6.2 Treatment Initiation: Line Connection, Prime Management, and Blood Pump Ramp-Up
Key Takeaways
- Priming clears the dialyzer and bloodlines of air and sterilant and wets the membrane fibers, so incomplete priming risks air embolism and residual germicide exposure; the CCHT-A prep guide identifies reducing the risk of clotting as a purpose of the pre-dialysis prime.
- Before the blood pump is started, the technician confirms the alarm limits are active, the venous and arterial pressure monitors are connected and unclamped, the air detector is armed, and the venous line is fully seated in the detector clamp.
- Blood is introduced gradually, starting the pump near 100 mL/min and increasing over several minutes to the prescribed rate while watching arterial and venous pressures and the patient's blood pressure response.
- The prime may be returned to the patient or discarded depending on prescription and hemodynamics; whichever is done must be reflected in the ultrafiltration goal so the fluid balance stays accurate.
- Initiation is complete only when the machine is verified against the prescription, the treatment clock is started, the initial vital signs are recorded, and the access site and all connections are left visible and unobstructed.
6.2 Treatment Initiation: Line Connection, Prime Management, and Blood Pump Ramp-Up
Quick Summary: Initiation is a choreographed sequence with no safe shortcuts. The circuit must be air free, germicide free, and pressure monitored; the patient must be assessed and hemodynamically ready; and blood must be introduced gradually, not at prescription speed.
Why the Circuit Is Primed
Priming with normal saline serves four purposes:
- Removes air from the dialyzer and both bloodlines, which is the primary defense against air embolism.
- Removes residual disinfectant - peracetic acid, formaldehyde, or heat-disinfection residual - and residual manufacturing sterilant such as ethylene oxide or gamma-irradiation byproducts.
- Wets the hollow fibers, opening the full membrane surface area so the delivered clearance matches the dialyzer's rating.
- Reduces the risk of clotting by displacing air-blood interfaces where the contact-activation cascade begins. NNCC's own preparation test identifies this as a purpose of pre-dialysis priming.
Priming is not a test of fiber bundle volume, does not prevent venous stenosis, and does not stop the spread of infection.
Prime volume is typically 500-1,000 mL depending on dialyzer and line set. Facility protocol determines whether heparin is added to the prime. The dialyzer is oriented and tapped or inverted per manufacturer instructions to sweep microbubbles out of the header and fiber bundle; bubbles trapped in the arterial header will migrate to the venous line once blood flow starts.
Where reuse is practiced, the residual germicide test must be performed and documented as negative before the dialyzer is connected to a patient, and the dialyzer label must match the patient's name and identifiers.
Pre-Initiation Verification
Run this list every time, in this order:
Patient
- Two identifiers confirmed against the prescription and the machine.
- Pre-treatment weight, standing and sitting blood pressure, heart rate, respiratory rate, and temperature recorded.
- Interdialytic history obtained - missed treatments, hospitalizations, new medications, bleeding, falls, fever.
- Access assessed by look, listen, and feel, and cleared for cannulation.
Machine and circuit
- Prescription re-verified: time, dialyzer, Qb, Qd, bath, temperature, ultrafiltration goal, anticoagulation.
- Independent second check of the ultrafiltration goal and dialysate bath per policy.
- Conductivity and temperature within alarm limits and the machine out of bypass.
- Total chlorine testing for the shift documented as acceptable.
- All alarm limits active - no monitor muted, overridden, or set to a limit that would not alarm.
- Arterial and venous pressure transducer protectors connected, dry, and unclamped. A wet transducer protector must be replaced, never dried and reused, because it is a direct route for blood-side contamination of the machine.
- Venous line fully seated in the air detector and the line clamp. A venous line lying outside the clamp is the single failure that turns a detected air event into an unstopped one.
- Circuit inspected end to end for air, kinks, open ports, and loose luer connections.
Connection and Ramp-Up
- Perform hand hygiene, don gloves, gown or fluid-resistant apron, and face protection. Cannulation and connection are anticipated splash procedures.
- Cannulate per the access plan, or complete the sterile catheter connection sequence.
- Draw pre-dialysis laboratory samples if ordered - before heparin, before saline.
- Administer the heparin bolus as prescribed and allow the prescribed circulation time before starting the pump.
- Connect the arterial line to the arterial needle or lumen with clamps closed, using a no-touch technique.
- Start the blood pump at approximately 100 mL/min and watch the blood-saline interface advance through the dialyzer.
- Connect the venous line when the interface reaches the venous drip chamber, and open the clamps.
- Increase the blood pump in stages over 2 to 5 minutes to the prescribed rate, pausing to watch arterial pressure, venous pressure, and the patient.
- Set the drip chamber levels so the air detector reads correctly, and confirm the detector is armed.
- Start the treatment clock and the ultrafiltration, then record initial on-treatment vital signs and machine parameters.
- Secure and expose. Tape needles so no traction reaches the insertion site, and leave the access site, needle sites, and all connections visible and uncovered. Nothing about the access should ever be hidden under a blanket, a coat, or a stack of belongings.
Why ramp gradually? Starting at 400 mL/min immediately pulls a large volume from the intravascular space into the circuit in seconds. In an elderly, hypovolemic, or cardiomyopathic patient that can precipitate immediate hypotension. Gradual ramping also lets you detect an inflow problem at a low, safe vacuum instead of at -300 mm Hg.
Prime Handling and Fluid Balance
Two acceptable practices exist:
- Return the prime to the patient as blood displaces it. Useful in patients who run hypotensive. The prime volume must then be added to the ultrafiltration goal, or the patient ends the treatment above dry weight.
- Discard the prime into a drain bag as blood advances. Preferred when the patient has minimal fluid latitude or when facility policy directs. Nothing is added to the goal.
Either way, the choice must be consistent with the programmed goal and recorded. An unaccounted 700 mL is the difference between a patient who leaves at dry weight and one who returns in two days with dyspnea.
Early-Treatment Watch Points
The first 15 minutes concentrate most initiation complications:
| Finding within minutes of initiation | Consider | Immediate action |
|---|---|---|
| Chills, rigors, fever, hypotension | Pyrogen reaction or catheter-related bloodstream infection | Stop, do not return blood, notify the nurse, save the circuit and dialysate for evaluation |
| Dyspnea, back or chest pain, itching, urticaria | Dialyzer reaction or anaphylactoid response | Stop the pump, clamp lines, do not return blood, notify the nurse, be ready with oxygen |
| Sudden hypotension | Excessive initial ultrafiltration or too rapid ramp-up | Reduce or stop ultrafiltration, place in Trendelenburg per protocol, notify the nurse |
| Burning at the venous site, cherry-red circuit blood | Hemolysis | Stop the pump immediately, clamp, do not return blood, notify the nurse |
| Alarming arterial pressure at low pump speed | Access inflow problem | Reduce pump speed, reassess the access, notify the nurse |
Recognizing these in the first minutes is precisely the Application-level judgment the CCHT-A is built to test.
According to NNCC's published preparation material, one purpose of priming the extracorporeal circuit before dialysis is to
A technician has cannulated a patient's arteriovenous graft and is ready to begin treatment. Which action best describes correct blood pump management at initiation?
A technician plans to return the 700 mL saline prime to the patient at initiation. What must also be done?