The Prismaflex (TM) is the newest generation of technology for CRRT (hemodialysis) offered by Gambro.

The following overview has been developed to provide a brief introduction to the Prismaflex (TM) machine. This information is intended to introduce participants to the main differences between the current technology and the Prismaflex.

Prismaflex educational sessions will provide more detailed instruction regarding the technology.

The Prismaflex(TM) consist of 5 pumps:

  • Blood Pump:

    The blood pump pulls blood from the access side of the dialysis catheter and returns the blood at the same rate of flow. Typical blood flow rates for Continuous Renal Replacement Therapy (CRRT) are 200-250 ml/min. Higher blood flow rates can improve clearance of solutes by exposing the blood to the dialysis fluid at a faster rate. Higher blood flow rates can also reduce clotting by shortening the opportunity for clot formation.

  • Dialysis Pump:

    The dialysis pump delivers dialysate fluid at the prescribed rate. Dialysate fluid enters the filter at the return side of the filter, flows into the filter cannister and around the outside of the hollow fibers of the filter, and exits into the effluent. Dialysate will be delivered AND removed from the filter at the same rate (e.g., if 1 litre of dialysate is administered, there will be 1 L of effluenct collected over and above any fluid removal).

    Dialysis fluid is used to promote solute removal based on the diffusion gradient. Increasing the rate that fresh dialysis fluid is administered can increase the rate of solute removal. Solute removal is referred to as "clearance".

  • Pre Blood Pump (PBP):

    The PBP delivers replacement fluid into the blood circuit immediately after the blood is pulled into the circuit at the access site. Consequently the PBP can be used to deliver anticoagulants, ensuring they enter the blood circuit as soon as possible We use the PBP for the administration of citrate.

    The PBP is a "replacement pump" is also a form of hemofiltration. Hemofiltration refers to the removal of large volumes of plasma water across the dialysis filter in order to "drag" even more solutes toward the effluent side than would be lost by diffusion gradients alone. Hemofiltration is used to promote clearance.

    All fluid that is administered via the PBP is administered to the blood circuit "before" or "pre" filter, therefore, any fluid that is administered via the PBP circuit is a form of predilution hemofiltration. The effluent removal rate always increases automatically to match the PBP rate to maintain a neutral balance.

  • Replacement Pump:

    The replacement pump delivers IV therapy at a prescribed rate. The replacement fluid is delivered into the blood circuit at the blood circuit either before or after the filter. The operator chooses the delivery location as "pre" or "post" dilution ot indicate the location of administration. The effluent pump will automatially increase the rate of effluent removal by the rate of replacement delivery (e.g., if the replacement pump is set to deliver 2 L per hour, the effluent collection rate will automatically increase by 2 L per hour to maintain a net neutral balance).

    Predilution replacement dilutes the blood before the plasma water is removed. This may be associated with less clotting in the filter. Post dilution replacement therapy removes the plasma water at the filter before the volume is replaced. This concentrates the blood in the filter to increase the diffusion gradient and is associated with more effective clearance.

    In practice, we are generally able to clear solutes with either pre or post replacement therapy. The Prismaflex has a deaeration chamber in the circuit just before the blood is returned to the patient. Some post replacement fluid should always be administered to maintain a steady flush into this deaeration chamber to prevent clot formation in the chamber. Because the only way to administer post replacement therapy is via the replacement pump, we always set the replacement pump to deliver "post' replacement therapy.


    Deaeration Chamber

  • Effluent Pump:
    The effluent pump pulls plasma water from the patient's blood stream across the dialysis filter at a preset volume. Total effluenct volume per hour will be equal to the net fluid removal + the sum of the dialysis, preblood pump and replacement volumes.

  • Syringe Pump:
    A syringe pump for the delivery of small volume anticoagulant dosing (e.g., heparin) is included in the circuit.

Any fluid administered on the replacement, dialysis or PBP pumps will be matched by equal effluent removal. Only fluids administered outside these circuits (e.g., IV therapy administered intravenously on infusion pumps or enteral feeding) need to be incorporated into fluid balance calculations.

Blood Flow and Access/Return Pressures:

The tubing for the Prismaflex(TM) is large with a low resistance to flow. The effort required to "pull" blood at the prescribed blood flow rate is influenced by the size of the tubing, the patency of the filter (less resistance required at the start of a therapy when the filter is new) and the blood flow rate. The higher the blood flow, the harder the "suck" required to pull the prescribed volume.

The Prismaflex cannot tell if a catheter is truly disconnected. Instead, it measures the amount of "suck" required to pull blood from the access port (negative pressure) and the amount of "push pressure" that is required to return the blood to the return side. The Prismaflex expect that it will take at least - 10 mmHg to pull the blood and at least + 10 mmHb of pressure to return the blood. If the blood flow rate is too low, the access pressure may not become negative enough or the return pressure may not become positive enough. Thus, an access that is more positive than - 10 mmHg or a return that is less positive than + 10 mmHg will trigger an access or return disconnect.

If an access or return disconnect alarm occurs, check the connection for integrity. If the luer lock device is intact, increase the blood flow rate until sufficient access and return pressures are generated.

Flow Rates

The usual flow rates in CCTC are:

  • Blood flow 200-250 ml/min
  • PBP 1-2.5 L/min
  • Replacement (always post) at 200-1000 ml/min
  • Dialysate 1-2 L/min

Patient size, clearance requirements and the use of citrate are factors that may influence the actual rates.

The Prismaflex(TM) has broad flow rate capabilities for blood flows, dialysate and replacement rates. The Prismaflex(TM) can deliver up to 8 L/hr per hour of therapy (dialysate, replacement plus PBP). To achieve maximum flow rates, a larger filter with higher blood flow capacity may need to be used and the circuit primed differently than the conventional priming. Maximum flow rates are not the usual practice in CCTC.

st 150 filter

Prismaflex initially setup in the maximum therapy mode of CVVHDF (Continuous Venous to Venous Hemodiafiltration), and we setuop with the syringe pump.  If we do not want to use any of the options, we turn the flow rate for the unneeded therapy is turned to "0" ml/hr. This maintains the option to add therapy at any time in the filter.

If the Prismaflex is started in a modified mode (e.g., CVVH only), the only way to add a therapy back is to tear down the filter and restart a new therapy.

The same Prismaflex(TM) filter can be used to administer predilution, postdilution, or a combination of both forms of hemofiltration therapy.

Gambro Training Manual 1 and 2
Slides from Gambro Training package, reproduced with permission

Created: 2007

Revised: July 2, 2013, January 30, 2015

Brenda Morgan

Clinical Nurse Specialist, CCTC