ATI RN Pharmacology for Nursing Dosage Calculation PDF

CHAPTER 3 UNIT 1 PHARMACOLOGICAL PRINCIPLES For dosages greater than 1.0: Round to the nearest tenth. Dosage Calculation For example (rounding up): 1.38 = 1.4. The calculated CHAPTER 3...

CHAPTER 3 UNIT 1 PHARMACOLOGICAL PRINCIPLES For dosages greater than 1.0: Round to the nearest tenth. Dosage Calculation For example (rounding up): 1.38 = 1.4. The calculated CHAPTER 3 dose is 1.38 mg. Look at the number in the hundredths place (8). Eight is greater than 5. To round to the tenth, add 1 to the 3 in the tenth place and drop the 8. The Basic medication dose conversion and rounded dose is 1.4 mg. Or (rounding down): 1.34 mL = 1.3 mL. The calculated calculation skills are essential for providing safe dose is 1.34 mL. Look at the number in the hundredths nursing care. place (4). Four is less than 5. To round to the tenth, drop the 4 and leave the 3 as is. The rounded dose is 1.3 mL. Nurses are responsible for administering the correct amount of medication by calculating the precise amount of medication to give. Nurses Solid dosage Example: A nurse is preparing to administer can use three different methods for dosage phenytoin 0.2 g PO every 8 hr. The amount available calculation: ratio and proportion, formula is phenytoin 100 mg/capsule. How many capsules should the nurse administer per dose? (Round the (desired over have), and dimensional analysis. answer to the nearest whole number. Use a leading zero if it applies. Do not use a trailing zero.) TYPES OF CALCULATIONS Solid oral medication USING RATIO AND PROPORTION Liquid oral medication STEP 1: What is the unit of measurement the nurse Injectable medication should calculate? Correct doses by weight IV infusion rates capsules STEP 2: What is the dose the nurse should administer? STANDARD CONVERSION FACTORS Dose to administer = Desired 1 mg = 1,000 mcg 0.2 g 1 g = 1,000 mg STEP 3: What is the dose available? Dose available = Have 1 kg = 1,000 g 1 oz = 30 mL 100 mg 1 L = 1,000 mL STEP 4: Should the nurse convert the units of measurement? 1 tsp = 5 mL Yes (g ≠ mg) 1 tbsp = 15 mL Set up an equation. 1 tbsp = 3 tsp 1 kg = 2.2 lb 1g 0.2 g 1 gr = 60 mg = 1,000 mg X mg Solve for X. GENERAL ROUNDING GUIDELINES X mg = 200 mg ROUNDING UP: If the number to the right is equal to or greater than 5, round up by adding 1 to the number Or you can use your knowledge of equivalents. on the left. 1 g = 1,000 mg (1 × 1,000) ROUNDING DOWN: If the number to the right is less than 5, round down by dropping the number, leaving the 0.2 g = 200 mg (0.2 × 1,000) number to the left as is. STEP 5: What is the quantity of the dose available? = Quantity For dosages less than 1.0: Round to the nearest hundredth. 1 capsule For example (rounding up): 0.746 mL = 0.75 mL. The calculated dose is 0.746 mL. Look at the number in the STEP 6: Set up the equation and solve for X. thousandths place (6). Six is greater than 5. To round to Have Desired hundredths, add 1 to the 4 in the hundredths place and = Quantity X drop the 6. The rounded dose is 0.75 mL. Or (rounding down): 0.743 mL = 0.74 mL. The 100 mg 200 mg calculated dose is 0.743 mL. Look at the number in the 1 capsule = X capsule(s) thousandths place (3). Three is less than 5. To round to the hundredth, drop the 3 and leave the 4 as is. The X capsule(s) = 2 capsules rounded dose is 0.74 mL. STEP 7: Round, if necessary. RN PHARMACOLOGY FOR NURSING CHAPTER 3 DOSAGE CALCULATION 19  STEP 8: Determine whether the amount to administer makes USING DIMENSIONAL ANALYSIS sense. If there are 100 mg/capsule and the prescription reads STEP 1: What is the unit of measurement the nurse 0.2 g (200 mg), it makes sense to administer 2 capsules. The should calculate? (Place the unit of measure being nurse should administer phenytoin 2 capsules PO. calculated on the left side of the equation.) X capsule(s) = USING DESIRED OVER HAVE STEP 2: Determine the ratio that contains the same unit as STEP 1: What is the unit of measurement the nurse the unit being calculated. (Place the ratio on the right side should calculate? of the equation ensuring that the unit in the numerator capsules matches the unit being calculated.) STEP 2: What is the dose the nurse should administer? = 1 capsule X capsule(s) Dose to administer = Desired 100 mg STEP 3: Place any remaining ratios that are relevant to 0.2 g the item on the right side of the equation along with any STEP 3: What is the dose available? Dose available = Have needed conversion factors to cancel out unwanted units of measure. 100 mg 1 capsule 1,000 mg 0.2 g STEP 4: Should the nurse convert the units of X capsule(s) = 100 mg x 1g x 1 measurement? Yes (g ≠ mg) Set up an equation. STEP 4: Solve for X. = 0.2 g × 1,000 mg X capsule(s) = 2 capsules X mg 1g STEP 5: Round, if necessary. X mg = 200 mg STEP 6: Determine whether the amount to administer Or you can use your knowledge of equivalents. makes sense. If there are 100 mg/capsule and the 1 g = 1,000 mg (1 × 1,000) prescription reads 0.2 g, it makes sense to administer 2 capsules. The nurse should administer phenytoin 0.2 g = 200 mg (0.2 × 1,000) 2 capsules PO. STEP 5: What is the quantity of the dose available? = Quantity 1 capsule STEP 6: Set up the equation and solve for X. = Desired × Quantity X Have 200 mg × 1 cap X capsule(s) = 100 mg X capsule(s) = 2 capsules STEP 7: Round, if necessary. STEP 8: Determine whether the amount to administer makes sense. If there are 100 mg/capsule and the prescription reads 0.2 g (200 mg), it makes sense to administer 2 capsules. The nurse should administer phenytoin 2 capsules PO. 20 CHAPTER 3 DOSAGE CALCULATION CONTENT MASTERY SERIES  Liquid dosage USING DESIRED OVER HAVE STEP 1: What is the unit of measurement the nurse Example: A nurse is preparing to administer should calculate? amoxicillin 0.25 g PO every 8 hr. The amount available is amoxicillin oral suspension 250 mg/5 mL. mL How many mL should the nurse administer per STEP 2: What is the dose the nurse should administer? dose? (Round the answer to the nearest tenth. Use a Dose to administer = Desired leading zero if it applies. Do not use a trailing zero.) 0.25 g USING RATIO AND PROPORTION STEP 3: What is the dose available? Dose available = Have STEP 1: What is the unit of measurement the nurse 250 mg should calculate? STEP 4: Should the nurse convert the units of mL measurement? Yes (g ≠ mg) Set up an equation: STEP 2: What is the dose the nurse should administer? Dose to administer = Desired 0.25 g × 1,000 mg X mg = 1g 0.25 g X mg = 250 mg STEP 3: What is the dose available? Dose available = Have Or you can use your knowledge of equivalents. 250 mg 1 g = 1,000 mg (1 × 1,000) STEP 4: Should the nurse convert the units of measurement? Yes (g ≠ mg) (Place the unit of measure 0.25 g = 250 mg (0.25 × 1,000) being calculated on the left side of the equation.) Set up an equation. STEP 5: What is the quantity of the dose available? = Quantity 1 mg 0.25 g 5 mL = 1,000 mg X mg STEP 6: Set up the equation and solve for X. X mg = 200 mg Desired × Quantity X mL = Have Or you can use your knowledge of equivalents. 250 mg × 5 mL 1 g = 1,000 mg (1 × 1,000) X mL = 250 mg 0.25 g = 250 mg (0.25 × 1,000) X mL = 5 mL STEP 5: What is the quantity of the dose available? = Quantity STEP 7: Round, if necessary. 5 mL STEP 8: Determine whether the amount to administer makes sense. If there are 250 mg/5 mL and the STEP 6: Set up the equation and solve for X. prescription reads 0.25 g (250 mg), it makes sense to Have Desired administer 5 mL. The nurse should administer amoxicillin = Quantity X 5 mL PO every 8 hr. 250 mg 250 mg = USING DIMENSIONAL ANALYSIS 5 mL X mL STEP 1: What is the unit of measurement the nurse X mL = 5 mL should calculate? (Place the unit of measure being STEP 7: Round, if necessary. calculated on the left side of the equation.) STEP 8: Determine whether the amount to administer makes X mL = sense. If there are 250 mg/5 mL and the prescription reads STEP 2: Determine the ratio that contains the same unit as 0.25 g (250 mg), it makes sense to administer 5 mL. The the unit being calculated. (Place the ratio on the right side nurse should administer amoxicillin 5 mL PO every 8 hr. of the equation ensuring that the unit in the numerator matches the unit being calculated.) 5 mL X mL = 250 mg RN PHARMACOLOGY FOR NURSING CHAPTER 3 DOSAGE CALCULATION 21  STEP 3: Place any remaining ratios that are relevant to USING DESIRED OVER HAVE the item on the right side of the equation along with any STEP 1: What is the unit of measurement the nurse needed conversion factors to cancel out unwanted units of should calculate? measurement. 5 mL 1,000 mg 0.25 g mL X mL = 250 mg x 1g x 1 STEP 2: What is the dose the nurse should administer? Dose to administer = Desired STEP 4: Solve for X. 8,000 units X mL = 5 mL STEP 3: What is the dose available? Dose available = Have STEP 5: Round, if necessary. 10,000 units STEP 6: Determine whether the amount to administer STEP 4: Should the nurse convert the units of makes sense. If there are 250 mg/5 mL and the measurement? No prescription reads 0.25 g, it makes sense to administer 5 mL. The nurse should administer amoxicillin 5 mL PO STEP 5: What is the quantity of the dose available? = Quantity every 8 hr. 1 mL STEP 6: Set up an equation and solve for X. Injectable dosage X mL = Desired × Quantity Have Example: A nurse is preparing to administer heparin 8,000 units subcutaneously every 12 hr. Available is heparin injection 10,000 units/mL. How many = 8,000 units × 1 mL X mL mL should the nurse administer per dose? (Round 10,000 units the answer to the nearest tenth. Use a leading zero if it applies. Do not use a trailing zero.) X mL = 0.8 mL STEP 7: Round, if necessary. USING RATIO AND PROPORTION STEP 8: Determine whether the amount to administer STEP 1: What is the unit of measurement the nurse makes sense. If there are 10,000 units/mL and the should calculate? prescription reads 8,000 units, it makes sense to administer 0.8 mL. The nurse should administer heparin mL injection 0.8 mL subcutaneously every 12 hr. STEP 2: What is the dose the nurse should administer? Dose to administer = Desired USING DIMENSIONAL ANALYSIS 8,000 units STEP 1: What is the unit of measurement the nurse STEP 3: What is the dose available? Dose available = Have should calculate? (Place the unit of measure being calculated on the left side of the equation.) 10,000 units X mL = STEP 4: Should the nurse convert the units of measurement? No STEP 2: Determine the ratio that contains the same unit as the unit being calculated. (Place the ratio on the right side STEP 5: What is the quantity of the dose available? = Quantity of the equation ensuring that the unit in the numerator 1 mL matches the unit being calculated.) STEP 6: Set up the equation and solve for X. 1 mL X mL = 10,000 units Have = Desired Quantity X STEP 3: Place any remaining ratios that are relevant to the item on the right side of the equation along with any 10,000 units 8,000 units needed conversion factors to cancel out unwanted units of = 1 mL X mL measurements. 8,000 units 1 mL X mL = 0.8 mL X mL = x 10,000 units 1 dose STEP 7: Round, if necessary. STEP 4: Solve for X. STEP 8: Determine whether the amount to administer X mL = 0.8 mL makes sense. If there are 10,000 units/mL and the prescription reads 8,000 units, it makes sense to STEP 5: Round, if necessary. administer 0.8 mL. The nurse should administer heparin injection 0.8 mL subcutaneously every 12 hr. 22 CHAPTER 3 DOSAGE CALCULATION CONTENT MASTERY SERIES  STEP 6: Determine whether the amount to administer STEP 8: What is the dose available? Dose available = Have makes sense. If there are 10,000 units/mL and the 100 mg prescription reads 8,000 units, it makes sense to administer 0.8 mL. The nurse should administer heparin STEP 9: Should the nurse convert the units of injection 0.8 mL subcutaneously every 12 hr. measurement? No STEP 10: What is the quantity of the dose available? = Quantity Dosages by weight 5 mL STEP 11: Set up the equation and solve for X. Example: A nurse is preparing to administer cefixime 8 mg/kg/day PO to divide equally every Have Desired = 12 hr to a toddler who weighs 22 lb. Available is Quantity X cefixime suspension 100 mg/5 mL. How many mL should the nurse administer per dose? (Round the 100 mg 40 mg = answer to the nearest whole number. Use a leading 5 mL X mL zero if it applies. Do not use a trailing zero.) X mL = 2 mL STEP 12: Round, if necessary. USING RATIO AND PROPORTION STEP 13: Determine whether the amount to give makes STEP 1: What is the unit of measurement the nurse sense. If there are 100 mg/5 mL and the prescription reads should calculate? 40 mg, it makes sense to give 2 mL. The nurse should kg administer cefixime suspension 2 mL PO every 12 hr. STEP 2: Set up an equation and solve for X. 2.2 lb Client’s desired weight in lb USING DESIRED OVER HAVE = 1 kg X kg STEP 1: What is the unit of measurement the nurse should calculate? 2.2 lb 22 lb = kg 1 kg X kg STEP 2: Set up an equation and solve for X. X kg = 10 kg Client's weight in lb × 1 kg What is the dose the nurse should calculate? Dose to X kg = 2.2 lb administer = Desired What is the dose available? Dose available = Have 22 lb × 1 kg X kg = 2.2 lb 100 mg X kg = 10 kg STEP 3: What is the unit of measurement the nurse should calculate? STEP 3: What is the unit of measurement the nurse should calculate? mg mg STEP 4: Set up an equation and solve for X. STEP 4: Set up an equation and solve for X. X mg × kg/day = X = Dose per kg × Client’s weight in kg X mg/day = mg/kg/day × Client’s weight in kg X mg = 8 mg × 10 kg X mg/day = 8 mg/kg/day × 10 kg X mg = 80 mg X mg/day = 10 kg/day STEP 5: The dose is divided equally every 12 hours. The dose is divided equally every 12 hours; therefore, Divide X by 2. divide X by 2. 80 mg = 40 mg 80 mg = 40 mg 2 2 STEP 6: What is the unit of measurement the nurse STEP 5: What is the unit of measurement the nurse should calculate? should calculate? mL mL STEP 7: What is the dose the nurse should administer? STEP 6: What is the dose the nurse should administer? Dose to administer = Desired Dose to administer = Desired 40 mg 40 mg RN PHARMACOLOGY FOR NURSING CHAPTER 3 DOSAGE CALCULATION 23  STEP 7: What is the dose available? Dose available = Have IV flow rates 100 mg Nurses calculate IV flow rates for large-volume continuous STEP 8: Should the nurse convert the units of IV infusions and intermittent IV bolus infusions measurement? No using electronic infusion pumps (mL/hr) and manual IV tubing (gtt/min). STEP 9: What is the quantity of the dose available? = Quantity 5 mL STEP 10: Set up an equation and solve for X. IV INFUSIONS WITH ELECTRONIC INFUSION PUMPS = Desired × Quantity X mL Infusion pumps control an accurate rate of fluid infusion. Have Infusion pumps deliver a specific amount of fluid during = 40 mg × 5 mL a specific amount of time. For example, an infusion pump X mL 100 mg can deliver 150 mL in 1 hr or 50 mL in 20 min. X mL = 2 mL Example: A nurse is preparing to administer dextrose 5% in water (D5W) 500 mL IV to infuse STEP 11: Round, if necessary. over 4 hr. The nurse should set the IV infusion STEP 12: Determine whether the amount to give makes pump to deliver how many mL/hr? (Round the sense. If there are 100 mg/5 mL and the prescription reads answer to the nearest whole number. Use a leading 40 mg, it makes sense to give 2 mL. The nurse should zero if it applies. Do not use a trailing zero.) administer cefixime suspension 2 mL PO every 12 hr. USING RATIO AND PROPORTION USING DIMENSIONAL ANALYSIS AND DESIRED OVER HAVE STEP 1: What is the unit of measurement the nurse STEP 1: What is the unit of measurement the nurse should calculate? (Place the unit of measure being should calculate? calculated on the left side of the equation.) mL/hr X mL/dose = STEP 2: What is the volume the nurse should infuse? STEP 2: Determine the ratio that contains the same unit as 500 mL the unit being calculated. (Place the ratio on the right side of the equation ensuring that the unit in the numerator STEP 3: What is the total infusion time? matches the unit being calculated.) 4 hr X mL = 5 mL STEP 4: Should the nurse convert the units of dose 100 mg measurement? No STEP 3: Place any remaining ratios that are relevant to STEP 5: Set up the equation and solve for X. the item on the right side of the equation along with any needed conversion factors to cancel out unwanted units of Volume (mL) X mL/hr = measurements. Time (hr) X mL/dose = 500 mL X mL/hr = 4 hr X mL = 5 mL × 8 mg × 1 kg × 22 lb × 1 day X mL/hr = 125 mL/hr dose 100 mg 1 kg 2.2 lb 1 day 2 dose STEP 6: Round, if necessary. STEP 4: Solve for X. STEP 7: Determine whether the IV flow rate makes sense. X mL = 2 mL If the prescription reads 500 mL to infuse over 4 hr, it STEP 5: Round, if necessary. makes sense to administer 125 mL/hr. The nurse should set the IV pump to deliver D5W 500 mL IV at 125 mL/hr. STEP 6: Determine whether the amount to give makes sense. If there are 100 mg/5 mL and the prescription reads 40 mg, it makes sense to give 2 mL. The nurse should USING DIMENSIONAL ANALYSIS administer cefixime suspension 2 mL PO every 12 hr. STEP 1: What is the unit of measurement the nurse should calculate? (Place the unit of measure being calculated on the left side of the equation.) X mL/hr = 24 CHAPTER 3 DOSAGE CALCULATION CONTENT MASTERY SERIES  STEP 2: Determine the ratio that contains the same unit as STEP 7: Determine whether the IV flow rate makes sense. the unit being calculated. (Place the ratio on the right side If the prescription reads 100 mL to infuse over 45 min (0.75 of the equation ensuring that the unit in the numerator hr), it makes sense to administer 133 mL/hr. The nurse matches the unit being calculated.) should set the IV pump to deliver cefotaxime 1 g in 100 mL 500 mL of 0.9% NaCl IV at 133 mL/hr. X mL/hr = 4 hr STEP 3: Place any remaining ratios that are relevant to USING DESIRED OVER HAVE the item on the right side of the equation along with any STEP 1: What is the unit of measure the nurse should needed conversion factors to cancel out unwanted units of calculate? measurements. 500 mL mL/hr X mL/hr = 4 hr STEP 2: What is the volume the nurse should infuse? STEP 4: Solve for X. 100 mL X mL/hr = 125 mL/hr STEP 3: What is the total infusion time? STEP 5: Round, if necessary. 45 min STEP 6: Determine whether the IV flow rate makes sense. STEP 4: Should the nurse convert the units of If the prescription reads 500 mL to infuse over 4 hr, it measurement? makes sense to administer 125 mL/hr. The nurse should Yes (min does not equal hr) set the IV pump to deliver D5W 500 mL IV at 125 mL/hr. 45 min x 1 hr X hr = 60 min X hr = 0.75 hr Example: A nurse is preparing to administer cefotaxime 1 g intermittent IV bolus over 45 min. STEP 5: Set up the equation and solve for X. Available is cefotaxime 1 g in 100 mL 0.9% sodium Volume (mL) chloride (0.9% NaCl). The nurse should set the X mL/hr = Time IV infusion pump to deliver how many mL/hr? (Round the answer to the nearest whole number.) 100 mL X mL/hr = 0.75 hr USING RATIO AND PROPORTION X mL/hr = 133.333333 mL/hr STEP 1: What is the unit of measurement the nurse STEP 6: Round, if necessary. should calculate? 133.333333 rounds to 133 mL/hr STEP 7: Determine whether the amount to administer STEP 2: What is the volume the nurse should infuse? makes sense. If the prescription reads 100 mL to infuse 100 mL over 45 min (0.75hr), it makes sense to administer 133 mL/hr. The nurse should set the IV pump to deliver STEP 3: What is the total infusion time? cefotaxime 1 g in 100 mL of 0.9% NaCl IV at 133 mL/hr. 45 min STEP 4: Should the nurse convert the units of USING DIMENSIONAL ANALYSIS measurement? STEP 1: What is the unit of measurement the nurse should Yes (min does not equal hr) calculate? (Place the unit of measure being calculated on 60 min 45 min the left side of the equation.) 1 hour = X hr X mL/hr = X hr = 0.75 hr STEP 2: Determine the ratio that contains the same unit as STEP 5: Set up an equation and solve for X. the unit being calculated. (Place the ratio on the right side X mL Volume (mL) of the equation ensuring that the unit in the numerator = matches the unit being calculated.) hr Time (hr) 100 mL X mL/hr = 30 min X mL 100 mL = hr 0.75 hr X mL/hr = 133.333333 mL/hr STEP 6: Round, if necessary. 133.3333 rounds to 133 RN PHARMACOLOGY FOR NURSING CHAPTER 3 DOSAGE CALCULATION 25  STEP 3 : Place any remaining ratios that are relevant to STEP 5: Set up the equation and solve for X. the item on the right side of the equation along with any Volume (mL) x drop factor (gtt/mL) needed conversion factors to cancel out unwanted units of X = Time (min) measurements. 100 mL 60 min 1,500 mL 15 gtt X mL/hr = × X gtt/min = × 45 min 1 hr 600 min 1 mL STEP 4: Solve for X. X gtt/min = 37.5 gtt/min X mL/hr = 133.333333 mL/hr STEP 6: Round, if necessary. STEP 5: Round, if necessary. 37.5 rounds to 38 133.333333 rounds to 133 STEP 7: Determine whether the IV flow rate makes sense. If the prescription reads 1,500 mL to infuse over 10 hr STEP 6: Determine whether the IV flow rate makes sense. (600 min), it makes sense to administer 38 gtt/min. The If the prescription reads 100 mL to infuse over 45 min nurse should adjust the manual IV infusion to deliver LR (0.75 hr), it makes sense to administer 133 mL/hr. The 1,500 mL IV at 38 gtt/min. nurse should set the IV pump to deliver cefotaxime 1 g in 100 mL of 0.9% NaCl IV at 133 mL/hr. USING DESIRED OVER HAVE STEP 1: What is the unit of measurement the nurse MANUAL IV INFUSIONS should calculate? If an electronic infusion pump is not available, regulate gtt/min the IV flow rate using the roller clamp on the IV tubing. When setting the flow rate, count the number of drops STEP 2: What is the volume the nurse should infuse? that fall into the drip chamber over 1 min. Then calculate 1,500 mL the flow rate using the drop factor on the manufacturer’s package containing the administration set. The drop STEP 3: What is the total infusion time? factor is the number of drops per milliliter of solution. 10 hr Example: A nurse is preparing to administer STEP 4: Should the nurse convert the units of lactated Ringer’s (LR) 1,500 mL IV to infuse over measurement? 10 hr. The drop factor of the manual IV tubing is Yes (hr does not equal min) 15 gtt/mL. The nurse should adjust the manual IV infusion to deliver how many gtt/min? (Round the 60 min x 10 hr X hr = answer to the nearest whole number. Use a leading 1 hr zero if it applies. Do not use a trailing zero.) X min = 600 min STEP 5: Set up the equation and solve for X. USING RATIO AND PROPORTION Volume (mL) x drop factor (gtt/mL) STEP 1: What is the unit of measurement the nurse X = Time (min) should calculate? gtt/min 1,500 mL 15 gtt X gtt/min = × 600 min 1 mL STEP 2: What is the volume the nurse should infuse? X gtt/min = 37.5 gtt/min 1,500 mL STEP 6: Round, if necessary. STEP 3: What is the total infusion time? 37.5 rounds to 38 10 hr STEP 7: Determine whether the IV flow rate makes sense. STEP 4: Should the nurse convert the units of If the prescription reads 1,500 mL to infuse over 10 hr measurement? No (mL = mL) Yes (hr ≠ min) (600 min), it makes sense to administer 38 gtt/min. The 1 hr 10 hr nurse should adjust the manual IV infusion to deliver LR 60 min = X min 1,500 mL IV at 38 gtt/min. X min = 600 min USING DIMENSIONAL ANALYSIS STEP 1: What is the unit of measurement the nurse should calculate? (Place the unit of measure being calculated on the left side of the equation.) X gtt/min = 26 CHAPTER 3 DOSAGE CALCULATION CONTENT MASTERY SERIES  STEP 2: Determine the ratio that contains the same unit as STEP 6: Round if necessary. the unit being calculated. (Place the ratio on the right side 33.333333 rounds to 33 of the equation ensuring that the unit in the numerator matches the unit being calculated.) STEP 8: Determine whether the IV flow rate makes sense. If the amount prescribed is 100 mL to infuse over 30 min, 10 gtt X gtt/min = it makes sense to administer 33 gtt/min. The nurse should 1 mL adjust the manual IV infusion to deliver ranitidine 150 mg STEP 3: Place any remaining ratios that are relevant to in 100 mL of 0.9% NaCl IV at 33 gtt/min. the item on the right side of the equation along with any needed conversion factors to cancel out unwanted units of measurements. USING DIMENSIONAL ANALYSIS STEP 1: What is the unit of measure to calculate? (Place 10 gtt 1,500 mL 1 hr X gtt/min = × × the unit of measure being calculated on the left side of the 1 mL 10 hr 60 min equation.) STEP 4: Solve for X. X gtt/min = X gtt/min = 37.5 gtt/min STEP 2: Determine the ratio that contains the same unit as STEP 5: Round, if necessary. the unit being calculated. (Place the ratio on he right side of the equation ensuring that the unit in the numerator 37.5 rounds to 38 matches the unit being calculated.) STEP 6: Determine whether the IV flow rate makes sense. 10 gtt If the prescription reads 1,500 mL to infuse over 10 hr X gtt/min = 1 mL (600 min), it makes sense to administer 38 gtt/min. The nurse should adjust the manual IV infusion to deliver LR STEP 3: Place any remaining ratios that are relevant to 1,500 mL IV at 38 gtt/min. the item on the right side of the equation along with any needed conversion factors to cancel out unwanted units of measurements. 10 gtt 100 mL Example: A nurse is preparing to administer X gtt/min = × 1 mL 30 min ranitidine 150 mg by intermittent IV bolus. Available is ranitidine 150 mg in 100 mL of 0.9% sodium STEP 4: Solve for X. chloride (0.9% NaCl) to infuse over 30 min. The X gtt/min = 33.333333 gtt/min drop factor of the manual IV tubing is 10 gtt/mL. The nurse should adjust the manual IV infusion STEP 5: Round if necessary. to deliver how many gtt/min? (Round the answer 33.333333 rounds to 33 to the nearest whole number. Use a leading zero if it applies. Do not use a trailing zero.) STEP 6: Determine whether the IV flow rate makes sense. If the amount prescribed is 100 mL to infuse over 30 min, it makes sense to administer 33 gtt/min. The nurse should USING RATIO AND PROPORTION adjust the manual IV infusion to deliver ranitidine 150 mg AND DESIRED OVER HAVE in 100 mL of 0.9% NaCl IV at 33 gtt/min. STEP 1: What is the unit of measurement the nurse should calculate? gtt/min STEP 2: What is the volume the nurse should infuse? 100 mL STEP 3: What is the total infusion time? 30 min STEP 4: Should the nurse convert the units of measurement? No STEP 5: Set up the equation and solve for X. Volume (mL) x drop factor (gtt/mL) X = Time (min) 100 mL 10gtt X gtt/min = × 30 min 1 mL X gtt/min = 33.333333 gtt/min RN PHARMACOLOGY FOR NURSING CHAPTER 3 DOSAGE CALCULATION 27  Application Exercises 1. A nurse is preparing to administer vancomycin 1 g by 5. A nurse is preparing to administer amoxicillin 20 mg/kg/ intermittent IV bolus. Available is vancomycin 1 g in day PO to divide equally every 12 hr to a preschooler 100 mL of dextrose 5% in water (D5W) to infuse over 45 who weighs 44 lb. The amount available is amoxicillin min. The drop factor of the manual IV tubing is 10 gtt/ suspension 250 mg/5 mL. How many mL should the mL. The nurse should adjust the manual IV infusion to nurse administer per dose? (Round the answer to the deliver how many gtt/min? (Round the answer to the nearest whole number. Do not use a trailing zero.) nearest whole number. Do not use a trailing zero.) 6. A nurse is preparing to administer heparin 15,000 units 2. A nurse is preparing to administer clindamycin 200 subcutaneously every 12 hr. The amount available mg by intermittent IV bolus. The amount available is heparin injection 20,000 units/mL. How many mL is clindamycin injection 200 mg in 100 mL 0.9% should the nurse administer per dose? (Round the sodium chloride (0.9% NaCl) to infuse over 30 min. answer to the nearest tenth. Do not use a trailing zero.) The nurse should set the IV pump to deliver how many mL/hr? (Round the answer to the nearest whole number. Do not use a trailing zero.) 7. A nurse is preparing to administer acetaminophen 650 mg PO every 6 hr PRN for pain. The amount available is acetaminophen liquid 500 mg/5 mL. 3. A nurse is preparing to administer furosemide 80 How many mL should the nurse administer per mg PO daily. The amount available is furosemide dose? (Round the answer to the nearest tenth. Use a oral solution 10 mg/1 mL. How many mL should leading zero if it applies. Do not use a trailing zero.) the nurse administer? (Round the answer to the nearest whole number. Do not use a trailing zero.) 8. A nurse is preparing to administer dextrose 5% in water (D5W) 750 mL IV to infuse over 6 hr. The 4. A nurse is preparing to administer haloperidol nurse should set the IV pump to deliver how 2 mg PO every 12 hr. The amount available is many mL/hr? (Round the answer to the nearest haloperidol 1 mg/tablet. How many tablets should whole number. Do not use a trailing zero.) the nurse administer? (Round the answer to the nearest whole number. Do not use a trailing zero.) 28 CHAPTER 3 DOSAGE CALCULATION CONTENT MASTERY SERIES  Application Exercises Key 1. 22 gtt/min Using Ratio and Proportion and Desired Over Have Using Dimensional Analysis STEP 1: What is the unit of measurement the STEP 1: What is the unit of measurement the nurse nurse should calculate? gtt/min should calculate? (Place the unit of measure being calculated on the left side of the equation.) STEP 2: What is the total infusion time? 45 min STEP 3: What is the volume the nurse should infuse? 100 mL X gtt/min = STEP 2: Determine the ratio that contains the same STEP 4: Should the nurse convert the units of measure? No unit as the unit being calculated. (Place the ratio on the STEP 5: Set up an equation and solve for X. right side of the equation ensuring that the unit in the numerator matches the unit being calculated.) Volume (mL) X gtt/mL = × Drop factor (gtt/mL) 10 gtt Time (min) X gtt/min = 1 mL 100 mL STEP 3: Place any remaining ratios that are relevant to the item on X gtt/mL = × 10 gtt/mL 45 min the right side of the equation along with any needed conversion factors to cancel out unwanted units of measurements. X gtt/mL = 22.222222 gtt/mL 100 mL 100 mL STEP 6: Round, if necessary. 22.2222 rounds to 22 X mL/hr = × 0.5 hr 45 min STEP 7: Determine whether the IV flow rate makes sense. If the STEP 4: Solve for X. amount prescribed is 100 mL to infuse over 45 min, it makes X gtt/min = 22.222222 gtt/min sense to administer 22 gtt/min. Adjust the manual IV infusion to deliver vancomycin 1 g in 100 mL of D 5W IV at 22 gtt/min. STEP 5: Round if necessary. 22.2222 rounds to 22 STEP 6: Determine whether the IV flow rate makes sense. If the amount prescribed is 100 mL to infuse over 45 min, it makes sense to administer 22 gtt/min. Adjust the manual IV infusion to deliver vancomycin 1 g in 100 mL of D 5W IV at 22 gtt/min. NCLEX® Connection: Pharmacological and Parenteral Therapies, Parenteral/Intravenous Therapies 2. 200 mL/hr Using Ratio and Proportion Using Desired Over Have Using Dimensional Analysis STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement the nurse should calculate? mL/hr the nurse should calculate? mL/hr the nurse should calculate? (Place the unit of measure on the left side of the equation.) STEP 2: What is the volume the STEP 2: What is the volume the nurse should infuse? 100 mL nurse should infuse? 100 mL X mL/hr = STEP 3: What is the total STEP 3: What is the total STEP 2: Determine the ratio that infusion time? 30 min infusion time? 30 min contains the same unit as the unit being calculated. (Place the ratio STEP 4: Should the nurse convert STEP 4: Should the nurse convert the units on the right side of the equation the units of measurement? Yes of measure? Yes (min does not equal hr) ensuring that the unit in the numerator (min does not equal hr) 30 min × 1 hr matches the unit being calculated.) 60 min = 30 min X mL/hr = 60 min 100 mL 1 hr X hr X hr = 0.5 hr X mL/hr = 30 min X hr = 0.5 hr STEP 5: Set up an equation and solve for X. STEP 5: Set up an equation and solve for X. STEP 3: Place any remaining ratios that Volume (mL) 100 mL are relevant to the item on the right X mL/hr = X mL/hr = Volume (mL) 100 mL Time (hr) 0.5 hr side of the equation along with any X mL/hr = X mL/hr = X mL = 200 mL needed conversion factors to cancel Time (hr) 0.5 hr out unwanted units of measurements. X mL = 200 mL STEP 6: Round, if necessary. STEP 6: Round, if necessary. STEP 7: Determine whether the IV flow 100 mL 60 min X mL/hr = × rate makes sense. If the prescription reads 30 min 1 hr STEP 7: Determine whether the IV flow rate makes sense. If the prescription reads 100 mL to infuse over 30 min (0.5 hr), it 100 mL to infuse over 30 min (0.5 hr), it makes sense to administer 200 mL/hr. Set STEP 4: Solve for X. makes sense to administer 200 mL/hr. Set the IV pump to deliver clindamycin 200 mg in 100 mL of 0.9% NaCl IV at 200 mL/hr. X mL/hr = 200 mL/hr the IV pump to deliver clindamycin 200 mg in 100 mL of 0.9% NaCl IV at 200 mL/hr. STEP 5: Round, if necessary. STEP 6: Determine whether the IV flow rate makes sense. If the prescription reads 100 mL to infuse over 30 min (0.5 hr), it makes sense to administer 200 mL/hr. Set the IV pump to deliver clindamycin 200 mg in 100 mL of 0.9% NaCl IV at 200 mL/hr. NCLEX® Connection: Pharmacological and Parenteral Therapies, Parenteral/Intravenous Therapies RN PHARMACOLOGY FOR NURSING CHAPTER 3 DOSAGE CALCULATION 29  3. 8 mL Using Ratio and Proportion Using Desired Over Have Using Dimensional Analysis STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement the nurse should calculate? mL the nurse should calculate? mL the nurse should calculate? (Place the unit of measure being calculated STEP 2: What is the dose the STEP 2: What is the dose the on the left side of the equation.) nurse should administer? Dose to nurse should administer? Dose to administer = Desired = 80 mg administer = Desired = 80 mg X mL = STEP 3: What is the dose available? STEP 3: What is the dose available? STEP 2: Determine the ratio that Dose available = Have = 10 mg Dose available = Have = 10 mg contains the same unit as the unit being calculated. (Place the ratio STEP 4: Should the nurse convert STEP 4: Should the nurse convert on the right side of the equation the units of measurement? No the units of measurement? No ensuring that the unit in the numerator STEP 5: What is the quantity of the STEP 5: What is the quantity of the matches the unit being calculated.) dose available? = Quantity = 1 mL dose available? = Quantity = 1 mL 1 mL STEP 6: Set up the equation STEP 6: Set up the equation X mL = 10 mg and solve for X. and solve for X. STEP 3: Place any remaining ratios that are relevant to the item on the right Have Desired 10 mg 80 mg Desired × Quantity side of the equation along with any = = X = Quantity X 1 mL X mL Have needed conversion factors to cancel out unwanted units of measurements. X mL = 8mL 80 mg × 1 mL X mL = 1 mL 80 mg STEP 7: Round, if necessary. 10 mg X mL = 10 mg × 1 STEP 8: Determine whether the amount X mL = 8 mL STEP 4: Solve for X. to administer makes sense. If there are 10 STEP 7: Round, if necessary. mg/1 mL and the prescription reads 80 X mL = 8 mL mg, it makes sense to administer 8 mL. STEP 8: Determine whether the amount to administer makes sense. If there are 10 STEP 5: Round, if necessary. Administer furosemide 8 mL PO daily. mg/1 mL and the prescription reads 80 STEP 6: Determine whether the amount mg, it makes sense to administer 8 mL. to administer makes sense. If there are 10 Administer furosemide 8 mL PO daily. mg/1 mL and the prescription reads 80 mg, it makes sense to administer 8 mL. Administer furosemide 8 mL PO daily. NCLEX® Connection: Pharmacological and Parenteral Therapies, Dosage Calculation 4. 2 tablets Using Ratio and Proportion Using Desired Over Have Using Dimensional Analysis STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement the nurse should calculate? tablet the nurse should calculate? tablet the nurse should calculate? (Place the unit of measure being calculated STEP 2: What is the dose the STEP 2: What is the dose the on the left side of the equation.) nurse should administer? Dose to nurse should administer? Dose to administer = Desired = 2 mg administer = Desired = 2 mg X tablet(s)/dose = STEP 3: What is the dose available? STEP 3: What is the dose available? STEP 2: Determine the ratio that Dose available = Have = 1 mg Dose available = Have = 1 mg contains the same unit as the unit being calculated. (Place the ratio STEP 4: Should the nurse convert STEP 4: Should the nurse convert on the right side of the equation the units of measurement? No the units of measurement? No ensuring that the unit in the numerator STEP 5: What is the quantity of the STEP 5: What is the quantity of the matches the unit being calculated.) dose available? = Quantity = 1 tablet dose available? = Quantity = 1 tablet 1 tablet X tablet(s)/dose = 1 mg STEP 6: Set up the equation STEP 6: Set up the equation and solve for X. and solve for X. STEP 3: Place the remaining ratios that are relevant to the item on the right Have Desired 1 mg 2 mg Desired × Quantity side of the equation along with any = = X = Quantity X 1 tablet X tablets Have needed conversion factors to cancel out unwanted units of measurement. X tablet(s) = 2 tablets 2 mg × 1 tablet X tablet(s) = 1 tablet 2 mg STEP 7: Round, if necessary. 1 mg X tablet(s)/dose = × 1 mg 1 dose STEP 8: Determine whether the X tablet(s) = 2 tablets STEP 4: Solve for X. amount to administer makes sense. If there is 1 mg/tablet and the STEP 7: Round, if necessary. X tablet(s)/dose = 2 tablets/dose prescription reads 2 mg, it makes sense STEP 8: Determine whether the STEP 7: Round, if necessary. to administer 2 tablets. Administer amount to administer makes sense. haloperidol 2 tablets every 12 hr. STEP 8: Determine whether the If there is 1 mg/tablet and the amount to administer makes sense. prescription reads 2 mg, it makes sense If there is 1 mg/tablet and the to administer 2 tablets. Administer prescription reads 2 mg, it makes sense haloperidol 2 tablets every 12 hr. to administer 2 tablets. Administer haloperidol 2 tablets every 12 hr. NCLEX® Connection: Pharmacological and Parenteral Therapies, Dosage Calculation 30 CHAPTER 3 DOSAGE CALCULATION CONTENT MASTERY SERIES  5. 4 mL Using Ratio and Proportion Using Desired Over Have Using Dimensional Analysis STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement the nurse should calculate? kg the nurse should calculate? kg the nurse should calculate? (Place the unit of measure being calculated STEP 2: Set up an equation and solve for X. STEP 2: Set up an equation and solve for X. on the left side of the equation.) 2.2 lb Client’s weight in kg Client’s weight in lb × 1 kg 1 kg = X kg = 2.2 lb X mL/dose= X kg STEP 2: Determine the ratio that 2.2 lb 44 lb 44 lb × 1 kg contains the same unit as the unit = X kg = 2.2 lb being calculated. (Place the ratio 1 kg X kg X kg = 20 kg on the right side of the equation X kg = 20 kg ensuring that the unit in the numerator STEP 3: What is the unit of measurement STEP 3: What is the unit of measurement matches the unit being calculated.) the nurse should calculate? mg the nurse should calculate? mg 5 mL STEP 4: Set up an equation and solve for X. X mL/dose = STEP 4: Set up an equation and solve for X 250 mg X = Dose per kg x Client’s weight in kg X = Dose per kg x Client’s weight in kg STEP 3: Place any remaining ratios that are relevant to the item on the right X mg = 20 mg/kg/day x 20 kg X mg = 20 mg/kg/day x 20 kg side of the equation along with any X mg = 400 mg/day X mg = 400 mg/day needed conversion factors to cancel out unwanted units of measurements. X mL 5 mL 20 mg 1 kg 44 lb 1 day 12 hr The dose is divided equally every The dose is divided equally every = × × × × × 12 hr; therefore, divide X by 2. dose 250 mg 1 kg 2.2 lb 1 day 24 hr 2 dose 12 hr; therefore, divide X by 2. STEP 4: Solve for X. 400 mg 400 mg = 200 mg = 200 mg X mL/dose = 4 mL/dose 2 2 STEP 5: What is the unit of measurement STEP 5: What is the unit of measurement STEP 5: Round, if necessary. the nurse should calculate? mL the nurse should calculate? mL STEP 6: Determine whether the amount STEP 6: What is the dose the STEP 6: What is the dose the to give makes sense. If there are 250 mg/5 nurse should administer? Dose to nurse should administer? Dose to mL and the prescription reads 200 mg, administer = Desired = 200 mg administer = Desired 200 mg it makes sense to give 4 mL. Administer amoxicillin suspension 4 mL PO every 12 hr. STEP 7: What is the dose available? STEP 7: What is the dose available? Dose available = Have = 250 mg Dose available = Have = 250 mg STEP 8: Should the nurse convert STEP 8: Should the nurse convert the units of measurement? No the units of measurement? No STEP 9: What is the quantity of the STEP 9: What is the quantity of the dose available? = Quantity = 5 mL dose available? = Quantity = 5 mL STEP 10: Set up the equation STEP 10: Set up an equation and solve for X. and solve for X. Desired × Quantity X = Have Desired 250 mg 200 mg Have = = Quantity X 5 mL X mL 200 mg × 5 mL X mL = 4 mL X mL = 250 mg STEP 11: Round, if necessary. X mL = 4 mL STEP 12: Determine whether the amount STEP 11: Round, if necessary. to give makes sense. If there are 250 mg/5 STEP 12: Determine whether the amount mL and the prescription reads 200 mg, to give makes sense. If there are 250 mg/5 it makes sense to give 4 mL. Administer mL and the prescription reads 200 mg, amoxicillin suspension 4 mL PO every 12 hr. it makes sense to give 4 mL. Administer amoxicillin suspension 4 mL PO every 12 hr. NCLEX® Connection: Pharmacological and Parenteral Therapies, Dosage Calculation RN PHARMACOLOGY FOR NURSING CHAPTER 3 DOSAGE CALCULATION 31  6. 0.8 mL Using Ratio and Proportion Using Desired Over Have Using Dimensional Analysis STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement STEP 1: What is the units of measurement the nurse should calculate? mL the nurse should calculate? mL the nurse should calculate? (Place the unit of measure being calculated STEP 2: What is the dose the STEP 2: What is the dose the on the left side of the equation.) nurse should administer? Dose to nurse should administer? Dose to administer = Desired = 15,000 units administer = Desired = 15,000 units X mL = STEP 3: What is the dose available? STEP 3: What is the dose available? STEP 2: Determine the ratio that Dose available = Have = 20,000 units Dose available = Have = 20,000 units contains the same units as the unit being calculated. (Place the ratio STEP 4: Should the nurse convert STEP 4: Should the nurse convert on the right side of the equation the units of measurement? No the units of measurement? No ensuring that the unit in the numerator STEP 5: What is the quantity of the STEP 5: What is the quantity of the matches the unit being calculated.) dose available? = Quantity = 1 mL dose available? = Quantity = 1 mL 1 mL STEP 6: Set up the equation and solve for X. STEP 6: Set up an equation and solve for X. X mL = 20,000 units Have Desired Desired × Quantity STEP 3: Place any remaining ratios that = X = are relevant to the item on the rights Quantity X Have side of the equation along with any 20,000 units 15,000 units 15,000 units × 1 mL needed conversion factors to cancel = X mL = out unwanted units of measurements. 1 mL X mL 20,000 units X mL = 0.75 mL X mL = 0.75 mL 1 mL 15,000 units X mL = × 20,000 units 1 STEP 7: Round, if necessary. 0.75 STEP 7: Round, if necessary. 0.75 rounds to 0.8 STEP 4: Solve for X. rounds to 0.8 STEP 8: Determine whether the amount STEP 8: Determine whether the amount X mL = 0.75 mL to administer makes sense. If there are to administer makes sense. If there are STEP 6: Set up the equation and solve for X. 20,000 units/mL and the prescription reads 10,000 units/mL and the prescription reads 15,000 units, it makes sense to administer 8,000 units, it makes sense to administer Have Desired = 0.8 mL. Administer heparin injection 0.8 mL. Administer heparin injection Quantity X 0.8 mL subcutaneously every 12 hr. 0.8 mL subcutaneously every 12 hr. 20,000 units 15,000 units = 1 mL X mL X mL = 0.75 mL STEP 7: Round, if necessary. 0.75 rounds to 0.8 STEP 8: Determine whether the amount to administer makes sense. If there are 10,000 units/mL and the prescription reads 8,000 units, it makes sense to administer 0.8 mL. Administer heparin injection 0.8 mL subcutaneously every 12 hr. NCLEX® Connection: Pharmacological and Parenteral Therapies, Dosage Calculation 32 CHAPTER 3 DOSAGE CALCULATION CONTENT MASTERY SERIES  7. 6.5 mL Using Ratio and Proportion Using Desired Over Have Using Dimensional Analysis STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement STEP 1: What is the unit of measurement the nurse should calculate? mL the nurse should calculate? mL the nurse should calculate? (Place the unit of measure being calculated STEP 2: What is the dose the STEP 2: What is the dose the on the left side of the equation.) nurse should administer? Dose to nurse should administer? Dose to administer = Desired = 650 mg administer = Desired = 650 mg X mL = STEP 3: What is the dose available? STEP 3: What is the dose available? STEP 2: Determine the ratio that Dose available = Have = 500 mg Dose available = Have = 500 mg contains the same unit as the unit being calculated. (Place the ratio STEP 4: Should the nurse convert STEP 4: Should the nurse convert on the right side of the equation the units of measurement? No the units of measurement? No ensuring that the unit in the numerator STEP 5: What is the quantity of the STEP 5: What is the quantity of the matches the unit being calculated.) dose available? = Quantity = 5 mL dose available? = Quantity = 5 mL 5 mL STEP 6: Set up the equation and solve for X. STEP 6: Set up the equation and solve for X. X mL = 500 mg Have Desired Desired × Quantity STEP 3: Place any remaining ratios that = X = are relevant to the item on the right Quantity X Have side of the equation along with any 500 mg 650 mg 650 mg × 5 mL needed conversion factors to cancel = X mL = out unwanted units of measurements. 5 mL X mL 500 mg X mL = 6.5 mL X mL = 6.5 mL 5 mL X mL = 500 mg STEP 7: Round, if necessary. STEP 7: Round, if necessary. STEP 4: Solve for X. STEP 8: Determine whether the amount STEP 8: Determine whether the amount to administer makes sense. If there are to administer makes sense. If there are X mL = 6.5 mL 500 mg/5 mL and the prescription reads 500 mg/5 mL and the prescription reads STEP 6: Set up the equation and solve for X. 650 mg, it makes sense to administer 6.5 650 mg, it makes sense to administer 6.5 mL. Administer acetaminophen liquid mL. Administer acetaminophen liquid Have Desired = 6.5 mL PO every 6 hr PRN for pain. 6.5 mL PO every 6 hr PRN for pain. Quantity X 500 mg 650 mg = 5 mL X mL X mL = 6.5 mL STEP 7: Round, if necessary. STEP 8: Determine whether the amount to administer makes sense. If there are 500 mg/5 mL and the prescription reads 650 mg, it makes sense to administer 6.5 mL. Administer acetaminophen liquid 6.5 mL PO every 6 hr PRN for pain. NCLEX® Connection: Pharmacological and Parenteral Therapies, Dosage Calculation 8. 125 mL/hr Using Ratio and Proportion and Desired Over Have Using Dimensional Analysis STEP 1: What is the unit of measurement the STEP 1: What is the unit of measurement the nurse nurse should calculate? mL/hr should calculate? (Place the unit of measure being calculated on the left side of the equation.) STEP 2: What is the volume the nurse should infuse? 750 mL STEP 3: What is the total infusion time? 6 hr X mL/hr = STEP 2: Determine the ratio that contains the same STEP 4: Should the nurse convert the units of measurement? No unit as the unit being calculated. (Place the ratio on the STEP 5: Set up the equation and solve for X. right side of the equation ensuring that the unit in the numerator matches the unit being calculated.) Volume (mL) 750 mL X mL/hr = X mL/hr = 750 mL Time (hr) 6 hr X mL/hr = 6 hr X mL/hr = 125 mL/hr STEP 3: Place any remaining ratios that are relevant to the item on the right side of the equation along with any needed conversion STEP 6: Round, if necessary. factors to cancel out unwanted units of measurement. STEP 7: Determine whether the IV flow rate makes 750 mL sense. If the prescription reads 750 mL to infuse over X mL/hr = 6 hr 6 hr, it makes sense to administer 125 mL/hr. Set the IV pump to deliver D 5W 750 mL IV at 125 mL/hr. STEP 4: Solve for X. X mL/hr = 1