ICU · Renal/Metabolic
Renal replacement therapy in the ICU: CRRT and IHD
Also known as Continuous renal replacement therapy (CRRT) · Intermittent haemodialysis (IHD) · Sustained low-efficiency dialysis (SLED) · CVVH, CVVHD, CVVHDF, SCUF · Regional citrate anticoagulation · Peritoneal dialysis
Renal replacement therapy (RRT) in the ICU includes CRRT (continuous, gentler, preferred in haemodynamically unstable patients), IHD (intermittent, faster, preferred in stable patients), and SLED (hybrid, 6-12h). CRRT modalities: SCUF (fluid removal only), CVVH (haemofiltration — convection), CVVHD (haemodialysis — diffusion), CVVHDF (both). Timing: AKIKI (early start immediately at KDIGO stage 3) and STARRT-AKI (accelerated start within 12 h) showed NO benefit vs delayed, indication-based start. Start RRT when: refractory hyperkalaemia, acidosis, fluid overload, uraemia, or specific toxin. Anticoagulation: regional citrate (preferred — no systemic anticoagulation) or heparin. Dose: effluent rate 20-25 mL/kg/h (higher doses do NOT improve outcomes — RENAL and ATN trials).
Checked against its sources on 5 Sept 2026
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Red flags
- AKIKI and STARRT trials: NO benefit of early RRT — start only when indicated (not just because AKI exists)
- Regional citrate anticoagulation is preferred — but monitor for citrate toxicity (metabolic acidosis, ionised Ca low with normal/ rising total Ca)
- Higher CRRT dose (>25 mL/kg/h) does NOT improve outcomes — standard dose is 20-25 mL/kg/h
- Do NOT stop CRRT for procedures unless absolutely necessary — each interruption reduces delivered dose
- Citrate accumulation: total Ca / ionised Ca ratio at or above 2.4 predicts mortality and tracks hepatic dysfunction — switch to heparin; avoid citrate in severe hepatic failure
- CRRT clears beta-lactams, vancomycin and aminoglycosides — underdosing is common (DALI: 16% of infected ICU patients missed the 50% fT>MIC beta-lactam target) and drives treatment failure
Meet the patient
A 64-year-old woman with septic shock from an obstructed urinary tract has been on noradrenaline for 36 hours. She has passed 30 mL of urine all shift, her potassium is 6.8 mmol/L with peaked T waves, her pH is 7.15, and she sits 6 litres net positive. The registrar asks whether to "start dialysis now before she arrests".[1]
Two questions decide her next hour, and they decide every ICU renal-replacement referral: is there an indication I must act on right now? and which modality fits her circulation? Hold those two and the whole topic slots into place — start for an indication, choose by stability, dose to twenty-five, citrate unless the liver fails, and dose the antibiotics up. [1][2][9][10]
References27ShowHide
- [1]Gaudry S, Hajage D, Schortgen F, et al. Initiation Strategies for Renal-Replacement Therapy in the Intensive Care Unit N Engl J Med, 2016.PMID 27181456
- [2]Bagshaw SM, Wald R, Adhikari NKJ, et al. Timing of Initiation of Renal-Replacement Therapy in Acute Kidney Injury N Engl J Med, 2020.PMID 32668114
- [3]Tsujimoto H, Tsujimoto Y, Nakata Y, et al. Pharmacological interventions for preventing clotting of extracorporeal circuits during continuous renal replacement therapy Cochrane Database Syst Rev, 2020.PMID 33314078
- [4]Zarbock A, Kellum JA, Schmidt C, et al. Effect of Early vs Delayed Initiation of Renal Replacement Therapy on Mortality in Critically Ill Patients With Acute Kidney Injury: The ELAIN Randomized Clinical Trial JAMA, 2016.PMID 27209269
- [5]Bellomo R, Cass A, Cole L, et al. Intensity of continuous renal-replacement therapy in critically ill patients N Engl J Med, 2009.PMID 19846848
- [6]Palevsky PM, Zhang JH, O'Connor TZ, et al. Intensity of renal support in critically ill patients with acute kidney injury N Engl J Med, 2008.PMID 18492867
- [7]Roberts JA, Paul SK, Akova M, et al. DALI: defining antibiotic levels in intensive care unit patients: are current β-lactam antibiotic doses sufficient for critically ill patients? Clin Infect Dis, 2014.PMID 24429437
- [8]Schwenger V, Weigand MA, Hoffmann O, et al. Sustained low efficiency dialysis using a single-pass batch system in acute kidney injury - a randomized interventional trial: the REnal Replacement Therapy Study in Intensive Care Unit PatiEnts Crit Care, 2012.PMID 22839577
- [9]Claure-Del Granado R, Clark WR Continuous renal replacement therapy principles Semin Dial, 2021.PMID 33819361
- [10]Bagshaw SM, Chakravarthi MR, Ricci Z, et al. Precision Continuous Renal Replacement Therapy and Solute Control Blood Purif, 2016.PMID 27562079
- [11]Lyndon WD, Wille KM, Tolwani AJ Solute clearance in CRRT: prescribed dose versus actual delivered dose Nephrol Dial Transplant, 2012.PMID 21896498
- [12]Zarbock A, Küllmar M, Kindgen-Milles D, et al. Effect of Regional Citrate Anticoagulation vs Systemic Heparin Anticoagulation During Continuous Kidney Replacement Therapy on Dialysis Filter Life Span and Mortality Among Critically Ill Patients With Acute Kidney Injury: A Randomized Clinical Trial JAMA, 2020.PMID 33095849
- [13]Tolwani AJ, Prendergast MB, Speer RR, et al. A practical citrate anticoagulation continuous venovenous hemodiafiltration protocol for metabolic control and high solute clearance Clin J Am Soc Nephrol, 2006.PMID 17699194
- [14]Link A, Klingele M, Speer T, et al. Total-to-ionized calcium ratio predicts mortality in continuous renal replacement therapy with citrate anticoagulation in critically ill patients Crit Care, 2012.PMID 22643456
- [15]Meier-Kriesche HU, Gitomer J, Finkel K, et al. Increased total to ionized calcium ratio during continuous venovenous hemodialysis with regional citrate anticoagulation Crit Care Med, 2001.PMID 11373461
- [16]Heintz BH, Matzke GR, Dager WE Antimicrobial dosing concepts and recommendations for critically ill adult patients receiving continuous renal replacement therapy or intermittent hemodialysis Pharmacotherapy, 2009.PMID 19397464
- [17]Ulldemolins M, Vaquer S, Llauradó-Serra M, et al. Beta-lactam dosing in critically ill patients with septic shock and continuous renal replacement therapy Crit Care, 2014.PMID 25042938
- [18]Peng Y, Cheng Z, Xie F Population Pharmacokinetic Meta-Analysis and Dosing Recommendation for Meropenem in Critically Ill Patients Receiving Continuous Renal Replacement Therapy Antimicrob Agents Chemother, 2022.PMID 36005753
- [19]Rybak MJ, Lomaestro BM, Rotschafer JC, et al. Therapeutic monitoring of vancomycin in adults summary of consensus recommendations from the American Society of Health-System Pharmacists, the Infectious Diseases Society of America, and the Society of Infectious Diseases Pharmacists Pharmacotherapy, 2009.PMID 19873687
- [20]Assefi M, Braik R, James A, et al. Impact of increasing post-filter ionised calcium target on regional citrate anticoagulation efficacy in ICU continuous renal replacement therapy: the non-inferiority randomised controlled Ca-CIBLE protocol BMJ Open, 2024.PMID 39327056
- [21]Patel N, Dalal P, Panesar M Dialysis disequilibrium syndrome: a narrative review Semin Dial, 2008.PMID 18764799
- [22]Gaudry S, Hajage D, Martin-Lefevre L, et al. Comparison of two delayed strategies for renal replacement therapy initiation for severe acute kidney injury (AKIKI 2): a multicentre, open-label, randomised, controlled trial Lancet, 2021.PMID 33812488
- [23]Stuard S, Hugh-Jones C, Chatoth D, et al. Uremic Toxins and Hemodiafiltration: From Molecular Mechanisms to Clinical Outcomes Toxins (Basel), 2026.PMID 42506732
- [24]Hui WF, Deep A Interpreting liver function markers in children on continuous renal replacement therapy for acute liver failure Eur J Pediatr, 2025.PMID 41073764
- [25]Parienti JJ, Thirion M, Mégarbane B, et al. Femoral vs jugular venous catheterization and risk of nosocomial events in adults requiring acute renal replacement therapy: a randomized controlled trial JAMA, 2008.PMID 18505951
- [26]Rotellar C, Sims SC, Freeland J, et al. Right atrium thrombosis in patients on hemodialysis Am J Kidney Dis, 1996.PMID 8629635
- [27]Kelton JG Heparin-induced thrombocytopenia: an overview Blood Rev, 2002.PMID 11914002