Prescribing During Peritoneal Dialysis

Peritoneal dialysis clears small molecules continuously but less efficiently than haemodialysis. Its clearance is about equal to a GFR of 5 to 10 mL/min, so systemic doses follow the band for a GFR under 10 mL/min unless residual kidney function is meaningful.

Residual function. It often contributes more than the dialysis itself. Preserve it by avoiding nephrotoxins, NSAIDs and aminoglycosides unless essential.

Route. Intraperitoneal antibiotics reach high local levels and are the preferred route for peritonitis. Systemic absorption from the peritoneum is substantial, especially during peritonitis.

Glucose measurement. Icodextrin gives a metabolite (maltose) that can cause falsely high readings on some glucose meters, so insulin overdose may follow. Use a glucose-specific method.

Peritonitis. Suspect it with cloudy effluent, abdominal pain and an effluent count over 100 cells/µL with over 50 percent neutrophils after a dwell of at least 2 hours. Send effluent for culture before antibiotics.

Empirical cover. Give a first-generation cephalosporin or vancomycin for gram-positive organisms, plus ceftazidime or an aminoglycoside for gram-negative organisms, adjusted to local resistance.

Oral drugs. Absorption may be altered by peritonitis and gut oedema. Metformin should be avoided.

Special groups.

• Children: dose by mg/kg and use weight-adjusted intraperitoneal doses.

• Pregnancy: needs specialist care.

• East Africa: acute peritoneal dialysis is often used for acute kidney injury where haemodialysis is unavailable, and fluid and antibiotic availability varies, so confirm local supply and compatibility.

Intraperitoneal regimens (each exchange with a dwell of at least 6 hours for intermittent dosing).

• Vancomycin: intermittent 15 to 30 mg/kg every 5 to 7 days. Continuous loading 20 to 25 mg/kg, then 25 mg/L in each bag.

• Cefazolin: intermittent 15 mg/kg once daily. Continuous loading 500 mg/L, then 125 mg/L in each bag.

• Ceftazidime: intermittent 1 to 1.5 g once daily. Continuous loading 500 mg/L, then 125 mg/L in each bag.

• Gentamicin: intermittent 0.6 mg/kg once daily. Continuous loading 8 mg/L, then 4 mg/L in each bag.

• Heparin 500 units/L in the bag can prevent fibrin blockage.

Duration. At least 2 weeks, and 3 weeks for Staphylococcus aureus, enterococci, Pseudomonas or a slow response.

Monitoring. Repeat effluent counts at 48 to 72 hours, measure vancomycin levels before re-dosing (aiming for over 15 mg/L), and check residual urine output.

Stop rules. Stop aminoglycosides after a short course because of ototoxicity and loss of residual function.

Referral and escalation. Remove the catheter for refractory peritonitis (no improvement by day 5), relapsing peritonitis, fungal peritonitis, or a tunnel infection with the same organism. Involve the renal team early.

Common errors. Under-dosing because of a presumed GFR of zero, reading icodextrin-affected glucose meters, and neglecting residual function.