Dialysis in Critically Ill

Dialysis in the Critically Ill

Fellow’s conferenceCheryl Pirozzi, MDFebruary 15, 2012

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Outline

AKI in the ICU Principles of RRT Modes of RRT Indications for RRT Optimal timing: When to start and stop Optimal modality: When to use what Optimal dosing RRT in specific clinical situations Conclusions

AKI in the ICU

AKI is common in the ICU Depending on definition of AKI, up to 50-60% of patients in the ICU

Up to 70% of these will require RRT Independent risk factor for mortality, 50 - 60% mortality in critically ill

•Miller's Anesthesia, 7th ed. 2009

Rondon-Berrios. Curr Opin Nephrol Hypertens. 2007 Mar;16(2):64-70.Foot. Current Anaesthesia and Critical Care 2005; 16:321-329

AKI in the ICU

Treatment of acute kidney injury (AKI) is principally supportive -- renal replacement therapy (RRT) indicated in patients with severe kidney injury.

Goal: optimization of fluid & electrolyte balance

Multiple modalities of RRT : Intermittent hemodialysis (IHD), continuous renal replacement therapies (CRRTs)

hybrid therapies, ie sustained low-efficiency dialysis (SLED)

Foot. Current Anaesthesia and Critical Care 2005; 16:321-329

Principles of dialysis Dialysis = diffusion = passive movement of solutes across a semi-permeable membrane down concentration gradient Good for small molecules

(Ultra)filtration = convection = solute + fluid removal across semi-permeable membrane down a pressure gradient (solvent drag) Better for removal of fluid and medium-size molecules

Faber. Nursing in Critical Care 2009; 14: 4Foot. Current Anaesthesia and Critical Care 2005; 16:321-329

Principles of dialysis

•Miller's Anesthesia, 7th ed. 2009•Foot. Current Anaesthesia and Critical Care 2005; 16:321-329

Hemodialysis = solute passively diffuses down concentration gradient Dialysate flows countercurrent to blood flow. Urea, creatinine, K move from blood to dialysate

Ca and bicarb move from dialysate to blood. Hemofiltration: uses hydrostatic pressure gradient

to induce filtration / convection plasma water + solutes across membrane.

Hemodiafiltration: combination of dialysis and filtration.

Modality of RRT

Intermittent hemodialysis (IHD) Continuous renal replacement therapy (CRRT)

Peritoneal dialysis Hybrid therapies, like SLEDD

Intermittent hemodialysis (IHD) Oldest and most common technique Primarily diffusive treatment: blood and dialysate are circulated in countercurrent manner Also some fluid removal by ultrafiltration due to pressure driving through circuit

Best for removal of small molecules typically performed 4 hours 3x/wk or daily

•Miller's Anesthesia, 7th ed. 2009Foot. Current Anaesthesia and Critical Care 2005; 16:321-329

Continuous RRT

Introduced in 1980s involve either dialysis (diffusion-based solute removal) or filtration (convection-based solute and water removal) treatments in a continuous mode with slower rate of solute or fluid removal

CRRT includes continuous hemofiltration, hemodialysis and hemodiafiltration, all of which can be performed using arteriovenous or venovenous extracorporeal circuits.

Continuous RRT Continuous venovenous hemofiltration (CVVH): Uses blood pump to remove fluids/solutes by convection

Continuous venovenous hemodialysis (CVVHD): Uses pump + dialysate run at low flow rate countercurrent to blood flow Slower fluid removal but greater solute removal

Continuous venovenous hemodiafiltration (CVVHDF): combines diffusion for small solute removal + convection for large solutes Large volume filtered fluid → Requires replacement fluid

Most commonly used modality at the U

Continuous RRT

Arteriovenous versions (CAVH, CAVHD and CAVHDF) are similar to venovenous except use AV access and systemic BP to run and blood pump not required. Downsides: requires arterial cannulation (+ venous)

Unreliable flow in pts with ↓ BP or severe PVD

Requires more anticoagulation VV preferred due to lower risk, only one dual lumen catheter, and faster/more reliable flow

Slow continuous ultrafiltration (SCUF): used for fluid removal in overloaded CHF patients

blood is driven through a highly permeable filter in a venovenous mode to primarily remove water, not solute.

The ultrafiltrate produced during membrane transit is not replaced so it corresponds to the fluid loss.


Peritoneal dialysis

Least useful form of CRRT in the ICU diffusive treatment: blood in capillaries of peritoneal membrane exposed to dialysate in abdomen

continuous or intermittent Inefficient solute/volume clearance if unstable or poor intestinal blood flow

Can’t use if intraabdominal pathology- risk of peritonitis

Respiratory burden Only two RCTs comparing to hemodialysis in AKI: found inferior or no difference

Vanholder. Critical Care 2011;15:204Foot. Current Anaesthesia and Critical Care 2005; 16:321-329

Sustained low-efficiency daily dialysis (SLEDD) AKA Extended daily dialysis (EDD) or slow continuous dialysis (SCD)

Hybrid therapy: IRRT at lower blood and dialysate flows for prolonged times (Usually ≥ 5 hrs)

Uses conventional dialysis machines Flexibility of duration and intensity Major advantages: flexibility, reduced costs, low or absent anticoagulation

Used at IMC but not U due to tech/nurse training

Anticoagulation CRRT requires continuous anticoagulation to prevent clotting in the CRRT circuit

Tricky bcs ICU pts often at increased risk of bleeding and hypercoagulable

Many options: Systemic anticoagulation with heparin (mst common), LMWH, heparinoids, thrombin antagonists

Regional citrate anticoagulation (preferred)

Other regional anticoagulation ie heparin/protamine

Davenport. NDT Plus (2009) 2: 439–447

Regional citrate anticoagulation Citrate infused into the blood at the start of the circuit

provides anticoagulation by chelating iCa++

Requires systemic Ca infusion to replace Ca lost with citrate

target extracorporeal blood citrate 4–6 mmol/l, pre-filter iCa++ <0.35 mmol/l


Regional citrate anticoagulation Advantages of RCA for CRRT:

avoids systemic anticoagulation (lower bleeding risk) and heparin risks (HIT)

act as a buffer by conversion through to bicarbonate

Disadvantages: potential metabolic complications: metabolic acidosis/alkalosis, hypoCa, HyperNa, hypoMag

complex protocols-- q6h monitoring of Na, K, Cl, iCa++, Mg, ABG, AG

More expensive


Indications for RRT

Acute management of life-threatening complications of AKI:

A: Metabolic acidosis (pH less than 7.1) E: Electrolytes -- Hyperkalemia (K >6.5 meq/L) or rapidly rising K)

I: Ingestion -- Certain alcohol and drug intoxications

O: Refractory fluid overload U: Uremia, ie. pericarditis, neuropathy, decline in mental status

Timing of initiation of RRT

Unclear if earlier RRT is better Theoretical benefits: may attenuate organ injury from acidemia, uremia, fluid overload, and systemic inflammation

Several non-randomized studies have reported improved outcomes (incl survival), associated with early RRT

One RCT: Bouman Crit Care Med. 2002;30(10):2205 106 ICU pts with UOP < 30 x 6 hrs and CrCl <20

assigned to early (≤ 12 hrs) high- or low- volume CVVH, vs late (BUN 40 mmol/L, K 6.5 mmol/L or severe pulmonary edema) low-volume CVVH→

Survival at 28 days and recovery of renal fcn equivalent. However, underpowered


Karvellas. A comparison of early versus late initiation of renal replacement therapy in critically ill patients with acute kidney injury. Critical Care 2011, 15:R72

Meta-analysis of 15 studies

Early RRT initiation associated with ↓mortality (pooled OR 0.45)

However, significant heterogeneity and bias

Some studies showed greater renal recovery, ↓ duration RRT and ICU length of stay


Earlier initiation of RRT in critically ill patients with AKI may have a beneficial impact on survival and outcomes but data is insufficient

Many recommend initiation of RRT prior to the development of advanced uremic symptoms, or when the BUN reaches 80 - 100 mg/dL

No known threshold of fluid overload for initiating RRT

Discontinuation of RRT

Until “evidence of recovery of kidney function” Improved UOP in oliguria Decreasing creatinine Creatinine clearance minimum 12 mL/min, some say 20 mL/min

Continuous vs intermittent dialysis Ongoing debate Theoretical benefits to both At least 7 RCTs and 3 meta-analyses have not demonstrated difference in outcome Eg Bagshaw Crit Care Med 2008, 36:610-617: metaanalysis of 9 randomized trials: No effect on mortality (OR 0.99) or recovery to RRT independence (OR 0.76).

suggestion that continuous RRT had fewer episodes of hemodynamic instability and better control of fluid balance

May be preferable in specific subpopulations

Vanholder et al. Pro/con debate: Continuous vs intermittent dialysis for acute kidney injury. Critical Care 2011, 15:204

Pro-continuous RRT

? Theoretical advantage of more hemodynamic stability allowing more adequate fluid removal

Metaanalysis of 15 RCTs (Rabindranath Cochrane Rev 2007, 3): no difference between CRRT and IRRT in haemodynamic instability or hypotension / escalation of pressors, or mortality or RRT independence. Patients on CRRT had significantly higher MAP

However most trials excluded pts with major hemodynamic issues

Some RCTs (but not all) show more negative fluid balances with CRRT vs IRRT

Vanholder et al. Critical Care 2011, 15:204

Pro-continuous RRT

? Better recovery of renal function due to preserved hemodynamic stability All RCTs and meta-analyses have failed to show superiority of CRRT in progression to CKD or RRT dependence

? Improved solute removal due to longer dialysis Studies have been inconsistent in showing improved clearance of creatinine and urea with CRRT

No evidence of improved removal of cytokines


Pro-continuous RRT

Specific patient populations who may benefit from CRRT Hemodynamic instability Combined acute renal and hepatic failure

Improved CV instability and intracranial pressure

Acute brain injury Decreased cerebral edema


Pro-intermittent RRT

Practicality and flexibility Uses same machines as chronic HD Multiple pts per day Easier to mobilize pts

Less expensive than CRRT (by about ½) Fewer bleeding complications

CRRT requires continuous anticoagulation Less filter clotting Superior solute clearance, more rapid removal of toxins (due to higher flows)


Pro-intermittent RRT

Specific patient populations benefitting from IRRT: High bleeding risk

Ie. after recent surgery Acute treatment of hyperkalemia, rhabdomyolysis, poisoning, tumor lysis syndrome


Is SLEDD the answer?

Hybrid therapy with flexibility of duration and intensity

SLEDD vs CRRT Major advantages: flexibility, reduced costs, low or absent anticoagulation

Similar adequacy and hemodynamics One small study (16 pts) showed slightly higher acidosis and lower BP (Baldwin 2007)

VA trial (Palevsky NEJM 2008) suggests similar outcomes as CRRT and IRRT.


Optimal dosing

Optimal intensity of RRT is controversial

VA/NIH Acute Renal Failure Trial Network. (NEJM 2008;359:7): RCT of 1124 critically ill pts with AKI and sepsis or at least one organ failure to intensive or less intensive renal-replacement therapy

Hemodynamically unstable pts received CRRT or SLEDD, stable pts IRRT

Intensive RRT= IRRT or SLEDD 6x/wk or CRRT at 35 ml/kg/hr

Less intensive RRT= IRRT or SLEDD 3x/wk or CRRT at 20 ml/kg/hr

Optimal dosing

VA/NIH Acute Renal Failure Trial Network No difference in mortality, recovery of kidney

function, or nonrenal organ failure

VA/NIH Acute Renal Failure Trial Network. NEJM 2008;359:7

Optimal dosing

The RENAL Replacement Therapy Study RCT of 1508 critically ill pts to CRRT of high vs

low intensity (40 vs 25 ml/kg/hr) No difference in 90 d mortality or RRT

independence

N Engl J Med. 2009 Oct 22;361(17):1627-38

Optimal dosing

Recommended dosing: IRRT: 3x/week CRRT: delivered effluent flow rate of at least 20 mL/kg/hr

Up To Date.com

The role of RRT in different clinical situations Sepsis and MODS Congestive heart failure


RRT in sepsis/MODS

RRT has been proposed as a “Extracorporeal blood purification therapy (EBPT)” as adjuvant therapy for sepsis/MODS for removal of harmful inflammatory mediators or endotoxemia

Some support from animal models and small clinical studies Eg cytokines can be demonstrated in dialysis effluent

•Miller's Anesthesia, 7th ed. 2009Foot. Current Anaesthesia and Critical Care 2005; 16:321-329

RRT in sepsis/MODS

Limited data, small studies: Cole. Crit Care Med. 2002 Jan;30(1):100-6

Phase II RCT of early CVVH x 48 h in 24 pts with septic shock/MODS

No ↓ in circulating cytokines and anaphylatoxins or organ dysfunction

RRT in sepsis/MODS

Limited data, small studies: Boussekey et al. Intensive Care Med. 2008 Sep;34(9):1646-53

Pilot RCT of 20 pts with septic shock and ARF to high volume hemofiltration [HVHF 65 ml/(kg h)] vs low volume hemofiltration [LVHF 35 ml/(kg h).

HVHF decreased vasopressor requirement and trend towards increase urine output but no effect on survival, LOS, RRT, mech ventilation

RRT in sepsis/MODS

Overall, no good data showing improved outcomes

Insufficient evidence to support a role for RRT as adjuvant therapy for septic shock unless severe acute renal failure is present.

Foot. Current Anaesthesia and Critical Care 2005; 16:321-329

RRT in congestive heart failure Slow continuous ultrafiltration (SCUF) effective for fluid removal in decompensated CHF

UNLOAD trial (UF versus intravenous diuretics for acute decompensated CHF): RCT 200 hypervolemic CHF pts to UF or diuretics

At 48 hrs, UF associated with improved weight and fluid removal, and ↓ 90 d rehospitalization and medical visits for CHF

•Costanzo et al J Am Coll Cardiol 2007; 49:675-683.

Conclusions

AKI in the ICU is common and associated with high mortality

The best time to initiate and stop RRT is controversial

No good data that CRRT is better than IRRT in the ICU, except for a few specific situations Consider CRRT if severely unstable pts, severe volume overload, combined renal/hepatic failure

IRRT best if bleeding risk or acute hyperkalemia/poisoning

SLEDD is the most flexible

Conclusions

More intense RRT dosing in the ICU does not improve outcome

Insufficient evidence to support a role for RRT as adjuvant therapy for septic shock unless severe acute renal failure is present

Ultrafiltration is effective for fluid removal in CHF

References

Miller: Miller's Anesthesia, 7th ed. 2009 Uchino S, Kellum JA, Bellomo R, et al: for the Beginning and

Ending Supportive Therapy for the Kidney (BEST Kidney) Investigators. Acute renal failure in critically ill patients: A multinational, multicenter study. JAMA 2005; 294:813-818.

Bouman CS, Oudemans-Van Straaten HM, Tijssen JG, Zandstra DF, Kesecioglu J. Effects of early high-volume continuous venovenous hemofiltration on survival and recovery of renal function in intensive care patients with acute renal failure: a prospective, randomized trial. Crit Care Med. 2002;30(10):2205.

Vanholder et al. Pro/con debate: Continuous vs intermittent dialysis for acute kidney injury. Critical Care 2011, 15:204

Uchino S, Bellomo R, Morimatsu H, et al: Continuous renal replacement therapy: A worldwide practice survey: The Beginning and Ending Supportive Therapy for the Kidney (B.E.S.T. Kidney) Investigators. Intensive Care Med 2007; 33:1563-1570.

Bagshaw SM, Berthiaume LR, Delaney A, Bellomo R: Continuous versus intermittent renal replacement therapy for critically ill patients with acute kidney injury: a meta-analysis. Crit Care Med 2008, 36:610-617.

Rabindranath K, Adams J, Macleod AM, Muirhead N: Intermittent versus continuous renal replacement therapy for acute renal failure in adults. Cochrane Database Syst Rev 2007, 3:CD003773.

References Palevsky PM, Zhang JH, O’Connor TZ, Chertow GM, Crowley ST, Choudhury

D, Finkel K, Kellum JA, Paganini E, Schein RM, Smith MW, Swanson KM; Thompson BT, Vijayan A, Watnick S, Star RA, Peduzzi P: Intensity of renal support in critically ill patients with acute kidney injury. N Engl J Med 2008, 359:7-20.

RENAL Replacement Therapy Study Investigators, Bellomo R, Cass A, Cole L, Finfer S, Gallagher M, Lo S, McArthur C, McGuinness S, Myburgh J, Norton R, Scheinkestel C, Su S. Intensity of continuous renal-replacement therapy in critically ill patients. N Engl J Med. 2009 Oct 22;361(17):1627-38.

Rondon-Berrios H, Palevsky PM. Treatment of acute kidney injury: an update on the management of renal replacement therapy. Curr Opin Nephrol Hypertens. 2007 Mar;16(2):64-70.

Palevsky P. Renal replacement therapy (dialysis) in acute kidney injury (acute renal failure) in adults: Indications, timing, and dialysis dose. UpToDate.com 2012

Boussekey N, Chiche A, Faure K, Devos P, Guery B, d'Escrivan T, Georges H, Leroy O. A pilot randomized study comparing high and low volume hemofiltration on vasopressor use in septic shock Intensive Care Med. 2008 Sep;34(9):1646-53.

Cole L, Bellomo R, Journois D, et al: High-volume hemofiltration in human septic shock. Intensive Care Med 2001; 27:978-986.

Cole L, Bellomo R, Hart G, et al: A phase II randomized, controlled trial of continuous hemofiltration in sepsis. Crit Care Med 2002; 30:100-106.

References

Costanzo MR, Guglin M, Saltzberg MT, et al: for the UNLOAD Trial Investigators: Ultrafiltration versus intravenous diuretics for patients hospitalized for acute decompensated heart failure. J Am Coll Cardiol 2007; 49:675-683.

Ronco C, Brendolan A, Lonnemann G, et al: A pilot study of coupled plasma filtration with adsorption in septic shock. Crit Care Med 2002; 30:1250-1255.

Carole L. Foot, John F. Fraser. So you need to start renal replacement therapy on your ICU patient? Current Anaesthesia & Critical Care (2005) 16, 321–329

Peter Faber and Andrew A Klein. Acute kidney injury and renal replacement therapy in the intensive care unit. Nursing in Critical Care 2009; 14: 4

Davenport A, Tolwani A. Citrate anticoagulation for continuous renal replacement therapy (CRRT) in patients with acute kidney injury admitted to the intensive care unit. NDT Plus (2009) 2: 439–447

Surviving sepsis 2008: D. Renal Replacement 1. We suggest that continuous renal replacement therapies and intermittent hemodialysis are equivalent in patients with severe sepsis and acute renal failure (grade 2B). 2. We suggest the use of continuous therapies to facilitate management of fluid balance in hemodynamically unstable septic patients (grade 2D

AKI in the ICU

In BEST Kidney trial: multinational observational trial of 29,269 ICU patients with AKI [oliguria (UOP < 200/12h, azotemia (BUN > 30) or RRT] 5.7% had AKI during their ICU stay 4.3% treated with RRT 47.5% due to septic shock 30% had preadmission CKD Overall hospital mortality 60.3%. Of survivors, 13.8% dialysis dependent at discharge

Independent risk factors for hospital mortality included the use of vasopressors, mechanical ventilation, septic shock, cardiogenic shock, and hepatorenal syndrome.

•Miller's Anesthesia, 7th ed. 2009•Uchino JAMA 2005; 294:813-818.

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Dialysis in Critically Ill