Renal replacement therapy (RRT) Flashcards
HD - frequency
- 3x/wk on alternate days
- 4 hrs each time
HD - types of substances
water, urea, Cr, uremic toxin, drug
HD - mechanism of transport
1) diffusion
- conc gradient
- factors affecting rate: solute conc, solute characteristic, dialyser composition, blood & diasylate flow rate
2) ultrafiltration
- move water across membrane due to hydrostatic/osmotic pressure
- primary mean for removing excess body water
3) convection
- drag solute across membrane w fluid transport
- factors affecting: hydrostatic pressure, pore size of dialyser
HD - component of dialysis
1) diayser
- large canister w small fibres (semi-permeable membrane)
- conventional: small pore (urea, Cr)
- high-efficiency: larger surface area (WAter, urea)
- high flux: large pore (high MW substance, drug)
2) diasylate
- adjusted to meet patient need
HD - process
- extrarenal vascular circuit
1) patient blood transferred in polyethylene tubing into dialyser through blood pump
2) anticoagulant introduced to prevent clotting
3) blood pass through dialyser on 1 side of semi permeable membrane, dialysate enter from opposite direction on other side
4) exchange of substances
5) cleansed blood return to patient through venous line
HD - types of access - general
- early referral cuz takes time to prepare (Create & mature to be functional)
HD - type of access - arteriovenous (AV) fistula
- preferred, permanent
- gradual increase in size over time & allow repeated needle insertion
- use more distal blood vessel in arm before moving upward
- advantage: longer survival, lowest complications
- disadvantage: >/= 2 month to dilate/thicken/mature, difficult in patient w small vein (old, DM, PVD)
HD - type of access - AV graft
- synthetic graft (polytetrafluroethylene) under skin, act as artificial vein for repeated needling, permanent
- used if vein too small for AV fistula
- advantage: quicker maturation time (2-3 wk)
- disadvantage: shorter survival, higher complciation rate
HD - type of access - venous catheter
- temporary access, not to be lef tin patient for long
- indication:
1) AKI (short term HD)
2) when AV not an option - disadvantage: short lifespan, prone to complication, low blood flow rate, proper cleaning & care required, no contact w water
HD - goals
- desired dry weight (normotensive & free of oedema/SOB)
HD - monitoring
1) urea reduction ratio (URR)
- goal: > 65%
- (predialysis urea - post)/predialysis urea X 100
2) Kt/V
- fraction of patient body water cleared of urea during dialysis
- K = dialyser clearance, t = time, V = distribution vol of urea
- goal: Kt/v around 1.4, min 1.2
HD - advantage
1) higher solute clearance
2) dialysis adequacy parameters better defined
3) low technique failure rate
4) closer patient monitoring
5) IV administration of some drugs
HD - disadvantage
1) multiple centre visit
2) complications
3) infections
4) Rapid decline in residual kidney function until anuria
HD - HD related complication - hypotension - causes
1) hypovolemia
2) excessive ultrafiltration (drop in urine vol)
3) anti HTN med
4) target dry weight too low
5) diastolic dysfunction
6) autonomic dysfunction
7) low Ca, Na in diasylate
8) high diasylate temperature
9) meal ingestion (Food = vasodilation), light snacks ok
HD - HD related complication - hypotension - management
1) lower position of head to maintain blood flow to head
2) Reduce rate/turn off ultrafiltration (other transport still possible)
3) administer fluids
4) increase diasylate Na conc
5) switch to bicarbonate-buffered diasylate (if diasylate contain lactate)
6) Accurately set up dry weight 7) lower diasylate temp
8) midodrine (alpha adrenergic agonist), CI w CVS hist
9) correct anaemia
10) Administer O2
11) avoid large meal before/during HD
HD - HD related complication - cramp - cause
1) muscle hypoperfusion
2) hypotension
3) electrolyte/acid-base imbalance
HD - HD related complication - cramps - management
1) correct/prevent vol contraction & excessive ultrafiltration
2) Vit E: 400 IU @ bedtime
3) other agent: skeletal muscle relaxant, benzodiazepine, pramipexole (restless leg syndrome)
HD - HD related complication - N/V
cause: hypotension, dialyser reaction
HD - HD related complication - headache
cause: disequilibrium syndrome, caffeine withdrawal (From HD)
HD - HD related complication - chest/back pain
unknown
HD - HD related complication - pruritus - cause
1) inadequate dialysis
2) dry skin
3) secondary hyperparathyroidism
4) electrolyte abnormalities
5) histamine release
6) mast cell production
HD - HD related complication - pruritus - management
moisturiser, antihistamine
HD - HD related complication - fever/chills
cause: endotoxin release, infection
HD - HD related complication - overall management
paracetamol, diphenhydramine, prochlorperazine
HD - catheter related thrombosis - general
- blood clot within/outside catheter
- intrinsic (inside lumen) vs extrinsic (outside)
- suspected when blood cannot be aspirated from catheter but saline flow normally
HD - catheter related thrombosis - management
1) non pharm
- forced saline flush
- mechanical thrombectomy
- catheter stripping/removal
- exchange catheter over guidewire
2) pharm: intraluminal thrombolytics to lyse thrombus
- Alteplase (r-TPA): small dose per catheter port and allowed to stay inside for awhile, attempt to aspirate after 30 mins, repeat if function not restored
- Urokinase: aspirate after 4 min, aspiration attempt every 5 min, secondary injection required