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Continuous renal replacement therapy (CRRT)
Continuous renal replacement therapy (CRRT) is a slow, round-the-clock form of dialysis given in intensive care to gently clean the blood and remove excess fluid when the kidneys suddenly stop working. It is used for critically ill patients whose blood pressure is too unstable for standard hemodialysis.
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Briefly about this treatment
Indications
Acute kidney injury in critically ill patients, especially with unstable blood pressure, severe fluid overload, dangerously high potassium or acid build-up, or uremic symptoms that do not respond to medication.
Risks
Bleeding, infection, filter clotting, low blood pressure and electrolyte shifts. Risks are minimized by continuous ICU monitoring, tailored anticoagulation and experienced critical-care teams.
Pre-procedure
Urgent blood tests (kidney function, potassium, acid–base balance), fluid and blood-pressure assessment, and ultrasound-guided placement of a dialysis catheter in the neck or groin under local anesthetic, sometimes with sedation. Fasting is not usually needed beforehand — the ICU team manages fluids, feeding and the anticoagulation plan.
Follow-up
Continuous bedside monitoring and frequent blood tests during therapy; daily checks of urine output and kidney function once CRRT stops; a nephrology review about 3 months after the kidney injury and long-term monitoring of kidney function and blood pressure.
What is Continuous renal replacement therapy (CRRT)? An expert explains
CRRT does not cure kidney failure — it buys the kidneys time to recover by taking over their filtering job. Blood is pumped out of the body through a large IV catheter (usually placed in the neck or groin), passed through a machine with an artificial filter that works like a kidney, and returned — continuously, hour after hour, instead of in one intense multi-hour hemodialysis session. Kidney specialists (nephrologists) and intensive care doctors decide together when CRRT is the right modality, based largely on how stable a patient’s blood pressure is. International KDIGO guidelines, which most ICU teams worldwide follow, recommend CRRT over standard intermittent dialysis specifically for hemodynamically unstable patients.
There are several CRRT modes, chosen by the ICU/nephrology team based on the patient’s needs:
- CVVH (continuous veno-venous hemofiltration) — removes fluid and waste mainly by convection (pulling fluid across the filter).
- CVVHD (continuous veno-venous hemodialysis) — removes waste mainly by diffusion, using a dialysis fluid.
- CVVHDF (continuous veno-venous hemodiafiltration) — combines both mechanisms.
- SCUF (slow continuous ultrafiltration) — removes fluid only, with minimal waste clearance, mainly for severe fluid overload.
Signs it may be time for Continuous renal replacement therapy (CRRT)
CRRT is started by the hospital’s ICU and nephrology team, not by the patient — but the body usually gives warning signs first. These are the things a person (or the family at the bedside) may notice when the kidneys are failing and the blood can no longer be kept in balance.
Symptoms you may notice
- Passing very little or no urine. This is often the earliest and clearest sign that the kidneys have stopped keeping up.
- Swelling and breathlessness. Fluid that the kidneys can’t remove collects in the legs, ankles and face, and can build up in the lungs, making breathing difficult.
- Nausea, vomiting and loss of appetite. A build-up of waste products in the blood can also cause itching or a metallic taste.
- Confusion or unusual drowsiness. Toxins that are not being filtered out can affect how clearly a person thinks.
- Muscle weakness or a fluttering, irregular heartbeat. These can signal dangerously high potassium.
- Faintness and feeling very unwell during a severe infection. Low blood pressure with sepsis is a common trigger for sudden kidney failure.
Conditions linked to CRRT
These are the kidney conditions most often connected with the need for CRRT:
- Acute Kidney Injury (AKI) — a sudden loss of kidney function from injury, infection or toxins, and the most common reason CRRT is started.
- Acute Tubular Necrosis (ATN) — damage to the kidney’s tubule cells from poor blood flow or toxins, a frequent cause of AKI in intensive care.
- End-Stage Renal Disease (ESRD) — the final stage of kidney failure, where CRRT may be used if a person on long-term dialysis becomes critically ill.
- Chronic Kidney Disease (CKD) — long-term, progressive loss of kidney function that makes the kidneys more vulnerable to a sudden crisis.
- Obstructive Nephropathy — kidney damage from blocked urine flow, which can lead to sudden kidney failure.
When to consult a specialist
CRRT is only used for the most serious cases in hospital, and most kidney problems never get that far — especially when they’re spotted early. If you’ve noticed any of the symptoms above, or you have diabetes, high blood pressure, heart disease or a known kidney condition, a simple blood test (creatinine and eGFR) and a urine test can show how well your kidneys are working. Many kidney problems can be managed well when they are found in time, so there’s no need to panic. If something doesn’t feel right, you don’t have to wait or work it out alone: Find a specialist and talk to a kidney doctor about your results.
How a session works
Unlike a single hemodialysis „session,” CRRT runs as one continuous therapy for days at a time. Here’s what the process typically looks like, step by step:
- Vascular access. A doctor places a large, two-channel catheter into a large vein — usually in the neck (internal jugular) or groin (femoral vein) — under local anesthetic, sometimes with light sedation. One channel draws blood out; the other returns filtered blood.
- Circuit setup. ICU nursing staff prepare the CRRT machine and its single-use filter circuit, priming the tubing with saline to remove air and reduce clotting risk.
- Connecting & starting therapy. The catheter is connected to the machine, and blood begins flowing out through the filter and back into the body in a continuous loop, driven by a pump.
- Choosing the mode. The nephrology/ICU team sets the specific CRRT mode — CVVH, CVVHD, CVVHDF or SCUF — and the target fluid-removal rate, based on the patient’s fluid balance, electrolytes and blood pressure.
- Anticoagulation. To stop the circuit and filter from clotting, the team usually uses regional citrate anticoagulation (citrate added before the filter, calcium replaced after) or, less often, systemic heparin — chosen based on bleeding risk.
- Continuous monitoring. Bedside ICU nurses check the circuit, vital signs, fluid balance and lab values (electrolytes, calcium, clotting) very frequently — often hourly — adjusting settings as the patient’s condition changes.
- Filter changes. Filters typically need replacing roughly every 24–72 hours as they gradually clot or lose efficiency; this is a normal, expected part of ongoing therapy, not a complication in itself.
- Running around the clock. Therapy continues 24 hours a day for as long as it’s needed, with brief pauses only for filter changes, transport for scans, or procedures.
Because it runs continuously rather than in short bursts, CRRT removes fluid and waste much more gradually than standard hemodialysis, which is what makes it tolerable for patients whose heart and blood pressure are too unstable for faster treatments.
Session duration
Continuous, several days
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Cost verify
$860–$4050
indicative range
Anesthesia
Local
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Remember: The exact steps, duration and preparation can vary with your indication, health and care setting. Confirm the current plan with your treating team.
Benefits
CRRT is chosen because it protects the patient while the kidneys rest and recover. For someone already critically ill, the way it works can matter as much as what it removes.
- Gentler on the heart and blood pressure. Slow, continuous removal of fluid and waste causes far smaller swings in blood pressure than standard hemodialysis, which is why it is preferred for patients with unstable circulation.
- Precise, flexible fluid control. The rate of fluid removal can be adjusted hour by hour as the patient’s condition changes, so the team can respond quickly.
- Steady chemical balance. Potassium, acids and other electrolytes are corrected gradually rather than all at once, avoiding sudden shifts that can be dangerous in critical illness.
- Room for full supportive care. Because fluid is removed continuously, patients can still receive the IV fluids, nutrition, blood products and medications they need without becoming overloaded.
Risks & side effects
CRRT has risks and trade-offs to discuss with your care team. The information below comes from this treatment data.
Bleeding, infection, filter clotting, low blood pressure and electrolyte shifts. Risks are minimized by continuous ICU monitoring, tailored anticoagulation and experienced critical-care teams.
The ICU team watches for each of these around the clock and acts early when something changes:
- Bleeding. The medicine used to stop blood clotting in the circuit can make bleeding more likely, so the team chooses the type and dose according to each patient’s bleeding risk.
- Infection. The catheter is a doorway into the bloodstream, so the insertion site is kept sterile and checked every day.
- Filter and circuit clotting. Clots can slow or interrupt treatment and mean the filter has to be changed earlier than planned.
- Low blood pressure. This is less common than with standard hemodialysis, but can still occur, especially in very unwell patients.
- Electrolyte imbalances. Low phosphate, potassium or calcium can develop, particularly with citrate anticoagulation, so blood is tested frequently and corrected.
- Low body temperature. Blood cools slightly as it travels through the machine, so patients are kept warm.
Who it may not suit: People who are stable enough for standard hemodialysis may do just as well with it, and those at very high risk of bleeding need an adjusted anticoagulation plan. These are general cautions, not a personal verdict. A qualified clinician must assess your full medical picture before recommending or delaying treatment.
What happens during & after
While CRRT is running, the patient stays in an ICU bed connected to the machine 24 hours a day. Movement is limited by the catheter and tubing, so nursing staff help with repositioning to prevent pressure injuries, and most patients remain in the ICU for the full course of therapy. Family visits are usually still possible — ask the unit about its visiting policy for patients on continuous therapies.
The ICU and nephrology team watches closely for signs the kidneys are starting to recover — most importantly, increasing urine output — alongside improving lab results. Once a patient is stable enough, the team will typically:
- Switch to intermittent hemodialysis, a faster, shorter treatment done a few times a week, once blood pressure and overall condition are more stable; or
- Stop dialysis altogether, if kidney function has recovered enough to keep up on its own.
This transition is a good sign — it usually means the sickest phase of the illness has passed — but it’s decided case by case by the treating team, not on a fixed schedule.
Possible complications
Most complications relate to how sick the patient already is rather than to CRRT itself, but it helps to know what the team will be watching for.
- Incomplete kidney recovery. Some people are left with reduced kidney function and develop chronic kidney disease, and a smaller number need long-term dialysis.
- Catheter-related problems. Infection or damage to the vein at the access site can happen and may mean the catheter has to be changed or moved.
- ICU-related effects. Any long critical illness can bring muscle weakness, delirium or skin breakdown, which the care team works to prevent and treat.
- Treatment adjustments. If bleeding, clotting or electrolyte problems keep recurring, the team may change the anticoagulation method or the CRRT mode.
Remember:
New or severe symptoms require prompt medical advice. Do not wait for a routine appointment if you feel seriously unwell.
Recovery
Recovery after CRRT has two parts: the kidneys healing, and the whole person getting back to strength after intensive care.
- Kidney recovery. Kidney function can return over days to weeks once the cause of the injury is treated. The first sign is usually more urine, followed by better blood tests. Some people recover fully, others only partly, and your team will explain which applies to you.
- Getting your strength back. After critical illness it is common to feel very tired and weak, sleep badly or have trouble concentrating for a while. Physiotherapy, good nutrition with a dietitian’s help and rest all support recovery.
- Follow-up care. A nephrology review about 3 months after the kidney injury is recommended, with blood tests (creatinine and eGFR), a urine test and a blood pressure check, because even people who recover well have a higher long-term risk of chronic kidney disease.
- Protecting your kidneys. Ask your doctor before taking anti-inflammatory painkillers (NSAIDs) or new medicines, and make sure every doctor you see knows you have had acute kidney injury.
Clinics offering Continuous renal replacement therapy (CRRT)
Verified kidney centres linked to this treatment in the KidneyGlobal directory.
Public Hospital
Dialysis & Chronic Kidney Disease
Joint CommissionLevel I Trauma CenterESRD Network Certified
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Specialty Hospital
Comprehensive Kidney & Urologic Care
Joint CommissionU.S. News Best HospitalCenter of Excellence
✓ 24/7 ER✓ ICU✓ Insurance
Mayo Clinic Kidney & Pancreas Transplant Center
✓ AccreditedAcademic Medical Center
Advanced Transplantation
Joint CommissionUNOS ExcellenceInternational Patient Center
✓ 24/7 ER✓ ICU✓ Insurance
Good questions
Most Common Questions
How is CRRT different from regular hemodialysis?
Regular hemodialysis runs for about 3–4 hours at a time and removes waste and fluid quickly. CRRT runs continuously, removing them slowly and gently, which is why it suits patients who are too unstable for the faster treatment.
How long will someone need CRRT?
It depends on the patient, but usually several days, sometimes longer. It continues until the kidneys start to recover or the patient is stable enough to switch to intermittent dialysis.
Does CRRT hurt, and will the patient be awake?
The filtering itself is not painful. Placing the catheter involves local numbing medicine, and many ICU patients are sedated for their critical illness regardless of CRRT. Lying connected to the machine can be uncomfortable, and the team will treat any discomfort.
Can CRRT be done outside the intensive care unit?
No. It needs round-the-clock specialist nursing and monitoring, so it is only given in intensive care.
Does needing CRRT mean dialysis for life?
Not necessarily. Many people's kidneys recover once the cause of the injury is treated. A smaller number need ongoing dialysis, and your nephrology team will assess this as you recover.
Is CRRT covered by insurance?
CRRT is usually billed as part of the hospital's intensive care stay, so cover depends on your country, insurer and policy. Ask the hospital's billing or patient-liaison team for an estimate and what your plan covers.
Sources
- KDIGO Clinical Practice Guideline for Acute Kidney InjuryKidney Disease: Improving Global Outcomes (KDIGO)
- Acute Kidney Injury (AKI): guidelines and resourcesNational Kidney Foundation (NKF)
- Acute kidney injury: prevention, detection and management (NG148)National Institute for Health and Care Excellence (NICE)
- Prescription of CRRT: a pathway to optimize therapy (Karkar & Ronco, 2020)Annals of Intensive Care, Springer Nature
- Cost of acute renal replacement therapy in the intensive care unit: results from the BEST Kidney StudyCritical Care, BioMed Central / Springer Nature
- Economics of dialysis dependence following renal replacement therapy for critically ill acute kidney injury patientsEthgen et al.