Dialysis

Question 1

3 major functions of kidneys

Answer 1

1. Filtration of the plasma, reabsorption of vital electrolytes and other substances, and excretion of potentially harmful waste products (byproducts of metabolism)
2. Production and release of important hormones
3. Homeostatic regulation of bp, plasma osmolality, plasma electrolyte concentrations, water balance, and plasma pH

Question 2

Glomerular filtration rate (GFR) for someone that needs dialysis

Answer 2

10-15% of normal

<15 mL/min

= ‘end stage renal disease’

Question 3

After 40 years of life…how much does kidney function decrease each year

Answer 3

1%

Question 4

5 stages of chronic kidney disease (CKD)

Answer 4

1 = normal or high GFR (>90 mL/min)

2 = mild CKD (60-89)

3A = moderate (45-59)

3B = moderate (30-44)

4 = severe (15-29)

5 = end stage (<15)

Question 5

Definition of dialysis

Answer 5

Process that facilitates removal of waste products and excess fluid from the body that build up when the kidneys have failed

Based on the diffusion of small molecules (such as urea and K+) down a concentration gradient from blood into a dialysis solution across a semi-permeable membrane

Question 6

Hemodialysis

Answer 6

Achieved through direct access to the blood supply primarily via a creation of a ateriovenous fistula

…2 needles placed

1 = one to bring the blood to the dialysis machine and membrane

2 = return the cleaned blood to the patient

Primary technique for dialysis centers

Question 7

Peritoneal dialysis

Answer 7

Access to blood supply is indirect and the peritoneum acts as the semi-permeable membrane

Solute and water transfer occurs from the peritoneal capillaries —> dialysis solution

Can be done at home

Blood supply to peritoneum = mesenteric artery and peritoneal capillaries

Exchange occurs by 3 different processes

1. Osmosis
2. Diffusion
3. Convection

Question 8

Peritoneal dialysis solution

Answer 8

Dextrose (glucose) and salts

Question 9

Dwell time

Answer 9

How long solution remains in the peritoneum

Question 10

How excess fluid is removed is peritoneal dialysis (PD)

Answer 10

Osmosis

Movement of water from low concentation of solute to a solution with a higher concentration of solute (dialysis solution = high dextrose)

Increase fluid removal by increasing dextrose concentration

Question 11

How toxins are removed in PD

Answer 11

Diffusion across the semi-permeable peritoneal membrane until equilibrium is achieved

Amount of transfer depends on…

1. Nature of patients peritoneum as a diffusion barrier
2. Time the dialysis solution is allowed to dwell in the peritoneal space

Question 12

Convection

Answer 12

‘Drag’ of water and solutes across the peritoneal membrane that occurs as part of osmotic ultrafiltration

Question 13

Fate of glucose in PD solution

Answer 13

Some will move relatively slowly from dialysis solution —> blood

Where it is metabolized by the body…which is why a glucose solution is used (safe)

Question 14

Why are electrolytes such as Na+, K+, Cl-, and HCO3- included in PD solution with glucose

Answer 14

So no net loss of essential plasma electrolytes

Question 15

What complications can occur from dialysis

Answer 15

Edema (excess retention) or dehydration (excess loss)