Cvvhdf on prisms flex

  1. HI everyone
    i would much appreciate if anyone could explain how does the cvvhdf works . I mean what is prebloodpump PBP, Dialysate and replacement and their mechanism. What does the PBP do, how is the fluids contained in each enter bag enter the filter , and through which mechanism does each one remove or add anything into the blood. How come the blood entering the filter is cleansed of urea and creatinine- am finding it hard to understand how does filtration! convection occur at the same time in the filter, how does the filter recognise oh this is urea I need to remove it before sending it back or this is glucose or potassium ... Am really at a loss to understand this process. Many thanks for answering in a most simplified way

    why should patients already receiving haemodialysis be started on the filter - why not dialyse them. And how long do patients need to be kept on cvvhdf although urea and creatinine levels have massively improved as well as base excess and lactate levels are now within normal range
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    About wykt

    Joined: Feb '14; Posts: 2


  3. by   Esme12
    Last edit by Esme12 on Feb 2, '14
  4. by   chare
    Another resource, specific to the Prismaflex: Prismaflex Machine
  5. by   DRCCRN
    Regarding questions on continuous renal replacement therapy (CRRT) versus hemodialysis(HD) and the use of CRRT.

    Your facility should have a thorough CRRT class (with hands on) available to all nurses that will be providing CRRT care. You should refer to information obtained from such a course to verify any information. CVVHDF or continuous veno-venoushemodiafiltration uses both dialysis and hemofiltration (which uses "replacement fluid" added to the blood and later removed.

    There are various forms of continuous renal replacement therapy (CRRT). Examples of CRRT treatments include:

    • SCUF - slow continuous ultrafiltration is intended to remove excess fluid.
    • CVVH - continuous veno-venous hemofiltration strives to provide convective clearance of excess waste products; middle/large molecules; balance of electrolytes, acid/base and excess fluid.
    • CVVHD - continuous veno-venous hemodialysis can deliver diffusive clearance of excess waste products; small molecules; balance of electrolytes, acid/base and excess fluid.
    • CVVHDF - continuous veno-venous hemodiafiltration aims to provide diffusive clearance of excess waste products; small molecules; removal of middle/large molecules; balance of electrolytes, acid/base and excess fluid.
    • Hemoadsorption - an extracorporeal blood purification technique that provides removal of target substances from the blood by adsorption of the target substances to a sorbent cartridge/filter.

    Basically, continuous renal replacement therapy (CRRT) is supposed to be better tolerated on hemodynamically unstable patients and may actually be better than HD for acute renal injury (AKI) patients. The type of CRRT therapy used (see the list above)varies based on whether it uses dialysate or replacement fluid, both (as in CVVHDF), or neither (as in SCUFF). The size of the molecules removed when dialysate is used (in hemodialysis) are small-sized molecules. The size of molecules removed when replacement fluid is used are medium to large-sized (as in CVVH) through convection and ultrafiltration.
    In answer to the questions about the filter and the prebloodpump (PBP). The blood filter basically contains numerous, semi-permeable, minute tubes inside it in which the blood travels. Dialysate flows on the other side of the semi permeable membrane, in the opposite direction of the blood, never coming into direct contact with blood, and is then removed into the ultrafitrate line after it passes through the outside of the filter. Hemodialysis allows fluid and small molecule solutes can travel through the semi permeable membrane of the tubes in the filter through diffusion and ultrafiltration.
    Replacement fluids, when used in CRRT, are added to the blood either before it enters the filter(pre-filter), or after it exits the filter( post-filter),or both. Replacement fluid travels in the same direction the blood travels and is then is removed out from the system(along with the molecules it removes through solvent drag) into the ultrafiltrate line. Even though it is named "replacement" fluid, it is removed from the system automatically and not given back to the patient.
    The prebloodpump (PBP) is the pump is the portion of the system that adds a pre-blood filter solution into the system, to the blood, which is later filtered out. The PBP can be used to give pre-blood filter replacement fluid or it can be used to give a pre-filter anticoagulant fluid, such as citrate, instead. (Either the PBP line can be used or a separate heparin syringe attached to a the system can be used to anti-coagulate the patient).
    In some systems, the replacement line, as well as the dialysate line, can travel one of two pathways. The dialysate line, when used for hemodialysis, follows a route that takes it in the opposite direction of the blood. The dialysate line can also be used for a post-filter replacement line (if it is not needed for hemodialysis) following a route that adds replacement after the filter-- in the same direction of the blood. If the PBP is used for citrate, the replacement line can follow a pathway that delivers a pre-filter replacement. The replacement line is often used for the pre- filter replacement fluid, while the dialysate line is used for the post filter replacement fluid when hemodialysis is not required (as in CVVH) and the PBP then used for citrate. If hemodialysis is needed, as well as both pre-filter and post-filter replacement, and pre-filter citrate is needed, any citrate has to be added separately, prior to the system, altogether. The PBP line then would add the pre-filter replacement fluid, and the replacement line would add post-filter replacement fluid to the system.
    For additional information other than the course your facility should provide you with,
    I suggest you find a CRRT course instruction on the web such as:

    You can find more information Gambro's website on their Prismaflex CRRT/HD machines at their website: The Prismaflex System - Gambro
  6. by   wykt
    Hi all - many tks 4 yr replies _ have browsed the links and the Prismaflex website is top
    n makes it so easy to understand.