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Basics of Continuous Renal Replacement Therapy
The document presents an overview of Continuous Renal Replacement Therapy (CRRT) in critical care medicine, detailing various case studies and patient scenarios illustrating the use of CRRT. It outlines the theory, principles, and objectives of CRRT, including its advantages over other renal replacement therapies like intermittent hemodialysis and peritoneal dialysis. Additionally, the document discusses the mechanisms of solute removal, indications for CRRT, and dosing strategies applicable to different patient conditions.
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Basics of Continuous Renal Replacement Therapy
- 1. Continuous Renal ReplacementTherapy (CRRT) Muhammad Asim Rana MBBS, MRCP, SF-CCM, EDIC, FCCP Critical Care Medicine King Saud Medical City Riyadh, Saudi Arabia
- 2. Dedication • Today’s presentationis dedicated to • Dr Mohammed Odat • Dr Waleed Tharwat Hasim • Being the PIONEERS in KSMC ICU to start lectures on CRRT
- 3. Case 1 • • • • • • • • • 35 yrsmale 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 • 75yrs 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 • • • • • • • 45 yrsmale 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 • • • • • • • • 56 yrsmale 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 • • • • • To understand thetheory 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 functionsof 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 RenalReplacement Therapy • Intermittent Hemo-Dialysis • Peritoneal Dialysis • Continuous Renal Replacement Therapy
- 10. Intermittent Hemodialysis • • • • The goldstandard 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 • • • • • Simple andcheap, but ……. Poor solute clearance Poor uremic control Risk of peritoneal infection Mechanical impedance – Pulmonary and cardiovascular function
- 13. Continuous Renal ReplacementTherapy • 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 • • • • • Precise volume control Veryeffective 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 • • • • Needs minimal training Saferfor patients with TBI & CVS disorders May have an effect in sepsis Probable advantage in terms of renal recovery
- 16. Disadvantages • • • • • • Expensive Anticoagulation Hypothermia Severe depletion ofelectrolytes – K+ and PO4 Complications of line insertion and sepsis Risk of line disconnection
- 17. Principal • 2 processesin waste product removal in RRT 1. Diffusion…………Dialysis 2. Convection…….Hemofiltration
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- 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.
- 23. Ultrafiltration • The passageof 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
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- 25. Convection • Movement ofsolutes 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.
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- 29. Adsorption • Adsorption isthe 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
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- 31. Dialysate Dialysate is anyfluid used on the opposite side of the filter from the blood during blood purification.
- 32. Replacement Fluids • Usedto 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.
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- 34. 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
- 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 dataavailable 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 4 Ronco et al 2000 and Saudan et al 2006 both dose/outcome studies suggested an early start. 5 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
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- 39. CRRT Modalities • CRRTincludes 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 ofultrafiltrate 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 solutesare 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.
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- 43. Let’s Revise • Primarytherapeutic 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 differentdoses 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
- 46. Effects of differentdoses 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 extremelyeffective 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 canbe 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.
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- 50. Let’s Revise • Primarytherapeutic 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. • • • • • • 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. • • • • • Effective for removalof 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.
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- 54. • • • • • • 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 • Primarytherapeutic 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 mostflexible 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 offluid 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.
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- 59. Let’s Revise • Primarytherapeutic 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 thinkthat’s enough
Editor's Notes
- #38 Not a homogenous group, not one shoe fits all and use of different modalities may confer different survival and benefits. But certainly in ARF with no hx CKD and an unlikely quick recovery would all suggest early initiation would be wise. No negative outcomes demonstrated. Concurred by the recent recommendation by the ICS jan 2009.
- #52 Dose is strictly speaking solute clearance. This is difficult to measure so dose is usually described as the amount of effluent fluid in mls/kg/h: