Med Math Conversions/ Tips Flashcards
lb in kg
2.2lb in 1kg
ex) pt is 160lb / 2.2 = 72.72 kg
cm in inches
2.54cm in 1in. Also remember that 12in = 1ft.
Ex) pt is 5’7 = 67in x 2.54 = 170.18 cm
Equation for how many L left in O2 tank based on PSI=
0.33 x PSI in the tank = L of gas left in the tank
ex) tank reads 750PSI
750 * 0.33 = 247.5 L
Equation for how many minutes left in tank if volume is known=
Find the known remaining volume in L, then divide by flow rate in L/min.
“x” L / (“y”L/min)
ex) The known volume remaining in a tank is 247.5L and the pt is receiving 4L/min. How many minutes remaining does te tank have at that rate?
247.5L / 4L/min = 61.87 ~ 62 min
1:100,000 Epi means what?
This means there is 1g in 100,000 mL of solution.
OR rewrite it as 1000mg / 100,000mL OR better yet, 1,000,000mcg / 100,000mL
-1g has many “nicknames”, the amount has not changed, just its units
1g/100,000mL = 1,000,000mcg/100,000mL=
10mcg/mL
How many mg/mL in a % conc solution?
Whatever the percent is, just move decimal one space to the right for mg/mL
Ex) 0.75% Bupivicaine = 7.5mg/mL
How to get % conc of a solution from mg/mL?
1g/100mL = %
OR
if in mg/mL already, just move decimal one place to left to get the % concentration
Ex) 500mg/mL solution= 0.5gm/mL [[*100 to get 100mL]] = 50gm/100mL OR 50% solution
Ex)500mg/mL solution = 50%
How to get mg/mL from a premixed bag?
Do math needed to get the volume of the bag to 1000mL (apply math to dose too) then divide by 1000
Ex) 4mg norepinephrine in 250mL bag
4 in 250 x 4 = 16mg/1000mL OR 0.016mcg/mL
Ex) Mag sulfate 2g in 100mL
2g in 100mL x 10 = 20g/1000mL OR 0.02g/mL Or 20mg/mL
How to: Double dilute Epi
Take 1mg/mL dose and dilute it in 9mL diluent(saline) to get new dose. Then do that again with another 9mL of diluent.
(In real life, epi comes in the brown box CPR amp we are all familair with that has a concentration of 1mg in 10mL(1:10,000) or it often comes in 1mg/mL vials (1:1,000). Pay attention to the concentration!! They are not always the same.)
ex) Someone hands you a vial of Epi that has 1:1,000 on it. Double dilute it and give dose in mcg/mL.
Step1: Figure out mg/mL from concentration.
-Epi vial 1:1,000 = 1g/1,000mL = 1,000mg/1,000mL = 1mg/mL OR 1,000mcg/mL
Step 2: Take 10ml syringe and draw up the 1mL of Epi, then draw up 9mL diluent(saline), giving you100mcg/10mL OR 100mcg/mL
Step 3: Take another 10mL syringe and draw up 1mL of that mixture, followed by another 9mL of saline, giving you 100mcg/10mL OR 10mcg/mL
MAP Equation (Memorize this! It will come back and haunt you more than once!)
MAP = [SBP+ (DBPx2)] / 3
IDEAL BW
IBW is usually expressed as kg and is used to find appropriate Vt and sometimes different loading or infusion doses. (Remifentanil, propofol, etc.)
There are 2 ways to learn how to do this, an easy and a hard way. Both ways you can get screwed on an exam if you forget the conversion for inches into cm (1in = 2.54cm) and lbs into kg (2.2lb=1kg). The exam questions can give you the patient’s data in feet or in cm and it is fair game. The easy way requires you to remember 2 basic equations. The hard way requires you remember 2 equations with flipped numbers and slightly more math. JUST LEARN THE EASY WAY
Hard way:
women = 100lb + (5lb x inches over 5’)
men = 105lb + (6lb x inches over 5’)
Easy way:
women IBW in kg = ht in cm - 105cm
men IBW in kg= ht in cm - 100cm
Ex) Hard way: What is the IBW in kg of a 166cm woman?
166cm / (1in/2.54cm) = 65.354in / (1ft/12in)= 5ft, 5.35 in
Equation= 100lb + (5lb x 5.35in) = 126.75lb (1kg/2.2lb) = 57.6kg
Ex) Easy way: A man is 6’5. What is his IBW in kg?
6ft 5 in = 72in + 5 in = 77in (2.54cm/1in)= 195.58cm
Equation= 195.58cm -100cm = 95.58kg
-Pretty simple, but see how much easier that would have been if they threw you the bone of giving their ht in cm off the bat?
BMI equation
Wt(in kg)/ [(Ht in m)^2]
ABL (know this for exams and careplans)
ABL = [EBV (preop Hct- final Hct)]
/
preop Hct
EBV (know this for exams and care plans!)
preme= 90-105mL/kg
full term= 80-90mL/kg
infant= 70-75mL/kg
men= 70mL/kg
women= 65mL/kg
“_% of medication errors occur in the OR”
81% :(
