Table 6.

Effect of pre- and posthemofilter replacement fluid infusion on end treatment plasma sodium concentration

VariableUnitsPredilution OnlyPre-/PostdilutionPre-/Postdilution
QPml/min200.0200.0200.0
QRFml/min50.050.050.0
Replacement fluid1.0/0.00.5/0.50.3/0.7
Pre-/postdilution ratio
DNaml/min40.044.446.5
NaAR0.760.800.81
PNa(1440)mM127.6128.0128.1
  • A hypothetical patient with Watson volume 40 L and PNa(0) 120 mM undergoes 24 hours of continuous venovenous hemofiltration with the following parameters: NaRF, 130 mM; QP, 200 ml/min, and QRF, 3 L/h. Three simulations are shown: predilution only and pre- and postdilution with QRF pre- and postdilution ratios of 0.5/0.5 and 0.3/0.7. DNa, NaAR, and PNa(1440) increase with an increasing proportion of postdilution QRF. The maximal PNa(1440) difference among the three pre-/posthemofilter combinations is 0.5 mM. QP, plasma flow rate; QRF, replacement fluid flow rate; DNa, dialysance of sodium; NaAR, sodium concentration adjustment ratio; PNa(0), PNa at t (0); PNa(1440), PNa at t = 1440 minutes; NaRF, replacement fluid [Na].