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.