hemodialysis & peritoneal dialysis

dialysis - epidemiology

Incidence and prevalence of dialysis has increased over the years

Incidence: No. of new ESKD pts on dialysis in a year. Measure of development of kidney disease in the population

Prevalence: Total no. of pts on dialysis. Describes the burden of kidney disease in the population

dialysis - initiation

Elective vs emergent

Start planning early

GFR < 20-30 ml/min/1.73m 2

Patient/family education

Options: HD, PD, home HD(?). Access for HD or PD

K/DOQI guidelines

Non-diabetics: GFR < 15 ml/min/1.73m 2

Diabetics: GFR < 20 ml/min/1.73m2

Most pts start when GFR < 10 ml/min/1.73m 2 or when signs/symptoms of kidney failure are present

indications for chronic dialysis

Azotemia (lab anomalies) vs uremia (azotemia + symptoms)

Symptoms: Fatigue, weakness, SOB, mental confusion, N/V, bleeding, loss of appetite, itching, cold intolerance, weight gain, neuropathy, uremic breath

Signs: Edema, changes in urine output, abdominal distension, pericardial rub, asterixis, critical lab values (Urea, SCr, K)

indications for acute/emergent dialysis

Acid-base imbalance (acidosis)

Electrolyte abnormalities

Intoxication (drug overdose)

Overload (fluid)

Uremia

hemodialysis - principles

Perfusion of blood and dialysate on opposite sides of a semipermeable membrane

N2 waste products and uremic toxins move from blood to dialysate for removal

hemodialysis - movement mechanisms

Diffusion: Movement of substances along a conc gradient

Factors affecting diffusion rate

Solute conc -> blood vs dialysate

Solute characteristics: size, MW, protein binding (lesser better), solubility

Dialyzer composition -> membrane type

Blood and dialysate flow rate

Ultrafiltration: Movement of water across membrane due to hydrostatic/osmotic pressure

Primary means for removal of excess body water (depends on pt water content)

Convection: Dragging of solutes across membrane with fluid transport

Depends on hydrostatic pressure and pore size of dialyzer

hemodialysis - dialyzer

Large canister with thousands of small fibers (semi-permeable membrane) that pts blood is passed through

Dialysate pumped around these fibers allowing wastes/toxins to pass into it for removal (countercurrent to blood flow)

3 types

Conventional: Small pores (urea, Cr)

High-efficiency: Larger surface areas (water, urea)

High flux: Large pores (high MW substances, drugs

hemodialysis - dialysate

Consists of purified water and electrolytes (isotonic)

Constituents conc set to approx normal values

Can be adjusted to meet specific pt needs

Pumped through dialyzer countercurrent to blood flow

Removes fluid, waste products, uremic toxins

hemodialysis - extrarenal vascular circuit

Typical schedule 3x/week (MWF/TTS)

4hr/treatment, depends on fluid status

hemodialysis - access

Allows permanent access to bloodstream for HD

Early referral to nephrology and vascular access

Preparation takes weeks to months before initiating dialysis

3 kinds of vascular access

Arteriovenous (AV) fistula, AV graft, venous catheter

hemodialysis - AV fistula

Preferred type

Advantages

Longest survival (years)

Lowest complication rate

Disadvantages

Requires >= 2 months to mature

May be difficult in certain pt (elderly, DM, PVD)

hemodialysis - AV graft

Use of synthetic graft (polytetrafluoroethylene)

Advantages

Requires 2-3 weeks

Disadvantages

Shorter survival

Higher rates of complications

hemodialysis - venous catheter

Temporary access -> should not be left inside for long

For AKI (short term HD), Planned for kidney transplant

When AV access not an option: Children, DM, severe PVD, obese, Failed multiple AVF, AVG attempts

Advantages: For emergent dialysis

Disadvantages

Short lifespan (weeks-months), Prone to complications

Low blood flow rates - compromise dialysis adequacy

Proper cleaning and care required -> cannot touch water

hemodialysis - goals

Desired dry weight (normotensive and free of edema/SOB)

Adequate removal of endogenous waste products

hemodialysis - urea reduction ratio (URR)

Goal URR > 65%

hemodialysis - Kt/V

Fraction of patient’s total body water that is cleared of urea during dialysis (fractional urea clearance)

where K = dialyzer clearance, t = time, V = distribution vol of urea

Usually calculated by dialysis machine

K/DOQI recommends goal Kt/V ~ 1.4 (min 1.2)

hemodialysis - complications

hypotension 20-30%)

cramps (5-20%)

N/V (5-15%): Causes: hypotension, dialyzer reaction

Headache (5%): Causes: disequilibrium syndrome, caffeine withdrawal (HD removal)

Chest/back pain (2-5%): Causes unknown, maybe dialyzer reactions

Fever/chills (<1%): Causes: endotoxin release, infection

Pruritus (5%): Causes: Inadequate dialysis (buildup of toxins on skin), Dry skin, Secondary hyperparathyroidism (high P + PTH), Electrolyte abnormalities, Histamine release, Mast cell production

HD complications - hypotension

Causes: Hypovolemia, Excessive ultrafiltration, Antihypertensive medications, Target dry weight too low, Diastolic dysfunction, Autonomic dysfunction, Low Ca, Na in dialysate, High dialysate temperature (low temp better, causes constricted vessels), Meal ingestion

Management

Place patient in Trendelenburg position, Reduce rate or turn off ultrafiltration

Administer fluids (NS): 100-200 ml bolus of IV NS

Increase dialysate Na conc, Switch to bicarbonate-buffered dialysate

Accurately set dry weight, Lower dialysate temp

Midodrine, α1 -adrenergic agonist 2.5-10 mg PO 30 min before HD (C/I in CVD)

Correct anemia, Administer O2, Avoid food before/during HD

HD complications - cramps

Causes: Muscle hypoperfusion, Hypotension, Electrolyte/acid-base imbalance

Management

Correct or prevent volume contraction and excessive ultrafiltration

Quinine (now not FDA approved)

Vitamin E 400 IU at bedtime

Other agents tried -> not much help

Skeletal muscle relaxants, Benzodiazepines, Pramipexole (restless leg syndrome)

hemodialysis - catheter related thrombosis

Catheter > grafts > fistulas

Intrinsic (within lumen) vs extrinsic (outside)

Suspected when blood cannot be aspirated from catheter yet saline flows in freely

Major cause of catheter failure

HD catheter related thrombosis - management

Non-pharmacological: Forced saline flush, Mechanical thrombectomy, Catheter stripping/removal, Exchange of catheter over guidewire

Pharmacological (intraluminal thrombolytics -> sits in catheter)

Alteplase (r-tPA): FDA approved for restoration of central venous catheter due to thrombosis

Instill 2 mg/2 ml per catheter port, attempt to aspirate after 30 min. May repeat if function not restored. Longer instillation duration may be required

Urokinase: Instill 1 ml (2000 units/ml); Aspirate after 5 min; aspiration attempts may be repeated every 5 min. Second injection may be necessary

Reteplase

hemodialysis - catheter related infections

Fever, chills, rigors, elevated white count

Obtain peripheral blood cultures and culture from catheter site before starting Abx

Those at risk for bacteremia (blood stream infection): DM, immunosuppressed, (+) history of cath-infections, S. aureus nasal carriage

Complications: Endocarditis, bacteremia, sepsis

HD catheter related infections - AV fistula and graft

AV fistula: Infections are race

Treat as subacute bacterial endocarditis x 6 weeks. May need to remove fistula if septic emboli

Synthetic AV grafts

Treat for 2-4 weeks

Resection of infected portion of graft may be required

HD catheter related infections - types

Exit site infections: May be with or without drainage

Topical antibiotics (mupirocin ointment) or IV (gram positive)

Proper local exit site care. No catheter removal unless infection fails to respond to therapy

Catheter-related bacteremia (with/without systemic signs/symptoms)

Gram-positive antibiotic (skin bacteria) coverage (cefazolin/vancomycin). Streamline therapy based on culture results

Remove catheter if symptomatic > 36 hr or clinically unstable

If stable and asymptomatic, provide culture-specific antibiotic coverage for a minimum of 3 weeks

Do not place new permanent access until blood cultures, performed after stopping antibiotics, have been negative for at least 48 hours

HD catheter related infections - management

Start empiric therapy: Cover gram-positive (staph aureus) and gram-negative microorganisms

MSSA - sensitive

Cefazolin 20 mg/kg (to nearest 500 mg) IV with each dialysis (usual: 1g daily or 2 g 3x/week after HD)

MRSA - resistant

Vancomycin 20 mg/kg IV loading dose, then 500 mg with each dialysis (usual: 1 g then 500 mg, 750 mg or 1 g based on levels)

Gram-negative coverage

Gentamicin 1-2 mg/kg IV after each dialysis

Ceftazidime 1 g IV after each dialysis (usual: 1 g daily or 2 g 3x/week after HD)

Streamline therapy based on culture results

HD catheter related infections - antibiotic lock therapy

Used in treatment of uncomplicated tunneled catheter infections usually in combination with systemic Abx

Involves instilling each catheter lumen with antibiotic solution at the end of dialysis and allowing it to dwell for a period of time (usually ≤ 48 h)

Withdraw solution before next HD. Repeated after every HD session. Goal is to salvage the catheter

Mean success rate ~ 67%

Common used antibiotics: cefazolin, vancomycin, gentamicin

Usually mixed with heparin or normal saline in sufficient vol to fill catheter lumen (2-5ml)

Usually not used alone but in combination with systemic abx for 7-14 days

HTN management in dialysis pt

Predialysis < 140/90 mmHg

Postdialyisis < 130/80 mmHg

Appropriate measurement -> cuff size, supine vs sitting vs standing

Adjustment of dry weight

Consider giving anti-HTN drugs at night to reduce nocturnal surge of BP and minimize intradialytic hypotension

In some patients, hold AM dose of anti-HTN drugs

Consider dialyzability of drugs in patients with difficult-to-control HTN

HTN management - fluid accumulation

Management of excess fluid accumulation b/w dialysis sessions

Counseling by dieticians, Fluid restriction (~800 ml), Na restriction

Increase ultrafiltration, Longer dialysis

Increase frequency of dialysis

Drugs that reduce appetite

HTN management - ACEi/ARB

ACEi/ARB may be restarted (DHP-CCB often used also)

Cause greater regression of LVH

Reduce sympathetic nerve activity

Reduce pulse wave velocity

May improve endothelial function

May reduce oxidative stress

peritoneal dialysis - principles

Peritoneum serves as an inert semi-permeable membrane which allows movement of solutes and fluid between dialysate and peritoneal capillaries

Dialysate instilled into peritoneal cavity through trans-abdominal catheter and allowed to dwell

Diffusion and ultrafiltration take place during the exchanges to remove metabolic wastes

Dialysate is subsequent drained. Cycle is repeated

Types of PD: CAPD (multiple times/day) vs. APD (overnight)

peritoneal dialysis - precautions

PD dose may be altered to increase osmotic gradient across the peritoneum and in turn increases UF and diffusion

Increase no. of exchanges per day, volume of each exchange, dextrose concentration in dialysate

Increase dwell time -> may not be effective

Equilibrium may be reached, No further water or solute removal, Reverse water movement may occur

Adequacy: Kt/V = 1.7/week (KDOQI) -> higher kidney clearance

peritoneal dialysis - considerations

Importance of preserving residual kidney function

Associated with decreased mortality. Continue use of ACEi, ARB, avoid nephrotoxins

PD is much less efficient compared to HD:

Blood is not in direct contact with peritoneal membrane, metabolic waste products must travel some distances to the dialysate-filled peritoneal cavity. No method of regulating blood flow to surface of peritoneal membrane. No countercurrent blood flow and dialysate

Continuous procedure needed to achieve acceptable clearance of metabolic wastes

May be suitable for pts:

Hemodynamically unstable, With sig residual kidney function

Ambulant and who desire self-care

Supported by fam, with good personal hygiene

peritoneal dialysis - dialysate solutions

Varying concentrations of electrolytes (Na, Cl, Ca, Mg, lactate)

Dextrose solutions (1.5, 2.5, 3.86, 4.25% dextrose or 7.5% icodextrin, a glucose polymer)

Dextrose: Hyperosmolar dextrose solutions induce ultrafiltration by crystalline osmosis.

Disadvantage: Incompatibility with peritoneal mesothelial cells or with peritoneal leukocytes

Icodextrin -> good for DM

Iso-osmolar. Produces prolonged ultrafiltration by “colloid osmosis”, Similar osmosis as 4.25% dextrose. Fewer metabolic effects such as hyperglycemia and weight gain

peritoneal dialysis - complications

Mechanical: kinking of catheter, inflow/outflow obstruction e.g. constipation

Infections: Peritonitis, catheter-related infections. Leading cause of morbidity, mortality, technique failure

Medical

glucose load

fibrin formation

PD complications - medical

Fluid overload (increase UF, diuretics if residual kidney function)

Electrolyte abnormalities ( or Ca, K ) esp if multiple times/day

Malnutrition (AA loss, muscle wasting, decreased appetite)

Glucose load

Fibrin formation in dialysate

PD complications - glucose load

Continuous supply of calories from dialysate containing dextrose

Exacerbation of DM; closer monitoring and adjustment of DM therapy may be required

IP administration of insulin (bioavailability 25-30%) -> not really in SG

Increase insulin requirements in PD patients due to:

Continued absorption of dextrose from peritoneal cavity

Adsorption of insulin to PVC bag and administration set

PD complications - fibrin formation

Fibrinogen secreted into peritoneal cavity results in fibrin formation (cloudy effluent)

Causes Intraperitoneal adhesions, outflow obstruction

Administer IP heparin 500 units/L (minimally absorbed due to high MW; limited systemic SE) to prevent catheter occlusion

peritoneal dialysis - peritonitis

Definition: Elevated dialysate WBC > 100/mm3 + > 50% PMN neutrophils

Clinical presentation: Abdominal pain, cloudy effluent, fever, nausea, vomiting, chills. Positive gram stain and culture of dialysate effluent

Sterile culture or culture-negative peritonitis may occur

40-60% of patients develop first episode within a year (incidence lower in APD)

Majority caused by gram(+) bacteria. No predominant gram(-) organism

Use of broad spectrum Abx for initial empiric therapy (near GIT which has gram (-) bacteria)

Modify therapy according to culture and sensitivities

peritonitis - prevention

Systemic prophylactic antibiotics should be administered immediately before catheter placement

Prophylactic therapy should include use of perioperative IV broad spectrum agents Gram(+): Cefazolin, vancomycin; Gram(-): AG (gentamicin)

Actual choice of prophylactic antibiotics should take into consideration institution’s local spectrum of abx resistance

Abx prophylaxis (broad spectrum coverage) also suggested prior to colonoscopy and invasive gynae procedures (mostly IV route)

Avoid/treat hypokalemia to reduce peritonitis risk. Avoid/limit use of H2RA to prevent enteric peritonitis

Avoid/treat GI problems e.g. constipation/enteritis (regular use of laxative to prevent constipation common in PD pts)

Use of anti-fungal prophylaxis during antibiotic therapy to prevent fungal peritonitis e.g. oral nystatin 500,000 units QID or fluconazole 200 mg q48h

peritonitis - treatment

Intra peritoneal (IP) administration of Abx preferred

Treatment duration: 14 to 21 days. Start as soon as possible

Intermittent (1 large dose into 1 exchange/day, min 6 h dwell) vs. continuous therapy (with each exchange)

Abx generally stable in dextrose and icodextrin (refer to stability table)
Systemic toxicities of IP regimens likely similar to IV and oral

If WBC remains high or no clinical improvement by 5 days on appropriate abx, remove PD catheter, initiate HD and continue IV abx for 2 more weeks

peritonitis - empiric therapy

Initial empiric therapy should include use of broad spectrum agents; adjust therapy based on culture/sensitivities

Gram(+): Cefazolin, vancomycin

Gram(-): AG, ceftazidime, cefepime - gram (-) + (+) (monoTx possible)

Increase dose empirically by 25% in pts with significant residual kidney function (urine output >100 mL/day) and drug is renally eliminated

peritonitis - antibiotics

IP AG: Daily intermittent dosing recommended

Prolonged courses to be avoided due to risk of ototoxicity

Adjunctive oral N-acetylcysteine therapy may help prevent AG ototoxicity

Vancomycin, cephalosporins and AG can be mixed in same bag

Do not add AG and penicillin (PCN) to same bag due to chemical incompatibility -> PCN inactivates AG

peritoneal dialysis - fungal peritonitis

Less common but associated with poor prognosis and high morbidity, mortality

Remove catheter immediately

Treatment: azoles (fluconazole), echinocandins (caspofungin), amphotericin B

peritoneal dialysis - catheter related infections

2 types: exit and tunnel infection

Frequency of exit-site infection ~ every 24 to 48 months

Majority caused by staph aureus (S. epidermidis < common)

Pseudomonas less common but can result in significant morbidity

Increase risk in pts who are nasal carriers of S. aureus, diabetics, those receiving immunosuppressants

PD Catheter-related infections - clinical presentation

Purulent discharge (if present, consider definitive exit site infection)

Erythema at exit site (may or may not be present)

Fever, chills

PD Catheter-related infections - prevention

Administer prophylactic antibiotics before catheter insertion e.g. nasal antibiotics for nasal S. aureus carriers

Leave exit site dressing intact for 7 days after catheter insertion

Training and education of patients and caregiver on care of exit site

PD Catheter-related infections - management

Oral antibiotic treatment for exit site infection

HD - advantages

Higher solute clearance allows intermittent treatment

Dialysis adequacy parameters better defined

Low technique failure rate

Allows closer monitoring of pt

Allows IV administration of some drugs

HD - disadvantages

Requires multiple visits to center

Disequilibrium, hypotension, cramps are common; may take months to adjust

Infections and thrombosis from vascular access

Rapid decline of residual kidney function

PD - advantages

More hemodynamically stable

Suitable for elderly & young pts

Increased clearance of larger solutes

Preserve residual kidney function

IP drug administration

Less blood loss and Fe deficiency

No systemic heparinization

SC dosing of ESA possible

PD - disadvantages

Greater protein and AA losses, glucose load, peritonitis

Risk of obesity with glucose absorption

Mechanical problems, catheter malfunction, exit-site infections

Inadequate UF and solute removal in certain pts

Pt burnout and high technique failure rate

Extensive abdominal surgery may preclude PD

No convenient access for IV medications