**CRRT in Medicine: A Concise Overview**
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| **CRRT in Medicine: A Concise Overview** |
CRRT in Medicine: A Concise Overview
CRRT stands for Continuous Renal Replacement Therapy. It is a form of renal replacement therapy (RRT) used primarily in critically ill patients with acute kidney injury (AKI) who are hemodynamically unstable and cannot tolerate conventional intermittent hemodialysis (IHD).
1. What is CRRT?
CRRT is a slow, continuous form of dialysis that runs 24 hours a day (or for extended periods) to gently remove fluid and solutes from the blood. It mimics the natural function of the kidneys more closely than intermittent dialysis, making it ideal for intensive care unit (ICU) patients with multi-organ failure or severe fluid overload.
2. Indications for CRRT
CRRT is typically indicated when:
- Hemodynamic instability is present (e.g., septic shock, vasopressor dependence)
- Severe fluid overload (e.g., pulmonary edema, heart failure)
- Refractory metabolic acidosis
- Life-threatening electrolyte imbalances (e.g., hyperkalemia)
- Uremic complications (e.g., pericarditis, encephalopathy)
- Need for precise fluid balance control in critically ill patients
3. Types of CRRT Modalities
There are several technical variations, but the three main types include:
| Modality | Full Name | Mechanism |
|---|---|---|
| CVVH | Continuous Venovenous Hemofiltration | Uses convection to remove solutes with replacement fluid |
| CVVHD | Continuous Venovenous Hemodialysis | Uses diffusion across a dialyzer membrane |
| CVVHDF | Continuous Venovenous Hemodiafiltration | Combines both diffusion and convection |
4. How CRRT Works
- Blood is drawn from the patient via a central venous catheter.
- It passes through a hemofilter (artificial kidney).
- Waste products, electrolytes, and excess fluid are removed slowly over 24 hours.
- Anticoagulation (e.g., citrate or heparin) is often used to prevent clotting in the circuit.
5. Advantages of CRRT vs. Intermittent Hemodialysis (IHD)
- Better hemodynamic stability
- Gradual correction of electrolytes and fluid balance
- Allows for precise control in unstable ICU patients
- Can be combined with nutritional support and other ICU therapies
6. Potential Complications
- Circuit clotting (despite anticoagulation)
- Electrolyte imbalances (e.g., hypophosphatemia, hypokalemia)
- Bleeding (especially with systemic anticoagulants like heparin)
- Infection risk from central lines
- Hypotension (less common than with IHD, but still possible)
7. Clinical Considerations
A CRRT prescription typically includes:
- Modality choice
- Blood flow rate (typically 100–200 mL/min)
- Effluent rate (often 20–25 mL/kg/h)
- Replacement/dialysate fluid composition
- Anticoagulation strategy
Regional citrate anticoagulation (RCA) is increasingly preferred over heparin due to lower bleeding risk and longer filter life.
8. When to Discontinue CRRT?
- Evidence of renal recovery (urine output >1 L/day, decreasing creatinine)
- Hemodynamic stability allowing transition to IHD or no dialysis
- Irreversible condition where continuing CRRT is futile (based on goals of care)
CRRT is not just “dialysis for unstable patients”—it’s a critical care tool that requires multidisciplinary coordination (nephrology, ICU, nursing, pharmacy) and careful monitoring to optimize outcomes.
Further Reading & Sources
- KDIGO Clinical Practice Guideline for Acute Kidney Injury (2012, updated considerations in 2024)
- Vincent JL, et al. “Acute Kidney Injury in the ICU: From Injury to Recovery.” Intensive Care Medicine, 2023.
- Uchino S, et al. “Continuous Renal Replacement Therapy: A Review.” JAMA, 2022.
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