ECC Dialysis

sihirlifil's version from 2018-05-02 15:24

ID patient that needs dialysis, complications & prognosis, fxn & methods

Question Answer
What is hemodialysis?Extracorporeal removal of uremic toxins: symptomatic tx, NOT a fix or tx of underlying cause!! Gives time for kidney to recover from AKI
(Dialysis 101)
What is the marker molecule for uremic toxins that are dialyzable?Urea (BUN)
The point of measuring BUN is to see how much dmg the urea is causing, right?NOPE! Urea does not cause uremia CS!!!!
What are the indications for dialysis?Uremic toxin buildup from kindey fxn failure
Volume overload (renal or non-renal cause!) e.g. oligo/anuria patients (can’t use diuretic! kidneys not working)
Toxin removal
AKI leads to what (that dialysis can help with)?Severe symptomatic uremia, volume overload, hyperkalemia
We could do dialysis in prep for…?stabilization for sx (ureteral obstruction, renal transplant)
T/F Kidney dz is an indication for dialysisNOT IN ITSELF!
AKI =potentially reversible injury to kidneys
Reversibility of AKI depends on (4)Stopping propogation of injury (treating the etiology & perfusing the kidneys)
Dmg to tubular basement membrane
Rate of regeneration vs. rate of fibrosis
Time (this is where dialysis comes in)
Phases of AKI recoveryTAKES 8 DAYS
How does dialysis work?Blood runs through tiny straws surrounded by semi-permeable membrane, countercurrent exchange of blood w/ dialysate solution
How it works: 3 main methods of removalDiffusion: uremic toxins
Convection: fluids, some solutes
Adsorption: toxins, especially protein-bound toxins (charcoal binds things to dialysis filter on purpose)
(Dialysis machine controls FYI)
What’s the dialysis problem with OSMOLARITY?Osmolarity shifts --> Dialysis Disequilibrium Syndrome
E.g. if pre-dialysis BUN = 300, and after dialysis it’s 8… brain osm is like 400 while fluid is only 296 (from equation we don’t have to know) --> Cerebral EDEMA! (idiogenic osmoles, adjusted to osmolarity over time)
*****Tx/prevent cerebral edemaMannitol NO MATTER WHAT pre-emptive if super high risk!!!
What’s the urea reduction ratio?Speed of stuff being removed. want to drop BUN just enough (but not any more) the first time doing dialysis, then slowly lower BUN (b/c it’s a marker for other uremic toxins)
How do we avoid disequilibrium syndrome?Guidelines for each BUN level for subsequent treatments. If high risk for dialysis disequilibrium syndrome (=high BUN), use the table to see %, then check back on the graph and match the numbers. When you find he urea reduction ratio you can find the rate!
If TOXIN: no risk of disequilibrium syndrome! Run at highest blood flow rate (b/c BUN was normal at the beginning)
What’s the dialysis problem with BLOOD VOLUME? How do we fix it?CLOTTING! Taking like 40% of their blood volume outside of their body!
Prime the system with 2-3 blood transfusions so when we plug the patient in they don’t lose colloidal support (like a blood transfusion over 2 min… usually too fast but we can do it b/c otherwise they will die). Use heparin b/c shorter half life, and if they need surgery have to wait until its completely out of their system (e.g. cats w/ bilat ureteral obstruction)
What is the dialysis tubing primed with?Synthetic colloids, plasma, whole blood, packed RBCs
Complications of dialysisDisequilibrium syndrome
Clotting OR hemorrhaging (b/c heparin)
Cats being cats, e.g. start to scratch your face out when they feel better and sill have to sit there for 4 hours (sometimes need sedative CRI) (CRI b/c most dialyzed out)
Types of dialysisIntermittent Hemodialysis (IHD)
Continuous Renal Replacement Therapy (CRRT)
Special forms: plasmapheresis, hemofiltration, hemoperfusion
How does Intermittent Hemodialysis (IDH) work?Uremic toxins removed over 6-8 hour sessions. # of total sessions depend on recovery of renal fxn
How does Continuous Renal Replacement Therapy (CRRT) work?Continuous, 24-h, slow rate of uremia removal (low urea reduction ratio) (low availability, not many centers do this)
What is plasmapheresis? used in who?Removal of inflammatory mediators, immune-mediated diseases
Indications of plasmapheresis e.g.Myasthenia gravis, polyneuritis (Guillan-Barre Syndrome)
Dialyzing toxins: Hemofiltration =Toxin removal via hemodialysis
Dialyzing toxins: Hemoperfusion =Activated charcoal filter
When do we use dialysis for toxins?Known exogenous toxin ingestion e.g. ethylene glycol, NSAIDs, etc (prevent AKI!!!)
Endogenous toxin removal e.g. liver failure
How does peritoneal dialysis work?The peritoneal membrane is semi-permeable! Exchanges fluid & e-lytes with blood/lymphatics. Indications same as dialysis (use this when hemodialysis not available or can’t get venous access)
Contraindications of peritoneal dialysisPericardial leakage (PPDH, hernias)
Recent abdominal or thoracic sx
How is the peritoneal dialysis catheter placed?Surgical, omentectomy (othersiwe omentum plugs holes in catheter), tunnel through subQ, closed system
Peritoneal dialysis procedureInfusion vol of warm dialysate over 10 min. Then 30 min rest in peritoneal cavity for molecule exchange, drained over 30-40 min using gravity & positional changes (roll them around)
Complications of peritoneal dialysisCatheter flow gets blocked 30% (fibrin clotting, kinking of line)
Exit site 50% (dialysate leaking into subQ tissue; infections, exudate)
(Pleural effusion, Dialysis Disequilibrium Syndrome)
Prognosis of AKI: Short term50% (which is a good thing! would have been 100% w/o dialysis)
Prognostic factors: Oligo/anuria, etiology, CATS: hypothermia on presentation
Prognosis of AKI: if infectious etiology? vs nephrotoxin?Infectious 60-70% survival while toxin = 20-30% :(
Prognosis of CKD: Long term~25% full renal recovery, >2 year survival w/ CKD (different from progressive CKD)