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

t½ = (0.7 x Vd)/CL

Question 3

Drug clearance

Answer 3

CL = (rate of elimination of drug)/(plasma drug concentation) = Vd x 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 tau)/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

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

Absolutive 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 = Stroke volume x heart rate

Question 18

Mean arterial pressure

Answer 18

MAP = cardiac output x total peripheral resistance

MAP = 2/3 diastolic + 1/3 systolic

Question 19

Ejection fraction

Answer 19

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

Question 20

Resistance

Answer 20

Resistance = driving pressure(change in P) / flow (Q)

= (8n (viscosity) x length)/ (pi r^4)

Question 21

Stroke Volume

Answer 21

SV = EDV - ESV

Question 22

Capillary fluid exchange

Answer 22

Jv = net fluid flow = Kf[(Pc - Pi) - ς(πc − πi)]

Question 23

Renal clearance

Answer 23

Cx = (UxV)/Px

Question 24

Glomerular filtration rate

Answer 24

GFR = Uinulin × V/Pinulin = Cinulin

GFR = Kf [(PGC – PBS) – (πGC – πBS)]

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 extracelular 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 - P L atrium)/cardiac output

Question 32

Alveolar gas equation

Answer 32

PAO2 = PIO2 - (PaCO2/R)