Continuous vs. intermittent RRT in the ICU

Salwa Ibrahim, MD FRCPE

Professor of Nephrology

Agenda

• Introduction

• Modalities of CRRT

• Clinical and laboratory effects of CRRT

• Outcome and cost analysis

• SLED therapy

• Take home message

Introduction

• Before the introduction of hemodialysis, the mortality rates of ARF were 90% -100%

• After that, the mortality of ARF improved to around 50% to 70%

• Those figures have not changed much during the last 3 decades

• IHD frequently induces hemodynamic instability and some patients could not safely complete dialysis therapy

Kramer 1977 first described CRRT for critically ill patients

Is an extracorporeal blood purification therapy intended to substitute impaired renal function over an extended period of

time and applied for 24 hours a day

– Bellomo R., Ronco C., Mehta R, Nomenclature for Continuous Renal Replacement Therapies, AJKD, Vol 28, No. 5, Suppl 3, November 1996

Continuous Renal Replacement Therapy (CRRT)

CRRT Modalities

20-25 ml/kg/hour

Potential advantages of CRRT

• CRRT by its lower rate of fluid removal can be used in hemodynamically unstable, critically ill patients with associated comorbid conditions eg. M.I, ARDS , sepsis

• CRRT can help in administration of parenteral nutrition and

inotropes through continuous ultrafiltration

Potential advantages of CRRT

• Hemofiltration modality may be effective in lowering intracranial Pressure v/s IHD which sometimes raises ICP

• Proinflammtory mediators of inflammation were shown to

have been removed by this modality eg.IL-1, IL-6, IL-8, TNF-a

Effect on Hemodynamics

Hemodynamic parameters (systemic arterial pressure [SAP],cardiac index [CI]) significantly increased during treatment and

norepinephrine doses decreased significantly

Intracranial pressure

ICP increases with IHD

ICP remained stable during CVVH

CYTOKINE REMOVAL

The plasma concentrations of the inflammatory cytokines decreased significantly in the first hour but No decreases were observed at other

time points

Outcome analysis

How to make unbiased clinical decisions

• Decisions in health care are being made on the basis of research based evidence rather expert opinion or clinical experience alone

• Randomized clinical trials involving large numbers of patients can provide strong evidence to support or decline a modality of therapy

• Structured systematic reviews (meta-analyses) can provide the highest standard of evidence

Evidence from randomized controlled trials

A total of 360 critically ill casesA total of 360 critically ill casesWere randomly assigned toWere randomly assigned toEither CRRT or IHDEither CRRT or IHD

60 days survival was 32% in60 days survival was 32% inIHD and 33% in CRRT groupsIHD and 33% in CRRT groups

Evidence from observational studies

• This metanylsis showed that no significant differences in mortality between those treated with CRRT vs. IHD

• Earlier studies favor CRRT as IHD was delivered using cellulose membrane and acetate based dialysate

• Late studies favor IHD as more

A. Biocompatible membranes were used

B. Volumetric controlled machines

C. Lower dialysate temperature and flow rates and

D. Bicarbonate dialysis

Evidence from systematic Review

No differences in mortality rates between the two groups

No differences in recovery rates of renal Function

No differences in hemodynamic stability

Higher incidence of clotting problems in CRRT group

Complications of CRRT

Potential risks of CRRT

• Bleeding risk

• Clotting of lines and filters

• Increased blood loss and anemia

• Expensive

• Needs special training of staff

Slow low Efficiency Dialysis

SLEDD

• Slow low efficiency daily dialysis was introduced as a hybrid therapy that mix the benefits of CRRT with the economics of IHD

• Daily sessions for 6-12 hours

• BFR 150 -250 ml/m

• DFR 100-350 ml/min

• Traditional dialysis machine

• Heparin anticoagulation /Saline flushes

CRRT vs. SLED

Hemodynamic stability

SLED therapies were more frequently associated with >20 % decline in MAP but Pressor dose escalation was observed more with CRRT

Survival analysis

Treatment assignment

• Patients allocated to SLED were assigned to receive 12-h of dialysis with a blood flow rate of 100 to 120 ml/min with high-flux polysulfone filters

• Patients assigned to the CVVH-group were treated with 35 ml/kg per hour replacement fluid. Treatment was scheduled for 24-h and blood flow was maintained between 100 and 120 ml/min with high-flux polysulfone filters

Schwenger et al. Critical Care 2012

No significant difference in survival among SLED and CRRT groups

Schwenger et al. Critical Care 2012

C-SLED

A COST ANALYSIS OF CRRT VS. SLED A COST ANALYSIS OF CRRT VS. SLED

ItemItem SLEDSLED CRRTCRRT

Machine $22,000.00$22,000.00 $42,000.00$42,000.00

R/O Consumables $300.00

Endotoxin Filter $155.00

Dialysis Filter $55.00 $265.00

Blood Lines $32.00

Concentrate $34.00 N/A

Hemofiltration Fluids N/A $38.50

Daily CostsDaily Costs $140.00$140.00 $642.00$642.00

• There is no evidence that CRRT results in better survival compared to IHD and SLED

• The only potential advantage of CRRT (higher MAP) can be offered By SLEDD as well

• SLEDD is less expensive technique as the same infrastructure is used

Key Message