What are the key parameters and management strategies for a patient undergoing Peritoneal Dialysis (PD) with impaired renal function?

Key Parameters and Management Strategies in Peritoneal Dialysis

Dialysis Adequacy Targets

The minimum delivered dose of total small-solute clearance should be a Kt/Vurea of at least 1.8 per week for patients with residual kidney function (RKF), and a peritoneal Kt/Vurea of at least 1.7 for anuric patients. 1

Measurement Frequency

• Measure total solute clearance within the first month after initiating dialysis and at least every 6 months thereafter 1
• For patients with RKF (urine Kt/Vurea >0.1/week), obtain 24-hour urine collections at minimum every 3 months to assess residual kidney clearance 1
• Once peritoneal Kt/Vurea reaches 1.7 or 24-hour urine output falls below 100 mL, monitoring RKF for adequacy purposes is no longer required 1
• All clearance measurements must be obtained when the patient is clinically stable and at least 1 month after resolution of peritonitis 1

Volume Calculation

• Calculate V (total body water) using sex-specific Watson or Hume equations in adults 1
• Consider using ideal or standard weight rather than actual weight in the calculation, particularly for obese patients 1

Residual Kidney Function (RKF) Preservation

Preserving RKF is critical as kidney urea clearance (not peritoneal clearance) is the primary predictor of 12-month mortality. 1

Nephrotoxic Avoidance

• Avoid aminoglycoside antibiotics whenever possible to minimize nephrotoxicity, ototoxicity, and vestibular toxicity 1
• Avoid NSAIDs as they can cause significant loss of RKF and render the PD prescription inadequate 1
• Do not use citrate salts simultaneously with aluminum-containing medications 1

Blood Pressure Management

• Avoid overzealous blood pressure control as this may lead to loss of RKF 1
• Consider "pre-kidney" and "post-kidney" causes when RKF decreases 1

Ultrafiltration and Volume Management

For volume-overloaded or hypertensive patients, ultrafiltration should never be negative (no fluid absorption) for any exchanges. 2

Dwell Time Optimization

• Use continuous 24-hour PD prescriptions (rather than intermittent) in patients with minimal RKF to maximize middle-molecule clearance 1
• Avoid long-duration dwells that cause net peritoneal fluid absorption, particularly problematic in APD with 8-16 hour daytime dwells 2
• For fluid overload, manual CAPD with 4-5 shorter exchanges per day prevents the fluid reabsorption seen with prolonged APD dwells 2

Icodextrin Use

• Use icodextrin solution for any necessary long dwells as RCTs demonstrate it increases peritoneal ultrafiltration and decreases extracellular fluid volume 2
• This is particularly important for the long daytime dwell in APD patients 2

Volume Prescription Strategies

• First increase instilled volume per exchange (target 1,000-1,200 mL/m² BSA, maximum 1,400 mL/m²) before increasing exchange frequency 1
• Increase supine exchange volumes first as this position has lowest intra-abdominal pressure 1
• Review PD effluent volume records monthly, paying particular attention to drain volume from overnight CAPD dwells and daytime CCPD dwells 1

Nutritional Monitoring

During monthly evaluations, assess nutritional status through serum albumin levels and dietary protein intake (DPI) estimates such as nPNA when obtaining 24-hour clearances. 1

Protein Requirements

• Target DPI of at least 1.2 g/kg/day (preferably 1.3 g/kg/day) with at least 50% high biological value protein to maintain neutral or positive nitrogen balance 1
• PD patients lose 5-15 g protein and 2-4 g amino acids per day in dialysate (equivalent to 0.2 g protein/kg/day), with higher losses in rapid transporters 1
• Protein losses double during peritonitis episodes 1

Energy Requirements

• Prescribe 35 kcal/kg/day for patients <60 years old and 30-35 kcal/kg/day for those ≥60 years old 1
• Low DPI and decreased appetite are acknowledged symptoms of uremia that may indicate inadequate dialysis 1

Nutritional Surrogates

• Serum albumin, subjective global assessment (SGA) scores, and DPI estimates are important predictors of mortality risk 1
• Peritoneal creatinine excretion rate can monitor muscle mass over time 1
• An isolated serum albumin level must be interpreted cautiously and followed longitudinally as it is influenced by many non-nutritional parameters 1

Dialysate Calcium Concentration

The dialysate calcium concentration should be 2.5 mEq/L (1.25 mmol/L) for both hemodialysis and peritoneal dialysis. 1

Indications to Increase Dialysis Dose

Regardless of delivered dose, if a patient is not thriving with no other identifiable cause besides possible kidney failure, increase the dialysis dose. 1

Specific Clinical Scenarios

• Failure to thrive with no alternative explanation warrants repeated clearance measurements to determine if uremia is contributing 1
• Development of uremic pericarditis or neuropathy indicates need for increased dialysis 1
• Nausea, vomiting, and appetite suppression are uremic symptoms requiring prescription adjustment 1

Common Causes of Inadequate Dialysis

• Intravascular volume depletion or inadvertent NSAID use causing loss of RKF 1
• Decreased dialysate dextrose concentration resulting in decreased ultrafiltration and clearance 1
• Patient changing timing of exchanges (shortening some, excessively lengthening others) 1
• Nonadherence with prescription—investigate by assessing supplies ordered, home inventory, and cycler memory system 1

Contraindications to PD

Absolute Contraindications

• Documented loss of peritoneal function or extensive abdominal adhesions limiting dialysate flow 1
• Physical or mental incapability to perform PD without a suitable assistant 1
• Uncorrectable mechanical defects (surgically irreparable hernia, omphalocele, gastroschisis, diaphragmatic hernia, bladder extrophy) 1

Relative Contraindications

• Fresh intra-abdominal foreign bodies (4-month wait after abdominal vascular prostheses, recent ventriculoperitoneal shunt) 1
• Peritoneal leaks 1
• Intolerance to PD volumes necessary for adequate dose 1
• Inflammatory or ischemic bowel disease 1
• Morbid obesity in short individuals 1
• Severe malnutrition 1
• Frequent diverticulitis episodes 1

Cardiovascular Considerations

PD offers advantages for patients with cardiovascular disease including better hemodynamic control, avoidance of acute electrolyte shifts that could cause arrhythmias, and better anemia control. 1

• PD has been successfully used to manage refractory heart failure even in patients without renal failure 1
• Acute hemodynamic changes are avoided compared to hemodialysis 1

Monitoring Aluminum Exposure

• Measure serum aluminum levels at least yearly and every 3 months in those receiving aluminum-containing medications 1
• Baseline serum aluminum should be <20 µg/L 1
• Dialysate aluminum concentration should be maintained at <10 µg/L 1

Critical Pitfalls to Avoid

• Do not assume APD provides superior volume control over CAPD—modality selection should prioritize ultrafiltration capacity over convenience in volume-overloaded patients 2
• Never ignore negative ultrafiltration in any exchange when managing volume overload as this directly worsens the clinical condition 2
• Do not rely on frequent hypertonic 4.25% glucose solutions to compensate for poor ultrafiltration as this damages the peritoneal membrane and causes adverse metabolic effects 2
• Do not assume children with previous extensive abdominal surgery cannot achieve successful PD—a trial is warranted with documented adequate dose delivery 1
• Do not confuse markers of "nutritional status" with actual nutritional status—serum albumin and other surrogates are influenced by many non-nutritional clinical parameters 1