6 Revision of nursing calculations
The following two exercises revise the calculations covered in Chapters 2–5.
Revision exercise 6A
1 450 mg of soluble aspirin is required. Stock on hand is 300 mg tablets. How many tablets should be given?
2 Warfarin tablets are available in strengths of 1 mg, 2 mg, 5 mg and 10 mg. Choose the best combination of whole tablets for each of the following dosages of warfarin. a 4 mg b 8 mg c 12 mg
3 A solution contains paracetamol 120 mg/5 mL. How many milligrams of paracetamol are in a 15 mL b 25 mL c 40 mL of the solution?
4 A patient is prescribed 360 mg of penicillin PO. The strength of the stock syrup is 125 mg per 5 mL. Calculate the volume required.
5 A patient is prescribed benzylpenicillin 1200 mg IV. Stock ampoules contain 1 g in 5 mL. Is the volume to be drawn up for injection equal to 5 mL, less than 5 mL or more than 5 mL?
6 Stock ampoules of erythromycin contain 300 mg/10 mL. Calculate the volume required for injection when a patient is prescribed erythromycin 135 mg IM.
7 400 mg of benzylpenicillin is to be given IV. On hand is benzylpenicillin 600 mg in 2 mL. What volume should be drawn up?
8 A male patient is receiving one litre of dextrose 5% at a rate of 25 mL/hr. How much of the solution will he receive over a 3 hr b 5 hr c 12 hr?
9 One litre of Hartmann’s solution is to be given over 12 hours. Calculate the required flow rate of a volumetric infusion pump.
10 140 mL of fluid containing 600 mg of vancomycin is to be given over 50 minutes. Calculate the required pump setting in mL/hr.
11 700 mL of Hartmann’s solution is to be given over 8 hours. The IV set delivers 20 drops/mL. What is the required drip rate?
12 A patient is to be given one unit of packed cells over 3 hours. Calculate the drip rate in drops/min if the unit of packed cells holds 250 mL and the giving set emits 20 drops per mL. Give the answer to the nearest whole number.
13 800 mL of fluid is to be given IV. The fluid is run at 70 mL/hr for the first 5 hours then the rate is reduced to 60 mL/hr. Calculate the total time taken to give the 800 mL.
14 A patient is prescribed pethidine 400 mg in 500 mL of normal saline. The solution is to be infused via an infusion pump at between 10 and 40 mL/hr, depending on the nurse’s assessment of the patient’s pain.
c At what rate should the pump be set to deliver 20 mg/hr? (Give the answer to the nearest whole number.)
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