ESRD- Dialysis

Question 1

1. Explain the concepts of diffusion, convection and ultrafiltration and describe their application to hemodialysis.

Answer 1

DIFFUSION – movement of solute down its concentration gradient. (constant gradient for diffusion is maintained due to dialysate flow causing movement of K+, H+ and uremic toxins out of the blood and bicarb moving into the blood)

CONVECTION – movement of solute in mass transfer along with movement of ultrafiltrate fluid. (consequence of ultrafiltration)

ULTRAFILTRATION – movement of fluid secondary to a pressure applied across the membrane. (causes decrease in fluid returned to the body)

Question 2

1. Explain the concepts of diffusion, convection and ultrafiltration and describe their application to peritoneal dialysis.

Answer 2

peritoneal dialysis uses the native intrabdominal vessels and peritoneal membrane to filter the blood

PD uses glucose in the dialysate to ultra filtrate by osmosis

can be accomplished by chronic ambulatory peritoneal dialysis or chronic cycler peritoneal dialysis (while sleeping)

Question 3

2. Describe the major complications of dialysis therapy.

Answer 3

hemodialysis: hypotension, infection (bacteremia, graft or catheter) or clotted access

PD: peritonitis, tunnel infection, exit site infections; malfunction of catheter

patients generally don’t feel well after volume contraction, takes a lot of time for dialysis

Question 4

3. List and explain the reasons for starting chronic dialysis.

Answer 4

symptomatic uremia

fluid (salt and water) overload that is not responsive to diuretics and salt restriction

hyperkalemia not controlled with diet or removal of meds

GFR> 10 cc/min (with diabetics this is not absolute)

Question 5

4. Describe the reasons of dialysis mortality and morbidity.

Answer 5

After dialysis initiation:
20% die within 1 year and 75% die within 5 years

50% DM die within 1 year
50% of patients over 70yo die within 1 year

top causes of death: CV and vascular disease (associated with elevated inflammation of ESRD, deposition or disregulated electrolytes), infections (ESRD pt. considered immunocompromised)

Question 6

Describe the different types of access used in hemodialysis. What are their advantages/disadvantages?

Answer 6

temporary: dialysis catheter, both tunneled and non tunneled (quick access, risk of infection or pneumothorax, uncomfortable for pt.)
permanent: ateriovenous shunts, either native fistula or a PTFE graft (under skin- less infection; requires surgery, steal phenomenon) greater risk of infection and clotting with graph but requires less time to mature

fistulas have been shown to confer better survival

Question 7

How do measure if a patient is being dialyzed to the right degree/level?

Answer 7

measure monthly the urea reduction ratio (optimally URR>70%); or alternatively Kt/V looking at the total blood volume of the patient and their time spent on dialysis

with PD you can judge based on uremic symptoms, measure of dialysate and urine clearance; monitoring weight, BP, edema etc.

Question 8

How do you increase solute clearance?

Answer 8

increased blood flow rate (transmembrane pressure)
increased surface area of dialyzer
increased time on dialysis

Question 9

What indications can be use to assess the dry weight of a dialysis patient?

Answer 9

using ultrafiltration to get a patient so their BP is normal and they have no peripheral or pulmonary edema

Question 10

List important parameters to consider when setting some one up for dialysis.

Answer 10

tx. acidosis, secondary hyperparathyoridism, anemia, and EC volume overload

refer for transplantation is GFR <20cc/min in non diabetics