21 Renal Replacement Therapy: Dialysis Transplantation Flashcards
1
Q
End stage renal disease (ESRD)
- Definition
- Incidence & prevalence
- Causes
- Treatment
- Mortality
- Economic costs
A
- Definition
- Permanent kidney failure requiring dialysis or transplant
- Incidence & prevalence
- > 600,000 ppl in the US
- ~100,000 new pts per year
- Rate of new cases: 4x higher in African Americans than whites.
- Causes
- DM
- HTN
- Glomerulonephritis
- Cystic kidney diseases
- Treatment
- Hemodialysis (in-center, home) – 64%
- Renal transplant– 30%
- Peritoneal dialysis – 6%
- Mortality
- 7x higher for dialysis pts than general population
- Transplant pts similar to non-ESRD pts
- Economic costs
- $50 billion/yr
- Largely covered by Medicare
2
Q
Initiation of dialysis / renal replacement therapy
- Indications
- Goals
- 4 elements of hemodialysis
A
- Indications
- A – Acidosis
- E – Electrolyte abnormalities (esp hyperkalemia w/ EKG changes
- I – Intoxications w/ water soluble drugs
- O – Overload w/ salt & water that is refractory to diuretics & cardiac drugs & causes pulmonary edema, CHF, & HTN
- U – Uremic symptoms including pericarditis, uremic bleeding, intractable nausea/vomiting, & anorexia
- Goals
- Remove uremic waste products & correct the secondary effects of uremia
- Replenish calcium & bicarbonate stores
- Remove excess water & salt
- 4 elements of hemodialysis
- Vascular access
- Dialysis filter (dialyzer)
- Dialysis solution (dialysate)
- Dialysis machine to power and mechanically monitor the procedure
3
Q
Removal of solute occurs primarily by diffusion
- Diffusion rates are determined by…
- The amount of diffusion that occurs is also dependent on…
- Blood and dialysate flow
- Low MW substances are dependent on…
- High MW substances are dependent on…
- Dialysate is composed of…
A
- Diffusion rates are determined by…
- Conc gradient of dissolved solutes on either side of the dialyzing membrane
- Surface area and pore sizes of the dialyzing membrane
- The amount of diffusion that occurs is also dependent on…
- Dialysate delivery rate
- ~500 mL/min of dialysate bathes the dialyzing membrane
- Rate of blood flow pumped through the dialyzer
- 300-400 mL/min, depending on the type of dialyzer & adequacy of the pt’s access
- Dialysate delivery rate
- Blood and dialysate flow
- Opposite directions (countercurrent) to maintain the conc gradient
- Low MW substances are dependent on…
- Flow rate
- High MW substances are dependent on…
- Surface area and pore size
- Dialysate is composed of…
- Sodium 135-145 mEq/L
- Potassium 0-4 mEq/L
- Calcium 2.5-3.5 mEq/L
- Magnesium 0.5-0.75 mEq/L
- Chloride 98-124 mEq/L
- Bicarbonate 30-40 mEq/L
- Dextrose 11 mEq/L
4
Q
Removal of solvent occurs primarily by ultrafiltration
- Water molecule size
- Water molecule movement
- Convective transport
A
- Water molecule size
- Small enough that they pass freely between the blood and dialysate compartments
- Water molecule movement
- Driven in one direction by increasing the hydrostatic pressure gradient between compartments
- Achieved practically by increasing resistance to blood flow as it leaves the dialyzer
- Convective transport
- Any molecules small enough will be carried with solvent (solvent drag)
5
Q
Vascular access for hemodialysis
- Arteriovenous (AV) fistulas
- Primary or “native” AV fistula
- Use
- “Fistula first”
- Synthetic AV fistulas (AV grafts)
- Use
- Construction
- Adverse effects
- Hemodialysis catheters
- Temporary hemodialysis catetheters
- Placed in…
- Tunneled dialysis cathether (TDC)
- Adverse effects
- Access complications
A
- Arteriovenous (AV) fistulas
- Primary or “native” AV fistula: anastomosis between an artery and vein
- Transmission of high arterial pressure into a low pressure venous system –> high flow AV fistula
- Over time the vein “arterializes”: increases diameter & wall thickness
- Optimal access for hemodialysis
- Require 6 - 8 weeks to mature
- Should be created 6 - 12 months before dialysis will be needed
- “Fistula first”
- National vascular access improvement initiative to support AV fistula placement in suitable hemodialysis patients, while reducing central venous catheter use.
- Primary or “native” AV fistula: anastomosis between an artery and vein
- Synthetic AV fistulas (AV grafts)
- For pts w/ poor peripheral vasculature (diabetics) & insufficient venous size to allow the creation of a native AV fistula
- Constructed of Polytetrafluoroethylene (PTFE)
- Endothelialize in 2-3 weeks
- This “maturation period” is necessary before they can be used.
- Adverse effects
- Higher rate of infection & clotting risk
- Shorter lived than “native” AV fistulas
- Hemodialysis catheters
- Temporary hemodialysis catetheters
- For 30 - 50% of pts w/ advanced chronic renal failure require immediate dialysis
- Placed in the internal jugular vein (or subclavian vein or femoral vein)
- Tunneled dialysis cathether (TDC)
- Placed if dialysis is required for > 3 weeks & construction of an AV fistula isn’t possible
- Reduces the risk of infection
- Avoid the subclavian site to reduce the risk of central venous stenosis
- Adverse effects
- Induction of venous stenosis
- Poor flows
- Thrombosis
- Temporary hemodialysis catetheters
- Access complications
- Thrombosis
- –> obstruction of the access & poor blood flow
- Outflow obstruction in an AV fistula –> localized extremity swelling
- Infection
- Local infections
- Sepsis or septic emboli to bone, heart valves or the lungs
- Steal syndromes
- AV fistulas can reduce blood flow to the hand distal to the anastomosis –> ischemia, pain, & gangrene.
- Cardiac overload
- An AV fistula increases CO by 10% –> high output CHF
- Thrombosis
6
Q
Hemodialysis prescription
A
- Dialyzer
- Type and size
- Blood and dialysate flow rates
- Duration and frequency
- 3x/week (MWF or TTS) for 4 hrs each treatment
- Dialysate composition
- Typically adjust sodium, potassium, calcium, bicarbonate
- Ultrafiltration
- Can specify the amount of fluid to be removed
- Anticoagulation
- Usually heparin
7
Q
Complications of hemodialysis
- Acute intra-dialytic complications
- Chronic complications
- Dialysis survival rates
A
- Acute intra-dialytic complications
- May occur during any dialysis session
-
HoTN
- Due to excessive ultrafiltration, autonomic neuropathy or peripheral vasodilation
- Usually responds to normal or hypertonic saline or administration of colloid in the form of salt poor albumin (SPA) or mannitol
-
Cramps
- Due to HoTN or inappropriately low dialysate Na conc
- Usually responds to saline, quinidine sulfate, muscle relaxant, or carnitine
-
Nausea & vomiting
- Due to HoTN or the disequilibrium syndrome (too brisk a reduction in uremic waste products, usually seen with initiation of dialysis)
- Usually responds to correction of HoTN & anti-emetics
- Access issues
- To prevent disequilibrium syndrome
- Less rigorous treatments at initiation of dialysis
- Gradually increase dialysis parameters to most efficient settings
- Chronic complications
- Develop due to CKD & continue after dialysis started
-
Malnutrition
- Best indicator of nutrition is serum albumin
- Low albumin is a strong predictor of mortality
-
HTN
- Treated w/ water & salt restriction & meds
-
Hyperlipidemia
- Increased triglycerides & LDL w/ decreased HDL
-
Pruritus
- Due to uremic toxins, elevated calcium-phosphorous product (>65), dry skin or allergies to components of the dialyzer or dialysate.
-
Mortality
- Major cause of death is CV disease
- Access issues
- Dialysis survival rates
- 80% at 1 yr
- 50% at 3 yrs
- 33% at 5 yrs
- 10% at 10 yrs
8
Q
Principles of peritoneal dialysis
- Peritoneal dialysis definition
- Peritoneal dialysis procedure
- Peritoneal “dialysis” membrane
- Water removal
- Ultrafiltration
- Forces affecting ultrafiltration
- Osmotic gradient
- Water movement
- Major osmotic driving force in peritoneal dialysis
- Hydrostatic pressure
- Osmotic gradient
A
- Peritoneal dialysis definition
- Fluid and solute exchange between the peritoneal membrane capillary blood and dialysis solution in the peritoneal cavity
- Peritoneal dialysis procedure
- Peritoneal membrane is used as a dialyzing membrane
- Dialysate fluid is instilled into the abdomen & left for a period of time (dwell time) to absorb waste & remove fluid, then drained & discarded
- Cycles / “exchanges” are repeated 4-5x/day
- Peritoneal “dialysis” membrane
- Vascular wall, interstitium, mesothelium & adjacent fluid films that make up the parietal and visceral peritoneal membrane
- Water removal occurs by ultrafiltration
- Ultrafiltration
- Bulk movement of water through a semipermeable membrane
- Osmosis = this ‘diffusion of water”
- Due to the interaction of solvent molecules w/ dissolved solute, ultrafiltration –> solute transport via “solvent drag”
- Forces affecting ultrafiltration
- Osmotic gradient
- Diffs in solute conc across a semipermeable membrane –> water moves from more to less dilute solution
- Water flux will continue until the conc of osmotically active particles is equal on either side of the semipermeable membrane
- Major osmotic driving force in peritoneal dialysis: supplied by dialysate glucose conc
- Increase glucose conc –> increase ultrafiltration
- This effect will dissipate as glucose is absorbed and as it is diluted out by water flux
- Diffs in solute conc across a semipermeable membrane –> water moves from more to less dilute solution
- Hydrostatic pressure
- Causes some fluid movement
- Plays a minor role in PD
- Osmotic gradient
- Ultrafiltration
9
Q
Principles of peritoneal dialysis:
Diffusion rates of solute (electrolytes & uremic waste) removal are affected by…
- Conc gradient of dissolved solutes on either side of the dialyzing membrane
- Greater difference –>
- Gradients are dependent on…
- Dialysate conc is similar to hemodialysis sol’n except…
- MW of the solute
- Charge on the solute
- Membrane resistances
A
- Conc gradient of dissolved solutes on either side of the dialyzing membrane
- Greater difference in solute conc b/n the 2 compartments –> more rapid flux of that solute from high to low conc
- Gradients are dependent on the delivery rates of dialysate and peritoneal blood flow rate
- Peritoneal blood flow is relatively constant even in shock
- Dialysate conc is similar to hemodialysis sol’n except…
- Substitution of lactate for bicarbonate
- Ca bicarb will precipitate if bicarb is mixed w/ Ca-containing sol’ns)
- Large dextrose conc (1.5 – 4.25 %)
- Substitution of lactate for bicarbonate
- MW of the solute
- Larger MW –> slower it can move through membrane pores
- Charge on the solute
- Charged particles are hindered as they pass through the lipid bilayer
- Membrane resistances
- Peritoneal membrane can be altered by disease states
- Acute peritonitis –> decreased membrane resistance & increased clearances
- Repeated episodes of peritonitis –> scarring & slowed transport
10
Q
Peritoneal dialysis:
Advantages & disadvantages
- Advantages
- Hemodynamic effects
- Location
- Process
- Diet
- Meds
- Disadvantages
- Efficiency
- Infection
- Requires…
- Long-term
- Can’t be used in pts w/…
- Can’t be used for…
A
- Advantages
- Few hemodynamic effects
- Method of choice in pts w/ a tenuous cardiac status
- Done at home
- Pts have greater freedom & independence for normal activities
- Travel is easier
- Supplies can be taken w/ the pt or delivered to the pt’s destination.
- Process is continuous
- Pts are less likely to have disequilibrium syndromes seen in hemodialysis where clearance is efficient but episodic
- Diet is more liberal
- Meds (ex. insulin, antibiotics) can be administered in the peritoneal dialysis sol’n
- Few hemodynamic effects
- Disadvantages
- Gentler but less efficient form of dialysis
- Dose may be inadequate in pts > 80 kg, who have lost residual renal function completely, or who are non-adherent with PD
- Infection
- Peritonitis due to poor technique: most common cause of transfer to hemodialysis
- Requires compulsiveness & intellect
- Pts on long-term PD can “burn out” due to the daily grind of doing their exchanges
- Can’t be used in pts w/ peritoneal fibrosis or adhesions
- Interferes w/ drainage
- Can’t be used for > 1 week following abdominal surgery
- Increases leaks at catheter site and infection
- Gentler but less efficient form of dialysis
11
Q
Peritoneal dialysis:
Peritoneal access
- Standard access
- Procedure
A
- Standard access
- 2 cuff Tenckhoff style catheter
- Made of silicone (catheter) & Dacron (cuffs)
- Variety of dif catheters are available
- Procedure
- Catheter is inserted into the peritoneal cavity by a surgeon
- Internal cuff is anchored in the muscle fascial layer immediately above the parietal peritoneum
- Catheter is tunneled through the subcutaneous tissues & brought through the epithelium 5 - 10 cm lateral of where the internal cuff was seated
- External cuff is usually 1 cm deep from the exit wound & causes local fibrosis, which seals the tunnel
12
Q
Types of peritoneal dialysis
- CAPD (Continuous Ambulatory Peritoneal Dialysis)
- Procedure
- Advantages
- Disadvantages
- CCPD (Continuous Cycler Peritoneal Dialysis)
- Procedure
- Advantages
- Disadvantages
- Less common
A
- CAPD (Continuous Ambulatory Peritoneal Dialysis)
- Procedure
- Instillation of 2 L of dialysate which dwells for 4 - 8 hours & then is drained
- Repeated 4x/day
- Advantages
- Long dwell times–> max solute removal
- Highest large solute clearances
- Extremely portable.
- Disadvantages
- Manual exchanges –> increased risk of infection
- Constant fluid in the abdomen may worsen gastroparesis
- Procedure
- CCPD (Continuous Cycler Peritoneal Dialysis)
- Procedure
- Pt connects to an automated peritoneal dialysis cycler at bedtime
- Device periodically instills dialysate, allows it to dwell, then drains & replaces it in the pt’s abdomen
- 3-5 exchanges / nocturnal period
- Machine instills a fresh aliquot of dialysate before the pt awakens & disconnects
- Exchange dwells during the day
- Daytime exchange is drained at bedtime when the pt connects to the machine
- Advantages
- Increased convenience by eliminating daytime exchanges
- Decreased manual hook-ups–> decreased chance of peritonitis
- Disadvantages
- Short dwell times –> ineffective large molecule clearance
- Requires excellent catheter function
- Poorly draining PD catheter may not allow rapid cycling at night
- Constant fluid in the abdomen may worsen gastroparesis
- Being attached to a machine at night may interfere with sexual function
- Pt connects to an automated peritoneal dialysis cycler at bedtime
- Procedure
- Less common
- Combo of daytime exchanges & nocturnal cycling
- Periods where the abdomen is “dry” (completely drained of fluid)
13
Q
Complications of peritoneal dialysis
- Mechanical
- Intraluminal catheter occlusion due to fibrin
- Catheter occlusion due to a full colon (constipation)
- Catheter malposition or kinks
- Dialysate leaks
- Subcutaneous dialysate leaks
- Past the internal cuff into the subcutaneous tissues
- Along the processus vaginalis
- Infections
- Can involve…
- Most torublesome PD infection
A
- Mechanical
- Intraluminal catheter occlusion due to fibrin
- Occurs due to direct catheter irritation of the peritoneal membrane
- Treatable w/ intraperitoneal heparin
- Catheter occlusion due to a full colon (constipation)
- Laxative treatment allows the catheter to reposition in the pelvic basin
- In refractory cases, catheter replacement may be required
- Catheter malposition or kinks
- Requires catheter replacement
- May be able to reposition w/ stiff wire under fluoroscopy
- Intraluminal catheter occlusion due to fibrin
- Dialysate leaks
- Peritoneal-pleural dialysate leaks
- Via large pores in the diaphragm –> pleural effusions
- May require switch to hemodialysis
- Peritoneal-pleural dialysate leaks
- Subcutaneous dialysate leaks
- Past the internal cuff into the subcutaneous tissues
- –> soft tissue swelling
- Resolves by allowing periods of time with a dry abdomen
- May require new catheter
- Along the processus vaginalis
- –> swelling of the scrotum or labia major
- Seen with inguinal hernias
- Requires hernia repair or reinforcement of the internal ring of the inguinal canal
- Past the internal cuff into the subcutaneous tissues
- Infections
- Can involve…
- Peritoneal cavity (peritonitis)
- Catheter tunnel (tunnel infection)
- Exit site (exit site infection)
- Most troublesome PD infection: peritonitis
- Can involve…
14
Q
Renal transplantation:
Process
- Major problem
- Patients w/ CKD are usually referred for transplant evaluation when…
- Goal
- Pt evaluation
- Cardiac health
- Malignancy screening
- Infectious disease
- HLA-typing or tissue typing
- Social issues
- Once the patient has successfully fulfilled these requirements…
A
- Major problem
- Lack of donor organs (17,000 transplants / 90,000 pts)
- Patients w/ CKD are usually referred for transplant evaluation when…
- Creatinine clearance < 20 ml/min
- Goal
- Transplantation before dialysis since post-operative management & graft survival is usually improved
- Pt evaluation
- Cardiac health
- Cardiac disease is common in pts w/ CKD & is the leading cause of death in transplant recipients
- Usually stress test + echo
- Malignancy screening (ex.s)
- Mammography for breast cancer
- Prostate specific antigen for prostate cancer
- Colonoscopy for colon cancer
- Infectious disease
- Screening for TB, hepatitis B or C, HIV, syphilis, & gonorrhea
- Vital since immune suppressive therapy can increase the risk or severity of malignancy or an infectious disease
- HLA-typing or tissue typing
- To find the best “matched” kidneys for pts
- Social issues
- Pts w/ poor adherence to meds & current history of drug abuse won’t be listed until they change their behavior
- Evidence of coercion or financial reward of a potential donor is also grounds for refusing a recipient a transplant
- Cardiac health
- Once the patient has successfully fulfilled these requirements…
- Their name is entered on the transplant waiting list
- Avg waiting time at UPMC: 3-5 years
15
Q
Renal transplantation:
Surgery
- Donor organs usually come from…
- Operation
A
- Donor organs usually come from…
- Living donors (50%)
- Living related donors (blood relatives)
- Emotionally related donors (most commonly spouses)
- ABO incompatible, + crossmatch
- National kidney registry (NKR)
- Brain dead or “deceased” donor (~7000/year)
- SCD (standard criteria), ECD (expanded criteria), CDC high risk, DCD
- Living donors (50%)
- Operation
- Takes 3-4 hours
- Incision along the inguinal ligament in right or left lower abdominal quadrant
- Transplanted organ is anastomosed into the common, external or internal iliac artery and vein and the ureter connected to the bladder.
- Pt is usually hospitalized for 5 days
- Follow-up afterwards is intensive w/ daily outpatient visits for several weeks
- If the transplant recipient does well, follow-up intervals progressively increase
