Small Ani. Med- Renal Replacement Therapies

wilsbach's version from 2016-05-02 16:00


Question Answer
What ARE good reasons to do dialysis? What is NOT a good enough reason?GOOD FOR: pts with AKI, removal of toxins, removal of fluid in CHF. It is NOT a good enough reason if the patient just has significant azotemia
AKI indications for using dialysis(NOT JUST HIGH AZOTEMIA THAT IS NOT A GOOD ENOUGH REASON!) (1) severe refractory hyperkalemia (2) Severe acid-base disturbances (3) overhydrated patients with anuria/oliguria (4) severe uremic toxicity
What is life threatening levels of K+, and how can you lower levels aside from dialysis?>7.5mEq/L is life threatening. Along with dialysis you can try to dilute it out with K free fluids (NaCl), loops are thiazide diuretics (these are not K sparing), sodium bicarb (alkalosis will pull H out of the cell and put K in), dextrose/insulin (pushes K into the cells), AND dialysis
in KAI, what kinda acid base disturbances would you expect?METABOLIC ACIDOSIS!! (Kidney cant excrete H) LOW HCO3 (all gone into buffering), low pH (hence acidosis), Low PCO2 (metabolic equal)
what is oliguira?the production of abnormally small amounts of urine.
what is normal urine output? What is considered oliguria? what is considered anuria?NORMAL is 1-2mg/kg/hr (think about the ROT 2ml/kg/hr for fluids-- same thing), oliguria is <0.5-1mg/kg/hr. Anuria is 0!!
what can you try to do for the overhydrated patient with oliguria or anuria before dialysis?DIURETICS! ESP FUROSEMIDE (avoid K+ sparing and also AVOID MANNITOL because can volume expand you when you can't pee...yikes).
what are problems that happen because of severe uremic toxemia (how do you know they have it?)delayed formation of 1* hemostatic plug, prolonged BMBT, abnormalities in platelet adhesion, aggregation, secretion abnormalities, oral or GIT ulceration, neuro signs (elevations in uremic toxins)
what are the 2 major factors of dialysis, what is the principals of them?principal: movement of solutes between 2 aqueous solutions (blood and dialysate) separated by a semi-permeable membrane (fluids are moving in countercurrent direction). the MAJOR FACTORS are diffusion and convection
the diffusion across the dialysis membrane depends on..(how does it work)conc gradient between compartments, solute charge, molecular weight, surface area, permeability of the membrane. (such as BUN being 60DA and is easily diffusible, but albumin is 66,400 and will not diffuse)
how does the "convection" for dialysis work?solutes dragged with water across a dialysis membrane (osmotic pressure gradients, hydrostatic pressure (solvent drag). The rate of the solute removal is dictated by water movement and pore size. This allows the removal of mid range and large weight solutes ( MW > 60,000 DA) So basically this relies on PRESSURE GRADIENTS instead of concentration gradients
which principal dialysis works on can remove bigger solutes?convection (gotta be careful can lose albumin)
what should the catheters be like in dialysis?LARGE gauge vascular catheters, placed as jugular catheters with catheter tip inserted into R atrium! (there are temp caths for a 2-3wk access), per caths have a cuff placed SQ and are used for life
what IS dialysate?fluid very similar to plasma (isotonic), allows for solute exchange via diffusion. Bi-direction of solute occurs (dialysate flows countercurrently to blood in machine), and the electrolytes that are in the dialysate depend on what you think the pt needs and what you think need to come out of the pt (K, Na, Ca, P, HCO3).
what are the modalities of dialysis (4)(1) INTERMITTENT HEMODIALYSIS (fast, high volume) (2) CONTINUOUS RENAL REPLACEMENT THERAPY (you dont stop till done- until they are better or stable enough for a kidney xplant. done at a slow rate so might be more physiological) (3) PERITONEAL DIALYSIS *NOT EXTRACORPOREAL* (4) HEMOPERFUSION- for non-dialyzable toxins (toxins that wont cross semi-permeable membrane- basically run blood over charcoal filter)
most common form of dialysis in vet med for AKI? downside?intermittent hemodialysis (IHD). Its a high maximum removal rate (short bursts of removing lots of blood)- low molecular solutes/time. A C/I for this type is a very small patient-- cant physically tolerate getting that much blood removed from them (there is a priming volume)
which modality of dialysis has a smaller priming volume so can be used for smaller patients?CONTINUOUS RENAL REPLACEMENT THERAPY (CRRT)-- micmics endogenous renal function. SLOWER. (therapy continued till pt is done)
therapy with continuous renal replacement therapy is continued till 1 of what 3 things happen?(1) renal fxn recovered (2) pt transferred to IHD (intermittent hemodialysis) (3) pt dies
along with filtering, what else can you do with dialysis while theyre getting dialyzed?can add stuff- like anticoags, etc.
what is going on in peritoneal dialysis? (bonuses of this)no special equipment or ppl needed, no blood needs to be removed from body. Great for super tiny patients. place fluid into peritoneum, peritoneal lining works AS the dialysis membrane, bad things diffuse into fluid you added, remove fluid. Has both diffusive (concentration gradients) and convective (pressure gradient). The more frequently you do this, the more maximal clearance you get.
what fluid you you use for peritoneal dialysate?/how do you do it?Must be sterile! infused into abd at a DEFINED VOLUME, and at a defined exchange rate (dwelling time). the ultrafiltration depends on the osmotic gradient, so diff agents with diff osmolarities are avail (home made, LRS, dextrose...)
important considerations with dialysisSUPER EXPENSIVE (IHDD, CRRT) but earaly initiation of the right pt can be cost saving in the long run. Also need to consider prog of pt vs cost.
changes of return to renal fxn with dialysis?20% change of renal recovery of toxin induced AKI. 50-75% chance of renal recovery if ischemic or infectious AKI
***CIs for continuous renal replacement therapy/ Intermittent hemodialysis?SMALL patient, coagulopathy, severe hypotension
***CIs of peritoneal dialysis?peritonitis, recent abd sx, hypoalbuminemia.