Equations

Question 1

Calculate filtration fraction

Answer 1

FF = GFR/RPF
RPF (Renal plasma flow) = RBF *(1-hct)

Note: GFR can be esp by inulin or Cr clearance
RPF can be estimated by PAH clearance
FF = Inulin clearance/PAH clearance

Question 2

MAP = CO X PVR

eg solve for PVR if MAP inc from 95-130mmHg and CO doubled

Answer 2

PVR = MAP/CO = 130%/200% = 65%

Question 3

Calculating FeNa

Answer 3

Filtered load = GFR x plasma Na

FeNA = Na excretion rate/filtered load

Question 4

Calculate maintenance dose

Answer 4

MD = (steady state plasma level x clearance)/bioavailability
Clearance = clearance x body wt

Question 5

Calculate GFR

Answer 5

GFR = (urine cr conc x urine flow rate)/plasma cr conc

Question 6

Calculate FeH20

Answer 6

FeH20 = urine flow rate/GFR

Question 7

Inulin clearance provides an estimate of what?

Answer 7

GFR

Question 8

Calculate Renal blood flow given PAH

Answer 8

RBF = PAH clearance/ (1-hct)
RBF = (renal artery pressure - renal v pressure)/renal vascular resistance
Note: RBF is not the same as renal plasma flow

Question 9

Calculate cardiac output

Answer 9

1. CO = SV x HR

2. CO = Rate of O2 consumption/arteriovenous O2 content difference

Question 10

Calculate volume distribution (L)

Answer 10

amount of drug given(mg)/plasma conc of drug (mg/L)

Question 11

Relative risk formula

Answer 11

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

Question 12

Odds ratio formula

Answer 12

OR = ad/bc

Question 13

Attributable risk percent in the exposed

eg RR = 5. 95% CI (2.9-7.1) calc percent of disease in patient attributed to exposure

Answer 13

ARR = 100 x [(risk in exposed - risk in unexposed)/risk exposed]
ARR = 100 x [(RR-1)/RR]
= 100 x [(5-1)/5)] = 80%

Question 14

minute ventilation (L/min)
Alveolar ventilation (L/Min)

Answer 14

MV = TV (liters) x RR (breaths/min)
AV = (TV-dead space vol) x RR