Y khoa - Dược - Chapter 8: Intravenous calculations

Math for the Pharmacy Technician: Concepts and CalculationsChapter 8: Intravenous Calculations Egler • BoothIntravenous Calculations2Learning ObjectivesIdentify the components and concentrations of IV solutions.Calculate IV flow rates. Calculate infusion time based on volume and flow rate.When you have successfully completed Chapter 8, you will have mastered skills to be able to:3Learning Objectives (con’t)Calculate infusion completion time based on flow rate.Calculate volume based on infusion time and flow rate. Calculate medications for intermittent IV infusions. 4Introduction Intravenous (IV) fluids are solutions including medication that are delivered directly into the bloodstream via a veinBlood is also delivered by IVIV fluids have a rapid effectAre necessary during emergencies or other critical care situations5Replacement fluidsMaintenance fluidsKVO (Keep Vein Open) fluidsTherapeutic fluidsIV Solutions-Functions6IV Replacement FluidsReplace electrolytes and fluids lost due to hemorrhage, vomiting, or diarrheaExamples:Whole bloodNutrient solutionsFluids to treat dehydration7IV Maintenance FluidsMaintain normal electrolyte and fluid balanceExample:Normal saline given during and after surgery8IV KVO FluidsTo keep the vein open (KVO or TKO)Example:5% dextrose in water9Therapeutic FluidsDeliver medication to the patient10IV LabelsSolutions are labeled withThe name of the componentsThe exact amount of the components11IV Labels (con’t)In abbreviations for IV solutions: Letters identify the componentNumbers identify the concentration12IV Labels (con’t)Example:An order for 5% dextrose in Lactated Ringer’s solution might be abbreviated in any of the following ways:D5LRD5LR5% D/LR D5%LR13Common AbbreviationsD W, H20S NS, NSS RLLR NSDextroseWaterSalineNormal SalineLactated Ringer’sRinger’s LactateHalf Normal Saline Solution(0.45% NaCl)(0.9% NaCl)14IV Concentrations5% DextroseIt contains 5 g of dextrose per 100 mL.Normal saline is 0.9% salineIt contains 900 mg, or 0.9 g, of sodium chloride per 100 mL.½ Normal saline is 0.45% salineIt contains 450 mg, or 0.45 g, of sodium chloride per 100 mL.15IV Concentrations (con’t)IsotonicThey have no effect on the fluid balance of the surrounding cells or tissues.Examples: D5W, NS, LRFluid moves across the cell membrane into surrounding cells and tissues.This movement restores the proper fluid level in cells and tissues of patients who are dehydrated.Examples: 0.45% NS, 0.33% NaCIHypotonic16HypertonicIV Concentrations (con’t)These solutions draw fluids from cells and tissues across the cell membrane into the bloodstream.They are helpful for patients with severe fluid shifts such as those caused by burns.Example: 3% saline17IV Concentrations (con’t)Patients with normal electrolyte levels are likely to receive isotonic solutions. Patients with high electrolyte levels will receive hypotonic solutions.Patients with low electrolyte levels will receive hypertonic solutions.18CompatibilityAdditivesMedications, electrolytes, and nutrients combined with IV solutionsCommon additives: potassium chloride, vitamins B and C, and antibioticsCome prepackaged in the solution or may need to be mixed19Compatibility (con’t)Before combining any medications, electrolytes, or nutrients with an IV solution, be sure the components are compatible.20Incompatible CombinationsExamplesAmpicillin + 5% dextrose in waterCefotaxime sodium + Sodium bicarbonateDiazepam + Potassium chlorideDopamine HCl + Sodium bicarbonatePenicillin + HeparinPenicillin + Vitamin B complexSodium bicarbonate + Lactated Ringer’sTetracycline HCl + Calcium chloride21Calculating Flow RatesTo calculate flow rates in milliliter per hour, identify the following:Use the formula method or dimensional analysis to determine the flow rate in milliliters per hour.V (volume) is expressed in millilitersT (time) must be expressed in hours (convert the units when necessary using calculation methods)F (flow rate) will be rounded to the nearest tenth 22Review and PracticeFlow rate = 200 mL/h Find the flow rate.Ordered: 500 mg ampicillin in 100 mL NS to infuse over 30 minutes23Calculating Flow Rates for Manual RegulationTo determine the flow rate (f) in drops per minute:Change the flow rate mL/h (F) to gtt(drops)/min (f) using the formula where F = the flow rate in milliliters/hourC = the calibration factor of the tubing in drops per mL60 = number of minutes in an hour24Review and PracticeFlow rate = 35 gtt/minFind the flow rate in drops per minute that is equal to 35 mL/hour using 60 gtt (Drops) /mL microdrop tubing.25Infusion Time and VolumeAn order may call for a certain amount of fluid to infuse at a specific rate without specifying the duration.You will need to calculate the duration or amount of time the IV will take to infuse.You may know the duration and flow rate and will have to calculate the fluid volume.26Calculating Infusion TimeTo calculate infusion time in hours (T), identify the:V (volume) expressed in millilitersF (flow rate) expressed in milliliters per hourFractional hours by multiplying by 60Use this formula or dimensional analysis to find T, the infusion time in hours.27Review and PracticeTotal time to infuse the solution is 13 hours and 20 minutesFind the total time to infuse.Ordered: 1000 mL NS to infuse at a rate of 75 mL/h28Review and PracticeT = 6 hours = total time to infuse the 750 mLFind the total time to infuse.Ordered: 750 mL LR to infuse at a rate of 125 mL/hr started at 11 p.m.29Calculating Infusion CompletionTimeTo calculate the time when an infusion will be completed, you must first know the time the infusion started in military time and the total time in hours and minutes to infuse the solution ordered.30Calculating Infusion Completion Time (con’t)Since each day is only 24 hours long, when the sum is greater than 2400 (midnight), you must start a new day by subtracting 2400. This will determine the time of completion, which will be the next calendar day.31Review and PracticeThe infusion will be complete at 0500 or 5:00 a.m. on 08/05/05Determine when the infusion will be completed.Ordered: 750 mL LR to infuse at a rate of 125 mL/hr, started at 11 p.m. on 08/04/0532Calculating Infusion VolumeUse the formula V = T X F or dimensional analysis to find V the infusion volume in mL, where the T (time) must be expressed in hoursF (flow rate) must be expressed in milliliters per hour33Review and PracticeV=175 mL or the volume that will infuse over 5 hoursFind the total volume infused in 5 hours if the infusion rate is 35 mL/h.34Review and PracticeV = 2400 mL = the volume that will infuse over 12 hoursFind the total volume infused in 12 hours if the infusion rate is 200 mL/h.35Intermittent IV InfusionIV medications are sometimes delivered on an intermittent basisDelivered through IV secondary line SalineHeparin lockCan be delivered with continuous IV therapy or when no continuous IV solutions are infusing36Secondary Lines (Piggybacks or IVPB)IV setup that attaches to a primary lineUsed to infuse medications or other compatible fluids on an intermittent basis (such as q6h)Uses shorter tubingIVPB bags are smaller: 50,100, or 150 mL37Intermittent Peripheral Infusion DevicesSaline or heparin locksAn infusion port attached to an already inserted IV needle or catheterAllow direct injection of medication or infusion of IV medicationsMedications ordered as IV push or bolus38Intermittent Peripheral Infusion Devices (con’t)Since there is no continuous flow of fluids through the IV line you must flush the device 2 to 3 times per day to prevent blockage.Saline lock -- is an infusion port attached to an already inserted catheter for IV access, flushed with saline. Heparin lock -- is an infusion port attached to an already inserted catheter for IV access, flushed with heparin. 39Preparing and Calculating Intermittent InfusionsFlow rate is calculated for prepared medications the same as regular IV infusions.Amount of fluid may be less and time to infuse may be less than an hour.Calculate the flow rate you will need to change the number of minutes into hours.40Preparing and Calculating Intermittent Infusions (con’t)When preparing medications for an intermittent IV infusion:Reconstitute the medication using the label and package insert.Calculate amount to administer and the flow rate.41Identify four functions of IV fluids.Review and PracticeAnswers:1. Replacement2. Maintenance3. KVO4. Therapeutic42How many mg of sodium chloride is in 100 mL of normal saline?Review and PracticeAnswer: 900 mg NaCl How many mg of sodium chloride is in 100 mL of 0.45% NS?Answer: 450 mg NaCl43Intravenous CalculationsTHE ENDAs a pharmacy technician you will need to know how to perform accurate IV calculations. Results can be fatal if the wrong medication or dosage is given44