139: Calculating Doses and Flow Rates and Administering Continuous Intravenous Infusions

PROCEDURE 139


Calculating Doses and Flow Rates and Administering Continuous Intravenous Infusions




PURPOSE: 


Calculation of doses and flow rates and administration of continuous intravenous infusions are performed to ensure accurate delivery of medications administered via the intravenous route. Many of the medications delivered via continuous intravenous infusion have potent effects and narrow margins of safety; therefore, accuracy in calculation and administration of these agents is imperative.



PREREQUISITE NURSING KNOWLEDGE




• Knowledge of aseptic technique is necessary.


• Nurses must be aware of the indications, actions, side effects, dosages, administration/storage, assessment, and evaluation for medications administered.


• Many different types of medications are delivered as continuous intravenous (IV) infusions in acute and critical care settings. These medications include, but are not limited to, vasoactive, inotropic, antidysrhythmic, sedative, and analgesic agents. Hemodynamic assessment and electrocardiographic (ECG) monitoring are frequently necessary to evaluate the patient’s response to the infusion. The nurse must be familiar with monitoring equipment such as cardiac monitors, arterial lines, pulmonary artery catheters, and noninvasive blood pressure cuffs.


• Titration is adjustment of the dose, either increasing or decreasing, to attain the desired patient response. Weaning is a gradual decrease of the dose when the medication is being discontinued.


• Alterations or interruptions of the flow rate can significantly affect the dose of medication being delivered and adversely affect the patient. For accurate delivery of IV medications, volume-controlled infusion devices are required


• “Smart technologies” are electronic devices, such as computers, bedside monitors, and infusion pumps, that perform calculations of doses and flow rates after information is entered and programmed by the user. Although these devices are not universally available, their use may help to reduce medication errors.4


• Smart pumps are infusion pumps with comprehensive libraries of drugs and dose calculation software that can perform a “test of reasonableness” to check that programming is within preestablished institutional limits before the infusion can begin, which can reduce medication errors, improve workflow, and provide a source of data for continuous quality improvement.10


• Use of smart infusion pumps with activated dosage error reduction software alerts the practitioner when safe doses and infusion rates have been exceeded.7 The clinician must use the technology consistently to avoid serious medication infusion errors.6


• Be aware that double key bounce and double keying errors may occur when pressing a number key once on an infusion pump, resulting in the unintended consequence of a repeat of that same number. This can result in infusing medications at a higher rate than expected.5


• Three factors are involved in the calculations for continuous IV infusions:



image The concentration is the amount of medication diluted in a given volume of IV solution (e.g., 400 mg dopamine diluted in 250 mL normal saline [NS] solution, resulting in a concentration of 1.6 mg/mL; or 2 g lidocaine diluted in 500 mL 5% dextrose in water [D5W], yielding a concentration of 4 mg/mL). The concentration is also expressed as amount of medication per milliliter of fluid.


image The dose of the medication is the amount of medication to be administered over a certain length of time (e.g., dopamine 5 mcg/kg/min, lidocaine 2 mg/min, or diltiazem 5 mg/hr). The units of measure for the dose differ for various medications. The length of time is 1 minute or 1 hour. If the medication is weight-based, the dose of the medication is per kilogram of patient weight.


image The flow rate is the rate of delivery of the IV fluid solution expressed as volume of IV fluid delivered per unit of time (e.g., 20 mL/hr). The unit of measure of the flow rate is milliliter per hour.


• All units of measure in the formula must be the same. It frequently is necessary to perform some conversions on the concentration before entering it into the formula. The units of measure of the concentration must be converted to the same units of measure of the dose (e.g., the concentration of dopamine is measured in milligrams, but the dose of dopamine is measured in micrograms).


• The mathematic formula for continuous IV infusion contains the three factors involved in continuous infusion (Table 139-1). When two factors are known, the third can be calculated with the basic formula. Therefore, when the concentration of the solution and the prescribed dose are known, the flow rate can be determined. When the concentration of the solution and the flow rate are known, the dose can be determined. Variations on the basic formula are used to allow for medications delivered per hour or per minute and for medications that are weight-based (Tables 139-2 and 139-3).


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Jun 4, 2016 | Posted by in CRITICAL CARE | Comments Off on 139: Calculating Doses and Flow Rates and Administering Continuous Intravenous Infusions

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