Table 1.
Formulae for calculation of renal variables
| Variable | Formulae |
|---|---|
| Renal blood flow (RBF) | (Unilateral renal vein blood flow × 2) + urine flow |
| Renal plasma flow (RPF) | RBF × (1 – hematocrit) |
| Filtration fraction (FF) | (RPF × [51Cr-EDTA arterial] – (RPF – urine flow) × [51Cr-EDTA renal vein])/(RPF × [51Cr-EDTA arterial]) |
| Glomerular filtration rate (GFR) | FF x RPF |
| Renal vascular resistance (RVR) | (MAP-CVP)/RBF |
| Arterial-renal vein (rv) oxygen content difference (RAVO2-diff) | (CaO2-CrvO2) |
| Renal oxygen consumption (RVO2) | RBF × (CaO2-CrvO2) |
| Renal oxygen extraction | (CaO2-CrvO2/CaO2) |
| Renal sodium filtration | GFR × [Na+]s |
| Renal sodium excretion | Urine flow × [Na+]s |
| Renal sodium reabsorption | (GFR × [Na+]s) – (urine flow × [Na+]u) |
51 Cr-EDTA, chromium ethylenediaminetetraaceticacid, MAP mean arterial pressure, CVP central venous pressure, CaO 2 arterial oxygen content, CrvO2 renal vein oxygen content, [Na + ] s serum sodium concentration, [Na + ] u urine sodium concentration