Nursing Mathematics PO AND IV CALCULATIONS DOSAGE Calculations: Desired Dose (mg) x Volume (ml) = Volume Desired Dose (ml) (mg) Flow Rate (Drip Rate): Infusion Time: Drip rate (gtt/min) = Volume to be infused (ml) x Drop factor of tubing (gtt/ml) Infusion time (hr) = Total Volume to be INFUSED (ml) Infusion Rate(mL/hr) Example One: The doctor s order reads NaCl 75 ml over a 24-hr shift. a) Calculate the ml/hr. b) How much NaCl will the client receive in a 6-hr shift? c) Calculate the drip rate using a drop factor of 15 gtt/ml. Solution: Part Set Up Operation Answer a) Rate (ml/hr) = Total Volume to be INFUSED (ml) Time(min) = 75 ml 24hr b) Volume (ml) = Rate (ml/hr) x Time (hr) = 31.25 ml x 6 hr hr 31.25 24)75. - 72 3-24 6-48 12-12 3125 x 6 1875 31.25 x 6 187.5 The rate is 31.25 ml. h hr The client will receive 187.5 ml of NaCl in a 6-hr shift.
c) Drip rate(gtt/min) = Volume to be infused (ml) x Tubing factor(gtt/ml) = 31.25 ml x 15 (gtt/ml) Step One 3125 x 15 15625 +3125 46875 31.25 x 15 468.75 Step Two 7.8125 6)468.75-42 487-48 75-6 15-12 3-3 The drip rate is 7.8175 gtt. min Example Two: An IV solution of 144.6 ml at a flow rate of 3 gtt/min using a drop factor of 15 gtt/ml has been ordered to be initiated at 1. a) Calculate the infusion time. b) Calculate the completion time. Solution: Part Set Up Operation & Answer a) Drip rate (gtt/min) = Volume to be infused (ml) x Tubing factor(gtt/ml) 3 (gtt/min) = Volume (ml) x15 (gtt/ml) = Infusion Rate (ml/hr) x15 (gtt/ml) Infusion Rate = 3 (gtt/min) 15 (gtt/ml) = 2 (ml/min) 12 (ml/hr) = 12 (ml/hr) =2 (ml/hr) Infusion time (hr) = Total Volume to be INFUSED (ml) Infusion Rate (ml/hr) = 144.6 ml 12 (ml/hr) b) 8.75 hr = 8 hr +.75 hr.75 hr x = Completion time: 1 + 843 8.75 12)1446. - 96 846-84 6-6 - 6 The infusion time is 8.75 hours. 75.75 x 6 x 6 423 42.3 Thus, 8.75 hours = 8hours 43 min. 1 + 843 1843 Thus, the completion time is 1843.
Practice (answers provided): IT IS IN YOUR BEST INTEREST TO ATTEMPT THE QUESTIONS BY YOURSELF BEFORE CHECKING THE ANSWERS. 1) Prepare an 8mg IV dosage from a vial labeled 5mg/1mL. 2) A dosage of.6 mg is ordered. The label reads 3 mcg/ml. How much will you administer? 3) To administer a dosage of fentanyl.1 mg from an ampule labeled Fentanyl 15 mcg in 2mL. 4) A. Calculate the correct dosage to be administered. Cleocin Phosphate.12 g po bid Source (for label): http://www.dailymedplus.com/monograph/view/setid/5a75685-af5-47c-ac57- e38c882b49d B. How much Cleocin Phosphate will the patient intake in a day?
5) Doctor s order: 36mg Source (for label): http://www.cwladis.com/math14/lecture4.php a. How much diluent should be added to the vial to reconstitute the medication?. b. What s the final concentration after reconstitution? c. How much of the reconstituted medication should be drawn up and added to the minibag? 6) The doctor s order: 1.5 L of NS to be infused in a 12-hr period. The drop factor is 6gtt/mL. Calculate: a. ml/hr b. gtt/min 7) The doctor writes an IV order at 125mL/hr. At the beginning (12) of your shift there is 45mL TBA. The drop factor is 1gtt/mL. a. Calculate the drip rate.
b. What time (military time) will you change the bag? 8) Mr. Jane has an IV order at 12cc/hr. Calculate the drip rate with a drop factor of 1gtt/mL 9) Ordered: Pencillin G potassium 1 million units IV q2h Amount of Sterile Water to be Added (ml): Pfizerpen Penicillin G Potassium 1,, units For Intravenous Infusion ONLY Final Dosage Strength (units/ml): 3 4, 2 6, 8 1,, For dosage information read the accompanying professional Caution: Federal law prohibits information. After reconstitution, discard the unused portion dispensing without prescription. after 24 hours. Source: Math For Meds,6E from Curren, A.M. & Munday, L.D. Ch.12 Pg.13 (modified questions) a. To make a solution with 6, units/ml strength, how much diluent should you add to the vial? b. If the medication in the vial is reconstituted with 8 ml of diluent, what solution strength should you write on the label? c. When reconstituted with 3 ml, how much solution should you administer? d. If doctor s IV order changes to 4,, units of Penincillin G in 27mL of Sterile Water and to infuse over 2 hours. The vial requires reconstitution with 8 ml of sterile water. How much of the medication would you administer now? e. If the drop factor is 1gtt/mL, what is the drip rate of Penincillin G IV?
ANSWER KEY 1) Desired Dose x Volume = 8 mg x 1 ml = 1.6 ml 5 mg 2).6 mg = 6 mcg Desired Dose x Volume = 3).1 mg = 1 mcg Desired Dose x Volume = 6 mcg x 1 ml = 2 ml 3 mcg 1 mcg x 2 ml = 1.33 ml 15 mcg 4) A..12 g = 12 mg Desired Dose x Volume = 12 mg x 5 ml = 1 ml 6 mg B. bid twice a day 1 ml x 2 times = 2 ml per day 5) a. 2 ml of sterile water must be added b. 225 mg/ml c. Desired Dose x Volume = 36 mg x 1 ml = 1.6 ml 225 mg 6) a. The answer must be in ml/hr. This indicates that we have to calculate the infusion rate. Infusion Rate(mL/hr) = Volume (ml) = 15 ml = 125 ml/hr Time (hr) 12 hr b. The answer must be in gtt/min. We must calculate the flow rate/drip rate. Two ways we can do this: Method one: Drip rate (gtt/min) = Volume (ml) x Drop factor (gtt/ml) = 15mL x 6 gtt/ml = 125 gtt/min 5 x Method two: Drip rate (gtt/min) = Volume (ml) x Drop factor (gtt/ml) = 125mL x 6 gtt/ml = 125 gtt/min 7) a. Drip rate (gtt/min) = Volume (ml) x Drop factor (gtt/ml) = 125mL x 1 gtt/ml = 2.83 gtt/min b. Infusion time (hr) = Volume (ml) = 45 ml = 3.6 hr Rate(mL/hr) 125 ml/hr
3.6 hr = 3hr +.6 hr.6 x = 36 min.6 hr = 36 min I will change the bag at: 12+ 336 = 1536 8) 1 cc = 1 ml Drip rate (gtt/min) = Volume (ml) x Drop factor (gtt/ml) = 12 ml x 1 gtt/ml = 2 gtt/min 9) a. We should add 2 ml of sterile water. b. The solution strength will be 1,, units/ml. c. When reconstituted with 3 ml, the dosage strength is 4, units/ml. Desired Dose x Volume = 1,, units x 1 ml = 2.5 ml 4, units d. When reconstituted with 8 ml, the dosage strength is 1,, units/ml. Desired Dose x Volume = 4,, units x 1 ml = 4 ml 1,, units e. Drip rate (gtt/min) = Volume (ml) x Drop factor (gtt/ml) = 27 ml x 1 gtt/ml 2 x = 22.5 gtt/min