1. RENAL REPLACEMENT THERAPY
Dr Jyoti Khare
FCCCM, Part II
PSRI Hospital, New Delhi

2. Introduction
It is estimated that a third of patients in the critical care setting have an AKI and approximately 5% will require renal replacement therapy.
The hospital mortality in patients with an AKI requiring RRT is as high as 60%
No specific treatments have been shown to reverse the course of AKI, so RRT forms the basis of further management.

3. Proposed Indications for RRT
Oliguria < 200ml/12 hours
Anuria < 50 ml/12 hours
Hyperkalaemia > 6.5 mmol/L
Severe acidaemia pH < 7.0
Uraemia > 30 mmol/L
Uraemic complications
Dysnatraemias > 155 or < 120 mmol/L
Hyper/(hypo)thermia
Drug overdose with dialysable drug

4. The Ideal Renal Replacement Therapy
Allows control of intra/extravascular volume
Corrects acid-base disturbances
Corrects uraemia & effectively clears “toxins”
Promotes renal recovery
Improves survival
Is free of complications
Clears drugs effectively (?)

5. Types of Dialysis
Dialysis is a way to clean blood of wastes, fluids and salts that build up in the body when the kidney fail. There are 2 kinds of Dialysis:
Peritoneal Dialysis:
Uses the peritoneal membrane as the filter. The membrane covers the abdominal organs and lines the abdominal wall. This takes place inside the body and requires placement of a catheter in the peritoneal cavity to allow fluid to be instilled and drained out.
Hemodialysis:
Uses a dialyzer or artificial kidney to filter the blood. This takes place outside the body and requires some form of access to the circulatory system. Accomplished with the use

6. Hemodialysis
Blood is circulated through an artificial kidney which has two compartments: Blood & Dialysate, separated by a thin semi-permeable membrane.
Waste and excess water pass from the blood side to the dialysate side and is discarded in the drain. The cleaned blood is returned to the patient.
It is diffusion-based mass transfer (BUN, Creat, lytes) & Pressure - driven water removal (ultrafiltration)
Usually done 3x/week ~ 4 hrs M-W or T-Th-Sat

7. Dialysis Therapy Extracorporeal: Intracorporeal:
Intermittent Hemodialysis
Slow Low Efficiency Dialysis (SLED)
Continuous Hemofiltration
CAVH
SCUF
CVVH
CAVHDF
CVVHDF
Intracorporeal:
Peritoneal Dialysis

8. Major Renal Replacement Techniques
Intermittent
Hybrid
Continuous
IHD
Intermittent haemodialysis
SLEDD
Sustained (or slow) low efficiency daily dialysis
CVVH
Continuous veno-venous haemofiltration
IUF
Isolated Ultrafiltration
CVVHD
Continuous veno-venous haemodialysis
SLEDD-F
Sustained (or slow) low efficiency daily dialysis with filtration
CVVHDF
Continuous veno-venous haemodiafiltration
SCUF
Slow continuous ultrafiltration

9. Solute Clearance - Diffusion
Small (< 500d) molecules cleared efficiently
Concentration gradient critical
Gradient achieved by countercurrent flow
Principal clearance mode of dialysis techniques

10. Solute Clearance – Ultrafiltration & Convection (Haemofiltration)
Water movement “drags” solute across membrane
At high UF rates (> 1L/hour) enough solute is dragged to produce significant clearance
Convective clearance dehydrates the blood passing through the filter
If filtration fraction > 30% there is high risk of filter clotting*
Also clears larger molecular weight substances (e.g. B12, TNF, inulin)

12. Dialysate Fluid
Bicarbonate buffer solutions is used in IHD to replenish serum bicarbonate levels and neutralise metabolic acids that are usually present in patients with renal failure.
Acetate buffer solutions present the body with a large acetate load to be metabolised by the skeletal muscle.
In critically ill patients the acetate levels rise due to decreased skeletal muscle metabolism.
Increased acetate levels have been associated with hypotension and hypoxia due to its negative inotrope effect and vasodilatation.
Lactate buffer solutions

13. Hemodialysis Requires access to the blood stream
Arterio – venous fistula
Arterio – venous graft
Temporary catheter
Long – term catheter

14. Temporary Hemodialysis Catheter

15. Hemodialysis ~ Graft

16. Complications of AVF and AVG
Thrombosis
Infection (10% for AVG, 5% for transposed AVF, 2% for non-transposed AVF)
Seromas
Steal (6% of B-C AVF, 1% of R-C AVF)
Aneurysms and pseudoaneurysms (3% of AVF, 5% of AVG)
Venous hypertension (usually 2/2 central venous stenosis)
Heart failure (Avoid AVFs in pts with severely depressed LVEF)
Local bleeding

17. Intermittent Therapies - PRO
(Relatively) Inexpensive
Flexible timing allows for mobility/transport
Rapid correction of fluid overload
Rapid removal of dialyzable drugs
Rapid correction of acidosis & electrolyte abnormality
Minimises anticoagulant exposure

18. Intermittent Therapies - CON
Hypotension 30-60%
Cerebral oedema
Limited therapy duration
Renal injury & ischaemia
Gut/coronary ischaemia

19. SLED(D) & SLED(D)-F : Hybrid therapy
Conventional dialysis equipment
Online dialysis fluid preparation
Excellent small molecule detoxification
Cardiovascular stability as good as CRRT
Reduced anticoagulation requirement
11 hrs SLED comparable to 23 hrs CVVH
Decreased costs compared to CRRT
Phosphate supplementation required

20. Continuous Renal Replacement Therapy:
Based on principles of Hemofiltration
Subsitute for impaired renal function over an extended period of time and applied for 24 hours a day.

21. Continuous Therapies - PRO
Haemodynamic stability => ??? better renal recovery
Stable and predictable volume control
Stable and predictable control of chemistry
Stable intracranial pressure
Disease modification by cytokine removal (CVVH)?

22. Continuous Therapies - CON
Anticoagulation requirements
Higher potential for filter clotting
Expense – fluids etc.
Immobility & Transport issues
Increased bleeding risk
High heparin exposure

23. Comparison of IHD and CVVH
Intermittent hemodialysis
Continuous hemofiltration
No osmotic cellular shift/ cerebral edema -
+++
Hemodynamic tolerance ++
24 hr volume and electrolyte balance
Nutritional support +
RRT dose/ adequate uremia control
(+) high ultra filtration volume necessary
Anticoagulation/ bleeding disorders
Patient’s mobility
Loss of nutrients, vitamins, trace elements
Drug/ antibiotic dosage
- No clear data on many drugs, different ultrafiltration rates! Filter down times!
Cost
Ootcome/ mortality ?

24. Intradialytic Hypotension: Risk Factors
LVH with diastolic dysfunction or LV systolic dysfunction / CHF
Valvular heart disease
Pericardial disease
Poor nutritional status / hypoalbuminaemia
Uraemic neuropathy or autonomic dysfunction
Severe anaemia
High volume ultrafiltration requirements
Predialysis SBP of <100 mm Hg
Age 65 years +
Pressor requirement

25. Peritoneal Dialysis
Uses the peritoneal membrane as the filter. The membrane covers the abdominal organs and lines the abdominal wall. The membrane size is 1 – 2 m2 and approximates the body surface area. Uses the following principles:
Diffusion: movement of solutes across the peritoneal membrane from an area of higher concentration to an area of lower concentration.
Osmosis: movement of water across the peritoneal membrane from an area of lower solute concentration to an area of higher solute concentration.
Ultrafiltration: water removal related to an osmotic pressure gradient with the use of various concentrations of dialysate fluid.

26. Indications Complications Bleeding tendency Hypotension
Diabetic nephropathy
Complications
Peritonitis
Injury of viscus
Abdominal hernia
Leakage of dialysate into pleural cavity or scrotom

27. Peritoneal Dialysis Patients
Must have a clean room to perform exchanges and a large enough area to store all supplies.
No pets allowed in the room.
Must learn to monitor their own weight and blood pressure.
Must be able to follow important instructions to prevent infection in the peritoneum.
Must also be able to determine the choice of dialysate fluid and when to use it.

28. Guidelines for Anticoagulation
Extracorporeal circuit will activate coagulation pathways and the premature clotting of a filter is a common problem.
Even a small amount of clot formation will reduce filter performance.
NON-PHARMACOLOGICAL MEASURES
Adequate central venous pressure.
Optimising vascular access.
Adding a proportion of the replacement fluid to the patients’ blood before it passes through the haemofilter (this is predilution)

29. Guidelines for no Anticoagulation
There is already a degree of coagulopathy.
INR > 2-2.5
APTT > 60 seconds
Platelet Count < 60 x 103 mm3
There is a high risk of bleeding
The patient is receiving activated protein C

30. Care of patients receiving hemodialysis
Variable
Goals
Dialysis dine
Urea kinetics model
Fluid balance
Individualised. Intradialytic weight gain should be less than 5% of IBW
Quality
Measure endotoxin and bacteria in the dialysate water
Anemia
Target a Hb of gms%. Avoid high dose erythropoietin
Vascular access
Monitoring. To establish AV access rather than indwelling catheters
Bone & Mineral
Calcium levels between 8.4 – 9.5 and a PO mg/dl
Blood pressure
Optimum targets & strategies not well defined
LDL cholesterol
< 100mg/dl
Quality of life indices
Support from the medical social worker

31. CRRT, Haemodynamics & Outcome
114 unstable (pressors or MAP < 60) patients
55 stable (no pressors or MAP > 60) patients
Responders = 20% fall in NA requirement or 20% rise in MAP (without change in NA)
Overall responder mortality 30%, non-responder mortality 74.7% (p < 0.001)
In unstable patients responder mortality 30% vs non-responder mortality 87% (p < 0.001)
Haemodynamic improvement after 24 hours CRRT is a strong predictor of outcome

32. Towards Targeted Therapy?
Non-septic ARF
Septic ARF
Cathecholamine resistant septic shock
Daily IHD
Daily IHD?
HVHF ml/kg/hour
for 96 hours
Daily SLEDD
Daily SLEDD?
CVVHD/F ? dose
EBT
PHVHF ml/kg/hour
for 6-8 hours then CVVH > 35 ml/kg/hour
35ml/kg/hour
CVVH > 35ml/kg/hour
? ml/kg/hour
Cerebral oedema

33. THANK YOU