Dialysis and Renal Replacement Therapies

What are the 3 primary treatments for end stage renal disease?

- Hemodialysis

- Peritoneal dialysis

- Kidney transplantation

Which stage of CKD is dialysis started?

Stage 4

What are the indications for dialysis?

Acid-base abnormalities

Electrolyte abnormalities

Ingestion

Overload

Uremia

What are the goals for dialysis?

- Removing toxic metabolites to reduce uremic symptoms

- Correcting electrolyte abnormalities

- Restoring acid-base balance

- Maintaining appropriate volume status

- Decrease morbidity and mortality

What is the most common type of renal replacement therapy?

Hemodialysis

What mechanisms allow substances to move from blood to dialysate in HD?

Passive diffusion and convection

Which waste product commonly removed by HD reflects kidney function?

Creatinine and Urea

What type of solution is used opposite the blood in HD?

Physiologic solution

Which dialysis membrane has small pores and removes smaller molecules?

Low flux

Which dialysis membrane has small pores and a larger surface area to increase removal of small molecules?

High efficiency

Which dialysis membrane is the most common, has larger pores, and is able to remove high molecular weight substances that allows for shorter treatment times?

High flux

In diffusion, solutes move from an area of ______ concentration to ______ concentration

Higher to lower

What type of molecules are primarily removed by diffusion during dialysis?

Small molecules

What factors affect the rate of diffusion in dialysis?

Difference in concentration, solute characteristics, and membrane composition

Why does membrane composition matter for diffusion?

It influences solute permeability across the membrane

What is ultrafiltration in dialysis?

Movement of water across a membrane due to hydrostatic or osmotic pressure

What is the primary method for fluid removal in dialysis?

Ultrafiltration

What is convection in dialysis?

Movement of dissolved solutes across the membrane along with water transport

What is the primary method for larger molecule removal?

Convection

What type of solutes are primarily removed by convection?

Larger molecules

How does increasing pore size affect convection?

Increases solute removal efficiency

What are the two main types of permanent hemodialysis access?

Arteriovenous (AV) fistula and arteriovenous (AV) graft

Which HD access has the longest survival time?

AV fistula

How long does an AV fistula require to fully mature before use?

1-2 months

How does survival time of an AV graft compare to an AV fistula?

Shorter survival time

How do infection and thrombosis rates compare between AV grafts and AV fistulas?

AV grafts have higher rates of infection and thrombosis

Which HD access should be preferred when feasible?

AV fistula

Which HD access matures faster but has higher complication rates?

AV graft

What is the central line placed in the femoral, subclavian, or internal jugular vein that has a shorter survival time and higher rates of infection/thrombosis?

Venous Catheter

How often are dialysis sessions?

3x week

What are the general complications of hemodialysis?

- Water soluble vitamin depletion

- Vitamins are removed during dialysis

- Treatment: multivitamin B complex + vitamin C

What are some side effects that are experienced during hemodialysis?

- Chest/back pain

- Muscle cramps

- Fever/Chills

- Headache

- Nausea/Vomiting

Why do muscle cramps occur during hemodialysis?

Excessive ultrafiltration

What is the treatment for muscle cramps induced by hemodialysis?

- Give fluids

- Supplement with vitamin E (400 IU)

What is a common blood pressure complication that can occur during hemodialysis?

Hypertension

What are potential effects of intradialytic hypertension?

Increased fatigue and increased risk of cardiovascular and all-cause mortality

Which drugs clearance is increased by hemodialysis?

Metoprolol, atenolol, ACE inhibitors

How can hypertension related to HD drug clearance be managed?

Switching to ARBs, carvedilol, or amlodipine

Why might switching from ACE inhibitors to ARBs be helpful in HD patients?

ARBs are less cleared by dialysis, maintaining antihypertensive effect

What is the most common complication of hemodialysis?

Hypotension

What is the treatment to hypotension in hemodialysis?

Midodrine (5 mg BID/TID)

What is the drug class for Midodrine?

Alpha-1 agonist

What is the MOA of Midodrine?

Increase arteriolar and venous tone thus increasing systolic and diastolic blood pressure

What is the boxed warning for Midodrine?

Supine hypertension is a risk factor for end organ damage and

cardiovascular events

What's dosing for Midodrine to treat hypotension from dialysis?

3 - 4 hours with last dose given no later than 6pm

Why does Midodrine need to be avoided within 4 hours of bedtime?

Decrease risk of supine hypoertension

What are the ADRs of Midodrine?

Bradycardia, Supine HTN, Paresthesia, Dysuria

What is the leading cause of mortality in HD patients?

Infection

What is the treatment for infection in HD?

- Broad-spectrum gram-positive antibiotic

- Remove graft if less than 1 month old

- Remove/change systemic tunneled catheter

What is the highest risk with venous catheter access?

Thrombosis

What are the 3 components in Virchow's triad that contribute to thrombosis?

- Endothelial injury

- Hypercoagulable state

- Venous stasis

What are the functions of the peritoneal membrane

How can a thrombosis caused by hemodialysis be prevented?

Heparin Flush

What is the treatment for a thrombosis caused by hemodialysis?

- Forceful Saline Flush (first-line)

- Alteplase Dwell

Which medication is an anticoagulant that inactivates thrombin and factor Xa to prevent fibrin clot formation and is used to preventing dialysis catheter from clotting off?

Heparin

Which medication is a thrombolytic agent that binds to fibrin to break apart the blood clot and salvages the dialysis catheter?

Alteplase

What structure within the abdominal cavity functions as the semipermeable membrane for peritoneal dialysis?

Peritoneal membrane

In peritoneal dialysis, what processes allow the peritoneal membrane to remove molecules from the blood?

Diffusion and ultrafiltration

What derivatives are used in the dialysate in peritoneal dialysis?

Glucose

What are the complications of peritoneal dialysis?

- Excessive catheter motion at exit site

- Inflow and outflow obstruction

- Kinking of the catheter

- Pain

- Infections

- Peritonitis (leading cause of morbidity)

- Elevated blood glucose

- Increased adipose tissue deposition

- Hyper/hypocalcemia

- Volume overload

How does a drug's lipophilicity affect its removal by dialysis?

Water-soluble drugs are more easily dialyzed because the dialysate is an aqueous solution; fat-soluble drugs are less dialyzable

How does molecular weight affect dialysis clearance?

The larger the MW, the harder it is to dialyze

How does protein binding affect drug clearance in dialysis?

Only free (unbound) drug can be dialyzed. Highly protein-bound drugs have limited clearance

What Vd is considered ideal for dialysis removal?

< 1 L/kg

How does the route of drug clearance affect its removal during dialysis?

- Primarily non-renally cleared drugs: less affected by dialysis

-Primarily renally cleared drugs: more likely to accumulate in reduced renal function or dialysis

When is continuous hemodialysis used?

Critically ill patients