PRIMING

When using an ST 150 filter, the CRRT circuit is primed with 2 L of 0.9 NaCl with 5,000 units heparin. If heparin is contraindicated, priming is done with plain 0.9 NaCl. Priming ensures the removal of any air bubbles (air bubbles can precipitate clotting) and debris. It also removes any residues from gas sterilization.

Ethylene oxide (EtO) is a bactericidal gas used to sterilize most medical disposables, including dialysis circuits. Most of the EtO is eliminated by mixing it with carbon dioxide to produce a 10% solution. This produces a harmless waste at the end of the sterilization process, if a 1-2 week deaeration period is provided.

It has been shown that some EtO residual may remain at the end of the deaeration period, especially in the filter. If this gets into the blood stream, it can produce an allergic reaction. To ensure that all EtO residual is eliminated, the circuit must be primed to rinse out the EtO. An interruption of the flow by > 10 minutes can cause the concentrations of EtO to rise. If the circuit was primed more than 10 minutes before the start of a treatment, reprime with heparinized saline. Manual prime of 200 ml is sufficient.

ANTICOAGULATION

Heparin:

Administer a heparin bolus at the initiation of a treatment. The usual dose is 80 units per ml (maximum dose 5,000 units). Keep in mind that the CRRT circuit has also been primed with 5 units per ml of heparin solution. There is approximately 250 ml of volume in the tubing that will be introduced into the patient at the start of the treatment (1250 units).

To adminiser the bolus at the start of the treatment, clamp the access limb, connect a syringe containing the heparin bolus, unclamp the access limb and inject the heparin into the catheter limb. The volume of heparin is less than the limb volume, therefore, the heparin bolus will not enter the blood directly. Reclamp the access limb and connect to the access tubing of the circuit. Start the treatment. As blood is pulled into the access limb of the catheter at the start of the treatment, the first blood to reach the filter will contain heparin.

PTT measurements for the purpose of titrating the heparin are only done q6h. Do not decrease heparin infusions before the 6 hour sample (unless active bleeding is the reason). Early reduction often leads to subtherapeutic levels. Systemic aPTTs should be drawn daily to monitor for screening of systemic levels..

Citrate

When using citrate, measure a systemic ionized calcium before starting the treatment to ensure normal systemic levels. Administer bolus of calcium chloride if required (according to sliding scale) before starting the treatment. Start the systemic calcium chloride infusion 15 minutes before starting a treatment.

The citrate infusion is administered via the PreBlood Pump of the Prismaflex(TM) and is titrated to the post filter ionized calcium levels. The PBP infusion volumes are automatically removed and incorporated into the net fluid balance. A calcium chlorde infusion is administered via a central line that is not part of the dialysis circuit, and titrated to maintain a normal systemic ionized calcium. The calcium chloride infusion IS NOT accounted for by Prismaflex, therefore, it must be incorporated into the fluid balance calculation the same way that IV fluid is addressed.

PrismOcal dialysate is used with citrate because it is calcium free. Use of calcium containing dialysate increases the citrate requirements, which increases the calcium chloride requirements. PrismOcal has 0 mmol/L of potassium, therefore, add potassium according to the sliding scale.

LINE BLOCKING

Line blocking to maintain catheter patency between dialysis runs is done using 4% citrate (available in multidose vials by pharmacy), instilled into each limb for all dialysis catheters. Aspirate and flush each limb with saline prior to line blocking. Use a separate syringe for each limb to ensure line sterility is maintained. Instill undiluted citrate solution equal to the limb volume plus .1 ml.

SALINE FLUSHES

When priming and connecting the Prismflex(TM) circuit, add a saline flush infusion to the Y connector at the access port. This will make retranfusion quick and easy and allow prn flushing to assess filter patency. If you want to retransfuse or clear the filter of blood to inspect for clots:

1. Close the stopcock to the access site and open it to the saline infusion
2. Saline will now be drawn into the circuit
3. Time the duration of time that the saline is open to calculate the volume administered (e.g., if the blood flow rate is 150 ml/min and the saline infuses for 30 seconds, the patient has received 75 ml).
4. Incorporate the saline flush volume into the intake and output calculation; increase the fluid removal by an equivalent amount (if tolerated)

Remember that you will need to estimate the saline volume and record it on the intake record (saline flushes are not removed by the pump). If clotting is present during flushing, retransfuse.

Always try to retransfuse before the filter clots. The entire circuit with the Prismflex(TM) using ST150 filters and heater tubing contains about 250 ml of blood.

REMINDERS

After changing a dialysate or replacement bag, remember to observe the fluid removal, dialysate and replacement volumes to ensure that the volumes are changing appropriately. Tubing impedance can occur on either the dialysate or replacement side. Kinked heater tubing, failure to fully crack the luer lock connection or a leak at the connection site can lead to over removal from the patient.

Any recurrent replacement, effluent or PBP alarm indicates that the bag volume is not changing according to the set flow rates. Before resetting the alarm, check for any clamps or flow restriction before resetting. Failure to do so will trigger a repeat alarm. For example, if the replacement clamp is closed and the replacement flow is set at 2 L per hour, the pump will automatically remove 2 L per hour of effluent, plus a volume equal to the net fluid removal + PBP volume. If the replacement flow is restricted, the same effluent volume will be removed. The missing replacement volume will be removed from the patient's plasma volume. To prevent excessive volume loss from the patient, safety alarms are in place. The pump will shut down permanently (necessitating the setup of a new system) if the volume removed is > ~300 ml (or the limit programmed into the pump) over and above the expected volume change.

Remember that everytime a bag is changed or a flow rate is adjusted, the pressures mayl change. The machine automatically resets the pressure limits each time the pump resumes. Upper and lower pressures are automatically set as 50 mmHg above and below the operating pressures (once the flow rates have re-established). A slow rise in the filter, access or return pressures can eventually trigger the upper pressure limit. The next time the pump is reset, the upper limits (50 mmHg above the operating pressures) will be higher. This can allow the pressures to creep up and suddenly reach a level high enough to shut the pump down with a "clotted filter" alarm. Monitor the pressure trends carefully..

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Last Update: January 21, 2009