Sunday, September 21, 2008

CRRT Pressures

Wake Forest Med Center has a note about pressures:
The Prisma measures pressures in several areas. It is very sensitive to changes in access pressures and return pressures. Therefore, if a patient is log rolled and the lines or catheter kink, the machine will stop and give an audible alarm. Most of the time this can be corrected by muting, identifying the problem and restarting the treatment.
This advice applies to every CRRT device (Prismaflex, Edwards, etc.) on the market, not just the Prisma, and presumably every dialysis system as well. Even a shift in position can change the pressure, moving the patient's bed up and down can increase or decrease the pressures. The access pressure alarm is most likely to be caused by patient position (lines or cather kinking, blocked, pinched, etc.), then the return pressure alarm. The effluent and filter pressure alarms are not directly influenced by patient position, but can trigger because of the access or return pressure being too high or low due to patient position.

While I believe change in position leading to pressure or kinking on the line or catheter is the most common cause of pressure alarms, additionally, the filter may be clotting, another line may be inadvertantly clamped (due to bag change or similar), or the access flow rate may be too high. More rarely a line could be leaking or the pressure transducer device or pod is failing or not calibrated correctly.

Depending on the pressure alarm, you may have to relieve the pressure by manually turning a pump backwards, consult the manual before doing so. It is important to note that while a pressure alarm is active, the blood pump is not moving, and clotting may occur in the tubing set or catheter if the problem is not fixed quickly (clotting can happen in as little as 5 minutes). Pressure alarms should be taken seriously and not ignored, every effort should be made to find and correct the problem before restarting the treatment, restarting blind and hoping the problem just goes away could lead to serious problems.

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