Download Physiology Equations

Physiology Equations
Intracellular = TBW – ECF
Interstitial = ECF – Plasma
Blood Volume = Plasma / (1-Hematocrit)
TBW = (140 * (BW*0.6)) / [Na+]*
*[Na+] is the abnormal concentration of Na+ in the blood
RBF (renal blood flow) = 1200 ml/min
RPF (renal plasma flow) = 650 ml/min (55% of RBF)
Flow (Q) = Change in Pressure (P) / Resistance (R)
Fick Equation
RBF = Renal O2 Consumption / Renal (a-v)O2
Starling Hypothesis
GFR = Kf [(Pc – Pi) - (p)]
Large Kf is the MAIN reason for high filtration rate in kidney
Tension
T = (Po – Pi) r
Clearance
C = U*V/P
Clearance
Urine concentration
Velocity of excretion
Plasma concentration
GFR = C(inulin)
GFR ~= C(creatinine)
Excretion rate (amount excreted per unit time) = U*V
Filtered Load (amount filtered per unit time) = P*GFR
Tx(reaborption) = (Px*GFR) – (Ux*V)
Tx(secretion) = (Ux*V) – (Px*GFR)
*note for GFR, Cin or Ccr can be substituted
Tx = tubular transport rate
RPF = Renal Plasma Flow
Q = RPF(A-V)
Q – rate
Renal Plasma Flow
Arterial plasma concentration (can also be P)
Venous concentration
PAH is used as an indicator
RPF*(Ppah) = U(pah)*V
RPF = Upah*V/Ppah = C (clearance) = ERPF (effective renal plasma flow)
Extraction ratio
E = A-V/A
Arterial plasma concentration
Venous concentration
True renal plasma flow
C/E
Filtration fraction
GFR/RPF = C(in)/C(pah)
Osmol Clearance
C(osmol) = U(osmol)*V/P(osmol)
Free water clearance
C(h2o) = V – C(osmol)