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Chronic Hemofiltration
Contents:
Hemofitration is an alternative treatment method of patients suffering from
ESRF.
Difference between
Hemodialysis and Hemofiltration:
-The basic difference between both modes of therapy is in the principle of
solute transport. In hemodialysis the solutes are removed by diffusion , while
in hemofiltration it is removed by convection (solvent drag).
-During hemofiltration fluid removal taken place by ultrafiltration in a large
amount. Fluid replacement, therefore , is essential with the composition of the
substitution fluid similar to plasma water.
The Membranes used for hemofiltration are coarse fine membranes
made of Polymide , Cellulose acetate , Polysulfone or Polacrylantrile.It allow
for efficient removal of solutes up to molecular weight of ~25000 D.
Technical Aspects:
Hemofiltration requires continuous administration of a substitute fluid. .At
present it is principally carried out by fully automatic machines.Basicaly the
blood access is linked to a typical hemodialysis monitor and the fluid balancing
system is connected to electronic scale with a computer controlled infusion
pump.
Treatment schedule is calculated automatically from desired exchange volume by
subtracting the desired weight loss from the filtration rate.
Hemofiltration prescription can be
calculated using the following formula:-
Ultrafiltrate L/week=
Protein intake X0.12 X7
0,70 g/L
Where
Daily protein intake ( g ) based on dietary
interview
0.12 =grams of nitrogen recovered per gram of
ingested protein
7= No of days
0,70 =Mean urea nitrogen concentration in the
ultrafiltrate.
The infusion rate is determined by filtration capacity of the filter. This
ensures a linear weight loss during the treatment. Hemofilters with various
membranes are available with filtration rate of more than 180 ml / minute (in
the presence of vascular access allows for blood flow rate of more than 500 ml /
min.)TMP can be changed at any time during treatment.
Advantages
1- Cardiovascular stability: Hemofiltration has beneficial effects on the
cardiovascular system in both hypotensive and hypertensive patients .It was
shown that the peripheral resistance increased during hemofiltration .Dialysate
sodium, prostaglandin (PGE2) , interleukins are contributory factors which
enhance the vascular stability during hemofiltration.
2- Hemofiltration considered to be preferable for hypertnsive patient.BP could
often normalized within months of hemofiltration commencement.
3-It ameliorate the acid base disturbance ,remove larger molecule and has no
impact on the ionized calcium(i.e. no effect on parathyroid gland).Removal of B2
microgloulin prevent amyloid associated dialysis.
4-Higher survival rate was observed in elderly patient treated by hmofiltration
than in hemodialysis.
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