Presentation on theme: "IV Administration – Dosage Calculation"— Presentation transcript:
1 IV Administration – Dosage Calculation Keith Rischer, RNTalk about chapter 13….alternate way to do problems.Dimensional analysisadvantages – conversions can be included in the problem.
2 Alternate Methods Dosage Calc. FormulaRatio proportionDimensional analysisTalk about chapter 13….alternate way to do problems. Remember in 3,2 1 calc, you have options to see problems calculated using all three methods.Formula: D X Q = XHD - dose ordered, H – dose on hand Q – quantity that contains the dose on handWe have used this method successfully to figure out oral med dosages, and we will use it again to figure out IV Push meds.Ratio Proportion: used to convert (like mg to grams) and also to determine oral med dosages.Ratio of dose on hand (on label) = ratio for desired dose (MD order)EX: order- 500 mg amoxicillan 250 mg = 500 mgAvailable – 250 mg/capsule 1 capsule X capX cap = 500 mg250 mgX = 2 capFormula method: mg X 1 cap = XDimensional analysis: advantages – conversions can be included in the problem. One stop shopping! Conversions needed are included on right side of equation – you must set up the equation so that all units cancel except for the one you are seeking! SEE notes on examples of dimensional analysis.
3 IV solutions Administered in plastic bags/bottles Administered continuously and/or intermittentlyComponents:WaterGlucose(dextrose)SalineElectrolytesSaltsIntravenous (IV) fluids come in plastic solution bags and glass bottles ranging from 50 mL to 1000 mL or more.Components of IV solutions vary depending on the needreplace fluidsmaintenance of fluids and electrolyte balanceadmin. Of medsnutritional support– they are administered continuously and/or intermittentlyBolus – solution over a short period of timeIV push – medication given using a syringe (pain med)Made up of water, glucose (dextrose), saline, electrolytes, and salts. Is specified combinations and concentrations.
4 IV solutions Labeled Letters – solution components Numbers – concentrationLR – Lactated RingersNS: Normal Saline 0.9% NaClD5W – 5% Dextrose in water= 5 g dextrose / 100 ml solutionD5 NS with 20 mEq KCLThe IV fluid is labeled using special abbreviations and notations. The letters indicate the solution components and the numbers indicate the concentration or solution strength. It is important to understand that when you administer IV fluids, you are not just giving fluid but different solutes or electrolytes such as dextrose.DEXTROSE AND NACL MOST COMMON IV COMPONENTSD5W – 5% dextrose in water= components are 5 g/ 100 ml of waterIn 1000 ml bag of D5W – how many grams of dextrose will be contained in it? (ans.= 50 grams)= Isotonic solution = 252 mOsmol/LD5LR – 5% dextrose in Lactated Ringers= 5 g dextrose in 100 ml and lactated ringers(contains specific amounts of K, NaCL, Cacl, Lactate.hypertonic solution = 525 mOsmol/LOften you will see electrolytes added in pharmacy like potassium
5 IV Solution Label Calculate components: D5 0.45% NS in 1000 mL
6 Tonicity of IV Solutions HypotonicIsotonicHypertonic0.9 NSD5WLR½ (0.45%) NS¼ (0.225%) NSD5 ½ NSD5 NSD5 LR3% NSCHOICE OF IV SOLUTIONS DRIVEN BY PATIENT NEEDS AND CURRENT LYTESHypotonic - < 250 mOsmol/L – dilute excess serum electrolytesLower tonicity½ NS¼ NSIsotonic – mOlmol/L – expand volume and maintain tonicitySame tonicity as blood and body serums.9 NSD5WLRHypertonic > 375 mOlmol/L – to correct electrolyte imbalances, as in loss from excess vomiting and diarrheaHigher tonicityD5 ½ NSD5NSD5LR3%NS
7 Calculating Flow Rates IV Pumps Total mL ordered = mL per hourTotal hours orderedVancomycin 1000 mg (250 mL) IV over 2 hours by infusion pumpVancomycin 750 mg (250 mL) IV over 1.5 hoursOrder Give Vancomycin 250 mL over the next two hours by infusion pumpRemember this: Infusion pumps only calibrate in mL/hr. There are pumps that infuse using more sophisticated mechanisms such as IV heparin can be infused in units…but for our purposes we will be using pumps which infuse in mL per hour. Step 1:thinkPump is set by the rate of mL per hourSo, if 250 mL is to be infused in two hours, how much will be infused in one hour?125 mL will be infused in one hourYou would set the pump at 125 mL per hourStep 2: Use the formulaTherefore set the pump at 125 ml/hrStep 2 Use the formula Step 2: Use the formula:
8 IV Flow Rate in mL per hour: Infusion Rate is less than 1 hour Total mL ordered X 60 min/hr = mL/hrTotal min orderedOrder:Ampicillin 500 mg IV in 50 mL NS over 30 minutesGive Amiodarone 150mg in 100 ml of D5W over 10 minutes(rounded to a whole number)
9 Setting Flow Rates for Manually Regulated IVs Adjusting the rate by handCounts drops per minuteUse the roller clamp to adjust rateWhen an electronic infusion device is not used, the nurse must set and adjust the IV rate by hand. The nurse counts the number of drops per minute in the drip chamber to set the rate of the IV. The roller clamp is the part of the IV tubing that regulates the flow. It is located below the drip chamber farther down on the tubing. To increase the flow rate, the roller clamp is rolled upward or opened. The roller clamp is rolled downward or closed to decrease the rate.
10 Calculating flow rates - Manually Formula methodV X C (gtt factor) = RTVolume (mL) X drop factor (gtt per mL)= Rate (gtt/min)Time (min)Physician orders: D5W IV at 125 mL/hr.The IV infusion set is calibrated with a drop factor of 10 gtt/mL.Calculate the IV flow ratePhysician orders: 0.9 NS IV at 75 mL/hr.Carry calculations to one decimalRound drops per minute to the nearest whole numberWatchCount only whole dropsAnswer 20.8 gtts=21 gtts/minuteRischer rule-divide by ¼-5 drops every 15 seconds…1 gtt every 3 seconds
11 Calculating gtts per/minute Once gtts/minute determined...Divide this total by a factor of 420 gtts/minute… 5 gtts every 15 seconds12 gtts/minute… 3 gtts every 15 secondsHow many gtts every 15 seconds?...Divide the gtts determined by 15 (seconds)This will be the seconds between each gtt5 gtts every 15 seconds15/5= x seconds3 gtts every 15 seconds15/3= x seconds
12 Calculation of Drops per min: Microdrip Drop Factor Volume (mL) X drop factor (gtt per mL)= Rate Time (min)Order:D5 NS IV at 50 mL per hDrop factor is 60 drops per mLCalculate gtt/minNotice order, 50 mL per hour, is the same as the flow rate of 50 drops per min when drop factor is 60 drops per mL
13 Drop Factor Constants Drop Factor Drop Factor Constant 10 drops per mL
14 Drop Factor Constants Physician orders: D5W IV at 125 mL/hr 6 10 gtts/mL manual infusion set125 mL=20.8 gtt/minute or 21 gtts6Physician orders: 0.9 NS IV at 75 mL/hr.75mL=Only works with hourly rates not less than 1 hour
15 Adjusting IV Flow RateCheck for institutional policy regarding correcting off-schedule IV rates and the percentage of variation allowedVariation should not exceed 25 percent% variation will be positive (+) if administration is slow and rate has to be increasedNegative () if administration is too fast and rate has to be decreasedSometimes rate is changed due to: gravity, condition of patient or movement. It helps to avoid problems with IV being off schedule if the IV is monitored every 30 min to 1hour.Tape bag with where it should be every hour to assess if on trackSafe rule of thumb when adjustment is necessary: rate per minute can be adjusted by 25% or less. (percent variation)Check with MD, hospital policy, and use good nursing judgment. You do not want to overhydrate or underhydrate your patient or significantly alter the electrolyte balance in a negative manner
16 Adjusting IV flow rates Follow three steps:Remaining volume = recalculated mL/hRemaining hoursV X C (gtt factor) = RTAdjusted gtt per min – ordered gtt per min = % variationOrdered gtt per minIf adjustment of the rate is permitted, then use the following formulas to recalculate the flow rate of an IV and determine the percent of variation:Next, the new rate is used to recalculate the drops per minute.Last, to figure out the percent of variation, which is how much the IV is off schedule, the original drops per minute rate is subtracted from the new drops per minute rate.NS 125 ml/hr over 8 hours (1000ml)After 4 hours 600ml remaining
17 Calculation of IV Flow Rate Adjustment Order: 500 mL LR to run over 10 hours at 50 mL per hourDrop factor is 60 drops per mL and IV is correctly infusing at 50 drops per minAfter 2 hours, 300 mL is remainingAlmost half of total volume infused in one-quarter the time
18 Calculation of IV Flow Rate Adjustment IV infusion is ahead of scheduleCompute a new rate of 300 mL to complete IV fluid order in remaining 7 hoursPatient would require close assessment for fluid overload
19 Calculation of IV Flow Rate Adjustment Adjusted flow rate11
20 Calculation of IV Flow Rate Adjustment Adjusted gtt per min – ordered gtt per minOrdered gtt per min40 – 50 = = = - 20%
21 Adjusting IV flow rates The physician orders 1000 mL of D5 0.45% NS at 100 mL per hour over 10 hours. Drop factor-10 gtt per mLWhat is the initial correct gtt/minuteHow many gtts/15 seconds…1 gtt every __ secs.After 5 hours only 300 mL has infused. The IV is behind schedule. Calculate the new flow rate. Is this new rate acceptable?Gtts/minute-16.6-round to 16/minute4 gtts every 15 seconds…appx 1 gtt 4 seconds700ml/5 remaining hours=140 ml140/6 gtt factor=23.3 or 24 gtts/minute24gtts-16gtts=816 gtts original rate…..8/16=50% difference…too high
22 IV Push InjectionsUse same calculations as other parenteral injectionsIMPORTANT – Follow manufacturer or hospital guidelines for rate of administrationDosage calculations for IV push injections are the same as calculations for other parenteral injections. When giving medications IV push, it is important to follow the manufacturer or hospital guidelines for the rate of administration.
24 Calculation of IV Push Rate Order: Furosemide (Lasix) 40 mg IV Push stat x1Supply: Furosemide 10 mg per mL with drug literature guidelines of “IV infusion not to exceed 20 mg over 1 minute”
25 Calculation of IV Push Rate How much Furosemide should you prepare?Step 1. ConvertNo conversion is necessaryStep 2. ThinkYou want to give more than 1 mL
26 Calculation of IV Push Rate How much Furosemide should you prepare?Step 3. Calculate
27 Calculation of IV Push Rate What is a safe infusion time?Use the formula:D X Q = XH40 mg X 1 min = 2 minutes20 mg2 minutes
28 Calculation of IV Push Rate How much should you infuse every 15 seconds?Push Factor Constant4 per minute15 seconds = 1/460 seconds4 mL over 2”Push factor is 8 (4x2”=8)Volume mL=0.5 mL push every 15 secondsPush Factor
29 Calculation of IV Push Rate Order: Dilantin 100 mg IV nowSupply: Dilantin 50 mg per mL with drug literature guidelines of “the infusion rate should not exceed 50 mg per min”.How much should you prepare?What is safe infusion time?How much should you infuse every 15 seconds?2 ml2 minutes0.25 ml every 15 seconds