Math for the Pharmacy Technician: Concepts and Calculations

1. Math for the Pharmacy Technician: Concepts and Calculations Egler • Booth Chapter 8: Intravenous Calculations

2. Intravenous Calculations

3. Learning Objectives • Identify 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:

4. Learning 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.

5. Introduction • Intravenous (IV) fluids are solutions including medication that are delivered directly into the bloodstream via a vein • Blood is also delivered by IV • IV fluids have a rapid effect • Are necessary during emergencies or other critical care situations

6. IV Solutions-Functions • Replacement fluids • Maintenance fluids • KVO (Keep Vein Open) fluids • Therapeutic fluids

7. IV Replacement Fluids • Replace electrolytes and fluids lost due to hemorrhage, vomiting, or diarrhea Examples: • Whole blood • Nutrient solutions • Fluids to treat dehydration

8. IV Maintenance Fluids • Maintain normal electrolyte and fluid balance Example: • Normal saline given during and after surgery

9. IV KVO Fluids • To keep the vein open (KVO or TKO) Example: • 5% dextrose in water

10. Therapeutic Fluids • Deliver medication to the patient

11. IV Labels • Solutions are labeled with • The name of the components • The exact amount of the components

12. IV Labels(con’t) • In abbreviations for IV solutions: • Letters identify the component • Numbers identify the concentration

13. IV Labels(con’t) Example: • An order for 5% dextrose in Lactated Ringer’s solution might be abbreviated in any of the following ways: • D5LR • D5LR • 5% D/LR • D5%LR

14. Common Abbreviations Dextrose D W, H20 S NS, NSS RL LR NS Water Saline Normal Saline (0.9% NaCl) Ringer’s Lactate Lactated Ringer’s Half Normal Saline Solution (0.45% NaCl)

15. IV Concentrations • 5% Dextrose • It contains 5 g of dextrose per 100 mL. • Normal saline is 0.9% saline • It contains 900 mg, or 0.9 g, of sodium chloride per • 100 mL. • ½ Normal saline is 0.45% saline • It contains 450 mg, or 0.45 g, of sodium chloride per 100 mL.

16. IV Concentrations (con’t) • Isotonic • They have no effect on the fluid balance of the surrounding cells or tissues. • Examples:D5W, NS, LR • Hypotonic • Fluid 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% NaCI

17. IV Concentrations(con’t) • Hypertonic • 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% saline

18. IV Concentrations(con’t) Patients withnormalelectrolyte levels are likely to receiveisotonicsolutions. • Patients withhighelectrolyte levels will receivehypotonicsolutions. • Patients withlowelectrolyte levelswill receivehypertonicsolutions.

19. Compatibility • Additives • Medications, electrolytes, and nutrients combined with IV solutions • Common additives: potassium chloride, vitamins B and C, and antibiotics • Come prepackaged in the solution or may need to be mixed

20. Compatibility(con’t) Before combining any medications, electrolytes, or nutrients with an IV solution, be sure the components are compatible.

21. Incompatible Combinations Examples • Ampicillin + 5% dextrose in water • Cefotaxime sodium + Sodium bicarbonate • Diazepam + Potassium chloride • Dopamine HCl + Sodium bicarbonate • Penicillin + Heparin • Penicillin + Vitamin B complex • Sodium bicarbonate + Lactated Ringer’s • Tetracycline HCl + Calcium chloride

22. Calculating Flow Rates To calculate flow rates in milliliter per hour, identify the following: V (volume) is expressed in milliliters T (time) must be expressed in hours (convert the units when necessary using calculation methods) F (flow rate) will be rounded to the nearest tenth Use the formula method or dimensional analysis to determine the flow rate in milliliters per hour.

23. Review and Practice Find the flow rate. • Ordered: 500 mg ampicillin in 100 mL NS to infuse over 30 minutes Flow rate = 200 mL/h

24. Calculating Flow Rates for Manual Regulation To 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/hour C = the calibration factor of the tubing in drops per mL 60 = number of minutes in an hour

25. Review and Practice • Find the flow rate in drops per minute that is equal to 35 mL/hour using 60 gtt (Drops) /mL microdrop tubing. Flow rate = 35 gtt/min

26. Infusion Time and Volume • An 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.

27. Calculating Infusion Time To calculate infusion time in hours (T), identify the: V (volume) expressed in milliliters F (flow rate) expressed in milliliters per hour Fractional hours by multiplying by 60 Use this formula or dimensional analysis to find T, the infusion time in hours.

28. Review and Practice Find the total time to infuse. Ordered: 1000 mL NS to infuse at a rate of 75 mL/h Total time to infuse the solution is 13 hours and 20 minutes

29. Review and Practice Find the total time to infuse. Ordered: 750 mL LR to infuse at a rate of 125 mL/hr started at 11 p.m. T = 6 hours = total time to infuse the 750 mL

30. Calculating Infusion CompletionTime To 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.

31. Calculating 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.

32. Review and Practice Determine 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 08/04/05 The infusion will be complete at 0500 or 5:00 a.m. on 08/05/05

33. Calculating Infusion Volume Use 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 hours • F(flow rate) must be expressed in milliliters per hour

34. Review and Practice Find the total volume infused in 5 hours if the infusion rate is 35 mL/h. V=175 mL or the volume that will infuse over 5 hours

35. Review and Practice Find the total volume infused in 12 hours if the infusion rate is 200 mL/h. V = 2400 mL = the volume that will infuse over 12 hours

36. Intermittent IV Infusion • IV medications are sometimes delivered on an intermittent basis • Delivered through • IV secondary line • Saline • Heparin lock • Can be delivered with continuous IV therapy or when no continuous IV solutions are infusing

37. Secondary Lines (Piggybacks or IVPB) • IV setup that attaches to a primary line • Used to infuse medications or other compatible fluids on an intermittent basis (such as q6h) • Uses shorter tubing • IVPB bags are smaller: 50,100, or 150 mL

38. Intermittent Peripheral Infusion Devices • Saline or heparin locks • An infusion port attached to an already inserted IV needle or catheter • Allow direct injection of medication or infusion of IV medications • Medications ordered asIV pushorbolus

39. Intermittent 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.

40. Preparing and Calculating Intermittent Infusions • Flow 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.

41. Preparing 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.

42. Review and Practice • Identify four functions of IV fluids. Answers: 1. Replacement 2. Maintenance 3. KVO 4. Therapeutic

43. Review and Practice • How many mg of sodium chloride is in 100 mL of normal saline? Answer:900 mg NaCl • How many mg of sodium chloride is in 100 mL of 0.45% NS? Answer:450 mg NaCl

44. Intravenous Calculations As 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 given THE END