This document discusses the basics of hemodialysis, including the main principles of diffusion, osmosis, filtration, and convection that hemodialysis is based on. It also describes the technique of hemodialysis, varieties of hemodialysis methods like conventional hemodialysis and online hemodiafiltration, and provides details on assessing hemodialysis treatment adequacy using Kt/V.

1. Dr. Osama El-ShahatDr. Osama El-Shahat
Consultant Nephrologist
Head of Nephrology Department
New Mansoura General Hospital (international(
ISN Educational Ambassador

2.  Basics of hemodialysis:Basics of hemodialysis:
◦ Definition.Definition.
◦ Technique of hemodialysis:Technique of hemodialysis:
◦ Main principles:Main principles:
 Diffusion.Diffusion.
 Osmosis.Osmosis.
 Filtration.Filtration.
 Convection.Convection.
◦ Varieties of hemodialysis.Varieties of hemodialysis.

3.  When a semi permeable membrane is placed between different
solutions the solutes move across this membrane until they
reach equilibrium
 This is the theory by which dialysis is based on

4.  Difussion:
The process by which particles, atoms or molecule move from
area of higher concentration to lower concentration across
semipermeable membrane.
Factors affecting :Factors affecting :
Concentration gradient
MW of solutes.

5. blood
membrane
dialysate

7. solutesolute bloodblood dialysatedialysate directiondirection
UREAUREA highhigh zerozero To DxTo Dx
OTHER TOXINSOTHER TOXINS highhigh zerozero To DxTo Dx
SodiumSodium 135-140135-140 135-140135-140 NONO
PotassiumPotassium Above 5Above 5 1.4-3.01.4-3.0 To DxTo Dx
MagnesiumMagnesium Above 1Above 1 0.5-1.00.5-1.0 To DxTo Dx
glucoseglucose +/-140 (8)+/-140 (8) 180 (10)180 (10) +/-+/-
chloridechloride 100-119100-119 100-119100-119 NONO
Ionized CalciumIonized Calcium 4.5-5 mg/dl4.5-5 mg/dl
2-2.5mEq/L2-2.5mEq/L
5-6 mg/dl5-6 mg/dl
2.5-3 mEq/L2.5-3 mEq/L
+/-+/-

8.  Dialysate delivered at a rate of 500ml/min
◦ 120 liters of dialysate / 4-hour session!!
 Concentrated solutions mixed with water
 Usually 1:34 or 1:40
 Conductivity is a measurement of electric conductivity of Na to check
if dilution is correct
 With proper dilution conductivity = 13-15
 Serious hyponatremia or hypernatremia occurs if dilution is incorrect

9.  H+ neutralized by Na HCO3 in the body
 Acetate
◦ Transformed in LIVER to HCO3 (10-15 min)
◦ BUT is a potent vasodilator
 Hypotension especially with liver disease
 Acetate intolerance in high flux dialyzers
 Bicarbonate
◦ Immediately neutralizes H+
◦ BUT precipitates Calcium salts (CaCO3)
 Should be delivered separately as NaHCO3
 Short life span of machine
 Needs a strong post dialysis acid rinse (citric acid)

10.  Attempts are made to increase the surface area of
contact between dialysate and dialyzer
◦ The Hollow fiber
◦ The parallel plate dialyzer

12.  TypesTypes
◦ Surface area.
◦ Low flux vs high flux.
◦ Biocompatibility.
◦ Technique of manufacture including hemo- adsorption.

13.  Cellulose membrane (Cuprophan)
◦ Is the first membrane to be used
◦ Contains free hydroxyl radicals
 They are able to activate complement  inflammatory reaction
chronic inflammation  protein catabolism + anorexia + malnutrition
 Cardiovascular accidents
 Cause dialysis related Amyloidosis
 Increased incidence of infection
 Rapid loss of residual kidney function

14.  Substituted Cellulose
◦ Chemically bonding the free hydroxyl group
 Cellulose di acetate
 Cellulose Triacetate
◦ Addition of a synthetic material to cellulose
 Hemophane (semi synthetic)
 Synthetic modified cellulose (SMC)
 Synthetic material
◦ Contains no cellulose
 Polysolphone
 PMMA
 PAN

15.  There is no definite techniques for biocompatibility
measurement
 There is no clear evidence for its superiority except in
AKI

16.  Ability of the dialyzer to clear urea from blood
 The more clearance the better the dialyzer
 Clearance can be calculated in vivo=
Qb x [BUN ART – BUN VEN]
BUN ART
 Clearance is closely related to the surface area of HF

17.  HF with a high urea clearance
◦ They contain pores bigger in number and size
◦ Must be with bicarbonate dialysis
◦ They perform more adequate dialysis
◦ Clearance of bigger molecules toxins e.g. (B2 microglobulin)
◦ expensive

18.  The more the patient’s weight the larger surface area (and clearance)
you need
 Patients with increased weight gain (volume overload) need a dialyzer
with high KUF
 Much debate is present with use of biocompatible membrane EXCEPT
in AKI
 High Flux dialyzer gives a better adequacy but is expensive

19.  ESRD patients are frequently oliguric
 If excess water is ingested 
accumulation of water in body 
edema, hypertension, pulmonary edema
 To remove water  Ultrafiltration
 Addition of hydrostatic force  squeezing out water from dialysate!!!
 may be –ve (machine UF)
 Or +ve (partial venous clamping)
 The net force is reflected by the transmembrane pressure (TMP)

20. 500 ml/min
700 ml/min
+ve
pressure
-ve
pressure
TMP

22. Problems with conventional diffusive hemodialysis
 Excessive cardiovascular mortality
 Insufficient removal of middle molecules
 Insufficient removal of phosphate
 High risk of intradialytic hypotension
 Suboptimal dialysate quality
 Chronic inflammation and protein-energy wasting

27.  FiltrationFiltration::
Is movement of fluid through a filter as a result of hydraulic
pressure.
In hemodialysis, ultrafiltration , is movement of water from
blood under pressure gradient effect.

29.  ConvectionConvection:
Transfer of heat and solute by
physical circulation or or movement
of parts of gas or liquid.
 Countercurrent circulationCountercurrent circulation

31. Hemoperfusion therapy (DHP) is a method of treatment to
eliminate causal substances of disease in the blood by adsorption
that takes place by passing the blood directly through an adsorbent.
DHP is characterized by a simple extracorporeal blood circuit and
easy operation. Activated charcoal, and either polymyxin B or
hexadecyl alkyl compound immobilized adsorbents, are clinically
available at present.
The DHP using activated charcoal is mainly applied in cases of
intoxication with either toxic substances or a drug overdose.
Hemodialysis or plasma exchange is also applied in these situations.
.

32. Application of either DHP, hemodialysis or plasma
exchange is done according to the characteristics of the
toxins or drugs.
DHP using PMX is applied in cases of septic shock, and
its efficiency is suggested to be due to the removal of
anandamide in addition to endotoxins in the blood.
DHP using BM-01 is applied to a specific disease, dialysis
related amyloidosis, for the purpose of elimination of β2-
microglobulin.

35.  Varieties of hemodialysis techniques:Varieties of hemodialysis techniques:
◦ Conventional hemodialysis.
◦ Online hemodiafilteration.
◦ SLEDD.
◦ CRRT.
◦ Hemo-adsorption.

36. HDFHDF is a blood purification therapy combining
diffusive and convective solute transport using a high-flux
membrane characterized by an ultrafiltration coefficient greater
than 2020 mL/h/mm Hg/m2 and a sieving coefficient (S) for β2-
microglobulin of greater than 0.6.
Convective transport is achieved by an effective convection
volume of at least 20%20% of the total blood volume processed.
Appropriate fluid balance is maintained by external infusion of
a sterile, non-pyrogenic solution into the patient's blood.

39.  Kt/VKt/V is a number used to quantify hemodialysis andis a number used to quantify hemodialysis and
peritoneal dialysis treatment adequacy.peritoneal dialysis treatment adequacy.
K - dialyzer clearance of urea
t - dialysis time
V - volume of distribution of urea, approximately equal to patient's
total body water
◦ Kt/V target is ≥ 1.3, so that one can be sure that the
delivered dose is at least 1.2. In peritoneal dialysis the target
is ≥ 1.7/week.

40. ©