Post on 29-Jul-2018
WHAT IS DIALYSIS?
The solute concentration of solution A (Blood) is altered by exposing it to solution B (Dialysate) through a semipermeable membrane
Small solutes and water can pass easily
Larger solutes can’t pass through
Clearance of a solute
Concentration
gradient
Membrane
Blood and
dialysate flow rate
Molecular weight
Several thousand hollow fibres Blood in the fibre lumen separated
from the dialysate by the semi-permeable membrane
Surface are 0.5 to 2 m2
DIALYSERS
DIALYSER PERFORMANCE
Qb 300 mls / min FX 60 FX 80 FX 100
Ultrafiltration coefficient (ml/h *mm of Hg)
46 59 73
Urea (ml/min) 193 197 198
Phosphate 177 185 189
Vitamin B12 135 148 161
The Blood Circuit
A Needle
V Needle
Dialyser
Pv
Pa Heparin Infusion
Ultrasonic Level Detector
Blood Pump
Venous Clamp
DIALYSIS MACHINE
Supplies dialysis fluid at the prescribed rate,
temperature and chemical composition
Monitors the extra corporeal circuit
Removal of UF by volumetric methods
BTM, BVM, OCM and BCM
Urea Creatinine Sodium Potassium
Sodium 140 Potassium 1.5 Bicarbonate 37 Calcium 1.75
Bloo
d (3
00 to
500
mls
/min
) D
ialysate (500 to 800 mls /m
in)
WATER AND DIALYSIS FLUID HD patients – 300 litres of water per week HDF patients – 12 to 25 litres infused directly to blood stream
Contamination Aluminium toxicity
Chloramines – haemolytic anaemia Water purification
HAEMODIALYSIS
Diffusive solute removal
Poor middle molecule clearance
UF pump
High flux HD -‐ highly permeable
Sieving curves for low-flux and high-flux dialysis membranes and human glomerular basement membrane.
Ledebo I , Blankestijn P J NDT Plus 2010;3:8-16
© The Author 2009. Published by Oxford University Press [on behalf of ERA-EDTA].
HAEMOFILTRATION Purely convective treatment Highly permeable membranes
High volume substitution fluid Removal of dissolved solutes
Excellent middle molecule clearance Well tolerated haemodynamically
Addition of convection to high flux HD
Improved small and middle molecule clearance
Delayed dialysis related amyloidosis
?Better stability and improved survival
Schematic illustration of the Nephros OLpūr™ MD 190 mid-dilution haemodiafilter.
Krieter D H et al. Nephrol. Dial. Transplant. 2005;20:155-160
Nephrol Dial Transplant Vol. 20 No. 1 © ERA-EDTA 2004; all rights reserved
Ledebo I , Blankestijn P J NDT Plus 2010;3:8-16
© The Author 2009. Published by Oxford University Press [on behalf of ERA-EDTA].
RBV – ratio of current blood volume to the blood volume at the start of dialysis
Principle – blood cells, Hb, plasma protein remain confined to the vascular system whilst the plasma water can pass both capillary membrane and dialyser membrane
BV – concentration change of these blood constituents
Sound velocity in the blood – temperature, density and compressibility of the blood
Mass fraction of proteins – HB and plasma proteins
UF – mass of plasma water will change but intravascular protein mass remain constant
Measures the velocity of the sound across the blood
85
87
89
91
93
95
97
99
101
00:0
0 00
:05
00:1
0 00
:16
00:2
2 00
:28
00:3
5 00
:41
00:4
7 00
:53
00:5
8 01
:05
01:1
0 01
:16
01:2
1 01
:27
01:3
4 01
:39
01:4
4 01
:49
01:5
5 02
:00
02:0
6 02
:11
02:1
7 02
:23
02:2
9 02
:34
02:4
0 02
:46
02:5
3 02
:58
03:0
4 03
:09
03:1
6 03
:22
03:2
8
RB
V
Time
RBV
RBV
RBV with Food
88
90
92
94
96
98
100
0:00
:00
0:03
:00
0:06
:00
0:10
:00
0:13
:00
0:16
:00
0:19
:00
0:23
:00
0:26
:00
0:29
:00
0:32
:00
0:36
:00
0:39
:00
0:42
:00
0:45
:00
0:48
:00
0:52
:00
0:55
:00
0:58
:00
1:01
:00
1:05
:00
1:08
:00
1:11
:00
1:14
:00
1:17
:00
1:21
:00
1:24
:00
1:27
:00
1:30
:00
1:34
:00
1:37
:00
1:40
:00
1:43
:00
1:47
:00
1:50
:00
1:53
:00
1:56
:00
1:59
:00
2:03
:00
2:06
:00
2:09
:00
Time
RB
V %
SODIUM PROFILING
Sodium in the dialysate fluid is manipulated in order to influence fluid shifts between the ICF and ECF
Higher concentration of sodium in the dialysate fluid than in the plasma prevents reduction in ECF osmolality, preventing IC water absorption; it may also support plasma refilling
Sodium profiling consists of changing the dialysate sodium (or conductivity) level from high to low or low to high in stepwise, linear or exponential fashion
May be beneficial in headache
Conductivity sensors to measure pre and post dialyser change in sodium concentration of dialysate
Ionic dialysance (net solute exchange) is
calculated from dialysis conductivity Correlates with urea clearance Adequacy of the treatment given
Combines bioimpedance spectroscopy with physiologic tissue model
Volume model – TBW and ECF
BCM – calculates over-hydration, lean tissue and adipose tissue from ECW and TBW