psa cheat sheat Flashcards
Appendix 1 interactions pages
list the 10 calculation types
- Changing units
- Divided doses
- Volumes
- Dilutions
- Percentages
- Rates
- Ratios
- ‘How much more’
- ‘How many’
- Conversions
mass conversion units
1000 nanograms (ng) = 1 microgram (mcg)
1000 micrograms (mcg) = 1 milligram (mg)
1000 milligrams (mg) = 1 gram (g)
what is important for 1.changing units
what are the key points for 2.divided doses type questions
- do not miss it
- remember to convert units if needed
key points and formula for 3.volumes questions
“What volume (ml) of [drug] is required?”
“What volume (ml) of [drug] should be given intravenously”
- not the dose and concentration
- check units
where can body surface area be found
key points for 4.dilutions questions
“What volume (ml) of diluted [drug] should be given intravenously? “
“What volume (ml) of sodium chloride 0.9% is required for this dilution?”
“What volume (ml) of glucose 5% is required for this dilution?”
what does this mean: “Drug B is initially available as a 2.5mg/1ml suspension but requires dilution with an equal volume of sodium chloride 0.9% prior to use.”
1ml + 1ml (adding equal amount) = 2ml
3.2.5mg/1ml = initial concentration
2.5mg/2ml = diluted concentration (x2, 1:2 dilution)
what dose this mean: “Drug B is initially available in 10ml ampoules of 50mg/25ml with each ampoule subsequently diluted with 90ml of sodium chloride 0.9% prior to use.”
10ml of drug with 90ml of diluting solution
1 part drug to 9 parts solution = 1:10 dilution
x10
25ml x 10 = 250ml
50mg/250ml is diluted concentration
how would you approach this question
note the given information
1. initial concentration
2. diluted concentration
3. diluted volume
Note what you need to calculate
1. dose (this doesn’t change) - use the diluted volume and diluted concentration (or whatever you have both of)
2. initial volume using the dose you calculated
what is the question asking for? - in this case what volume of the solution needs to be added to dilute the dose - diluted volume - initial volume
what does concentration mean eg. 25mg/5ml
25mg - amount of drug
5ml - volume of drug solution
so 25mg in a 5ml solution
what does this mean: “Drug B is initially available at a concentration of 2mg/5ml. 1 part of drug B is diluted with 9 parts of glucose 5% prior to use.”
1:10 dilution (x10)
2mg/50ml is diluted concentration
what does this mean: “Drug B is initially available at a concentration of 5mg/1ml. This must be diluted 1-in-20 with sodium chloride 0.9% prior to use.”
dilution 1:20 (x20)
5mg/(1ml x 20)
5mg/20ml - final concentration
key points for 5.rates questions
important thing not to miss when providing the answer for this question
convert min to hours (x60)
key points with 6.percantages
key points about percentages
key points about 7.ratios questions
key points about how much more questions
What additional volume (ml) of [drug] can the patient receive before reaching the maximal dose?
volume = dose/concentration
Calculate the maximal volume:
maximum dose =
Concentration = eg. % = g in mls =g/ml
maximum volume = max dose / concentration
Work out the answer by maximal volume - received volume:
max volume - received volume = answer
key points about 9.how many more questions
eg. “How many 250mg vials of drug B does she require to last her 7 days?”
work out dose
note how much each vial contains
work out how many vials would be needed - eg. dose/amount in vials
round if needed eg. vials need to be discarded
work out how many for 1 day
work out how many for days needed
Steps:
Calculate dose
Calculate vials needed per dose…then per day…then per week
“How many 100ml bottles of drug B does she require to last her 6 weeks?”
Steps:
Calculate dose
Convert units
Calculate bottles needed per dose…then per day…then per week…then per 6 weeks
key points about conversions
“What volume of FerroEss syrup (to the nearest 5ml) is required per day to meet the elemental iron content of her ferrous fumerate tablets?”
Ferrous fumerate 210mg tablets = 70mg elemental iron
70mg x 2 = 140mg elemental iron per day = dose
FerroEss syrup = 45mg/5ml elemental iron = concentration
volume = dose/concentration
volume = 140mg / (45mg/5ml)
= 15.6ml
= 15ml (to the nearest 5ml)
*distractor
oral morphine to subcut conversion
total oral morphine dose + breakthrough doses divided by 2
calculations cheat sheet
