Equations Flashcards
Calculate filtration fraction
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
MAP = CO X PVR
eg solve for PVR if MAP inc from 95-130mmHg and CO doubled
PVR = MAP/CO = 130%/200% = 65%
Calculating FeNa
Filtered load = GFR x plasma Na
FeNA = Na excretion rate/filtered load
Calculate maintenance dose
MD = (steady state plasma level x clearance)/bioavailability Clearance = clearance x body wt
Calculate GFR
GFR = (urine cr conc x urine flow rate)/plasma cr conc
Calculate FeH20
FeH20 = urine flow rate/GFR
Inulin clearance provides an estimate of what?
GFR
Calculate Renal blood flow given PAH
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
Calculate cardiac output
- CO = SV x HR
2. CO = Rate of O2 consumption/arteriovenous O2 content difference
Calculate volume distribution (L)
amount of drug given(mg)/plasma conc of drug (mg/L)
Relative risk formula
RR = [a/(a+b)] / [c/(c+d)]
Odds ratio formula
OR = ad/bc
Attributable risk percent in the exposed
eg RR = 5. 95% CI (2.9-7.1) calc percent of disease in patient attributed to exposure
ARR = 100 x [(risk in exposed - risk in unexposed)/risk exposed]
ARR = 100 x [(RR-1)/RR]
= 100 x [(5-1)/5)] = 80%
minute ventilation (L/min) Alveolar ventilation (L/Min)
MV = TV (liters) x RR (breaths/min) AV = (TV-dead space vol) x RR