USMLE Prep - Medical Reference Library

Acute Kidney Injury in the ICU - CRRT vs Intermittent Dialysis

System: Critical Care • Reviewed: Aug 31, 2025 • Step 1Step 2Step 3

Synopsis:

Use KDIGO criteria for staging, correct reversible causes, and choose CRRT for hemodynamic instability or cerebral edema while intermittent hemodialysis suits stable patients.

Key Points

  • Stabilize ABCs; begin targeted evaluation without delaying life-saving therapy.
  • Use system-specific risk tools to guide testing and disposition.
  • Order high-yield tests first; escalate imaging when indicated.
  • Start evidence-based initial therapy and reassess frequently.

Algorithm

  1. Primary survey and vitals; IV access and monitors.
  2. Focused history/physical; identify red flags and likely etiologies.
  3. Order system-appropriate labs and imaging (see Investigations).
  4. Initiate guideline-based empiric therapy (see Pharmacology).
  5. Reassess response; arrange consultation and definitive management.

Clinical Synopsis & Reasoning

Approach AKI by distinguishing pre‑renal, intrinsic, and post‑renal causes. Trend creatinine and urine output, perform urinalysis with microscopy, and assess hemodynamics and exposures (nephrotoxins, contrast, ACEi/ARB, NSAIDs). Point‑of‑care ultrasound helps evaluate volume status and obstruction. Anticipate complications—hyperkalemia, acidosis, and fluid overload—that drive urgent interventions.


Treatment Strategy & Disposition

Optimize perfusion with judicious fluids when hypovolemic; discontinue nephrotoxins and adjust drug dosing. Treat hyperkalemia and severe acidosis promptly; initiate renal replacement therapy for AEIOU indications. Coordinate imaging with contrast only when benefits outweigh risks, using preventive strategies. Disposition depends on trajectory and complications—ICU for refractory electrolyte/volume issues or hemodynamic instability; otherwise monitored ward care.


Epidemiology / Risk Factors

  • Risk factors vary by condition and patient profile

Investigations

TestRole / RationaleTypical FindingsNotes
CBCBaseline hematologyAbnormal counts
BMPElectrolytes/renalDerangements

Modality Selection

ScenarioPreferred modality
Hemodynamic instabilityCRRT
Raised intracranial pressureCRRT
Stable ICU patientIntermittent hemodialysis

Pharmacology

MedicationMechanismOnsetRole in TherapyLimitations
Balanced crystalloidsVolume expansionImmediatePre-renal AKIFluid overload risk; ICU context
Hold nephrotoxinsN/AImmediateStop NSAIDs, ACEi/ARBs if needed—; ICU context
Loop diuretic (for overload)Na-K-2Cl inhibitionHoursSymptomatic volume removalElectrolyte loss; ICU context

Prognosis / Complications

  • Prognosis depends on severity, comorbidities, and timeliness of care

Patient Education / Counseling

  • Explain red flags and when to seek emergent care.
  • Reinforce medication adherence and follow-up plan.

Notes

Coordinate with pharmacy for drug dosing during renal replacement. Consider regional citrate anticoagulation where expertise exists.


References

  1. KDIGO AKI Guideline — Link
  2. ADQI Consensus - RRT in ICU — Link