Calculating Doses, Flow Rates, and Administration of Continuous Intravenous Infusions 1237

Unit IX Calculating Medication Doses

PROCEDURE Calculating Doses, 141 Flow Rates, and Administration of Continuous Intravenous Infusions

Shelley Burcat and Maribeth Kelly PURPOSE: Calculation of doses and ﬂ ow rates and administration of continuous intravenous (IV) infusions are performed to ensure accurate delivery of medications administered via the IV route. Many of the medications delivered via continuous IV infusion have potent effects and narrow margins of safety; therefore accuracy in calculation and administration of these agents is imperative.

PREREQUISITE NURSING • Smart pumps are infusion pumps with comprehensive KNOWLEDGE libraries of medications and dose calculation software that can perform a “test of reasonableness” to check that pro- • Knowledge of aseptic technique is necessary. gramming is within preestablished institutional limits • Nurses must be aware of the indications, actions, side before the infusion can begin, which can reduce medica- effects, dosages, administration/storage, assessment, and tion errors, improve workfl ow, and provide a source of evaluation for medications administered. data for continuous quality improvement.10 • Many different types of medications are delivered as con- • Use of smart infusion pumps with activated dosage error tinuous IV infusions in acute and critical care settings. reduction software alerts the nurse when safe doses and These medications include, but are not limited to, vasoac- infusion rates have been exceeded. 7 The nurse must use tive, inotropic, antidysrhythmic, sedative, and analgesic the technology consistently to avoid serious medication agents. infusion errors. 6 • Hemodynamic assessment and electrocardiographic • Be aware that double key bounce and double keying errors (ECG) monitoring are frequently necessary to evaluate the may occur when pressing a number key once on an infu- patient ’ s response to medication infusions. The nurse must sion pump, resulting in the unintended consequence of a be familiar with monitoring equipment such as cardiac repeat of that same number. This can result in infusing monitors, arterial catheters, pulmonary artery catheters, medications at a higher rate than expected.5 and noninvasive blood pressure cuffs. • Three factors are involved in the calculations for continu- • Titration refers to the adjustment of the dose of a medica- ous IV infusions: tion, either increasing or decreasing, to attain the desired ❖ The concentration is the amount of medication diluted patient response. in a given volume of IV solution (e.g., 400 mg dopa- • Alterations or interruptions of the fl ow rate can signifi - mine diluted in 250 mL normal saline [NS] solution, cantly affect the dose of medication being delivered and resulting in a concentration of 1.6 mg/mL, or 2 g lido-

adversely affect the patient. For accurate delivery of IV caine diluted in 500 mL 5% dextrose in water [D 5 W], medications, volume-controlled infusion devices are yielding a concentration of 4 mg/mL). The concentra- required. tion is also expressed as amount of medication per • “Smart technologies” are electronic devices, such as com- milliliter of ﬂ uid. puters, bedside monitors, and infusion pumps, that perform ❖ The dose of the medication is the amount of medication calculations of doses and ﬂ ow rates after information is to be administered over a certain length of time (e.g., entered and programmed by the user. Although these dopamine 5 mcg/kg/min, lidocaine 2 mg/min, or diltia- devices are not universally available, their use may reduce zem 5 mg/hr). The units of measure for the dose differ medication errors.4 for various medications. The length of time is 1 minute

1236 141 Calculating Doses, Flow Rates, and Administration of Continuous Intravenous Infusions 1237

or 1 hour. If the medication is weight based, the dose BOX 141-1 Basic Formula* of the medication is per kilogram of patient weight. ❖ The fl ow rate is the rate of delivery of the IV fl uid 1. To determine an unknown fl ow rate: solution expressed as volume of IV fl uid delivered per Dose() mg/hr or mcg/hr = Flow raate() mL/hr unit of time (e.g., 20 mL/hr). The unit of measure of Concentration() mg/mL or mcg/mL the fl ow rate is milliliter per hour. 2. To determine an unknown dose: • All units of measure in the formula must be the same. It Flow rate() mL/hr× Concentration ( mg/mL or mcg/mL ) frequently is necessary to perform some conversions on = Dose( mg/hr or mcg/hr) the concentration before entering it into the formula. The 3. To determine the concentration of drug in 1 mL of fl uid: units of measure of the concentration must be converted Total amount of drug() mg or mcg ()mg or mcg to the same units of measure of the dose (e.g., the concen- = Cooncentration tration of dopamine is measured in milligrams, but the Total volume of fluid() mL ()mL dose of dopamine is measured in micrograms). Example: When fl ow rate is unknown, diltiazem 125 mg/125 mL • The mathematical formula for continuous IV infusions D 5 W to be administered at 10 mg/hr. uses three factors ( Box 141-1 ). When two factors are A. Calculate concentration of drug in 1 mL of fl uid: 125 mg 1mg known, the third can be calculated with the basic formula. = Therefore when the concentration of the solution and the 125 mL mL prescribed dose are known, the fl ow rate can be deter- B. Enter known factors into the formula and solve: Flow rate() mL/hr× Concentration ( mg or mcg/mL ) mined. When the concentration of the solution and the fl ow rate are known, the dose can be determined. Varia- = Dose( mg or mcgg/mL) 10 mL/hr tions on the basic formula are used to allow for medica- = 10 mL/hr tions delivered per hour or per minute and for medications 1mg/mL

that are weight based ( Boxes 141-2 and 141-3 ). Example: When dose is unknown, diltiazem 125 mg/125 mL D5 W is • Calculations for weight-based medications include the infusing at 15 mL/hr. patient ’ s weight in the formula. The choice of which A. Calculate concentration of drug in 1 mL of fl uid: weight to use can be challenging. Much disagreement and 125 mg 1mg = inconsistency are found in the literature as to which weight 125 mL mL to use, ideal body weight, actual body weight, or dry body B. Enter known factors into the formula and solve: 2,7 weight. Distribution of specifi c medications across fat 15mL/hr×= 1 mg/mL 15 mg/hr and fl uid body compartments varies, thus affecting the therapeutic level. Because most medications are titrated * Because there are units on the top of the equation and units on the bottom of to patient response and a desired clinical endpoint, a con- the equation, to ensure that the fi nal units are correct, the units on the bottom sistent approach is to use the patient ’ s admission weight of the equation must be inverted and multiplied by the units of the top of the for initial dose calculations. The clinical pharmacist then equation. 1800 mcg/hr 9 ×mL should be consulted for obese patients and for medications Example: = = 9 mL/hr that have potentially dangerous toxicities. 200 mcg/mL hr • Central IV access should be used for vasoconstrictive medications and medications that can cause tissue damage when extravasated.3 Mechanisms and agents that may cause tissue damage include osmotic damage from hyper- EQUIPMENT osmolar solutions, ischemic necrosis caused by vasocon- strictors and certain cation solutions, direct cellular • Prepared IV solution with medication to be administered toxicity caused by antineoplastic agents, direct tissue • IV tubing damage from pH strong acids and bases, and direct • IV infusion device irritation. 9 • Nonsterile gloves • The Joint Commission goal for medication safety includes • Alcohol pads standardization and limiting the number of drug concen- Additional equipment, to have available as needed, includes trations available in organizations.11 Standardized dosing the following: methods for the same medications reduce IV infusion • Calculator errors.7 • Medication compatibility table • The Institute of Healthcare Improvement (IHI) recommendations for IV medication safety include conducting PATIENT AND FAMILY EDUCATION independent double checks, dose calculation aids on IV solution bag labels, use of IV smart infusion pumps with • Explain the indications and expected response to the phar- safety features, and use of premade dose and fl ow-rate macological therapy. Rationale: Patients and families charts.1 need explanations of the plan of care and interventions. • A review found there is insuffi cient evidence to suggest • Instruct the patient to report adverse symptoms, as indi- that medication errors are caused by nurses ’ poor calcula- cated. Reportable symptoms include, but are not limited tion skills. More research and direct observational studies to, pain, burning, itching, or swelling at the IV site; diz- are required to examine calculation errors in practice.8 ziness; shortness of breath; palpitations; and chest pain. 1238 Unit IX Calculating Medication Doses

BOX 141-2 Variation for Medication BOX 141-3 Variation for Weight-Based Doses Measured Per Minute Medication Doses Measured (mg/min or mcg/min)* Per Minute (mcg/kg/min)* 1. To determine unknown fl ow rate: 1. To determine unknown fl ow rate: Dose() mg/min or mcg/min× 60 min/hr Dose() mcg/kg/min××60 min/hr Patient weight () kg = Flow rate() mL/hr = Flow rate() mL/hr Concentration( mg/mL or mcg//mL) Concentration (mmcg/mL) 2. To determine unknown dose: 2. To determine unknown dose: Flow rate() mL/hr× Concentration ( mg/mL or mcg/mL ) Flow rate() mL/hr× Concentration ( mcg/mL ) = Dose() mcg/kg/min 60 min/hr 60 min/hr× Patient weigght() kg = Dosse() mg/min or mcg/min Example: When fl ow rate is unknown, dopamine 400 mg/250 mL Example: When fl ow rate is unknown, nitroglycerin 50 mg/250 mL D 5 W to infuse at 5 mcg/kg/min. Patient weighs 100 kg. A. Convert the concentration to like units of measure: D 5 W to be administered at 30 mcg/min. 400 mg 1000 mcg 400, 000 mcg A. Convert the concentration to like units of measure: ×= 50 mg 1000 mcg 50, 000 mcg 250 mL 1mg 250 mL ×= 250 mL 1mg 250 mL B. Calculate concentration of drug in 1 mL of fl uid: 400,mcg 000 1600 mcg B. Calculate the concentration of medication in 1 mL of fl uid: = 50,mcg 000 200 mcg 250 mL 1mL = 250 mL 1mL C. Enter known factors into the formula and solve: 5mcg/kg/min×× 60 min/hr 100 kg C. Enter known factors into the formula and solve: = 18. 75 mL/hr 30mcg/min× 60 min/hr 1600 mcg/mL = 9 mL/hr 200 mcg/mL Example: When dose is unknown, dobutamine 500 mg/250 mL D5 W is infusing at 15 mL/hr. Patient weighs 70 kg. Example: When the dose is unknown, lidocaine 2 g/500 mL D5 W is infusing at 30 mL/h. A. Convert the concentration to like units of measure: 500 mg 1000mcg 50, 000 mcg A. Convert the concentration to like units of measure: ×= 2 g 1000 mg 2000 mg 250 mL mg 250 mL ×= 500 mL 1g 500 mL B. Calculate concentration of drug in 1 mL of fl uid: 50,mcg 000 2000 mcg B. Calculate the concentration of drug in 1 mL of fl uid: = 2000 mg 4 mg 250 mL mL = 500 mL mL C. Enter known factors into the formula and solve: 15mL/hr× 2000 mcg/mL C. Enter known factors into the formula and solve: = 714. mcg/kg/min 30mL/hr× 4 mg/mL 60min/hr× 70 kg = 2 mg/min 60 min/hr * The patient ’ s weight in kilograms and the time factor of 60 min/hr must be added to the basic formula. * The time factor of 60 min/hr must be added to the basic formula.

Rationale: Reporting assists the nurse to evaluate the parameters that are affected by various medications in response to the pharmacological therapy and to identify order to note the effi cacy of the medications and to ensure adverse reactions. their safe delivery.2 PATIENT ASSESSMENT AND Patient Preparation PREPARATION • Ensure that the patient and family understand information. Answer questions as they arise, and reinforce information Patient Assessment as needed. Rationale: Understanding of previously taught • Assess medication allergies. Rationale: Assessment pro- information is evaluated and reinforced. vides identifi cation and prevention of allergic reactions. • Weigh the patient, if the medication is weight based. • Obtain vital signs and hemodynamic parameters. Ratio- Rationale: Calculation of the correct dose based on patient nale: The need for vasoactive agents is established, and weight is permitted. If the patient’ s weight has changed baseline data are provided to evaluate the response to during hospitalization because of edema or other causes, therapy. use of the baseline admission weight is preferable. 12–14 • Assess the patient ’ s cardiac rate and rhythm. Rationale: • Verify patency or obtain patent, appropriate IV access. Assessment establishes the need for antidysrhythmic Rationale: Delivery of the medication into the IV space therapy and provides baseline data. is ensured. Some continuous infusion medications require • Obtain other assessments relevant to the medication being central line access to prevent irritation or damage to administered (e.g., sedation scale for continuous IV seda- smaller peripheral veins and to reduce the risk for tives). Rationale: Patients are assessed for specifi c extravasation. 141 Calculating Doses, Flow Rates, and Administration of Continuous Intravenous Infusions 1239

Procedure for Calculating Doses and Flow Rates and Administering Continuous Intravenous Infusions Steps Rationale Special Considerations 1. Verify the prescribed medication Ensures accuracy of medication A medication order should include the order. administration. medication, route, dose, and parameters for titration of the medication. The concentration of the solution and the diluent should be indicated in the order or determined by institutional standards. 2 . HH 3 . PE 4. Verify the fi ve rights of Reduces the potential for medication medication administration: right administration error. patient, right drug, right dose, right time, and right route. Verify the correct patient with two identifi ers.1–3,11 (Level E * ) 5. Connect and fl ush the IV solution Prepares the IV system. (with prescribed medication) through the tubing system. 6. Place the IV infusion in the Prepares the infusion system. Refer to the infusion device user’ s infusion device. There are two manual for specifi c instructions on methods to perform the next step; the use of specifi c devices. choose either Step 7 or Step 8 or both as a double-check. (Level M * ) 7. Determine the correct fl ow rate Ensures the prescribed dose is Make sure the accurate rate based on with manual mathematic administered the prescribed dose is entered into calculation method. the infusion pump. A. Convert the concentration of All units of measure must be the the solution to the same units same to perform the mathematic of measure as the dose. functions. B. Calculate the concentration of Necessary for the medication the medication per milliliter calculation. of fl uid. C. Enter the concentration and Necessary for the medication Use alternate formulas if medication the dose into the formula and calculation. dose is a per-minute or weight- solve for the fl ow rate. Entering information into the device based dose (see Boxes 141-1, is required for the device to infuse 141-2, and 141-3 ). at the prescribed rate. 8. Determine the correct fl ow Prevents errors in medication Refer to the manufacturer’ s user rate with electronic devices. administration. guide for accurate programming of (Level M * ) smart pump calculations. Refer to the institutional policy regarding what medications should be infused with smart device capabilities (i.e., Guardrails, Alaris Medical Systems, San Diego, CA).

* Level E: Multiple case reports, theory-based evidence from expert opinions, or peer-reviewed professional organizational standards without clinical studies to support recommendations. * Level M: Manufacturer ’ s recommendations only.

Procedure continues on following page 1240 Unit IX Calculating Medication Doses

Procedure for Calculating Doses and Flow Rates and Administering Continuous Intravenous Infusions—Continued Steps Rationale Special Considerations A. Enter the necessary Ensures patient safety. Prevents information into the device, mathematic errors or data entry and including, but not limited to, programming errors. patient weight, medication name, concentration of solution, and dose prescribed. B. Program the device to electronically calculate the fl ow rate. 9. Double-check the fl ow rate Independent double-checks may calculations or programming with reduce errors made when another qualifi ed individual. calculating dosages or programming pumps. 10. Set the fl ow rate on the infusion Prepares for medication pump. administration. 11. Connect the infusion system to Initiates the therapy. Alcohol should always be used to the intended IV line or catheter cleanse the IV port (hub) before the and initiate the infusion. infusion is connected. 12. Remove PE and discard used supplies. 13. HH

Expected Outcomes Unexpected Outcomes • The desired patient response is achieved • Adverse reactions to the medication occur • The correct dose of medication is administered • The incorrect dose of medication is administered • The dose is titrated to achieve/maintain the desired • The desired patient response is not achieved or patient response maintained • I n ﬁ ltration or extravasation of medication occurs

Patient Monitoring and Care Steps Rationale Reportable Conditions These conditions should be reported if they persist despite nursing interventions. 1. Evaluate the patient response by Medications given as continuous • Adverse reactions monitoring the indicated infusions often have potent effects • Hemodynamic instability parameters for the medication and potentially serious adverse • Cardiac dysrhythmias being infused. effects. Most medications given as • Excessive sedation continuous infusions have a quick • Respiratory depression onset of action. Frequent monitoring of parameters is necessary during initiation of the infusion. 141 Calculating Doses, Flow Rates, and Administration of Continuous Intravenous Infusions 1241

Patient Monitoring and Care —Continued Steps Rationale Reportable Conditions 2. If the patient response is The patient’ s response to many • Desired response not achieved inadequate, titrate the infusion as continuous infusions is dose- within an acceptable dosage range prescribed following the prescribed dependent. To achieve the desired parameters. response, titration of the dose is necessary. 3. Assess the IV access for catheter Ensures delivery of the medication • Extravasation of any medication placement, catheter patency, and into the venous system. Prevents • Intravenous line inﬁ ltration signs of inﬁ ltration or interruptions in delivery of the extravasation every 1–4 hours and medication. Provides early as needed. recognition of complications.

Documentation Documentation should include the following: • Name of the medication and the type of solution in • Parameters monitored and patient response which the medication is diluted; concentration of the • Adverse reactions and interventions to treat the solution; dose; ﬂ ow rate; and administration times reaction • Patient and family education • Titration • Assessment of the IV access and site

References and Additional Readings For a complete list of references and additional readings for this procedure, scan this QR code with any freely available smartphone code reader app, or visit http://booksite.elsevier.com/9780323376624 .