Renal replacement therapy

Main indications of renal replacement

• non-obstructive oliguria, or anuria

• GFR < 8-10 ml/min

• azotemia progression w/o clinical sign (urea > 36 mmol/L)

• hyperkalemia > 6 mmol/L

• metabolic acidosis pH < 7.15

• uremic symptoms

• diuretic refractory fluid retention - lung edema

• intoxications

At what level of urea is it considered azotemia?

urea > 36 mmol/L

Further indications of renal replacement

• endogen toxins (Ca2+, Mg2+, ammonia, light chain)

• conservative treatment are exhausted

• hyper/hyponatremia

Why do we recommend PD primarily?

preservation of residual kidney function

PD considerations from the patient’s side

• comorbid status

• compliance

• anatomy → abdominal status, body surface, obesity

What does optimal hemodialysis require?

Access to vessels that can provide extracorporeal blood flow

• 300-435 mL/min

• for 3-4 hours

• 3x/week

Definition of arteriovenous fistulas

connection bw native artery and vein

end-to-side (vein-artery) anastomosis

Definition of arteriovenous grafts

graft material placed bw artery and vein (plastic)

Definition of central venous catheter

devices with subcutaneous tunnel

w/ or w/o a cuff

ensure adequate blood flow

When to use hemodialysis catheters?

• failure to create AV fistulas

  • arterial occlusion

  • central venous outflow occlusion

• patient’s request

• limited life expectancy - tumor

Types of arteriovenous fistulas

radio-cephalic

brachio-cephalic

Long term complications of AV grafts

narrowing of venous anastomosis

thrombosis

What is ultrafiltration?

fluid removal

Convective transport

During ultrafiltration, fluid moves molecules with it

What’s the size of albumin?

~ 60 kDA

Dialysis membrane types

• regenerated cellulose

• cellulose acetate

• polyacrylonitrile

• polysulfone, different pore

• polypropylene

Small uremic toxins

• myoinositol - neurotoxicity

• purines

• oxalate

• dimethylarginine

Medium sized uremic toxins

• peptides

• parathormone

• β2 macroglobuline

• AGE modified proteins

Bicarbonate dialysis

Na+ 140 mmol.L

K+ 2 mmol/L

Ca2+ 1.25 mmol/L

Mg2+ 0.75 mmol/L

Cl- 105 mmol/L

bicarbonate 35 mmol/L

pH 7.2

glucose 1g/L

Measurement of effectiveness of hemodialysis

based on urea clearance

Ideal Kt/V

> 1.2

How can efficiency be improved?

increase K → bigger capillary

increase t → dialysis time

Possible anti-coagulants for extracorporeal treatment

• heparin - Na+ heparin

• huridin - if heparin allergy

• citrate

• prostacyclin - platelet aggregation inhibitor

• coumarin derivatives - VK antagonist

Dialysis complications

• blood escape, air embolism

• disequilibrium syndrome

• arrhythmia, pericardial tamponade

• hemolysis - low dialyse sodium

• hypotension

What causes hypotension in dialysis?

• excessive IV volume reduction

• quick ultrafiltration

• serious complications

• elevated blood temperature

• decreased vascular responsiveness

• decreased vasoconstriction

• insufficient preload

• sclerotic arteries

Hypotension treatment

• stop ultrafiltration

• Trendelenburg position

• volume replacement

• vasoconstrictors

• increase in dialysate sodium content

Disequilibrim syndrome

cerebral edema due to osmotic reasons - high initial urea

Hemoperfusion

detoxification process - drug intoxication

• thyrotoxicosis

• toxic substances - mushroom

Fractionated plasma separation and adsorption

liver support therapy when patient is on the waiting list for transplant

What’s the leading cause of death in liver failure?

failure to produce complement proteins → lack of opsonisation → infection

PD treatment is contraindicated

• multiple abdominal surgeries, extensive pelvis adhesions

• ischemic and IBS

• end-stage tumor disease, abdominal metastases

• obesity

• spinal disorders

• malnutrition

• disproportion, large polycystic kidneys

PD treatment is beneficial

• diuretic resistant HF, IHD, arrhythmias

• young age < 5 years

• arteriovenous fistulas not possible

• patients live far from dialysis center

• DM

• free travel lifestyle

PD dialysate components

Na+ 132 mmol/L

Ca2+ 1.25-1.75 mmol/L

Mg2+ 0.25-0.75 mmol/L

Cl- 100 mmol/L

lactate 35-40 mmol/L

glucose 75-213 mmol/L

osmolality 334-214 mmol/L

pH 5.5

Definition of high transporter

high D/P

• UF rate is low

• rapid absorption of glucose

PD complications

PD fluid induced abdominal pressure → hernias

PD catheter infection

PD peritonitis

SEP: sclerosing encapsulating peritonitis

What is SEP?

Sclerosing encapsulating peritonitis

• glucose in low pH form AGE → damage endothelial cells

• bacterial penetration abscess formation