Continuous Renal Replacement Therapy(CRRT)

Muhammad Asim RanaMBBS, MRCP, SF-CCM, EDIC, FCCP

Critical Care MedicineKing Saud Medical City

Riyadh, Saudi Arabia

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

Case 1

• 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

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

Case 3

• 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

Case 4

• 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

Objectives

• 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

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

Options for Renal Replacement Therapy

• Intermittent Hemo-Dialysis• Peritoneal Dialysis• Continuous Renal Replacement Therapy

Intermittent Hemodialysis

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

Advantages/Disadvantages

• Very efficient• Hemodynamic instability in ≤ 30 % of patients• Causes rapid shifts in osmolarity

– (Disequilibrium syndrome)• It is “Intermittent”

Peritoneal Dialysis

• Simple and cheap, but …….• Poor solute clearance• Poor uremic control• Risk of peritoneal infection• Mechanical impedance

– Pulmonary and cardiovascular function

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

Advantages

• 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)

Advantages

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

Disadvantages

• Expensive• Anticoagulation• Hypothermia• Severe depletion of electrolytes – K+ and PO4

• Complications of line insertion and sepsis• Risk of line disconnection

Principal

• 2 processes in waste product removal in RRT

1. Diffusion…………Dialysis

2. Convection…….Hemofiltration

Diffusion/Dialysis

Semipermiable Membrane

Semipermiable Membrane

Molecular Weights (Dalton) 100000 50000

10000 5000

1000 500 100

50

10

Albumin (55000 – 60000)

Beta 2 Microglobulin (11800) Inulin (5200)

Vit B12 (1355)

Aluminium/Desforoxamine complex (700)Glucose (180) Uric Acid (168) Creatinine (113) Phosphate (80)

Urea (60) Potassium (35) Phosphorus (31) Sodium (23)

Diffusion

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

Ultrafiltration

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.

Convection

Convection

Convection

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

Adsorption

Dialysate

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

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.

Replacement Fluids

Comparison Pre & Post Dilution

PRE-FILTER

– 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

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 A E I O U

Dialysable or NotDialysable Barbiturates

Lithium Alcohols, Amglcoside Salicylates

Theophyllin Penicillins,

Carbapenems, Cephalo

Non-Dialysable Digoxin

Tricyclic AntidepressentsPhenytoin BenzodiazepinesB-blockers

(atenolol is removed)Metformin

PC-B L A S T

Timing

• Inadequate data available to answer this Q

• Observational data suggests better outcomes are associated with early RRT initiation

Getting et al 19992. Urea 15.2 vs 33.7 conferred survival benefit.

Ronco et al 20003 and Saudan et al 20064 both dose/outcome studies suggested an early start.

Liu et al 20065 observational PICARD study (Urea 27) suggested an early start– RENAL study, NEJM 2009, 1508 pts.– Demirkilic 2004, Elahi 2004, Piccini 2006

Early Initiation means…

• 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.

CRRT Modalities

Slow Continuous Ultrafiltration (SCUF)

• 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.

• 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.

Understanding Flow

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

SCUF Dosage Writing

• 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

Effects of different doses in CVVH on outcome of ARF Ronco & Bellomo study. Lancet . july 00

• Prospective study on 425 patients - 3 groups:

• Study: – survival after 15 days of HF stop– recovery of renal function

306100135

100

90

80

70

60

50

40

30

20

10

0

Group 1(n=146)

(Uf = 20 ml/h/Kg)

Group 2 (n=139)

(Uf = 35 ml/h/Kg)

Group 3 (n=140)

(Uf = 45 ml/h/Kg)

41 % 57 % 58 %

p < 0.001 p n..s.

p < 0.001

Surv

ival

(%)

Effects of different doses in CVVH on outcome of ARF - Ronco & Bellomo study. Lancet . july 00

Continuous Veno-venous Hemofiltration (CVVH)

• 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.

• 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.

Understanding Flow

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

CVVH Dosage

• 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=2100mlReplacement fluid

SoThis Replacement can be

divided into pre & post filterDepending upon physician

Ex, 500 pre and 1500ml post(All can be pre or post)

Continuous Veno-venous Hemodialysis (CVVHD)

• 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.

Understanding flow

CVVHD Dosage

• Blood flow: 80 – 200 ml/min • Duration: As advised by physician• Ultrafiltration: 20 -100 ml/hr (or total volume)• Anticoagulation:• Dialysate: 600 – 1800 ml/hr (up to 3 lit/hr).• Replacement fluid….NO

Dosage:45ml/kg/hr

70x45=3150mlDialysatefluid

SoDialysate can be 3 liters /hr

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

Continuous Veno-venous Hemodiafiltration (CVVHDF)

• 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.

• 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.

Understanding Flow

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

CVVHDF Dosage • Blood flow: 80 – 200 ml/min• Duration: As advised by the physician • Ultrafiltration: 20-100 ml/hr (or total volume)• Anticoagulation:• Dialysate: 600 – 1800 ml/hr (up to 3 lit/hr)• Replacement fluid: 1000-2000 ml/hr, pre or post filter (up to 3 lit/hr)

Dosage:45ml/kg/hr

70x45=3150ml½ as Dialysate& ½ as

Replacement fluidSo

1500ml as Dialysate1500ml as Replacement can be divided into pre & post

filterDepending upon physician

Ex, 500 pre and 1000ml post

Thank you I think that’s enough