Equation Review

Question 1

Volume of distribution

Answer 1

Vd = amount of drug in the body/plasma drug concentration

Question 2

Half-life

Answer 2

t 1/2 = (0.7 x Vd)/Cl

Question 3

Drug clearance

Answer 3

Cl = rate of elimination of drug/plasma drug concentration = Vd x Ke
Ke = elimination constant

Question 4

Loading dose

Answer 4

LD = (Cp x Vd)/F

Question 5

Maintenance dose

Answer 5

D = (Cp x Cl x t)/F

Question 6

Sensitivity

Answer 6

Sensitivity = TP/(TP+FN)

Question 7

Specificity

Answer 7

Specificity = TN/(TN+FP)

Question 8

Positive predictive value

Answer 8

PPV = TP/(TP+FP)

Question 9

Negative predictive value

Answer 9

NPV = TN/(FN+TN)

Question 10

Odds ratio (for case-control studies)

Answer 10

OR = (a/c)/(b/d) = ad/bc

Question 11

Relative risk

Answer 11

RR = (a/(a+b))/(c/(c+d))

Question 12

Attributable risk

Answer 12

AR = (a/(a+b)) - (c/(c+d))

Question 13

Relative risk reduction

Answer 13

RRR = 1 - RR

Question 14

Absolute risk reduction

Answer 14

ARR = (c/(c+d)) - (a/(a+b))

Question 15

Number needed to treat

Answer 15

NNT = 1/ARR

Question 16

Number needed to harm

Answer 16

NNH = 1/AR

Question 17

Cardiac output

Answer 17

CO = rate of O2 consumption/(arterial O2 content - venous O2 content) 
CO = SV x HR

Question 18

Mean arterial pressure

Answer 18

MAP = CO x TPR
MAP = 2/3diastolic BP + 1/3systolic BP

Question 19

Ejection fraction

Answer 19

EF = SV/EDV = (EDV-ESV)/EDV

Question 20

Resistance

Answer 20

R = driving pressure/flow = (8n x l)/(pi x r to the 4th)

Question 21

Stroke volume

Answer 21

SV = EDV-ESV

Question 22

Renal clearance

Answer 22

Cx = UxV/Px

Question 23

Capillary fluid exchange

Answer 23

Jv = net fluid flow = some insanity (look it up)

Question 24

GFR

Answer 24

GFR = Uinulin x V/P inulin = Cinulin

Question 25

Effective renal plasma flow

Answer 25

eRPF = Upah x (V/Ppah) = Cpah

Question 26

Renal blood flow

Answer 26

RBF = RPF/(1 - Hct)

Question 27

Filtration fraction

Answer 27

FF = GFR/RPF

Question 28

Henderson-Hasselbalch equation (for extracellular pH)

Answer 28

pH = 6.1 + log [HCO3/0.03Pco2]

Question 29

Winters formula

Answer 29

PCo2 = 1.5[HCO3-] + 8 +/- 2

Question 30

Physiologic dead space

Answer 30

Vd = Vt x ((PaCO2 - PECO2)/PaCO2)

Question 31

Pulmonary vascular resistance

Answer 31

PVR = (Ppulm artery - Pl atrium)/cardiac output

Question 32

Alveolar gas equation

Answer 32

PAo2 = PIo2 - (Paco2/R)