Ensure that patient and health care provider safety standards are met during this procedure including:

  • Risk assessment and appropriate PPE
  • 4 Moments of Hand Hygiene
  • Procedural Safety Pause is performed
  • Two patient identification
  • Safe patient handling practices
  • Biomedical waste disposal policies
  • Sharps handling


  1. Dons PPE and Hand Hygiene
  2. Performs Saline Flush
  3. Retransfuses Blood
  4. Accesses Catheter
  5. Prevents Blood Exposure
  6. Blocks Catheter
  7. Adds Medication Label
  8. Disposes of Circuit
  9. Documents
  10. Catheter Disconnection Checklist

Equipment Required:

  • Appropriate PPE—always include a mask with a face shield
    Sterile dressing tray (the dressing tray includes the sterile drapes and a place to inject blood for clot inspection).
  • 2 pair non sterile gloves
  • 2 large (1.5 mL) chlorhexidine 2% swabs (without alcohol) (use 4 wipes if catheter or clamps are visibly soiled.
  • 2 empty 3 mL syringes
  • 2 - 4 10 mL NS syringes
  • 1 Sterile 4X4 gauze
  • Non-sterile gauze (for clot assessment)
  • 2 Citrate syringes
  • 2 luer lock needleless access caps, primed with citrate
  • Red medication label
  • Gauze (to cover limbs)
  • Yellow Biohazard Waste Bucket


If CRRT treatment is being terminated electively, prepare sterile field and equipment required to access and block the dialysis catheter prior to starting.

If treatment is being terminated urgently, perform blood return immediately using normal saline flush to prevent clotting and blood loss (Step 2-3).

At the end of a treatment, blood that is contained within the CRRT circuit is retransfused to the patient. This is done by drawing saline into the access limb (instead of blood) until the blood has been displaced into the return limb of the catheter (blood becomes dilute or translucent on the return side).

The entire circuit (including heater tubing) contains ~270 ml of volume. If saline is drawn into the access end of the circuit until blood in the return side appears dilute, the patient has received a fluid bolus of ~270 ml. This “bolus” is the same volume of blood that is removed from the patient at the onset of treatment (and remains extracorporeally until returned at the end of the treatment).

When evaluating haemoglobin changes in a patient on CRRT, the timing of treatment should always be considered (e.g., haemoglobin may drop after initiation of treatment, and increase following retransfusion. If the filter is allowed to clot before retransfusion, a drop in haemoglobin may be identified.

It is always better to retransfuse early than to allow the filter to clot completely.


At any time during a treatment, a saline flush can be performed. This uses the same process as retransfusion. Saline is drawn into the access limb until clear fluid is observed passing through the filter. A volume of 50 – 100 ml of saline is sufficient to assess the filter. Intermittent flushing can also be performed to maintain filter patency.

Saline flushing OR retransfusion is accomplished by maintaining a saline infusing at the access limb. A 3-way stopcock positioned between the access limb and access end of the circuit enables a quick switch from blood drawing to saline drawing into the circuit. By leaving the roller clamp of the saline open and the stopcock closed to the saline infusion, flushing (or retransfusion if clotting appears imminent) can be initiated by simply turning the stopcock off to the access limb.

The volume of saline administered can be calculated by assessing the blood flow rate and duration that the saline is open. For example, if the blood flow is set at 200 ml/min, a 15 second flush will provide a 50 ml saline bolus. This can be removed over the subsequent hour by increasing the fluid removal rate by 50 ml.



Dons PPE and Hand Hygiene

Perform hand hygiene, don appropriate PPE including mask with face shield.


Saline Flush

Keep saline infusion open (roller clamp and slide clamp). Turn off and on with stopcock only.

Determine blood flow rate. Adjust if desired to make volume calculation easier (e.g., 200 ml/hr).

For example, if the blood flow is set to 200 ml/hr and the saline flush is opened for 30 seconds, the patient will receive a 100 ml bolus. Determine in advance the duration of flushing in seconds.

When ready to flush, turn stopcock "closed" to the access lumen and open between the saline and dialysis circuit.  Saline will be drawn in to the circuit instead of blood.

Watch as the saline reaches the filter. Blood in the filter will clear, allowing for visible inspection of the amount of clotting.

Close the clamp when sufficient flushing has occurred.

Adjust the fluid removal for the next hour to remove the volume of the saline flush.

Saline will be drawn into the access side of the circuit upon starting blood return. By keeping the IV clamps open, saline flushing can be performed quickly by a single stopcock adjustment.


Ends Treatment

Inspect return side of circuit for signs of clotting.

Press stop on the machine and follow the on-screen instructions to “End Treatment” and “Return Blood” (if there are no clots in the blood line and filter is not completely clotted).

Because you already have a bag of sterile saline (as flush) attached to your access line, skip the screen directing you to “hang a bag of sterile saline on the priming hook.

Turn stopcock off to the access limb and open between saline flush and access tubing. This enables rapid retransfusion of blood if filter is starting to fail.

The auto-return feature can also be used if non-urgent retransfusion is required.

Choose “auto-return” from the screen.

  • Change the blood return rate if needed.
  • Watch for the filter and return line to clear as the saline is drawn from the flush line.
  • Note the “auto return” soft key becomes inactive once blood has been successfully returned.
  • If additional flushing is required use the manual return key (must be held to be active.
  • Blood flow rates will be adjusted and volume for retransfusion calculated by the machine when the PrisMax/Flex software is used to guide retransfusion.

  • Using the “auto return” allows the precise amount of blood volume in the lines and filter to be returned to the patient.



Accesses Catheter

Prepare equipment and access catheter as per CCTC procedure for Accessing a Temporary Double Lumen Dialysis Catheter.

Check for clots and flush vigorously as per procedure.


Prevents Blood Exposure

As soon as each end of the circuit is disconnected, drop the end of the CRRT tubing into the biohazardous waste bin or connect.


Blocks Catheter

Obtain two syringes of 4% citrate solution (for catheter blocking) and two needleless access cap. Connect each syringe to one access cap and prime the cap with citrate.

Attach the needleless access cap and infuse a volume equal to the limb volume plus 0.1 ml into each of the lumens.

For citrate, up to 2.5 ml can be injected into each limb without concern over administration into the patient.

If heparin is being used to block a line, limit the volume to exactly the limb volume plus 0.1 ml.

If TPA is being used to block a line, the limb volume plus 0.3 ml should be ordered.

The overage volume is used to ensure that the drug reaches the end of the catheter.  For heparin, it is important to avoid additional administration to prevent systemic heparinization.


Adds a Medication Label

Wrap the ends of the limbs with gauze net and add a completed medication sticker to identify citrate solution


Disposes of Circuit

Ensure all CRRT lines are clamped, then unload CRRT filter and tubing from the machine. Dispose set and any other supplies with blood exposure in the yellow biohazardous waste bucket.

Do not place non-blood contaminated products in the biohazardous container (such as Hemosol or saline bags).


Documents Blood Return

Document whether blood was successfully retransfused or lost within a clotted filter.

Record the volume of blood that was returned (if blood was successfully retransfused, the volume of blood that was returned is the same as the volume lost at the time of therapy initiation).

Developed: November 30, 2017, Reviewed: February 2, 2021
Brenda Morgan CNS CCTC


LHSC Renal Program Procedures