Renal replacement therapy

CRRT vs IHD vs SLED

Reviewed Nov 2026·1 references
New· views rounded down, updated weekly

Choose the modality by haemodynamics, brain risk, resources and cost; understand convection vs diffusion and vascular access.

Definition
IHD: 3-5 h sessions, fast clearance, more hypotension. CRRT (CVVH/CVVHD/CVVHDF): 24 h, gentle fluid removal, best for unstable patients and raised ICP. SLED/PIRRT: 6-12 h on a standard machine with low blood and dialysate flows: a cheaper hybrid.

At the bedside

  1. 1

    Choose by haemodynamics

    Shock on vasopressors or needing large fluid removal: CRRT or SLED. Stable patients: IHD. KDIGO: use CRRT and IHD as complementary therapies.

  2. 2

    Brain at risk

    Acute liver failure, TBI, cerebral oedema: CRRT preferred (avoids osmotic shifts and hypotension).

  3. 3

    Choose the technique

    Convection (CVVH: replacement fluid; better middle-molecule removal) vs diffusion (CVVHD: dialysate) vs both (CVVHDF). Outcome differences are not proven; follow unit practice.

  4. 4

    Vascular access

    Non-cuffed dialysis catheter, ultrasound-guided. Preference: right internal jugular (12-15 cm) > femoral (19-24 cm) > left internal jugular (15-20 cm) > subclavian (avoid: stenosis risk for future fistula).

  5. 5

    Prescribe fluid removal

    Net ultrafiltration usually 0-2 mL/kg/h, adjusted hourly to haemodynamics; very high net UF (> 1.75 mL/kg/h) associated with worse outcomes in observational data.

  6. 6

    Monitor

    Electrolytes (K, PO4, Mg) 6-12 hourly on CRRT, ABG, temperature (CRRT cools), drug levels, circuit pressures.

Modalities compared

FeatureIHDSLED / PIRRTCRRT
Duration3-5 h, 3-6x/week6-12 h dailyContinuous 24 h
Blood flow250-400 mL/min150-200 mL/min150-250 mL/min
Haemodynamic stabilityLeastIntermediateBest
Raised ICPAvoidCautionPreferred
Anticoagulation needOften noneLow/noneUsually needed (citrate/heparin)
Cost in IndiaLowestLow-moderateHighest (fluids, filters)
Drug dosingDose after sessionDose after sessionContinuous clearance (CrCl ~ 25-50)
Red flag · call your senior now
Hypotension at the start of IHD/SLED: reduce UF, lower blood flow initially, cool dialysate, increase vasopressor; switch to CRRT if recurrent.
Pitfall
Subclavian dialysis catheters: high central vein stenosis risk that ruins future AV fistula access.
Pitfall
Forgetting that CRRT removes heat: hypothermia masks fever.
Pearl
SLED on a standard haemodialysis machine using online dialysate is the cost-effective choice for unstable patients in many Indian ICUs.

References

  1. 1

    Kidney Disease: Improving Global Outcomes (KDIGO) AKI Work Group. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Int Suppl 2012;2:1-138 (summary: Nephron Clin Pract 2012;120:c179-84).

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