ICU PROCEDURES: Continuous Renal Replacement Therapy (CRRT)
ICU Procedures: Continuous Renal Replacement Therapy (CRRT)
Overview: Continuous Renal Replacement Therapy (CRRT) is a blood purification therapy used in the ICU for critically ill patients with acute kidney injury (AKI) or fluid overload. Unlike intermittent hemodialysis (IHD), CRRT is performed continuously over 24 hours, allowing for gentle and gradual removal of solutes and fluids, making it more suitable for hemodynamically unstable patients.
Indications:
- Acute kidney injury (AKI)
- Severe fluid overload
- Electrolyte imbalances (e.g., hyperkalemia, severe acidosis)
- Sepsis or multi-organ failure with compromised renal function
- Drug overdose or poisoning that requires renal clearance
Types of CRRT:
- Continuous Venovenous Hemofiltration (CVVH):
- Removes fluid and small to medium-sized molecules through convective clearance.
- Large volumes of fluid are filtered and replaced with replacement fluids to maintain hemodynamic stability.
- Continuous Venovenous Hemodialysis (CVVHD):
- Primarily uses diffusion for the removal of small solutes (e.g., urea, creatinine).
- Blood passes through a semipermeable membrane with dialysate flowing on the other side, allowing solutes to diffuse.
- Continuous Venovenous Hemodiafiltration (CVVHDF):
- Combines both convective and diffusive clearance, providing removal of solutes of various sizes and fluid.
- Utilizes both dialysate and replacement fluid for enhanced solute clearance.
- Slow Continuous Ultrafiltration (SCUF):
- Primarily used for fluid removal (ultrafiltration) without significant solute clearance.
- Used for patients with fluid overload and less concern for solute removal.
Procedure:
- Vascular Access:
- Site selection: A large-bore central venous catheter (e.g., femoral, jugular, or subclavian vein) is required for CRRT.
- Catheter insertion: Similar to Central Venous Catheter (CVC) insertion, using sterile techniques and ultrasound guidance to place the catheter in a large vein.
- Machine Setup:
- Priming the circuit: The CRRT machine must be primed with saline or replacement solution before connecting to the patient to prevent air embolism or clot formation.
- Connecting to the patient: Blood is drawn from the patient, passes through the filter in the CRRT machine, and returns to the patient.
- Filtration: Blood passes through the semipermeable membrane, where solute and fluid removal occurs based on the chosen modality (CVVH, CVVHD, CVVHDF, or SCUF).
- Monitoring and Adjustments:
- Blood flow rate: Typically set at 100-200 mL/min to ensure continuous and gradual solute and fluid removal.
- Dialysate or replacement fluid rate: Adjusted depending on the solute clearance needs.
- Anticoagulation: Regional anticoagulation with citrate or systemic anticoagulation (e.g., heparin) may be used to prevent clotting in the extracorporeal circuit.
- Fluid balance: Achieving the desired fluid balance is crucial. Net ultrafiltration is adjusted to control fluid removal based on the patient’s condition.
- Replacement Fluids/Dialysate:
- Composition: Replacement fluids or dialysate must contain appropriate concentrations of electrolytes (e.g., sodium, potassium, bicarbonate) to maintain the patient’s electrolyte balance.
- Customization: Tailored to the patient’s needs, taking into consideration acid-base imbalances and electrolyte levels.
- Monitoring During CRRT:
- Hemodynamic stability: Continuous monitoring of blood pressure, heart rate, and perfusion is essential since CRRT can influence fluid volume and hemodynamics.
- Electrolyte levels: Frequent checks on electrolytes like potassium, calcium, and bicarbonate to prevent imbalances.
- Coagulation status: If anticoagulation is used, monitor for signs of bleeding or clot formation.
- Fluid status: Monitor for signs of dehydration or fluid overload; adjust the ultrafiltration rate accordingly.
- Complications:
- Hypotension: Due to excessive fluid removal or sensitivity to fluid shifts.
- Clotting of the filter: May occur if anticoagulation is inadequate or due to prolonged use of the circuit.
- Electrolyte imbalances: Such as hypokalemia or hypocalcemia, requiring frequent monitoring and adjustment of the replacement fluid or dialysate.
- Infection: Associated with the central venous catheter.
- Bleeding: Especially if systemic anticoagulation is used.
Discontinuation:
- When to stop CRRT: CRRT is typically discontinued once the patient’s renal function recovers, or they become stable enough to transition to intermittent hemodialysis (IHD) or other forms of renal support.
- Gradual weaning: Fluid removal may be tapered off, and monitoring is continued to ensure the patient maintains electrolyte and fluid balance.
Key Points:
- CRRT is a life-saving intervention for critically ill patients with acute kidney injury and fluid overload.
Indications for CRRT:
- Acute Kidney Injury (AKI): In cases of severe AKI where conventional dialysis is not tolerated.
- Fluid Overload: When diuretics fail to manage fluid overload, CRRT can slowly remove excess fluid.
- Severe Electrolyte Imbalances: Life-threatening imbalances like hyperkalemia or severe acidosis.
- Sepsis or Multisystem Organ Failure: CRRT helps manage metabolic waste and fluid balance.
- Toxin Removal: Can be used for removing certain toxins or drugs from the blood.
Nursing Management:
- Assessment:
- Monitor vital signs, particularly blood pressure and heart rate.
- Perform regular assessments of fluid balance, including input/output charting.
- Frequent checks of blood electrolytes, urea, and creatinine levels.
- Care of the Access Site:
- Ensure the catheter site remains clean and sterile to prevent infection.
- Check for signs of infection, such as redness, swelling, or discharge at the site.
- Patient Education:
- Explain the procedure and its purpose to the patient and family.
- Inform about potential complications and the need for regular monitoring.
- Emergency Interventions:
- Be prepared to manage complications such as bleeding, catheter dislodgement, or hemodynamic instability.