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PAPER 2 – Applied Dialysis Therapy Technology

UNIT 2: PD Apparatus | UNIT 3: PD Process & Evaluation | UNIT 4: PD Complications & Management

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UNIT 2: PD APPARATUS

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1. Solution (Peritoneal Dialysate)

• Sterile and pyrogen-free
• Physiologically compatible
• Available in plastic bags (1 L, 2 L, 2.5 L, 3 L, 5 L)

Composition of Standard PD Solution

Glucose Concentrations Available

• 1.5% (1.36%) - Low osmolality; used when minimal UF needed
• 2.5% (2.27%) - Intermediate; standard use
• 4.25% (3.86%) - High osmolality; used when maximum UF needed (fluid overload)

Higher glucose = greater osmotic gradient = more fluid removal, but also higher glucose absorption by the patient, worsening hyperglycemia and dyslipidemia.

Alternative Osmotic Agents

• Average molecular weight 13-19 kDa
• Higher osmotic efficiency (σ ~0.5) across small pores
• Inefficient across aquaporin-1 (unlike glucose)
• Removes fluid primarily through small pores (~90%)
• Used for the long dwell (day dwell in APD / overnight in CAPD)
• Prevents fluid reabsorption; useful in fast transporters and UF failure

• Used as nutritional supplement for malnourished PD patients
• Typically one exchange per day replaced with amino acid solution

pH of PD Solutions

• Traditional: pH 5.2 (acidic, due to glucose degradation products - GDPs)
• Biocompatible solutions: pH 7.0–7.4 (neutral pH, low GDP content)
• Biocompatible solutions cause less mesothelial cell injury and peritoneal membrane damage

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2. Transfer Set

Functions

• Allows fill, dwell, and drain phases
• Provides a disconnect point to reduce infection risk

Types

• Standard Y-set (disconnect system): The most widely used. Patient connects a Y-shaped tubing - one arm to the new bag, one arm to the drain bag. Before filling, a small amount of fresh dialysate is flushed into the drain (the "flush before fill" technique), which washes out any contaminating organisms that may have entered the line during the connection step.
• Straight set: Older design; higher peritonitis risk; largely replaced by Y-sets and twin-bag systems.
• Twin-bag (double-bag) system: New bag and drain bag are pre-connected in a closed system; further reduces peritonitis rates by minimizing connection steps.

Key Principle: Flush Before Fill

• A small amount (100-200 mL) of fresh dialysate is flushed into the drain bag before the peritoneal cavity is filled.
• This removes any bacteria that may have contaminated the tubing during the spike.
• Significantly reduces peritonitis rates.

Transfer Set Change

• Sets are changed every 6 months or as per manufacturer/center protocol.
• Always changed under strict aseptic conditions.

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3. Connectologies

Evolution of Connectologies

Key Features of Modern Connectors

• Luer-lock mechanism: Ensures secure, leak-proof connection
• UV germicidal connector (UVXD): Uses UV light to sterilize the connection point
• Minicap: A protective cap soaked in antiseptic (povidone-iodine or betadine) placed on the catheter end after each exchange to prevent contamination
• Break/twist caps: One-time use caps that indicate if the line has been tampered with

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4. Access for PD (Peritoneal Access)

The PD Catheter

• Multiple holes along the intraperitoneal segment for fluid flow
• Two Dacron (polyester) cuffs:
  • Deep cuff: Placed inside the rectus abdominis muscle - tissue ingrowth encapsulates it, preventing migration and leaks
  • Superficial (subcutaneous) cuff: Placed 2-4 cm from the exit site - acts as a bacterial barrier

Types of PD Catheters

• Straight-tip (Tenckhoff): Simple design; standard
• Coiled-tip: Better dispersion of dialysate, less inflow pain

• Straight intercuff
• Swan neck: Pre-formed bend in the intercuff segment - positions the exit site downward, reducing infection risk

• Single cuff (less common)
• Double cuff (standard; preferred)

Catheter Insertion Techniques

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5. Catheter and Exit Site Care

Exit Site

• The point where the catheter exits through the skin
• Optimal position: pointing downward or laterally (swan-neck catheters)
• Avoid exit sites in skin folds, belt lines, or obese pannus

Exit Site Care Protocol

1. Daily cleaning with sterile normal saline or chlorhexidine
2. Dry gauze dressing or transparent dressing
3. Topical antibiotic prophylaxis:
   • Mupirocin cream applied to exit site daily - significantly reduces Staphylococcus aureus exit site infections and peritonitis
   • Alternatively: Gentamicin cream (reduces both gram-positive and gram-negative infections)
4. Avoid submerging catheter in bath water (showering preferred)
5. Catheter must be kept immobilized to prevent tugging/trauma

Exit Site Assessment (Scoring)

Tunnel

• The subcutaneous path between the deep and superficial cuffs
• Tunnel infection: Diagnosed by pain, redness, swelling along the tunnel tract; detected by ultrasound
• Tunnel infections often require catheter removal

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UNIT 3: PD PROCESS AND EVALUATION OF THE PERITONEUM

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1. PD Therapies - Intermittent and Continuous

Basic Steps of Every PD Exchange

1. Fill - Sterile dialysate instilled into peritoneal cavity
2. Dwell - Fluid stays in cavity; diffusion and UF occur
3. Drain - Used dialysate drained out by gravity

A. Continuous Ambulatory Peritoneal Dialysis (CAPD)

• Manual technique; no machine required
• Patient performs 3-5 exchanges per day, 7 days/week
• Each exchange: 2 L dialysate (occasionally 2.5 L)
• Dwell time: 4-8 hours per exchange
• Continuous therapy: dialysis occurring 24 hours/day
• One overnight long dwell (~8-10 hours)
• Preferred in low- and middle-income countries (cost-effective, no cycler)
• Patient or caregiver performs all exchanges

B. Automated Peritoneal Dialysis (APD)

C. Intermittent PD (IPD)

• Performed 3 times per week in a clinical setting (like HD schedule)
• Long session (10-12 hours) with rapid short-cycle exchanges
• Used for acute kidney injury or initiation of PD
• Less effective than CAPD for long-term chronic treatment

Incremental PD

• Starting PD at lower doses (e.g., 2-3 exchanges/day instead of 4)
• Suitable for patients with residual kidney function (RKF)
• Reduces treatment burden early in therapy
• Dose increased as RKF declines

Comparison: CAPD vs APD

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2. Assessment of Peritoneal Membrane Permeability

The Three-Pore Model

Peritoneal Equilibration Test (PET)

1. Patient drains overnight dwell
2. Instill 2 L of 2.27% (2.5%) glucose dialysate over 10 minutes (patient rolls side to side)
3. Collect dialysate samples at 0, 2, and 4 hours
4. Collect blood sample at 2 hours
5. Drain at 4 hours and measure total drain volume

• D/P creatinine (dialysate creatinine / plasma creatinine) at 4 hours
• D/D₀ glucose (dialysate glucose at 4 hours / dialysate glucose at time 0)
• Total ultrafiltration volume

Variants of PET

• Mini-PET: Uses 3.86% glucose; 1-hour dwell; measures sodium to assess free water transport (AQP-1 function)
• Double mini-PET: Evaluates both free water transport and osmotic conductance of glucose
• Modified PET (with 4.25% glucose): Used specifically to assess UF capacity

Ultrafiltration Failure (UFF)

• Defined as UF volume < 400 mL after a 4-hour dwell with 4.25% (3.86%) glucose
• Causes:
  • Fast peritoneal solute transport rate (PSTR)
  • Reduced AQP-1 function (low osmotic conductance)
  • Increased lymphatic reabsorption
  • Catheter malposition

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3. Adequacy of Peritoneal Dialysis

Kt/V (Urea)

• Most widely used measure of PD adequacy
• K = clearance, t = time, V = volume of distribution of urea
• Measured from 24-hour dialysate and urine collection
• Target: Kt/V ≥ 1.7 per week (total - dialysate + residual kidney function combined)

Creatinine Clearance (CrCl)

• Also used as measure of adequacy
• Target: ≥ 50 L/week/1.73 m² (CAPD)

How to Measure

• Collect 24-hour dialysate effluent (all drain bags over 24 hours)
• Collect 24-hour urine (if any residual kidney function)
• Blood sample for urea and creatinine
• Calculate:
  • Dialysate Kt/V = (dialysate urea concentration × drain volume) / (serum urea × V)
  • Add residual renal Kt/V to get total weekly Kt/V

Residual Kidney Function (RKF)

• RKF contributes significantly to total clearance, especially early in PD
• PD preserves RKF better than hemodialysis
• As RKF declines, PD prescription must be increased
• Use of NSAIDs should be avoided as they reduce RKF
• Measure residual GFR every 3-6 months

Factors Affecting Adequacy

• Body surface area / V (larger patients need more exchanges)
• Transport type (fast transporters clear solutes well but have poor UF)
• Residual kidney function
• Number of exchanges, dwell volumes, dwell times
• Compliance with prescribed regimen

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UNIT 4: PD COMPLICATIONS AND MANAGEMENT

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1. Non-Infectious Complications of PD

A. Mechanical Complications

• Normal inflow: 2 L fills in ≤ 15 minutes
• Causes: kinking of tubing/catheter, fibrin plug, constipation (bowel displacement), omental wrapping, catheter migration
• Management:
  • Check for kinks and open clamps
  • Flush vigorously with 20 mL heparinized saline
  • Add heparin (500 U/L) to dialysate to prevent fibrin clots
  • If blocked: urokinase 5000 U or tPA 2 mg instilled for 1 hour
  • Plain abdominal X-ray to check catheter position
  • Catheter migration: reposition by stiff wire guide, laparoscopic manipulation, or laxatives

• Most common cause: constipation (compressing the rectosigmoid around the catheter)
• Others: catheter tip migration to upper abdomen, fibrin, omental wrap
• Management: treat constipation (laxatives), check catheter position on X-ray, positional changes (standing, walking)

• Catheter tip curls into upper abdomen instead of remaining in pelvis
• Seen on plain X-ray
• Results in poor drainage
• Management: laxatives, repositioning maneuvers, laparoscopic revision

• Inflow pain: Jet of cold or acidic dialysate hitting the bladder/bowel; use tidal PD or warm dialysate
• Drain pain: Suction effect on empty peritoneum; use tidal PD (leave residual volume)
• Shoulder tip pain: Diaphragmatic irritation from air introduced during fill

• Common in females around menstruation (retrograde bleeding)
• Also: trauma, rupture of ovarian cyst, catheter injury
• Management: flush with heparinized dialysate (500 U/L); usually self-limiting; culture fluid to rule out infection

B. Mechanical - Leaks

• Dialysate leaks around catheter at insertion site
• Risk: using catheter too early after insertion (< 2 weeks)
• Prevention: break-in period; use low volumes (1 L) supine in early phase
• Management: rest for 1-2 weeks on APD (dry day or reduced volumes)

• Fluid visible leaking from exit site or incision
• Confirmed by measuring high glucose in the leaking fluid
• Is a risk factor for infection

• Fluid tracking into abdominal wall layers
• Presents as localized or diffuse abdominal wall edema
• Investigated by: CT peritoneography (CT with IP contrast) or 99mTc-DTPA scintigraphy

• Dialysate tracking through patent processus vaginalis or inguinal hernia
• Scrotal/labial swelling
• Management: surgical repair of hernia; temporary HD

• Dialysate leaks across diaphragmatic defect into pleural space
• More common on the right side
• Presents as acute breathlessness after PD fill
• Diagnosis: pleural fluid glucose very high; confirm with radionuclide scan
• Management: temporary HD; thoracoscopic repair of diaphragmatic defect

C. Metabolic Complications

• Glucose absorbed from dialysate (100-150 g/day with standard CAPD)
• Worsens glycemic control in diabetics
• Increases insulin requirements
• Management: use lowest effective glucose concentration; icodextrin for long dwell; intraperitoneal insulin (in diabetics)

• Caloric load from glucose absorption (300-400 kcal/day)
• Long-term leads to obesity, dyslipidemia

• Hypertriglyceridemia (from hepatic stimulation by glucose and amino acid absorption)
• Hypoalbuminemia (protein loss in dialysate: 5-15 g/day)

• Protein loss into dialysate
• Anorexia from abdominal fullness
• Increased with peritonitis episodes
• Management: dietary counseling; amino acid PD solutions (one exchange/day)

• Failure to achieve adequate UF
• Associated with fast transporters
• Management: higher glucose concentration, icodextrin, reduce fluid intake, increase exchanges

• Common in PD (unlike HD) due to continuous potassium removal
• Potassium is absent from standard PD solutions
• Management: dietary supplementation; potassium-containing solutions rarely required

• From water retention or free water transport via AQP-1

• Rare but severe complication; progressive fibrosis of the peritoneum
• Forms a thick "cocoon" encasing the bowel
• Presents with: bowel obstruction, anorexia, weight loss
• Associated with: long duration on PD (>5 years), repeated peritonitis, high glucose exposure
• Management: discontinue PD; immunosuppression (tamoxifen, corticosteroids); surgery in severe cases

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2. Infectious Complications of PD

A. Peritonitis

• Most common route: intraluminal contamination during bag exchange (touch contamination)
• Other routes: periluminal (exit site/tunnel infection spreading inward), transmural (from gut), hematogenous

• Gram-positive (most common): Staphylococcus epidermidis (coagulase-negative), S. aureus, Streptococci
• Gram-negative: E. coli, Klebsiella, Pseudomonas (worst prognosis)
• Culture-negative: 10-20%
• Fungal (Candida): rare but severe; usually requires catheter removal

1. Symptoms: Abdominal pain, cloudy dialysate effluent, fever (not always present)
2. Dialysate cell count: > 100 WBC/µL with > 50% neutrophils
3. Positive culture of dialysate

• Empiric therapy must cover both gram-positive and gram-negative organisms
• Preferred route: intraperitoneal (IP) administration
• Empiric regimens (ISPD guidelines):
  • Gram-positive cover: Vancomycin (IP, 15-30 mg/kg every 5-7 days) OR cephalosporin
  • Gram-negative cover: IP gentamicin (0.6 mg/kg/day intermittent dosing)
• Adjust after culture results (48 hours)
• Duration depends on organism:
  • Coagulase-negative Staph: 14 days
  • S. aureus: 21 days
  • Enterococcus: 21 days
  • Gram-negative bacilli: 21 days
  • Pseudomonas: 21-28 days (two antibiotics based on sensitivity)
  • Fungal: catheter removal + antifungals

• Fungal peritonitis
• Refractory peritonitis (no improvement after 5 days)
• Relapsing peritonitis
• Mycobacterial peritonitis
• Fecal peritonitis (multiple organisms)

B. Exit Site Infection (ESI)

• Staphylococcus aureus (most common and most dangerous - can lead to tunnel infection and peritonitis)
• Pseudomonas aeruginosa (second most common; associated with poor outcomes)

• Purulent discharge ± erythema, crusting, pain at exit site

• Oral or topical antibiotics based on culture
• S. aureus ESI: oral/IP flucloxacillin or cloxacillin (if MSSA); vancomycin (if MRSA)
• Pseudomonas ESI: ciprofloxacin orally; may need IP antibiotics

• Daily mupirocin cream or gentamicin cream to exit site
• Proper exit site hygiene
• Immobilization of catheter to prevent trauma

C. Tunnel Infection

• Infection in the subcutaneous tunnel between cuffs
• Presents with: pain, swelling, redness along the catheter tunnel; may be detected by ultrasound (fluid collection around catheter)
• Often associated with ESI
• Pseudomonas and S. aureus tunnel infections frequently lead to peritonitis
• Management: prolonged antibiotics; often requires catheter removal

D. Other Infectious Considerations

• Prophylactic antibiotics at catheter insertion (cefazolin or vancomycin)
• Flush-before-fill technique with disconnect systems
• Proper patient training and retraining
• Exit site prophylaxis with mupirocin/gentamicin
• Regular audit of peritonitis rates and root cause analysis after each episode

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3. Patient Education

Goals of Patient Education

• Enable independent, safe performance of PD exchanges at home
• Recognize and respond to complications early
• Maintain good technique to prevent infection
• Adhere to dietary and fluid restrictions
• Understand medications

Training Content

• Step-by-step exchange procedure (fill, dwell, drain)
• Aseptic technique (handwashing - minimum 15-20 seconds; mask use)
• Preparation of the environment (clean surface, no pets, no fans)
• Connecting and disconnecting the transfer set
• Flush-before-fill technique
• Recognition of cloudy bag (potential peritonitis)

• Daily cleaning technique
• Application of topical antibiotics
• How to assess the exit site (normal vs. infected)
• Catheter immobilization

• Cloudy effluent → call dialysis team immediately
• Abdominal pain, fever → potential peritonitis
• Swelling at exit site → potential ESI
• Poor drainage → catheter malfunction
• Swelling of genitals / abdomen → leak

• Fluid restriction based on UF output + residual urine
• Low phosphorus, moderate protein diet
• Potassium intake (may need supplements)
• Caloric awareness (glucose absorption from dialysate)

• Phosphate binders (take with meals)
• Erythropoietin-stimulating agents (ESAs) and iron
• Antihypertensives
• Intraperitoneal heparin (500 U/L when fibrin seen)

• Daily log: fill volume, drain volume, UF, appearance of drain bag
• Blood pressure and weight recording
• Fluid balance monitoring

• When to call the dialysis center
• What to do if patient has fever, cloudy bag, or drain failure

Training Duration and Assessment

• Initial training: typically 1-2 weeks
• Return demonstration: patient performs exchanges independently under observation
• Retraining: after any peritonitis episode; if technique errors identified
• Home visits: to assess home environment and technique
• Regular follow-up: monthly initially, then 3-monthly

Special Considerations

• Elderly patients: May need simplified procedures or caregiver training
• Diabetics: Blood glucose monitoring, insulin adjustments for dextrose load
• Visually impaired: Tactile aids, automated systems

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