Dosage Calculation using Dimensional Analysis Part 1 NURS B 260

 Between systems:  kg and lb., gr. and mg., oz. and grams, oz. and mL., in. and cm., tsp and mL., tbsp. and mL., Within systems  Lb. and oz., mL and L, mg and g., tsp and tbsp., quarts and gallon, pints and qts., cup and oz., pints and oz., hours and minutes Conversions to Know

 0.5 and above: Round Up  0.49 and below: Round Down  Drops/min: round to whole number  Round at the end  Follow rounding directions  Answers must be rounded correctly for the answer to be graded as correct on dosage calculation exams Rounding Rules

 For answers less than one, a zero must precede the decimal point  Example: 0.5 mg. not.5 mg.  For answers that are whole numbers, write the number only.  Example: 5 mL. not 5.0 mL.  These rules must be followed on exams Other Key Concepts

 Read each problem accurately. Determine pertinent information  Determine what you need to solve for (x) and place to left of problem  Correctly set up the problem. Start with the same unit of measure as (x)  Cancel units of measure and reduce fractions as needed  Perform checks and balances  Solve the problem  Round appropriately!!!!!  Evaluate for logic and accuracy  Transcribe answer accurately Steps to Follow

 Your client weighs 124 pounds. Convert the weight to kg. and round nearest tenth.  X kg = 1 kg x 124 lb 2.2 lb 1  Answer: 56.4 kg. Competency 1: Convert units of measure to another

1.Your client weighs 15.6 kg. Convert this to the nearest whole pound. 2.Your client’s incision is 5 inches long. Convert this to cm. State your answer in tenths. 3. The client is on a fluid restriction of 1500 mL. per day How many ounces per day is this? Competency 1 Practice

1.X lb. = 2.2 lb. x 15.6 kg. 1 kg X cm. = 2.54 cm x 5 in. 1 in. 1 3.X oz. = 1 oz. X 1500 mL. 30 mL. 1 Answers: 34 pounds, 12.7 cm., 50 oz.

1.The client is on a fluid restriction of 1.5 L per day How many ounces per day is this? X oz. = 1 oz. x 1000 mL x 1.5 L 30 mL. 1 L 1 Conversions with 2 steps

 The health care provider orders Pepcid 20 mg. p.o. twice per day. Pepcid 10 mg. tablets are available. How many tablets will you give for one dose? Competency 2: Calculate the measurement of medication when the strength is not available

 X tabs. = 1 tab x 20 mg. 10 mg. 1  Answer: 2 tablets

1.Morphine Sulfate 2 mg. is ordered IV push now. The vial reads Morphine Sulfate 8 mg./1 mL. How many mL. will you give? Answer: 0.25 mL 2.Potassium Chloride 20 mEq. p.o. is ordered now. The available liquid is 40 mEq./15 mL. How many mL. will you give? Answer: 7.5 mL. 3.Atenolol 25 mg. is ordered p.o. once per day. Atenolol 50 mg. tablets are available. How many tablets will you give? Answer: ½ tablet Competency 2 Practice

 Amoxicillin suspension 100 mg. p.o. is ordered every 8 hrs. The label reads 125 mg./5 mL. The bottle contains 120 mL. How many doses are in this bottle of suspension? Competency 3: Calculate the number of doses available from bulk supply

X dose = 1 dose x 125 mg. x 120 mL 100 mg. 5 mL. 1 Answer: 30 doses

 Advil 400 mg. is ordered 3 times daily after oral surgery. The bottle contains 25 tablets that are 200 mg. each. How many full doses are in the bottle? X dose = 1 dose x 200 mg. x 25 tabs 400 mg. 1 tab 1 Answer: 12 doses Competency 3 practice

 The order reads Ampicillin 375 mg. IM now. The 500 mg. vial is to be diluted with 1.8 mL. of normal saline to yield a concentration of 250 mg./ 1 mL. How many mL. will you give? Competency 4: Reconstitute dry drugs with diluents and calculate the proper volume to be administered

X mL. = 1 mL x 375 mg. 250 mg. 1 Answer: 1.5 mL.

Competency 4 Practice Medication: Penicillin G Sodium DiluentUnits/mL 4 mL1,000,000 units/mL  Order: Penicillin G Sodium 2 million units IM. How many mL would you administer?

 X mL = 1 mL x 2,000,000 units 1,000,000 units 1 Answer: 2 mL would be injected. Dilution would be with 4 mL prior to drawing up the medication

 1 mL syringe (may be called TB syringe_  Marked with tenths and hundredths  Insulin syringes (units for U100 insulin) typically orange  100 unit syringes marked in 2 units  50 unit lo-dose syringes marked in 1 unit  3 mL syringes  Marked with 0.1 mL and 0.05 mL  5 mL syringes  Each line is 0.2 mL  10 mL syringes and larger available for other uses (special IV lines, feeding tubes) Competency 5: Demonstrate on a syringe how to administer medication

 Key concepts  Drops per minute for IV infusing by gravity  Electronic IV pumps/Smart Pumps  Macrodrip sets  gtt per mL  Microdrip sets  60 gtt per mL Competency 6: Calculate the Infusion Rate for IV fluids

 Your client is receive 1000 mL of Normal Saline over 8 hours. The drop factor is 20 gtt./mL. Calculate the drip rate of this infusion in gtt./min. X gtt = 20 gtt x 1000 mL x 1 hr. Min 1 mL 8 hours 60 min Answer: 42 gtt./min Competency 6 Practice: Manual or Gravity IV infusions

 Your client is receive 1000 mL of Normal Saline over 8 hours. At what rate should you set the IV pump (in mL./hr.)? X mL. = 1000 mL hr.8 hrs. Answer: 125 mL/hr. Competency 6 Practice: Electronic Pump IV infusions

Order: 300 mL of D5W over 12 hours. The drop factor is 60 gtt./mL. Calculatethe drip rate in gtt./min. Order: Zosyn 2 g in 50 mL. of NS IVPB to infuse via pump over 30 minutes. At what rate in mL./hr will you set the pump? Competency 6 Practice

X gtt = 60 gtt. X 300 mL x 1 hr. min 1 mL. 12 hr. 60 min. Answer: 25 gtt./min. X mL = 50 mL x 60 min. hr. 30 min 1 hr. Answer: 100 mL/hr.

 The IV bag has 450 mL remaining. It is infusing at 35 gtt/min via tubing that has a drop factor of 15gtt/mL. How many hours will it take for this volume of fluid to infuse? X hrs. = 1 hr. x 1 min x 15 gtt. x 450 mL 60 min. 35 gtt. 1 mL hours or 3 hours and 12 minutes Competency 7: Calculate the running time of IV fluid

1.Calculate the gtt. per minute rate needed to infuse 250 mL over 3 hours using IV tubing with a drop factor of 20 gtt./mL. 2.A 50 mL. IVBP bag is infusing at 50 gtt./min via tubing with a drop factor of 60 gtt./mL. How many minutes will it take the IV to infuse? Competency 7 Practice

X gtt. = 20 gtt. x 250 mL x 1 hr. min. 1 mL 3 hrs. 60 min. Answer = 28 gtt./min. X min. = 1 min. x 60 gtt. x 50 mL. 50 gtt. 1 mL 1 Answer = 60 min.

 The confused client pulls out his IV after the infusion of only 150 mL of an IV bag containing Vancocin 500 mg. in 200 mL. of NS. How many mg. of Vancocin did the client receive? X mg. = 500 mg. X 150 mL. 200 mL 1 Answer: 375 mg. Competency 8: Calculate the amount of medication received when only a portion of the IV bag infused

1.The client’s IV “infiltrates” after the infusion of only 100 mL of an IV bag containing Vancocin 1 g. in 250 mL. of NS. How many mg. of Vancocin did the client receive? million units of Penicillin G K in 150 mL of D5W is ordered to infuse over 45 minutes. The IV stops after 20 minutes. How many units of Penicillin remain in the bag? (Answer as whole number) 3.The infusion of Aminophylline 200 mg. in 500 mL of D5W stopped after 350 mL had infused. How many mg. of Aminophylline remain in the bag? Competency 8 practice

X mg. = 1000 mg. x 1 g. x 100 mL. 1 g 250 mL. 1 Answer: 400 mg. X units = 1,600,000 units x 20 min. 45 min.1 Answer: 711,111 units infused. 1,600,000 – 711,111 = 888,889 units X mg. = 200 mg. X 350 mL 500 mL 1 Answer: 140 mg. infused. 200 mg. – 140 mg. = 60 mg remaining