2. Definition :
• Renal replacement therapy is a term used to encompass life-
supporting treatments for renal failure.
• It includes a variety of treatment modalities.
5. Indications-
• Acute kidney injury
• Chronic renal failure /ESRD with following complications:
i)severe hyperkalemia- >6.5 meq/l not responding to medical
treatment
ii)fluid overload/ pulmonary oedema, anasarca
iii)severe metabolic acidosis pH-<7.10
iv)UOP< 200ml/12hrs
v)uremia i.e, BUN >80mg/dl or s.creatinine > 4mg/dl
vi)severe dysnatremia- Na <115 meq/l or 160 meq/l
vii)uremic pericarditis/encephalopathy
viii)hyperthermia>40 deg C
6. Principles of dialysis
• diffusion = passive movement of
solutes across a semi-permeable
membrane down concentration
gradient
– Good for small molecules
• convection = solute + fluid
removal across semi-permeable
membrane down a pressure
gradient (solvent drag)
– Better for removal of fluid and
medium-size molecules
7. Principles of dialysis
•Miller's Anesthesia, 7th ed. 2009
•Foot. Current Anaesthesia and Critical Care 2005; 16:321-329
Hemodialysis = solute passively diffuses down
concentration gradient
Dialysate flows countercurrent to blood flow.
Urea, creatinine, K move from blood to dialysate
Ca and bicarb move from dialysate to blood.
Hemofiltration: uses hydrostatic pressure gradient to
induce filtration / convection plasma water + solutes
across membrane.
Hemodiafiltration: combination of dialysis and filtration.
8. Hemo dialysis :
• The 3 essential components of HD are :
Dialyzer
Composition of dialysate
Blood delivery system
DIALYZERDIALYZER ::
• Hollow-fiber dialyzer, the most commonly used type of dialyzer, is
composed of bundles of capillary tubes through which blood circulates
and the dialysate travels on the outside of the fiber bundles.
• The blood and the dialysate may circulate in opposite direction
9. Dialysis membrane :
• It can be synthetic or biological.
Cellulose :
.has low flux
.poor in removing middle MW molecules.
. More complement and leucocyte activation.
10. • SYNTHETIC :
High flux membranes.
Made up of Polyamide, Polysulphone (PS).
Allows removal of middle MW substances.
13. Vascular access in HD/CRRT
Site Advantages disadvantages
IJV Straight access Swings in flow
associated with
respiration.
Subclavian Least association with
infection.
Swings in flow as
above.
Risks of pneumothorax
Femoral Ease of access Infection rates high.
14. PHARMACOLOGICAL MEASURES
• Unfractionated or low molecular weight heparins
• Unfractionated heparin (UFH) [5-30kDa] is the most
commonly used anticoagulant
• typical regime involves a 40-70 IU.kg-1 bolus followed by
a pre-filterinfusion at 5-10 IU.kg.-1hr-1
• It is the most cost effective anticoagulant and is fully
reversible with protamine.
15. • Low molecular weight heparins (LMWH) [4.5-6kDa]
• They are dependant on renal elimination so in this
setting their dosing needs to be guided by anti-factor Xa
levels (aiming for 0.25-0.35 IU.ml-1
• The half life of LMWHs is longer than for UFH (2-6 hrs
versus 1.5-3hrs) and their effect can only be partially
reversed with protamine.
17. Prostaglandins
Prostaglandins (prostacyclin or prostaglandin E2) inhibit
platelet function and can either be used on their own or in
combination with heparin ,they have a synergistic effect.
short half life ,administered as an infusion 4-8ng/kg/hr
anticoagulant effect stops within 2 hours of discontinuing
the infusion
The main side effect is vasodilation
18. Regional citrate anticoagulation
• It is alternative to heparin
• Sodium citrate is infused into the circuit pre-filter which
chelates calcium and inhibits clot formation.
19. Intermittent hemodialysis
• Diffusive process
• Movement of solutes occur along an electrochemical
gradient
• A low permeability cellulose base membrane is
employed
• Dialysate sol flows countercurrent to blood flow
• Smaller molecules are removed efficiently
• Solute removal is proportionate to dialysate n blood flow
rate Qb- 150-300ml/min, Qd- 300-500ml/min
• Typically performed 4hrs thrice weekly or daily
20. IALYSIS DOSE MEASUREMENT / ADEQUACYIALYSIS DOSE MEASUREMENT / ADEQUACY :
• UREA REDUCTION RATIO :
URR = Pre dialysis BUN – Post dialysis BUN * 100
Pre dialysis BUN
Ideally it should be >65%
• Single pool urea kinetics :
= K T
v k = clearance of urea in ml/min
t = time of dialysis in hrs
V = vol of distribution
Ideally it should be above 1.3
21. advantages disadvantages
Relatively inexpensive
Rapid correction of acidosis
Rapid correction of fluid overload
Minimizes anticoagulant exposure
Mobility possible
Cannot be used in hemodynamically
unstable pts( i.e. shock)
23. SLOW CONTINUOUS ULTRAFILTRATION
(SCUF) :
• Qb-100-250ml/min, Quf- 5-15ml/min
• No fluids are administered either as dialysate or replacement
fluids.
• Indicated in CCF refractory to diuretics and in volume
overload.
24. CONTINUOUS VENO-VENOUS HEMOFILTRATIONCONTINUOUS VENO-VENOUS HEMOFILTRATION
(CVVHF)(CVVHF) ::
• Solute clearance occurs by convection.
• No dialysate , Qb-100-250ml/min,Quf-15-60ml/min
• Replacement fluid provided to replace the excess volume that is being
removed and replenish desired solutes.
• Effective method of solute removal.
• Major advantage is that solute can be removed in large quantities
25. CONTINUOUS VENO-VENOUS HEMODIALYSISCONTINUOUS VENO-VENOUS HEMODIALYSIS
(CVVHD)(CVVHD) :
• blood is driven through a low permeability dialyzer
• Qb= 100-250ml/min, Qd= 15-60ml/min, Quf= 1-8ml/min
• Solute clearance is mainly diffusive,
and efficiency is limited to small solutes only.
26. CONTINUOUS VENO-VENOUS
HEMODIAFILTRATION (CVVHDF) :
• blood is driven through a highly permeable dialyzer
• A replacement solution is needed to maintain fluid
balance
• Has benefits of both diffusion and convection for solute
removal.
• Qb=100-250ml/min,Qd=15-60ml/min,Qf=15-60ml/min
27. SLOW LOW- EFFICIENCY DIALYSIS : ( SLED )SLOW LOW- EFFICIENCY DIALYSIS : ( SLED )
•Uses dialysate low flow rates & low blood flow rates
•Excellent small molecule detoxification.
•Reduced anticoagulant requirement.
•11 hrs SLED is comparable to 24 hrs of CHD .
•Decreased costs compared to CRRT.
29. 2. The patient`s cardiovascular status•
CRRT causes less rapid fluid shifts and is the preferred option if
there is any degree of cardiovascular instability.
3. The availability of resources
• CRRT is more labour intensive and more expensive than IHD
• Availability of equipment may dictate the form of RRT.
4. The clinician`s experience
• It is wise to use a form of RRT that is familiar to all the staff
involved.
5. Other specific clinical considerations
• Convective modes of RRT may be beneficial if the patient has
septic shock
• CRRT can aid feeding regimes by improving fluid management
• CRRT may be associated with better cerebral perfusion in patients
with an acute brain injury or fulminant hepatic failure.
30. PERITONEAL DIALYSISPERITONEAL DIALYSIS :
• In peritoneal dialysis, 1.5 – 3 L of peritoneal dialyzate solution
is infused into the peritoneal cavity and allowed to dwell for a
set period of time, usually 2 to 4 hours.
• The rate of diffusion diminishes with time and eventually
stops when equilibration between plasma and dialyzate is
reached
31. COMPLICATIONSCOMPLICATIONS :
• Peritonitis .
• Catheter associated infections .
• Protein loss .
• Interference with diaphragm function .
• Residual uremia .
• Peritoneal membrane failure.
32.
33. Complications common to IHD, CRRT,
and hybrid therapies
1.Complications related to the vascath (including line-
related sepsis)
2.Haemodynamic instability
3. Air emboli
4. Platelet consumption
5. Blood loss
6. Electrolyte imbalances
7.Hypothermia
8.Effects of anticoagulation (bleeding or specific side-effects
of the anticoagulant used e.g. heparin induced
thrombocytopenia).
34. Dialysis Disequilibrium Syndrome
• self-limited condition characterized by nausea, vomiting, headache,
altered consciousness, and rarely seizures or coma.
• It typically occurs after first dialysis in very uremic patients.
• triggered by rapid movement of water into brain cells following
development of transient plasma hypo-osmolality as solutes rapidly
cleared from bloodstream during dialysis.
• incidence has fallen in recent yrs with more gradual institution of
dialysis, precise prescription of dialysis to include such variables as
membrane size, blood flow rate, and sodium profile.
Dialysis is a process which uses diffusion which is…
Filtration is a process using convection which is..
Convective transport of small and middle molecular weight solutes in same direction as water. Usually requires substitution fluid to prevent excess fluid removal.
Although the use of
pump-driven venovenous circuits increases the technical
complexity of therapy, the elimination of the hazards of
prolonged arterial cannulation and the provision of higher
solute clearances make these the preferred modes of
therapy [28]. Theoretically, convective therapies (hemofiltration)
provide greater clearance of higher molecular
weight solutes than diffusive therapies (hemodialysis);
however, no studies have demonstrated an association
between the mechanism of solute transport and clinical
outcomes.
