, expected effects and adverse effects to report, and proper techniques for drug administration. Teach the patient and family to develop a plan for rotating injection sites. The front view in Fig. 4.14 shows areas usually used for subcutaneous self-injection. The back view shows less commonly used areas that may be accessed for injection by the family. FIG. 4.14 Body rotation sites for subcutaneous injections. Giving IM Drugs Drugs given by the intramuscular (IM) route are deposited deep into the muscle 116 mass (Fig. 4.15), where the rich blood supply allows for a more rapid drug absorption as compared with the subcutaneous route. The muscles also contain large blood vessels and nerves, so it is important to place the needle correctly to avoid damage to these structures. FIG. 4.15 Anatomy of skin showing placement for IM injections. IM injections for adults typically range from 1 to 3 mL, and infants and children rarely receive more than 1 mL. If more than 3 mL of drug is ordered for an adult patient, you will need to divide the total drug dose between two syringes, and two injections at two different sites are given. To give an IM injection, choose a 20- to 22gauge needle with a length of 1 to 1.5 inches to allow deeper placement into the muscle. You will need to make adjustments for very thin or very obese patients, who will require a shorter or longer needle for proper drug placement. The sites for IM injections include the deltoid, vastus lateralis, and ventrogluteal muscles. Each site has advantages and disadvantages, and you must be able to correctly identify each site for giving IM drugs safely. Table 4.2 describes the advantages and disadvantages of each IM injection site. The dorsogluteal site is not recommended because the presence of nerves and blood vessels in the area increase the risk for tissue damage. Table 4.2 IM Injection-Site Advantages and Disadvantages INJECTION SITE Deltoid (upper arm) Vastus lateralis (thigh) Ventrogluteal (hips) ADVANTAGES DISADVANTAGES Easily accessible Useful for vaccinations in adolescents and adults Preferred site for infant injections Relatively free of large blood vessels and nerves Easily accessible Used for children aged 7 years or older and adults Less likely to be inadvertently injected subcutaneously Poorly developed in young children Only small amounts (0.5–1 mL) can be injected Intake of drug is slower than the arm but faster than buttocks Patient anxiety because of unfamiliarity with site and visibility of site during injection From Workman ML, LaCharity L: Understanding pharmacology, ed 2, St. Louis, 2016, Elsevier. Top Tip for Safety The dorsogluteal site is not recommended for IM injections because the presence of nerves and blood vessels in the area increase the risk for tissue damage. 117 Before preparing the IM drug for injection, carefully select the site and identify the landmarks. Figs. 4.16 through 4.18 show how to identify sites for IM injections. Position the patient properly to be able to access the injection site. Wash your hands and put on gloves. Clean the injection area with alcohol. Insert the needle firmly, at a 90-degree angle, and inject the drug. Aspiration is not recommended for IM injection of vaccines or immunizations. If aspiration is required for a certain drug, pull back the plunger after inserting the needle and check for the presence of blood being drawn up into the syringe. If this occurs, remove the needle and discard the drug and syringe properly. You will then need to prepare a new dose of the drug and inject into a different site. After withdrawing the needle, apply gentle pressure to the site with a dry cotton ball. Avoid massaging the area of injection. Rotate the site of injection when repeated injections are needed. Note the time and site of the injection, and be sure to check the patient for both expected and adverse effects of the drug; document your findings. FIG. 4.16 Deltoid IM injection-site landmarks. (From Workman ML, LaCharity L: Understanding pharmacology, ed 2, St. Louis, 2016, Elsevier.) 118 FIG. 4.17 Ventrogluteal IM injection-site landmarks. (From Potter PA, Perry AG: Fundamentals of nursing: Concepts, process, and practice, ed 8, St. Louis, 2013, Mosby.) FIG. 4.18 Vastus lateralis (thigh) IM injection-site landmarks. (From Workman ML, LaCharity L: Understanding pharmacology, ed 2, St. Louis, 2016, Elsevier.) The Z-track technique may be used for IM injections of drugs that can stain the skin or are known to be irritating to the tissues (Fig. 4.19). To give drugs using the Ztrack technique, draw up the drug as usual, plus 0.1 to 0.2 mL of air. The injection of the air seals the injection site, preventing leakage of the drug. Drugs of the type that require the Z-track technique are injected into the ventrogluteal site. Once the injection site is prepared, pull the tissue downward and away from the injection site. Inject the drug and allow the skin to move back into place before you remove the needle. This action allows the tissue to make a seal over the injection site, sealing the drug in place. Do not massage the injection site. FIG. 4.19 Z-track injection technique. (A) Pull the tissue laterally. (B) Insert the needle 119 straight down into the muscle and inject the drug. (C) Release the tissue as the needle is withdrawn; this allows the skin to slide over the injection track and seal the drug inside. Giving IV Drugs Intravenous drugs are delivered by IV “push” or bolus route, IV “piggyback” or intermittent infusion, or continuous IV infusion. The IV route injects a drug directly into the vein, where it enters the bloodstream immediately. The rate of absorption and the onset of action are faster for the IV route than for the oral and IM routes because IV drugs have not been exposed to other enzymes or tissues before reaching the bloodstream. In addition, s