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: http://www.orlandohealth.com/pdf%20f...%20replace.pdf
You can find more information Gambro's website on their Prismaflex CRRT/HD machines at their website: The Prismaflex® System - Gambro