Peritoneal dialysis (PD)

• Sterile dialysate fluid is introduced into the peritoneal cavity via a catheter and exchanged at intervals

  • Typically, the dialysate is infused, allowed to dwell for a period of time, and then drained; this cycle is repeated a number of times

    • Exception: continuous flow peritoneal dialysis

• Rather than using an extracorporeal dialyzer/filter, the patient's peritoneal membrane serves as the semipermeable membrane

  • The presence of small pores aquaporin channels allow water to move through the membrane.

  • The peritoneum is highly vascular and the presence of capillaries allows for transfer of solutes.

Why it works

• Within the peritoneal membrane (between the abdominal wall and the peritoneal cavity) there are capillaries, lymphatic vessels, and interstitial spaces

  • These enable the absorption of particles from the dialysate (in the peritoneal cavity) into the rest of the body

  • The peritoneal capillaries enable the movement of water (by ultrafiltration) into the peritoneal cavity

• Transport in PD is an interaction of diffusion, ultrafiltration, and fluid absorption

Peritoneal transport: "three pore" conceptual model

• Large pores (>20 nm [>200 Å] diameter)

  • <10% of the pores in the peritoneal membrane

  • Permit transport of proteins (e.g., immunoglobulins) and other large molecules

  • Can be increased with significant inflammation such as peritonitis

• Small pores (4-6 nm [40-60 Å] diameter)

  • ~90% of pores in the peritoneal membrane

  • Transport most small molecules

• Ultrasmall pores (0.3-0.5 nm [3-5 Å] aquaporins)

  • 1-2% of pores in the peritoneal membrane

  • Responsible for nearly half of water transport

Diffusion in PD: key factors

• Concentration gradient of solute: dialysate/plasma (D/P) ratio

• Mass transfer area coefficient (MTAC)

  • Effective peritoneal surface area (analogous to the K₀A in HD)

    • Surface area of the peritoneal membrane

    • Vascularity: how many peritoneal capillaries are in the peritoneum

  • Diffusive characteristics of membrane for solute in question (permeability)

    • Varies from patient to patient

    • Changes in individuals over time

• Particle size:

  • Small molecules diffuse rapidly

  • Large molecules take a longer time to diffuse across the peritoneal membrane

Ultrafiltration in PD: key factors

• Osmotic gradient: fluid removal (ultrafiltration) is accomplished using osmotic pressure rather than hydrostatic pressure

  • The osmotic gradient is created by including an osmotic agent (e.g., dextrose, icodextran) in the dialysate

    • Increasing the concentration of the osmotic agent generates a greater osmotic gradient and results in more fluid removal

    • Using dialysate with higher dextrose concentration generates a greater osmotic gradient and results in more fluid removal

• Reflection coefficient: how resistant a particle in the dialysate is to being absorbed (i.e., how well it stays in the dialysate), on a scale of 0 to 1

  • An osmotic agent with a reflection coefficient of 1 would be an ideal osmotic agent: it would draw water into the peritoneal cavity without being absorbed

• Ultrafiltration coefficient (of the membrane): depends on the surface area and the number of pores

• Hydrostatic pressure

  • Filling the peritoneal cavity with dialysate increases the hydrostatic pressure

• Oncotic pressure gradients

  • Related to changes of protein levels inside the bloodstream as water is removed from the peritoneal cavities

Fluid absorption

• Peritoneal fluid is absorbed during peritoneal dialysis:

  • Direct lymphatic absorption

  • Tissue absorption (into the interstitium) of peritoneal fluid

• Fluid absorption limits ultrafiltration and mass transfer

  • Higher levels of peritoneal absorption reduces the net ultrafiltration

• PD is generally the preferred chronic dialysis modality in pediatrics

  • Depends on patient and family preference, institutional practice and availability

Advantages

• Better outcomes (vs HD) in the US

  • Gentler fluid removal over longer time period avoids cardiac stunning seen in hemodialysis

  • Better preservation of remaining kidney function

  • Better outcomes after kidney transplantation

  • Better growth

  • Improved fluid balance

    • Also reduces need for antihypertensive medications

• Daily clearance

  • Less accumulation of toxins (e.g., phosphorus, potassium) between sessions

• Better quality of life

  • Home treatment (less frequent travel to the dialysis unit)

  • Self control of the therapy

  • No needles

  • Facilitates school attendance/employment

  • Extended travel is possible

  • Fewer dietary restrictions

• Less technically difficult, especially in babies

  • Teaching usually takes 3-5 days

Disadvantages

• Risk of infection: peritonitis, exit site and tunnel infections

• Hernias

• Decreased appetite

• Body image disturbance

• Labor intensive

• Drawbacks of home PD:

• • Caregiver burden

  • Requires a lot of physical space to keep supplies

  • Requires a savvy family

    • However, even with poor educational background (e.g., illiteracy) can be trained to be competent

Contraindications to PD

• • Anatomical

    • Multiple prior abdominal surgeries with lots of scarring

    • Compromised diaphragm with communication between abdominal and thoracic cavities (e.g., diaphragmatic hernia, surgical complication)

    • Other congenital abnormalities: omphalocele, gastroschisis, bladder exstrophy

  • ≥2 prior episodes of peritonitis

  • Obliterated peritoneal cavity

    • E.g., from prior surgeries, trauma, infections

  • Peritoneal membrane failure

  • Relative contraindications:

    • Presence of ileostomies/colostomies

      • Ideally would locate as far away as possible from the PD exit site to avoid contamination

    • Infants with significant organomegaly

    • Impending abdominal surgery

    • If expecting transplant soon (typically <3-6 months), usually prefer to initiate HD

      • Significant time investment of planning surgery, waiting for tract to mature, training of patient/family

    • Lack of appropriate caregiver(s)

    • Lack of appropriate home environment

Infection Prevention

• For all PD patients on antibiotics, they should also be on antifungal prophylaxis (usually Nystatin 10,000 units/kg/day) while on antibiotics and for 7 days after

  • This also applies to dental prophylaxis (typically just one dose of amoxicillin given 1 hour prior to dental appointment)

Microbiology of Peritonitis

• [***graphs]

Treatment of peritonitis

• Start empiric IP antibiotics as soon as possible

  • Allow to dwell for 3-6 hours

  • Monotherapy with cefepime

    • If allergy, if not available, or if high MRSA prevalence:

      • Gram-positive: 1st generation cephalosporin or glycopeptide (e.g., vancomycin)

      • Gram-negative: ceftazidime, aminoglycoside

• Dosing:

  • Continuously or intermittently

  • In pediatric we tend to dose continuously

    • Loading dose with 3-6 hour dwell

    • Lower maintenance for subsequent dwells

Pathogen-directed therapy

• Gram positive (*** ispd 2012)

• Length of therapy for specific agents [***]

Culture-negative peritonitis

• 25-30% of all peritonitis episodes

• Without an organism it is difficult to be confident about providing directed therapy

• It becomes challenging to provide reeducation for patients and caregivers, as the pathogen usually provides clues as to the etiology

• Management:

  • Empiric antibiotics

  • Day 3: if improved, then continue for 2 weeks

    • If on dual therapy, consider discontinuing aminoglycoside and switching to ceftazidime as it has better side effect profile

  • If no clinical improvement by day 5, then it is considered refractory and the catheter should be removed

• Fungal peritonitis

  • 2-8% of all peritonitis episodes

  • High risk of technique failure

  • Systemic antifungal therapy: fluconazole

    • do not use amphotericin

  • Remoe catheter

  • Continue treatment for 2 weeks past resolution of symptoms

  • Need at least 2-3 weeks after removal until catheter can be replaced

• Relapsing peritonitis

  • Definition: peritonitis recurs with same organism within 4 weeks of completion of antibiotic therapy

  • Reinitiate empiric therapy

    • Cover for prior organism

    • Avoid cefazolin monotherapy

  • Fibrinolytic instillation

  • Relapsing + tunnel infection, or if second relapse: remove catheter

• Indications for catheter removal

  • Refractory peritonitis

  • Refractory exit site or tunnel infection

  • Fungal peritonitis'

  • Peritonitis + exit site or tunnel infection

    • [***]bugs

  • Relapsing with coag negative staph

  • [***] one more thing

• Outcomes of peritonitis

  • 76.6% of infections resolved with antimicrobial treatment alone

  • 59.6% required hospitalization

  • 6% temporary catheter removal

  • [*** more]

  • [***who most likely to need cath removal]

Modifiable practices to reduce risk of peritonitis

• Insertion bundle

  • Intraoperative care

    • Lateral/downward exit site

    • Prophylactic preoperative antibiotics [*** ISPD guideline ]

    • No sutures at the exit site

  • Postoperative care

    • No exit site dressing change through POD 7 unless it is soiled/wet

    • Until exit site healed: sterile dressing change, [***]

    • Do not use PD catheter prior to 14 days

• Training bundle

  • Qualified RN trains

  • [***]

• Follow up care bundle

  • Exit site scored per IPPN tool

  • Review: hand hygiene, exit site care, aseptic connection technique

  • Ask about touch contaminations/ breaks in aseptic technique

  • Repeat training every 6 months or after any episode of peritonitis [***]

Peritonitis rates

• 19 sites participating from inception of SCOPE collaborative since 2011

• Very high compliance with follow up care bundle led to significant and

Catheter related infections

• Exit site infection:

  • Definitions:

    • Peri-catheter swelling, redness, tenderness

    • Score of 2+ on IPPD tool with an organism or 4+ with/without organism

    • In adults: purulent draining with or without erythema

  • 
    

• Tunnel infection:

  • Definitions:

    • redness, edema, tenderness along catheter with or without purulent drainage

    • Score of 2+

    • Adults: inflammation or ultrasound evidence of infection along the catheter length

• Outcomes: [***]

• Progression of the

• Risk factors:

  • Higher IPPN score

  • Poor compliance with exit site care training (training bundle) or exit site care review (follow up bundle)