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Acute renal replacement therapy – intermittent vs continuous modality

Acute renal replacement therapy – intermittent vs continuous modality. Dr. Overview. Introduction Acute RRT: Modalities CRRT versus IHD CRRT versus SLED Conclusions. Introduction. Acute kidney injury (AKI) is Frequent complication of hospitalization

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Acute renal replacement therapy – intermittent vs continuous modality

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  1. Acute renal replacement therapy – intermittent vs continuous modality Dr.

  2. Overview • Introduction • Acute RRT: Modalities • CRRT versus IHD • CRRT versus SLED • Conclusions

  3. Introduction • Acute kidney injury (AKI) is • Frequent complication of hospitalization • Associated with substantial morbidity, mortality and health care expenditures • Prevalence: 1–25% and • Mortality: 20–60% associated with AKI in hospitalized patients Nephron Clin Pract 2009;112:c222–c229

  4. Introduction • Although understanding of the epidemiology of AKI has improved, there are • No proven therapies that reverse the course of established AKI • Renal replacement therapy (RRT) • Key component of the supportive care given to patients with severe AKI Nephron Clin Pract 2009;112:c222–c229

  5. Introduction • RRT in AKI • Approx. 4% of all critically ill patients will require RRT • Among RRT-requiring patients who survive the critical phase of their illness, the majority will be free of RRT at the time of hospital discharge JAMA 2005; 294: 813–818, Crit Care 2005; 9: R700–R709.

  6. Acute RRT: Modalities • RRT Modality Choice • Intermittent hemodialysis (IHD), • Continuous renal replacement therapies (CRRT) and • Sustained low-efficiency dialysis (SLED) are • principal RRT modalities that are used in the acute setting Nephron Clin Pract 2009;112:c222–c229

  7. Acute RRT: Modalities • Although institutional policies may determine the local availability of these modalities, • CRRT and SLED tend to be used in patients with greater hemodynamic instability • There is likely substantial intercenter variability with respect to how each of these forms of RRT is utilized and prescribed

  8. Acute RRT: Modalities Table: Practical comparison of acute RRT modalities Nephron Clin Pract 2009;112:c222–c229

  9. Acute RRT: Modalities • IHD • Typically administered with conventional dialysis machinery that is used in the chronic dialysis population with session length ranging from 3 to 5 h Nephron Clin Pract 2009;112:c222–c229

  10. Acute RRT: Modalities • CRRT • Is applied with an intended treatment time of 24 h and generally requires dedicated machines that operate at comparatively lower blood and dialysate pump speeds • Hemodialysis (continuous venovenous hemodialysis, CVVHD), • Hemofiltration (continuous venovenous hemofiltration, CVVH) or a • Combination of these (continuous venovenous hemodiafiltration, CVVHDF) Nephron Clin Pract 2009;112:c222–c229

  11. Nomenclature

  12. Continuous renal replacement therapies CRRT is generally better tolerated than conventional therapy, since many of the complications of intermittent hemodialysis are related to the rapid rate of solute and fluid loss CRRT involves either Dialysis (diffusion-based solute removal) or Filtration (convection-based solute and water removal) treatments that operate in a continuous mode

  13. Continuous renal replacement therapies Continuous venovenous hemofiltration (CVVH) Dialysis solution is not used, instead large volumes of replacement fluids are given Continuous venovenous hemodialysis (CVVHD) Dialysate is passed through at a slow rate continuously Continuous venovenous hemodiafiltration (CVVHDF) Combination; both dialysate and replacement fluids are used Slow continuous ultrafiltration (SCUF)  Sustained low efficiency or extended daily dialysis (SLED)

  14. Advantages of CRRT In addition to better control of azotemia, fluids and hemodyanmic stability ? Enhanced clearance of inflammatory mediators, which may provide benefit in septic patients, particularly using convective modes of continuous therapy. ? Among patients with acute brain injury or fulminant hepatic failure, continuous therapy may be associated with better preservation of cerebral perfusion.

  15. Caveats to CRRT No evidence from randomized trials to support survival advantage Risk of complications related to anticoagulation is higher Training and equipment costs

  16. Acute RRT: Modalities • SLED • sometimes referred to as extended dialysis, is considered a ‘hybrid’ of IHD and CRRT • Administered using conventional dialysis technology but typical sessions run for 8–12 h using blood and dialysis flows that are intermediate to those prescribed in IHD and CRRT Nephron Clin Pract 2009;112:c222–c229

  17. Initial Choice of RRT for AKI • IHD Hemodynamically stable Severe hyperkalemia • CRRT Hemodynamically unstable Can not tolerate fluid removal Intracranial bleed • PD

  18. CRRT versus IHD • Most trials that addressed the question of optimal RRT modality compared CRRT and IHD Table: Results of individual RCTs comparing CRRT to IHD Nephron Clin Pract 2009;112:c222–c229

  19. CRRT versus IHD • A trial by Mehta et al. revealed higher ICU mortality in patients treated with CRRT as compared to IHD (59.5 vs. 41.5%) • This finding was tempered by apparent baseline imbalances between the groups, whereby patients randomized to CRRT had a greater severity of illness • Renal recovery did not differ between the groups Nephron Clin Pract 2009;112:c222–c229

  20. CRRT versus IHD • In a larger multicenter RCT conducted in France comparing CRRT and IHD in critically ill patients with AKI, • 60-day mortality was not reduced by CRRT, and there was no significant difference in the duration of RRT dependence • Three additional trials have shown no survival benefit with CRRT Nephron Clin Pract 2009;112:c222–c229

  21. CRRT versus IHD • The presumption of greater hemodynamic stability with CRRT also remains controversial • Three RCTs suggested no advantage with CRRT as compared to IHD, while others demonstrated more favorable hemodynamics with CRRT • Even if CRRT confers a hemodynamic benefit, • It is unclear whether this translates into improvements in the patient-relevant outcomes of survival and renal recovery Nephron Clin Pract 2009;112:c222–c229

  22. CRRT versus SLED • In addition to the absence of a survival advantage, CRRT is more costly than IHD and is associated with a number of obstacles such as • Continuous patient immobilization, • The requirement for anticoagulation and • The need for specialized machines and premixed commercial solutions • This has stimulated a search for a strategy that • Incorporates the putative hemodynamic benefits of CRRT without the associated logistic and resource constraints • SLED meets many of these criteria Nephron Clin Pract 2009;112:c222–c229

  23. CRRT versus SLED • SLED • Observational data from single centers suggest that SLED is a feasible way of providing RRT that is • Adequate, hemodynamically well tolerated, potentially anticoagulation-free and possibly cost-effective • However, only two small RCTs have compared SLED and CRRT Nephron Clin Pract 2009;112:c222–c229

  24. CRRT versus SLED • Kielstein et al. randomized 39 critically ill patients with AKI to receive • Either 24 h of CVVH or 12h of SLED • Using invasive monitoring, these authors found • No significant differences in all measured hemodynamic parameters (mean arterial pressure, systemic vascular resistance, cardiac output) with comparable removal of creatinine and urea Am J Kidney Dis 2004; 43: 342–349.

  25. CRRT versus SLED • A smaller study randomized 16 patients to receive three sessions with either CVVH or SLED (with an added hemofiltration component), and showed that • fluid removal and hemodynamic parameters were similar in both groups Nephron Clin Pract 2009;112:c222–c229

  26. CRRT versus SLED • Utilization of slow low-efficiency dialysis may help to optimize the need for continuous renal replacement therapy in Indian ICUs • A Majumdar, S Basu et al, AMRI Hospitals, Kolkata, • The aim was to study the practice pattern of using the modern modalities of RRT, • SLED and CRRT in hemodynamically unstable critically ill patients in an Indian ICU Critical Care 2009, 13(Suppl 1):P271

  27. CRRT versus SLED • Indian study continued • Methods A retrospective observational study of hemodynamically unstable patients with AKI who needed RRT in ICUs of a tertiary-care hospital • All patients who underwent SLED and/or CRRT from September 2005 to April 2008 were taken up for analysis • To maintain a mean arterial pressure (MAP) >70 mmHg, • Patients who required noradrenaline >0.5 μg/kg/minute were treated with CRRT whereas those requiring ≤0.5 μg/kg/minute received SLED • Depending on haemodynamic stability patients were switched from CRRT to SLED, or vice versa Critical Care 2009, 13(Suppl 1):P271

  28. CRRT versus SLED • Indian study continued • Results From September 2005 to April 2008, 214 haemodynamically unstable AKI patients, deemed unfit for intermittent haemodialysis, underwent SLED/CRRT (CVVH/CVVHDF) • Ten patients were switched to SLED after a median 48 hours of CRRT Critical Care 2009, 13(Suppl 1):P271

  29. CRRT versus SLED Indian study continued Results Critical Care 2009, 13(Suppl 1):P271

  30. CRRT versus SLED Indian study continued Results Critical Care 2009, 13(Suppl 1):P271

  31. CRRT versus SLED • Indian study continued • Conclusions the need for RRT in hemodynamically unstable patients with AKI was significantly higher in the medical patients, the commonest cause of AKI being sepsis • Patients who were equally sick (comparable APACHE II scores) could be effectively dialysed by SLED, as compared with CRRT • Hemodynamic stability was maintained in the patients on SLED, as none needed switchover to CRRT • The patients undergoing SLED were dialysed during daytime by the haemodialysis nurse, eliminating the need for a specialist nurse in the night Critical Care 2009, 13(Suppl 1):P271

  32. CRRT versus SLED • Indian study continued • Conclusions • After a median 48 hours of CRRT, it was possible to switch to SLED, resulting in optimal utilization of resources • SLED was much cheaper than CRRT • In a country like India where often there are economical constraints, the judicious use of SLED will help us optimize the need for CRRT Critical Care 2009, 13(Suppl 1):P271

  33. CRRT versus SLED • Although these preliminary data suggest that SLED may supplant CRRT as the modality of choice for hemodynamically unstable patients with AKI, • further studies that utilize patient-relevant outcomes are required to define the precise role of SLED Nephron Clin Pract 2009;112:c222–c229

  34. CRRT versus SLED • A strategy has recently been described whereby • CRRT machinery was applied over a contracted treatment time of 9 h, using increased blood and effluent flow rates • Termed accelerated venovenous hemofiltration, this modality retains many of the feasibility advantages of SLED, • but dedicated commercial solutions were still required • A retrospective case series demonstrated • adequate solute removal, acceptable hemodynamic tolerability and the ability to avoid systemic anticoagulation Am JKidney Dis 2008; 51: 804–810.

  35. PD Vs CRRT

  36. PD • IPD, CAPD, CCPD,CFPD • Common modality in pediatric patients • Limitations: - Effect on respiratory status - ? in using it in abdominal sepsis or abdominal surgery - Relative inefficiency in removing waste products in a catabolic patient -High incidence of associated peritonitis

  37. PD vs CRRT • Patients with severe falciparum malaria (48 patients) and sepsis (22 patients) • Assignment: 34 to hemofiltration and 36 to PD. • PD: 70 liters/ day of dialyzate was used • CVVH: 25 liters of replacement fluid was used Replacement fluid was lactate based with glucose of 2g/L Dialyzate was Acetate based with glucose of 15g/L • Results: PD has Lower rate of resolution of acidosis Slower rate of decline in plasma Creatinine Markedly increased risk of death

  38. Conclusions • Despite the conceptual advantages of CRRT, multiple RCTs have shown no evidence of improved patient outcomes with this modality, as compared to conventional IHD • The logistic challenges associated with CRRT and the relatively high costs of this modality may stimulate the increased use of SLED • However, well-designed RCTs are still needed to better characterize the reported benefits of SLED prior to its widespread adoption

  39. Conclusions • The current balance of evidence suggests that among hemodynamically unstable patients, CRRT need not be administered at doses higher than 20 ml/kg/h, and in more stable patients, alternate day IHD is acceptable

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