Part A Numeracy

     Example-2

 In what rate you would set the infusion pump to run ?



Equation you can use,

Rate =   Volume divided by Number of hours,

800 ÷ 10 = 80 ml per hour 

Set infusion rate in mg per hour 

An infusion may also be prescribed as a dose in a given amount of fluid to run at ‘x’ mg / hour e.g. 50mg Pethidine in 50mls of Sodium Chloride 0.9% to run at 4mg / hour. Most infusion pumps are set in ml / hour so you need to establish what rate is required

Use the formula,

 
Example,

The prescription reads 100mg of morphine in 50ml of water to run a 5mg / hour. At what rate should you set the pump?

Apply above formula,

5mg ÷ 100mg  X 50 mL  = 2.5 mL per hour

Calculate dose with weight

Body weight is measured in kilograms (kg) and so this dose is usually quoted as mg per kg. Other drugs (particularly cytotoxins) are prescribed in terms of the patient’s body surface area, which is obtained from nomograms. Surface area is measured in square metres and so dosage is quoted as mg per square metre (m²). Therefore, for an individual patient, dosage required is obtained by MULTIPLYING the number of milligrams by that patient’s weight or surface area. 

Example: 70kg man is to have gentamicin 2mg per kg. Dose required: 70 x 2 = 140mg

 
First find out dose required based on the weight, 0.5mg/kg,  for 88 kg 0.5 X 88 = 44 mg
Dose required based on the weight = 44 mg 

Now use the formula,