Dosage Calc Help Needed Please...

[chamrob]

hi -- i am stumped on a few of my practice dosage calcs. can you please clarify if i am setting up correctly or show me the correct way??

order: d5w at 50 ml/hr

how much dextrose is the patient getting per hour?

i know that d5w is 5g of dextrose and 5 g = 5000 mg/ml

from there i am not sure, but have worked it 5000 mg/50ml per hour = 100 mg

do i need to incorporate the 1000 ml/bag into the equation? if so, how?

also, when calculating ml/hr, can you verify i am rounding correctly?? some sample problems i have are:

vancomycin 625mg/50ml over 1-1/2 hours = 33.33 = 33 ml/hr

order: rocephin 500 mg im

have: rocephin powder instructions state to dilute with 2ml lidocaine to yield a concentration of 325 mg/ml

i worked it out as: 500 mg / 325 mg x 1 ml = 1.538 = 1.5 ml

order: diflucan 6mg/kg/day on the first day. then 3 mg/kg/day days 2-14.

supply:diflucan 10mg/ml

child's weight: 7.74 kg

how many millileters would you give on day 1?

i worked it out as: (6mg x 7.4kg x 1ml) / (10mg x 1 day) = 4.644ml = 4.64ml (rounded to hundredths because it is a child)

thank you!!

[2ndyearstudent, CNA]

D5W means 5% Dextrose in Water. % = grams per 100 ml.

So if there are 5g per 100ml and the pt gets 50 ml per hour...they are getting 2.5 g grams per hour.

Your rounding looked OK.

[chamrob]

2ndyearstudent thanks for taking time to respond!!! MUCH Appreciated!!!

OK -- We have the same thought process on D5W = 5% Dextrose in H20 = 5 g/100mL

to that I add = 5000mg/mL and then divide by 2 = 2500mg the patient is receiving (since the requested answer is in mg)???

How would you work it out? This one is just not clicking with me...

[anonymousstudent]

2ndyearstudent thanks for taking time to respond!!! MUCH Appreciated!!!

OK -- We have the same thought process on D5W = 5% Dextrose in H20 = 5 g/100mL

to that I add = 5000mg/mL and then divide by 2 = 2500mg the patient is receiving (since the requested answer is in mg)???

How would you work it out? This one is just not clicking with me...

What you are doing is exactly correct. You know that there are 5000 mg/100 mL of D in D5W. So if you want to go up, you multiply it by the number of mg by the same number you multiply the mL by.

So 1000 mL of D5W is 10 times more than 100 mL. So multiply your 5000 mg of D by 10 = 50,000 mg of D in 1L (1000 mL) of D5W.

Part of looking at IV fluids is realizing what amount of mg is normal. The mg of meds we give is very small usually in comparison. The amount of D is going to be a HUGE number when looked at in mg.

[2ndyearstudent, CNA]

2ndyearstudent thanks for taking time to respond!!! MUCH Appreciated!!!

OK -- We have the same thought process on D5W = 5% Dextrose in H20 = 5 g/100mL

to that I add = 5000mg/mL and then divide by 2 = 2500mg the patient is receiving (since the requested answer is in mg)???

How would you work it out? This one is just not clicking with me...

Yes, 2.5 grams per hour is 2500 mg per hour. For the purposes of the question, you don't care about the size of the bag hanging.