. 2020 Aug 17;8(1):e000816. doi: 10.1136/bmjdrc-2019-000816

Table 1.

Equations to calculate different parameters

Parameter (unit)	Equation
Clearance at, eg, 90 min after NMP (mL/min)	$\frac{U r i n e p r o d u c t i o n_{t 60 \to t 90} \cdot u r i n e c o n c e n t r a t i o n_{t 90}}{P e r f u s i o n f l u i d c o n c e n t r a t i o n_{t 90}}$
Creatinine clearance (mL/min/100 g)	$\frac{\frac{U r i n e c r e a t i n i n e [μ m o l / L] \cdot u r i n e p r o d u c t i o n [m L / m i n]}{P e r f u s i o n f l u i d c r e a t i n i n e [μ m o l / L]}}{K i d n e y w e i g h t [100 g]}$
Metformin clearance (mL/min/100 g)	$\frac{\frac{U r i n e m e t f o r m i n [m g / L] \cdot u r i n e p r o d u c t i o n [m L / m i n]}{P e r f u s i o n f l u i d m e t f o r m i n [m g / L]}}{K i d n e y w e i g h t [100 g]}$
Metformin-to-creatinine clearance ratio	$\frac{M e t f o r m i n c l e a r a n c e [m L / m i n / 100 g]}{C r e a t i n i n e c l e a r a n c e [m L / m i n / 100 g]}$
Fractional sodium excretion (%)	$100 \cdot \frac{U r i n e s o d i u m [m m o l / L] \cdot p e r f u s i o n f l u i d c r e a t i n i n e [μ m o l / L]}{P e r f u s i o n f l u i d s o d i u m [m m o l / L] \cdot u r i n e c r e a t i n i n e [μ m o l / L]}$
Oxygen consumption (mLO₂/min/100 g)	$\frac{F l o w [L / m i n] \cdot (a r t e r i a l o x y g e n c o n t e n t [m L O_{2} / L] - v e n o u s o x y g e n c o n t e n t [m L O_{2} / L])}{K i d n e y w e i g h t [100 g]}$
Oxygen content in porcine model (mLO₂/L)	$24.794 [\frac{m L O_{2}}{H b \frac{m m o l}{L}} a t 37 ℃] \cdot S O_{2} [f r a c t i o n] \cdot h e m o g l o b i n [\frac{m m o l}{L}]$ $+ 0.225 [m L O_{2} / k P a] \cdot P O_{2} [k P a]$

Units of the parameters used within the equations are depicted with hard brackets to avoid confusion with regular brackets. In the porcine study, a total oxygen binding capacity of hemoglobin of 24.8 mLO₂/mmol and 0.225 mLO₂/kPa oxygen solubility in water at 37°C was assumed.

NMP, normothermic machine perfusion; PO₂, arterial or venous partial pressure of oxygen; SO₂, arterial or venous oxygen saturation.