A very simple yet comprehensive presentation to understand the concept of CRRT and its implementation in Intensive Care Unit. Intended for the very beginners in ICU. After going through the presentation you will be able to say "Now I know it!"

1. Continuous Renal Replacement Therapy
(CRRT)
Muhammad Asim Rana
MBBS, MRCP, SF-CCM, EDIC, FCCP
Critical Care Medicine
King Saud Medical City
Riyadh, Saudi Arabia

2. Dedication
• Today’s presentation is dedicated to
• Dr Mohammed Odat
• Dr Waleed Tharwat Hasim
• Being the PIONEERS in KSMC ICU to start
lectures on CRRT

3. Case 1
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35 yrs male pt, involved in RTA
Massive crush injury to legs
Severe Rhabdomyolysis, AKI Creat 250
Trauma to liver and spleen post laparotomy
Received 15 Blood transfusions in OR
Severe DIC, metabolic acidemia pH 7.0
TRALI…ARDS FiO2 100%, Sat O2 80%
Shocked on 2 inotropes moderate doses
Seen by ICU consultant decided.. CRRT

4. Case 2
• 75 yrs female pt, DM, IHD, mild renal
impairment
• Admitted with SOB with high BP
• CXR showed B/L infiltration “BAT Wing”
• ECHO… EF 45%
• Diagnosed as acute pulmonary edema
• Lasix trial failed, pt intubated for worsening
dyspnea and hypoxia

5. Case 3
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45 yrs male pt, known drug addict
Admitted with decreased LOC
ABGs showed severe metabolic acidemia
Creatinin 180, BUN 10
Urine positive for oxalate
Papilloedema
Rx ………..CRRT

6. Case 4
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56 yrs male pt, no past medical hx
Admitted with bilateral pneumonia
Ventilted developed MOF, Septic Shock
ABGs showed severe metabolic acidemia
Creatinin 300, BUN 29
Urine out put 10 ml/hr
Fluid Balance +13L
Rx ………..CRRT

7. Objectives
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To understand the theory of CRRT
To appreciate the difference b/w IHD & CRRT
Understanding the modes of CRRT
To learn the indications and timing of CRRT
Dosage writing

8. Introduction
• Main functions of the kidney:
maintenance of fluid balance
maintenance of acid base balance
elimination of waste products
• 20 – 30 % of ICU patients develop AKI
• Many ICU are already on IHD

9. Options for Renal Replacement Therapy
• Intermittent Hemo-Dialysis
• Peritoneal Dialysis
• Continuous Renal Replacement Therapy

10. Intermittent Hemodialysis
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The gold standard
Usually 2 – 3 times a week for 3 – 4 hours
Involves a vascular access
Pump, filter, dialysate & anticoagulation

11. Advantages/Disadvantages
• Very efficient
• Hemodynamic instability in ≤ 30 % of patients
• Causes rapid shifts in osmolarity
– (Disequilibrium syndrome)
• It is “Intermittent”

12. Peritoneal Dialysis
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Simple and cheap, but …….
Poor solute clearance
Poor uremic control
Risk of peritoneal infection
Mechanical impedance
– Pulmonary and cardiovascular function

13. Continuous Renal Replacement Therapy
• Concept- dialyze patients more physiologically
• Avoids the accumulation of waste products
• Avoids the rapid shifts in volume & osmolarity
• Avoids disadvantages of Peritoneal Dialysis

14. Advantages
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Precise volume control
Very effective control of uremia and ↑ K⁺
Rapid control of metabolic acidosis
Suitable for hemodynamically unstable pts
Improved nutritional support
– (no need for volume restriction)

15. Advantages
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Needs minimal training
Safer for patients with TBI & CVS disorders
May have an effect in sepsis
Probable advantage in terms of renal recovery

16. Disadvantages
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Expensive
Anticoagulation
Hypothermia
Severe depletion of electrolytes – K+ and PO4
Complications of line insertion and sepsis
Risk of line disconnection

17. Principal
• 2 processes in waste product removal in RRT
1. Diffusion…………Dialysis
2. Convection…….Hemofiltration

18. Diffusion/Dialysis

19. Semipermiable Membrane

20. Semipermiable Membrane

21. (Dalton)
100000
50000
10000
5000
Molecular Weights
Albumin (55000 – 60000)
Beta 2 Microglobulin (11800)
Inulin (5200)
Vit B12 (1355)
1000
500
100
50
10
Aluminium/Desforoxamine complex (700)
Glucose (180)
Uric Acid (168)
Creatinine (113)
Phosphate (80)
Urea (60)
Potassium (35)
Phosphorus (31)
Sodium (23)

22. Diffusion

23. Ultrafiltration
• The passage of water through a membrane
under a pressure gradient.
• Driving pressure can be
+ve (push fluid through the filter)
–ve (pull fluid to other side of filter)
• Pressure gradient is created by effluent pump

24. Ultrafiltration

25. Convection
• Movement of solutes through a membrane by
the force of water.
“solvent drag”
• The water pulls the molecules along with it as
it flows through the membrane.
• Can remove middle and large molecules, as
well as large fluid volumes.
• Maximized by using replacement fluids.

26. Convection

27. Convection

28. Convection

29. Adsorption
• Adsorption is the removal of solutes from the
blood because they cling to the membrane.
– Think of an air filter. As the air passes through it,
impurities cling to the filter itself.
– Eventually the impurities will clog the filter and it
will need to be changed.
• The same is true in blood purification. High
levels of adsorption can cause filters to clog
and become ineffective

30. Adsorption

31. Dialysate
Dialysate is any fluid used on the opposite side of the filter from
the blood during blood purification.

32. Replacement Fluids
• Used to increase the amount of convective
solute removal in CRRT.
• Replacement fluids do not replace anything.
• Fluid removal rates are calculated
independently of replacement fluid rates.
• The common replacement fluid is 0.9% saline
• Can be pre or post filter.

33. Replacement Fluids

34. Comparison Pre & Post Dilution
PRE-FILTER
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Increases filter life
Increases convective
transport
Reduced solute clearance
Some of delivered
replacement fluid lost by
hemofiltration
Lower anticoagulation
requirements
Higher UF required given
loss of replacement fluid
through filter
POST-FILTER
– No solute dilution,
improved diffusion and
solute clearance
– Increased
hemoconcentration
– Higher delivered dose
of hemofiltration

35. Indications
• Acidemia (pH <7.1)
• Electrolytes
– Hyperkalemia (K⁺ > 6.5 mEq/L)
– Severe dysnatremia (Na⁺ <115 or >160 mEq/L)
• Ingestions (Toxins, Drugs)
• Overload/ Oliguria (urine output <200 mL/12 h)
• Uremia (urea >30 mg/dL)
– Uremic encephalopathy
– Uremic pericarditis
– Uremic neuro-myopathy
AEIOU

36. Dialysable or Not
Dialysable
Barbiturates
Lithium
Alcohols, Amglcoside
Salicylates
Theophyllin
Penicillins,
Carbapenems, Cephalo
PC-B L A S T
Non-Dialysable
Digoxin
Tricyclic
Antidepressents
Phenytoin
Benzodiazepines
B-blockers
(atenolol is removed)
Metformin

37. Timing
• Inadequate data available to answer this Q
• Observational data suggests better outcomes
are associated with early RRT initiation
2
 Getting et al 1999 . Urea 15.2 vs 33.7 conferred survival benefit.
3
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 Ronco et al 2000 and Saudan et al 2006 both dose/outcome studies suggested an early
start.
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 Liu et al 2006 observational PICARD study (Urea 27) suggested an early start
– RENAL study, NEJM 2009, 1508 pts.
– Demirkilic 2004, Elahi 2004, Piccini 2006

38. Early Initiation means…

39. CRRT Modalities
• CRRT includes several treatment modalities
that use a veno-venous access.
• The choice will depend on the needs of the
patient and on the preference of the
physician.

40. • Removal of ultrafiltrate at low rates
• without administration of a substitution solution.
• The purpose is to prevent or treat volume overload
• when waste product removal or pH correction isn’t
necessary.
• Primary indication for SCUF - fluid overload
• Mechanism of water transport is Ultrafiltration.
• No dialysate or replacement fluid is used.

41. • Other solutes are removed but are negligible
• The amount of fluid in the effluent bag is the
same as the amount removed from the pt.
• Removal rates are closer to 100 ml/hour.

42. Understanding Flow

43. Let’s Revise
• Primary therapeutic goal:
– Safe management of fluid
• Primary indications:
– Fluid overload without metabolic imbalance
• Principle used:
Ultrafiltration
• Therapy characteristics:
– No dialysate or substitution solutions
Fluid removal only

44. • Blood flow:
80 – 200 ml/min
• Duration:
(as advised by the physician)
• Ultrafiltration:
20-100 ml/hr (or total volume)
• Anticoagulation…. Acc to physician
• Dialysate …….. NO
• Replacement fluid….. NO

45. Effects of different doses in CVVH on outcome of ARF
Ronco & Bellomo study. Lancet . july 00
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Prospective study on 425 patients - 3 groups:
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Study:
– survival after 15 days of HF stop
– recovery of renal function

46. Effects of different doses in CVVH on outcome of ARF - Ronco
& Bellomo study. Lancet . july 00
100
p < 0.001
90
Survival (%)
80
70
p < 0.001
p n..s.
60
50
40
30
20
41 %
57 %
58 %
10
0
Group 1(n=146)
Group 3 (n=140)
(Uf = 20 ml/h/Kg)
306100135
Group 2 (n=139)
(Uf = 35 ml/h/Kg)
(Uf = 45 ml/h/Kg)

47. • An extremely effective method of solute removal and
is indicated for uremia or severe pH or electrolyte
imbalance with or without fluid overload.
• Particularly good at removal of large molecules,
because CVVH removes solutes via convection.
• Convective removal of waste products (small and
large molecules) utilizing a substitution solution.
• pH is affected with the buffer contained in the
substitution solution.

48. • Solutes can be removed in large quantities
while easily maintaining a net zero or even a
positive fluid balance in the patient.
• The amount of fluid in the effluent bag is
equal to the amount of fluid removed from
the patient plus the volume of replacement
fluids administered.
• No dialysate is used.

49. Understanding Flow

50. Let’s Revise
• Primary therapeutic goal:
– Solute removal and safe fluid management
• Primary indications:
– Uremia, severe acid/base or electrolyte imbalance
– Removal of larger mol wt substances
• Principle used:
convection
• Therapy characteristics:
– Substitution solution to drive
– No dialysate solution
Effective at removing small and large molecules

51. •
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Blood flow:
80 – 200 ml/min
Duration:
As advised by physician
Ultrafiltration:
20-100 ml/hr (or total volume)
Replacement Fluid:
1000 – 2000 ml/hr,pre or post filter
Anticoagulation
Dialysate…. NO
Dosage:
30ml/kg/hr
70x30=2100ml
Replacement fluid
So
This Replacement can be
divided into pre & post filter
Depending upon physician
Ex, 500 pre and 1500ml post
(All can be pre or post)

52. •
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Effective for removal of small to medium sized molecules.
Solute removal occurs primarily due to diffusion.
No replacement fluid is used.
Dialysate is run on the opposite side of the filter.
Fluid in the effluent bag is equal to the amount of fluid
removed from the patient plus the dialysate.
• Continuous diffusive removal of waste products (small
molecules) utilizing a dialysis solution.
• pH is also affected with the buffer contained in the
dialysate.

53. Understanding flow

54. •
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Blood flow:
80 – 200 ml/min
Duration:
Dosage:
As advised by physician
45ml/kg/hr
70x45=3150ml
Ultrafiltration:
Dialysatefluid
20 -100 ml/hr (or total volume)
So
Dialysate can be 3 liters /hr
Anticoagulation:
Dialysate:
600 – 1800 ml/hr (up to 3 lit/hr).
Replacement fluid….NO

55. Let’s Revise
• Primary therapeutic goal:
– Solute removal and safe management of fluid volume
• Primary indications:
– Uremia, severe acid/base or electrolyte imbalance
• Principle used:
Diffusion
• Therapy characteristics:
– Requires dialysate solution to drive diffusion
– No substitution solution
Effective at removing small to medium molecules

56. • The most flexible of all the therapies, and
combines the benefits of diffusion and
convection for solute removal.
• The use of replacement fluid allows adequate
solute removal even with zero or positive net
fluid balance for the patient.

57. • Amount of fluid in the effluent bag equals the fluid
removed from the patient plus the dialysate and the
replacement fluid.
• Dialysate on the opposite side of the filter and
replacement fluid either before or after the filter.
• Continuous diffusive and convective removal of
waste products (small and large molecules)
• Utilizing both dialysate and substitution solution.
• pH is also affected with the buffer contained in the
dialysate and substitution solution.

58. Understanding Flow

59. Let’s Revise
• Primary therapeutic goal:
– Solute removal and safe management of fluid volume
• Primary indications:
– Uremia, severe acid/base or electrolyte imbalance
– Removal of large molecular weight substances is required
– Unstable haemodunamics
• Principle used:
diffusion and convection
• Therapy characteristics:
– Requires dialysate fluid and substitution solution to
drive diffusion and convection
• Effective at removing small, medium and large
molecules

60. •
Blood flow:
Dosage:
80 – 200 ml/min
45ml/kg/hr
• Duration:
70x45=3150ml
½ as Dialysate& ½ as
As advised by the physician
Replacement fluid
• Ultrafiltration:
So
1500ml as Dialysate
20-100 ml/hr (or total volume)
1500ml as Replacement can
• Anticoagulation:
be divided into pre & post
filter
• Dialysate:
600 – 1800 ml/hr (up to 3 lit/hr) Depending upon physician
Ex, 500 pre and 1000ml post
• Replacement fluid:
1000-2000 ml/hr, pre or post filter (up to 3 lit/hr)

61. Thank you
I think that’s enough