Calculations IV: Clinical Flashcards
IBW/AdjBW, TBW, BMI, flow rates, CrCl, ABG (acid/base), % ionization, calcium salt calculations, ANC calc
BMI equation
BMI = kg/m2
IBW equations
male: 50 + (2.3 x “ >5ft)
female: 45.5 + (2.3 x “ >5ft)
AdjBW equation
ABW = IBW + 0.4(TBW-IBW)
When TBW is >/= ____% of IBW, must consider drug in question for which body weight to use
When TBW >/= 120% of IBW
When TBW >/= 120% of IBW, which medications require IBW for calculations
aminophylline
theophylline
acyclovir
levothyroxine
When TBW >/= 120% of IBW, use TBW for these drugs
LMWH
UFH
vancomycin
When TBW >/= 120% of IBW, use AdjBW for these drugs
aminoglycosides
CrCl equation
[140-Age] x IBW (x0.85 if female)
72 x SCr
Acid Base normal values
7.35 / 40 / 24
pH /CO2/HCO3
Anion Gap
equation
normal value
AG = Na - Cl - HCO3
Normal is <12
When pH = pKa, ___% will be ionized and ___% will be in salt form (unionized)
50% and 50%!!
What equation is used to determine the pH of a solution with a weak acid
pH = pKa + log [salt/acid]
What equation is used to determine the pH of a solution with a weak base
pH = pKa + log[base/salt]
How to calculate pKa from pKb
pKa + pKb = 14
equation for % ionization of an acid
% ionization = 100
1+ 10^(pKa-pH)
equation for % ionization of an base
% ionization = 100
1+ 10^(pH-pKa)
Calcium carbonate is ___% elemental Ca and calcium citrate is ___% elemental Ca
A. 40% and 21%
B. 21% and 40%
C. 50% and 21%
D. 21% and 45%
E. 40% and 20%
A. 40% and 21%
a patient is taking aminophylline, but the provider wants to change to theophylline. How do we convert?
aminophylline (0.8) = theophylline
how are aminophylline and theophylline dosed?
based on IBW
How are UFk, LMWH and vanco dosed
based on TBW
How are aminoglycosides dosed
based on adjBW
AdjBW = IBW + 0.4(TBW-IBW)
How do we calculate ANC?
What are the thresholds for neutropenia, severe neutropenia and profound neutropenia?
ANC = WBC x (% segs + %bands)/100
<1000 = neutropenia
<500 = severe neutropenia
<100 = profound neutropenia
