Dialysis Flashcards
What do a lot of patients with CKD die off before they reach end stage kidney disease ?
CV problems - as CKD is a major risk factor for the development of CV problems
What is dialysis in general terms ?
- It is where you essentially have a high concentration of solutes on one side and a low concentration of solutes on the other side divided by a semi-permeable membrane
- Solutes will then diffuse across the semi-permeable from the high concentration to the low concentration, until the two concentration become equal
What is the movement of substances between the patient and dialysis fluid ?
This allows for removal of toxins which build-up in end stage kidney disease such as:
- Urea
- K+
- Excess Na+
It also allows for the infusion of bicarbonate as most patients will be acidotic because the kidneys cant remove the excess H+
How does haemodialysis work ?
- Blood (high solute concentration) is passed over a semi-permeable membrane against dialysis fluid flowing in the opposite direction (low solute concentration).
- So blood goes out flow against the dialysate, its cleared and then passes back into the body
- The dialysate flows in (has certain levels of K and Na as don’t want to remove all of them just excess levels, and high levels of HCO3 to have this diffuse across into the blood)
Define filtration in dialysis
Also known as convection - this is the movement of water (and all solutes dissolved in it) across a semipermeable membrane in response to a pressure gradient.
In haemodialysis how is H20 filtered out of the blood into the dialysate ?
By filtration where a negative pressure is generated which sucks the H20 (and solutes dissolved in it) across from the blood into the dilysate
Is diaylsis efficient ?
No - get a GFR of about 10-12 so not efficient at all
What restrictions are put on a patient on dialysis ?
- Fluid restriction - 1L per day if they pass no urine, 1.25-1.5L if they pass some urine and free fluids if they pass lots of urine
- Low salt diet
- Low potassium diet
- Low phosphate diet + phosphate binders
Note they are also often given calcium replacement with e.g. alfacalcidol
How do we gain access to the blood to do haemodialysis ?
- Gold standard Areteriovenous Fistula
- Tunneled Venous Catheter
Which mode of access in haemodialysis more commonly becomes infected and how are these infections treated ?
- Tunneled Venous Catheter
- Vancomycin given to treat this and the line is taken out
What are the main complications which can occur for patients on haemodyalsis ?
- Fluid overload
- Blood leaks - from the needle inseted to gain access
- Loss of vascular access - been on diaylsis so long that there is no more sites to gain access
- Hypokalaemia and cardiac arrest
- Intradialytic hypotension - the removal of H20 from the intravascular space (in the fistual) leads to H20 moving from ICF to the ECF to the intravascular space, but if this isn’t done at a constant rate then decrease in blood in the vasculature ==> hypotension
How does peritoneal work ?
Peritoneal membrane used as a semi-permeable membrane
- The solute is removal by diffusion of solutes across the peritoneal membrane.
- The dialysis fluid has high glucose levels so H20 then also moves into this fluid to dilute this (allowing removal of water)
- Glucose will diffuse into the patient from the bag due to it being at a high concentration
What are the problems associated with peritoneal dialysis ?
- Infection - Peritonitis or Exit site infection
- Membrane fialure - so unable to remove enough H20 across the membrane
- Hernias - due to increase abdominal pressure
What are some of the organisms which can cause infection in patients on peritoneal dialysis ?
Contamination:
- Staphylococci
- Streptococci
- Diptheroids
Gut Bacteria:
- E.coli
- Klebseilla
What is the treatment for patients on peritoneal dialysis and have an infection ?
IV Amoxicillin + Metronidazole + Gentamicin
