• Renal replacement therapy is a term used
to encompass life-supporting treatments
for renal failure.
• It includes a variety of treatment
• First hemodialysis in human being was
done by Dr. HASS in 1924.
• First to construct a working dialyzer was
Dr . WILLIAM KOLFF in 1943.
• Most current consensus diagnostic criteria
for AKI is abrupt ( 48 hrs ) reduction in
kidney function , defined as :
absolute increase in S. Cr of
a % increase in S. Cr > 50% .
reduction in urine output –
documented oliguria of <0.5ml/kg/hr for
Classification of AKIClassification of AKI :
R - RISK
Increase in S. Cr > 1.5
Decrease in GFR >25%
urine output < 0.5 ml/kg/
hr for > 6 hrs.
I - INJURY
Increase in S.Cr > 2
Decrease in GFR > 50 %
Urine output <
0.5ml/kg/hr for > 12hrs
F - FAILURE
Increase in S.Cr > 3
Decrease in GFR > 75 %
Urine output <
0.3ml/kg/hr for >24hrs
(or) Anuria for > 12hrs
L- LOSS OF FUNCTION
Persistent loss of kidney
function for > 4wks . -
Persistent loss of kidney
function for > 3 months -
INDICATIONS FOR RRT :
• RENAL :
Nephrogenic pulmonary edema
Metabolic acidosis.(pH< 7.2 )
Relatively high urea and creatinine
NON – RENALNON – RENAL :
• SIRS / sepsis.
• Fluid imbalance.
• Drug overdosage.
• Temperature control.
• Severe acute liver failure as a bridge to
• Whatever be the technique of RRT, the
fundamental principle is the removal of
unwanted SOLUTES & WATER through a semi-
• WATER :
Removal of water occurs through a
process of ULTRAFILTRATION.
• It is achieved by generating a TRANS MEMBRANE
PRESSURE , which is greater than the plasma oncotic
pressure ( HF, IHD)
( or )
By increasing the osmolarity of the dialysate ( PD)
SOLUTE REMOVAL :SOLUTE REMOVAL :
• It occurs by either DIFFUSION or by
CONVECTION ( SOLVENT DRAG ).
• In diffusion an electro-chemical gradient is
created across the membrane with a
Modes of RRTModes of RRT :
• EXTRACORPOREAL :
Slow low efficiency dialysis (SLED)
INTRACORPOREAL : Peritoneal dialysis
Hemo dialysisHemo dialysis ::
• The 3 essential components of HD are :
Composition of dialysate
Blood delivery system
• 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 the same or in opposite
directions in co-current and countercurrent techniques, respectively
Dialysis membrane :
• It can be synthetic or biological.
.has low flux
.poor in removing middle MW molecules.
. More complement and leucocyte activation.
. Not desirable in ICU patients.
. Worsening of the organ damage.
• SYNTHETIC :
High flux membranes.
Made up of PMMA, PAN, Polyamide, Polysulphone (PS).
Allows convective therapy and removal of middle MW substances.
Better biocompatibility, less leucocyte/complement activation and
end organ dysfunction.
Blood delivery systemBlood delivery system :
• Consists of the extracorporeal circuit in the dialysis machine and the
dialysis access .
• Types of vascular access can be
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 :
SP = K T
V k = clearance of urea in ml/min
t = time of dialysis in hrs
V = vol of distribution
SP of 1 indicates that TBW is cleared of urea once.
Ideally it should be above 1.3
SLOW LOW- EFFICIENCY DIALYSIS : ( SLED )SLOW LOW- EFFICIENCY DIALYSIS : ( SLED )
• Conventional dialysis treatment .
• Uses dialysate flow rates of 300 ml/min & low blood flow pump
speeds of 200ml/min for 6 – 12 hrs a day.
• Excellent small molecule detoxification.
• Reduced anticoagulant requirement.
• 11 hrs SLED is comparable to 24 hrs of CHD .
• Decreased costs compared to CRRT.
• Treatment occurs 24 hrs a day .
• Blood flow of 100-200ml/min .
• Dialysate flow of 15-40 ml/min .
• Membranes are of high flux .
• Useful in hemodynamically unstable patients with ARF , CRF, life
threatening electrolyte imbalances , major burns and drug overdose.
CONTINUOUS VENO-VENOUS HEMOFILTRATIONCONTINUOUS VENO-VENOUS HEMOFILTRATION
• Solute clearance occurs by convection.
• No dialysate , 1-2 l/hr of ultrafiltration rates used.
• 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 ,
maintaining a net zero or even a positive fluid balance.
CONTINUOUS VENO-VENOUS HEMODIALYSISCONTINUOUS VENO-VENOUS HEMODIALYSIS
• Employs diffusion to replace renal function.
• Dialysate is run through the filter at 1-2lit/hr.
• This results in urea clearance of 17-34ml/hr.
• It is very much similar to traditional HD.
• Effective for removal of small to medium molecules.
HEMODIAFILTRATION (CVVHDF) :
• Patient is placed on CRRT machine with dialysate running in
opposite side of the filter and replacement fluid either before or after
• Has benefits of both diffusion and convection for solute removal.
• Use of replacement fluid allows for adequate removal of solutes with
zero or positive net fluid balance.
SLOW CONTINUOUS ULTRAFILTRATION
• Ultrafiltration at a rate of 100-300ml/hr is performed to maintain fluid
• No fluids are administered either as dialysate or replacement fluids.
• Indicated in CCF refractory to diuretics and in volume overload.
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..
• Lactate is the preferred buffer.
• icodextrin, has been found to be associated with more efficient
ultrafiltration than dextrose-containing solutions.
• It may be associated with the complication of ENCAPSULATING
• Peritonitis .
• Catheter associated infections .
• Weight gain .
• unpredictable hyperglycemia .
• Protein loss .
• Interference with diaphragm function .
• Residual uremia .
• Peritoneal membrane failure.
ANTI-COAGULANTS IN DIALYSISANTI-COAGULANTS IN DIALYSIS :
• Interacting of blood with dialyzing membrane causes activation of
clotting cascade – thrombosis-dysfunction.
• Commonly used anti-coagulant is HEPARIN .
• SYSTEMIC ANTICOAGULATIONSYSTEMIC ANTICOAGULATION :
Administered in doses of 50-100u/kg at the initiation followed by
a bolus of 100u/hr.
• REGIONAL ANTICOAGULATION :
circuit alone is anti-coagulated by administering 500-750 u/hr into
the arterial line and by parlalel administration of protamine
1mg/100u of heparin.
• VARIANT OF REGIONAL ANTI-COAGULANT :
uses sodium citrate with dialysate containing no calcium. used
for patients with high risk of bleeding.
• DIALYSIS WITHOUT ANTI-COAGULANTS :
Uses the saline flush technique .
HD is initiated at a higher rate to reduce the thrombogenicity
and dialyzer is flushed every 15-20min with 50ml of saline.
• DIRECT THROMBIN INHIBITORS :
Hirudin, lepirudin, Argatroban
• Plasma is removed from the patient and exchanged with fresh
frozen plasma (FFP) and a mixture of colloid and crystalloid
• A plasma filter is used instead of hemofilter.
• Replacement (postfilter) fluid can also be a 50/50 combination of
FFP and albumin.
• CRRT is now firmly established throughout the world as perhaps the
most commonly used form of RRT.
• Dialysis has a century long history of pioneering physicians.
• It generally works through osmosis and filtration of fluid across a
semi-permeable membrane with the use of dialysate.
• There are 2 types – hemodialysis, peritoneal dialysis.
• PD is often conducted in the patient’s home or extended care
• The prevalence of patients with ARF requiring CRRT is high. These
patients were associated with a high ICU mortality (64%).
• One of the predicting factors of better outcome is high serum
creatinine and, for worse outcome, is the requirement of MV during
the ICU stay.