Pre-reg June 2011 - Calculation Revision Section (Leading upto the exam)

[montblanc]

Hi

Ive decided to create this thread as a revision aid, to help with calculations in the upcoming june 2011 exam. I`ll post a question without the answer and let you lot solve it. After that i`ll include the method to solve it. The questions will be similar to the ones in the actual exam. Get your thinking caps on

P.s No cheating & strictly no calculators allowed. Let the solving commence


Mrs X is 45 years old and is concerned that she is overweight. You ask her for her height and weight in order to calculate her body mass index. She weighs 64Kg and she is 1.7m tall.

BMI = [ Weight (kg) ] / [ Height (m) ]2

First statement Second Statement
Mrs X is overweight. A BMI greater than 25kg/m2 indicates that a patient is overweight.


Answer:

A. TRUE TRUE (1st statement true, 2nd statement correct explaination of 1st statement)
B. TRUE TRUE (1st statement true, 2nd statement true, but not correct explaination of 1st)
C. TRUE FALSE
D. FALSE TRUE
E. FALSE FALSE

[JayEm]

D?

[montblanc]

D?

Well done, your right

Its a very straight forward calculation

1.7x1.7 = 2.89

64kg/2.89 = 22kg per m2

Answer is D, she is not overweight. Her bmi is ok. bmi over 25 is overweight

[montblanc]

A 70Kg patient requires a dose of 5mcg/kg/min of dopamine for 2 hours. What rate should a 0.4% w/v infusion be set?

Any brave people want to answer this question

[Nik]

0.0875ml/min

[johnep]

Can you set rate of infusion to four places of decimals?
johnep

[Nik]

Just a generic answer, no options available so just gave in mls/min - otherwise equivalent to 5.25mls/hr. 0.4%w/v dopamine should be given via central line (anything greater than 3.2mg/ml given centrally). One way of calculating inf rate at this strength is as follows:

Inf rate (ml/hr) = Wt (kg) x required rate (mcg/min) x 60/conc of prepared inf (mcg/ml)

Answer after using this is also 5.25mls/hr

[johnep]

So, how are infusion pumps set up mls/min or mls/hour? and are they all the same to avoid confusion?
johnep

[Nik]

Well all depends on vol of infusion to be given. Volumetric pumps used to deliver medium - large volume infusions and can vary rate between 1-999ml/hr usually. For rates lower than 5ml/hr would give by syringe pump as % error increases at this rate. Syringe pumps calibrated in mls/hr (usually 0.1-99ml/hr). If rate to be given is <0.5ml/hr would use an alternative pump, ideally one more specialised for that purpose. Syringe drivers of course run at mm/hr.

[Nik]

A patient is on a continuous intravenous drip of drug B. He needs to be dosed at a rate of 25 mg/h. The drip is set to administer 10 drops of fluid/h, with 4 drops equalling 1 mL in volume. Which of the following is the concentration of drug B in the intravenous fluid?

A 1 mg/mL
B 10 mg/mL
C 5 mg/mL
D 2.5 mg/mL
E 25 mg/mL