renal dialysis Flashcards
what is the main method of solute ion movement / removal in haemodiafiltration?
convection
what is fluid removal in haemodialysis also known as?
subfiltration
what are the 4 methods of vascular access in haemodialysis?
Arteriovenous Fistula (AVF) (gold standard)
Arteriovenous Graft (AVG)
Tunnelled Central Venous Catheter (TCVC)
Temporary Venous Catheter (Vascath)
what fluid is used in haemodialysis?
dialysate 500ml/ min (120L in 4 hr treatment)
what do you need for haemodialysis?
vascular access
dialysis machine
artificial kidney to receive blood and dialysate
dialysate
what is ultrafiltration in dialysis?
convection
The movement of water, and all solutes dissolved in it, known as
convective solute drag
across a semi-permeable membrane in response to a pressure gradient
what is adsorption?
plasma proteins stick to the membrane surface and are removed by membrane binding
high flux membranes adsorb protein-bound solutes better than low flux membranes
describe haemodiafiltration
The greater the convective force, the greater will be the generated volume of the pressure-driven ‘ultrafiltrate’
Large volumes of ultrafiltrate add enormously to solute drag - especially for the larger “middle molecule” solute classes
There is still diffusion down engineered concentration gradients
what is a tunneled central venous catheter (TVTC) and what are the pros and cons?
catheter inserted into large vein typically internal jugular
pros- easy to insert, can be used immediately
cons- high infection risk, can become blocked, can cause damage (thrombosis or stenosis) to central veins causing future line insertion to be difficult
what are the investigations and treatment for TVTC infection?
usually staph aureus- can cause endocarditis or discitis
investigations - blood culture, FBC and CRP, exit site swab
give vancomycin + gentamicin, remove or exchange line
what is an AV fistula?
artery and vein surgically connected- venous part develops creating an enlarged thick walled vessel
common sites are radio-cephalic, brachio-cephalic and brachio-basilic transposition
what are the pros and cons of AV fistula?
pros-
good blood flow, less likely to become infected
cons-
needs surgery, 6-12 week wait before it can be used, can cause steal syndrome (limits blood flow to distal arm), can thrombose or stenose
what are the complications of dialysis?
hypotension
haemorrhage (rupture of AVF)
loss of vascular access due to thrombosis, stenosis or infection
arrhythmia
cardiac arrest
what is peritoneal dialysis?
Solute removal by diffusion of solutes across the peritoneal membrane (semi-permeable membrane)
water removal by osmosis driven by high glucose conc in dialysate
what are the 2 types of peritoneal dialysis?
continuous ambulatory PD - 4 x 2L bag exchanges per day, 20-30 mins per exchange
automated PD - dialysate drainage in and out of peritoneal cavity controlled by APD machine overnight - 9-10 hours. 1 bag of fluid stays in all day
