Rationale: often required with RRT to prevent circuit clotting (although patients with thrombocytopenia or coagulopathy may be managed without anticoagulation)
Agents
Citrate (see Sodium Citrate, [[Sodium Citrate]]): citrate is infused into afferent blood line and functions to bind calcium, preventing coagulation
Removal of Citrate is Dependent on the Dialysate Flow and/or Ultrafiltration Rate
Citrate May Enter the Systemic Circulation, Resulting in Hypocalcemia: may require intravenous calcium supplementation
Citrate Metabolism May Be Impaired in Patients with Liver Failure
Regional Citrate Anticoagulation (Trisodium Citrate) Has Been Studied in the L-CAT Trial with CCVHD in Patients with Liver Failure and is Considered Safe and Efficacious (Crit Care, 2015) [MEDLINE]
Heparin (see Heparin, [[Heparin]]): less commonly used, as compared to citrate
Choice of Dialysis Technique for Renal Replacement Therapy
Preferred Hemodialysis Modality in Specific Clinical Scenarios
Burns (see Burns, [[Burns]]): protracted high-flux hemodialysis or hemodiafiltration (with high blood and dialysate flow) is recommended to remove iodine, which may accumulate in these patients (iodine molecular weight is 253, with similar clearance to that of small solutes such as urea)
Chronic Hyponatremia: low-efficiency RRT (CVVH) is recommended to avoid rapid changes in serum sodium
Ethylene Glycol Intoxication (see Ethylene Glycol, [[Ethylene Glycol]]): HD
Hepatorenal Syndrome (see Hepatorenal Syndrome, [[Hepatorenal Syndrome]]): no data exist to guide using one RRT modality over another
Isoniazid Intoxication (see Isoniazid, [[Isoniazid]]): HD
Lithium Intoxication (see Lithium, [[Lithium]]): HD
Metformin Intoxication (see Metformin, [[Metformin]]): HD
Methanol Intoxication (see Methanol, [[Methanol]]): HD
Ongoing Large Fluid Requirements: CVVHD is preferred over intermittent HD, due to the better ability to maintain fluid balance with CVVHD
Rhabdomyolysis (see Rhabdomyolysis, [[Rhabdomyolysis]]): intermittent HD is preferred ovr CVVHD, due to the more rapid solute removal with intermittent HD
Salicylate Intoxication (see Salicylate, [[Salicylate]]): HD may be used in patients with severe salicylate intoxication with fluid overload and cerebral edema
Severe Accidental Hypothermia: while cardiopulmonary bypass is the preferred modality, HD (without coagulation, as hypothermia is associated with coagulopathy) may alternately be used to warm a hemodynamically stable patient
Severe Cerebral Edema/Increased Intracranial Pressure (see Increased Intracranial Pressure, [[Increased Intracranial Pressure]]): CVVHD is preferred over intermittent HD, due to rapid solute changes and potential for hypotension in intermittent HD (which may exacerbate cerebral ischemia)
Severe Hyperkalemia (see Hyperkalemia, [[Hyperkalemia]]): intermittent HD is preferred ovr CVVHD, due to the more rapid solute removal with intermittent HD
Severe Lactic Acidosis (see Lactic Acidosis, [[Lactic Acidosis]]): CVVHD is preferred, as dialysis is more efficient in removing small molecules (such as lactate) and continuous method prevents intradialytic rebound
Valproic Acid Intoxication (see Valproic Acid, [[Valproic Acid]]): HD
Clinical Efficacy
French HEMODIAFE Multi-Center Randomized Trial of Intermittent vs Continuous Hemodialysis in AKI Associated with Multi-Organ Dysfunction in Critically Ill Patients (Lancet, 2006)
Provided That Precautions to Improve Tolerance and Metabolic Control are Used, Almost All Critically Ill Patients Can Be Dialyzed with Intermittent Hemodialysis with No Change in the Mortality Rate
Precautions: less aggressive ultrafiltration (with increased treatment duration and hemodynamic measurements to guide therapy), increasing dialysate sodium and calcium concentrations, adapting the dialysate temperature to obtain isothermic dialysis, connecting afferent and efferent bloodlines simultaneously at the start of the procedure, using low blood flow (<150 mL/min) and low dialysate flows, using biocompatible membranes, and using ultrapure water
Single Center Randomized CONVINT Trial of Intermittent vs Continuous Hemodialysis in AKI in Critically Ill Patients (Crit Care, 2014)
No Difference in Mortality Rate or Renal-Related Outcomes Between Intermittent and Continuous Hemodialysis
Timing of Initiation of Renal Replacement Therapy
Clinical Efficacy
AKIKI Trial Studying Early vs Delayed Renal Replacement Therapy for AKI in the ICU (NEJM, 2016) [MEDLINE]: multicenter randomized trial
No Difference in Mortality Between Early Initiation vs Delayed Initiation of Renal Replacement Therapy
ELAIN Trial of Early vs Delayed Renal Replacement Therapy for AKI in the ICU (JAMA, 2016) [MEDLINE]: single-center German randomized trial
Early Initiation of Renal Replacement Therapy in Critically Ill Patients Decreased the 90-Day Mortality Rate, as Compared to Delayed Initiation
More Patients in the Early Group Recovered Renal Function by 90 Days
Early Initiation Decreased the Duration of Renal Replacement Therapy and Hospital Length of Stay
Early Initiation Had No Effect on Requirement for Renal Replacement Therapy After 90 Days, Organ Dysfunction, and Length of ICU Stay
Recommendations
Timing of Initiation of Renal Replacement Therapy in Critically Ill Patients Remains Unclear: standard clinical indications should be used to determine the timing of initiation of hemodialysis in critically ill patients
Colonic Ischemia (Ischemic Colitis) (see Colonic Ischemia, [[Colonic Ischemia]]): due to underlying atherosclerosis, diabetes, and hemodialysis-induced hypotension
Hemodialysis-Associated Hypoxemia (see Hypoxemia, [[Hypoxemia]])
Physiology
Complement Activation by Bioincompatible Dialysis Membrane (Cuprophane): results in WBC aggregation within pulmonary microcirculation -> V/Q mismatch
Hypocapnia-Induced Hypoventilation: when acetate dialysate is used, there is net loss of bicarbonate from patient across dialyzer and also a flux of acetate into patient (decreasing respiratory quotient)
Induced Metabolic Alkalosis: use of dialysates with bicarbonate >37 mEq/L causes alkalemia -> decreases central respiratory drive
Not seen as much with dialysate bicarbonate <35 though
Prevention
Use Biocompatible Membranes: such as polyacrylonitrile/polysulfone/polymethyl methacrylate
Note: use of bioincompatible membranes may also prolong the course of AKI
Decrease Dialysate Bicarbonate to <35 mEq/L
Avoid Acetate-Based Dialysate: it also depresses myocardium and may increase hemodynamic instability
Other Adverse Effects/Complications
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References
Hemodialysis-associated hypoxemia. Am J Nephrol. 1984;4(5):273-9 [MEDLINE]
Hemodialysis associated hypoxia extends into the post-dialysis period. Int J Artif Organs. 1997 Apr;20(4):204-7 [MEDLINE]
Hemodynamic tolerance of intermittent hemodialysis in critically ill patients. Usefulness of practice guidelines. Am J Respir Crit Care Med 2000, 162:197-202 [MEDLINE]
Continuous venovenous haemodiafiltration versus intermittent haemodialysis for acute renal failure in patients with multiple-organ dysfunction syndrome: a multicentre randomised trial. Lancet. 2006;368:379–385 [MEDLINE]
84-year-old woman with hemodialysis-associated shortness of breath. Mayo Clin Proc. 2009 Feb;84(2):187-90; quiz 187-9. doi: 10.1016/S0025-6196(11)60827-6 [MEDLINE]
Clinical review: use of renal replacement therapies in special groups of ICU patients. Crit Care. 2012;16:201 [MEDLINE]
The effect of continuous versus intermittent renal replacement therapy on the outcome of critically ill patients with acute renal failure (CONVINT): a prospective randomized controlled trial. Crit Care. 2014;18(1):R11. doi: 10.1186/cc13188 [MEDLINE]
Safety and efficacy of regional citrate anticoagulation in continuous venovenous hemodialysis in the presence of liver failure: the Liver Citrate Anticoagulation Threshold (L-CAT) observational study. Crit Care. 2015 Sep 29;19:349. doi: 10.1186/s13054-015-1066-7 [MEDLINE]
AKIKI Trial. Initiation Strategies for Renal-Replacement Therapy in the Intensive Care Unit. N Engl J Med. 2016 Jul 14;375(2):122-33. doi: 10.1056/NEJMoa1603017. Epub 2016 May 15 [MEDLINE]
ELAIN Trial. 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;315(20):2190 [MEDLINE]