Nursing care
Continuous Renal Replacement Therapy: the nurse's role, start to finish
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Continuous renal replacement therapy (CRRT) is a slow, round-the-clock form of dialysis used for critically ill patients whose blood pressure cannot tolerate the rapid fluid shifts of intermittent haemodialysis. It runs 24 hours a day through a central venous catheter, removing fluid and solutes gradually rather than in a few hours, which keeps haemodynamics stable.
When it is done and why
CRRT is chosen for patients in acute kidney injury who are too haemodynamically unstable for intermittent haemodialysis. Most are in ICU, often on vasopressors, with sepsis, cardiogenic shock, or multi-organ failure driving the kidney injury. The deciding factor is rarely the creatinine alone; it is whether the patient's blood pressure can withstand the rapid fluid and solute removal that intermittent dialysis demands.
Intermittent haemodialysis pulls fluid off over three to four hours. That rate of shift can drop mean arterial pressure sharply in someone already on norepinephrine. CRRT removes the same volume, or more, across 24 hours, so the haemodynamic hit per hour is far smaller. That gentleness is the entire rationale for choosing it: it lets clinicians correct uraemia, acidosis, hyperkalaemia and fluid overload in a patient who cannot afford the swings that faster dialysis would cause.
Preparing the patient
Confirm vascular access first. CRRT runs through a large-bore, dual-lumen central venous catheter, usually placed in the internal jugular or femoral vein. Check the insertion site for bleeding or haematoma, confirm placement by chest X-ray if it is a new jugular line, and flush and aspirate both lumens to confirm patency before connecting the circuit.
Baseline data matters more here than for most procedures, because the whole run is judged against it. Record weight, vital signs, and a full set of electrolytes, including potassium, phosphate, magnesium and bicarbonate, along with coagulation studies if anticoagulation is planned. Review the ordered fluid balance target with the prescriber, and confirm whether anticoagulation will be regional citrate or systemic heparin, since that changes what you monitor once the circuit starts.
The steps that matter for safety
Priming the circuit correctly is the first safety checkpoint. Air in the line, a poorly primed filter, or a miscalibrated scale can each cause harm once blood is flowing, so this is checked against the manufacturer's protocol before connection, not estimated. Two nurses typically verify the settings: blood flow rate, dialysate and replacement fluid rates, and the net ultrafiltration target, against the prescription.
Anticoagulation is the second checkpoint. Regional citrate anticoagulation requires matched calcium replacement to prevent systemic hypocalcaemia, so citrate and calcium infusions are checked together, not in isolation. If systemic heparin is used instead, a baseline activated clotting time or aPTT is drawn before starting and rechecked on the schedule the unit specifies. Getting either of these wrong risks either filter clotting or bleeding, so they are never assumed correct from the order alone; they are confirmed against what is actually infusing.
During the procedure — the nurse's role
Once running, the nurse is watching three things continuously: the circuit, the patient, and the fluid balance. Circuit pressures (access, filter, return) are reviewed hourly for trends that suggest clotting or kinking. A rising transmembrane pressure or filter pressure often means the filter is clotting and needs early attention before it fails outright.
Vital signs and haemodynamics are checked at least hourly, since even the gentler fluid removal of CRRT can still drop blood pressure if the ultrafiltration rate is set too aggressively for the patient's current volume status. Electrolytes, particularly potassium, phosphate and calcium, are rechecked on the unit's schedule, commonly every four to six hours, because CRRT removes these steadily and replacement fluids need adjusting in response. Net fluid balance is documented hourly against the prescribed target, not left to add up at shift end.
After: monitoring and complications
The complications to watch for cluster around three causes: the access, the circuit, and the electrolyte shifts. Catheter-related bloodstream infection is a real risk with any dwelling central line running continuously; site checks and dressing changes follow the unit's central line care bundle. Circuit clotting causes blood loss when the filter is discarded, so a clotted circuit is both a mechanical problem and, if it happens repeatedly, a source of cumulative blood loss worth tracking.
Electrolyte derangement is the complication nurses catch earliest, because it shows on the monitor before it shows on labs. Hypokalaemia and hypophosphataemia are more common than the hyperkalaemia CRRT was started to correct, since continuous removal can overshoot if replacement fluids are not matched to losses. Hypothermia is also common, since blood is circulating through an external circuit continuously; most machines have an inline warmer, and temperature is trended alongside vital signs, not checked once and left.
Documentation and teaching
Documentation for CRRT is hourly, not per-shift: fluid in, fluid out, net balance, circuit pressures, anticoagulant infusion rates, and any alarms with the action taken. This record is what the next nurse and the nephrology team use to judge whether the current settings are working, so gaps or estimates undermine the whole plan.
Patient and family teaching focuses on what they will see and why it looks different from the dialysis they may have heard about. Explain that the machine runs continuously rather than for a few hours, that the patient will be sedated or at least kept still because the access lines cannot tolerate much movement, and that this is a temporary bridge while the kidneys recover or a longer-term dialysis plan is arranged. Correcting the common assumption that CRRT means permanent dialysis is often the single most useful thing you can say to a frightened family member.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our renal and genitourinary practice questions are the closest set to what this page covers.
Common questions
Why is CRRT used instead of regular dialysis in ICU?
Because it removes fluid and solutes slowly over 24 hours rather than over three to four hours. That slower rate avoids the sharp blood pressure drops that intermittent haemodialysis can cause in a haemodynamically unstable patient, which is why CRRT is the default choice for critically ill patients on vasopressors.
What anticoagulation is used for CRRT and why does it matter to the nurse?
Either regional citrate anticoagulation or systemic heparin, chosen based on the patient's bleeding risk and liver function. Citrate requires matched calcium replacement to avoid systemic hypocalcaemia, and heparin requires regular clotting checks, so the nurse's monitoring differs depending on which is prescribed.
What does a rising filter pressure on CRRT usually mean?
It usually signals early filter clotting, often from inadequate anticoagulation or a kinked line. Catching the trend early and reporting it allows the team to adjust anticoagulation or flush the circuit before the filter fails and has to be replaced, which causes blood loss.
How often are electrolytes checked during CRRT?
Commonly every four to six hours, though this varies by unit protocol. Potassium, phosphate, calcium and magnesium are the priorities, since CRRT removes them continuously and replacement fluid rates need adjusting in response rather than left on a fixed setting.
Is CRRT a permanent form of dialysis?
No. It is used as a temporary measure in acute kidney injury while the kidneys recover, or as a bridge to intermittent haemodialysis once the patient is stable enough to tolerate it. This is a key point for family teaching, since the continuous nature of the therapy is often mistaken for permanence.