Slow continuous ultrafiltration and prolonged intermittent renal replacement therapy: Tailoring renal replacement therapy in intensive care unit

Table 3 Standardized prolonged intermittent renal replacement therapy prescription

Standardized PIRRT prescription
Modality	PIRRT mode: Continuous venovenous hemodiafiltration
Indication	Acute kidney injury kidney disease: Improving Global Outcomes stage 3 with hemodynamic instability or inability to tolerate standard intermittent hemodialysis
Duration/frequency	10-12 hours per session, daily (adjust based on clinical needs: 8-16 hours possible)
Blood flow	200 mL/minute (range: 150-250 mL/minute)
Dialysate flow	1500 mL/hour (25 mL/kg/hour for 60 kg patient), adjust based on weight: 20-30 mL/kg/hour target
Pre-dilution replacement	1200 mL/hour (20 mL/kg/hour for 60 kg patient), ratio: 80% of dialysate flow
Post-dilution replacement	0-300 mL/hour (optional, use if need higher efficiency), typically 0 mL/hour for standard PIRRT
Total effluent	2700 mL/hour (dialysate 1500 + pre-dilution 1200), effective dose: Approximately 22-24 mL/kg/hour
Net ultrafiltration	According to fluid balance goals (typical 100-300 mL/hour), for 12 hours session: 1.2-3.6 L net removal
Filtration fraction	Target: < 20% formula: Filtration fraction = ultrafiltration flow rate/[blood flow × (1 - hematocrit/100)] × 100 example (blood flow = 200, hematocrit = 30%): Filtration fraction = 1200/60/(200 × 0.7) = 14%
Anticoagulation	Option 1 (preferred): Regional citrate anticoagulation per protocol. Option 2: Heparin - activated partial thromboplastin 45-60 sec or anti-Xa 025-0.35 U/mL. Option 3: None - if contraindicated (increase blood flow to 250 mL/minute, use PBP 40% + pre 60%)
Vascular access	Double-lumen dialysis catheter (11.5-13 Fr) preferred sites: Internal jugular > femoral > subclavian
Filter	High-flux hemofilter, 1.5-2.0 m2 surface area biocompatible membrane (polysulfone, polyethersulfone)
Dialysate/replacement composition	Standard composition: Na+ 140 mEq/L; K+ 2-3 mEq/L (adjust based on serum K+: 0 mEq/L if K+ > 6.0); Ca2+ 3.0-3.5 mEq/L (if not using citrate); Mg2+ 1.0 mEq/L; bicarbonate 32-35 mEq/L
Monitoring	Blood pressure: Every 30 minutes. Fluid balance: Hourly. Electrolytes: Pre-treatment, mid-treatment (6 hours), post-treatment. Blood gas/pH: Pre and post-treatment. TMP, pressures: Continuous. BUN, Creatinine: Daily. Filter inspection: Visual check every 2-4 hours for clotting
Dose calculation	Target: 20-25 mL/kg/hour effective dose. Example for 70 kg patient: Target total dose: 70 kg × 22 mL/kg/hour = 1540 mL/hour. With pre-dilution: Need approximately 1800-1900 mL/hour prescribed. Prescription: Dialysate flow 1500 + pre 1200 = 2700 mL/hour. Effective dose: 2700/1.17 approximately 2300 mL/hour or approximately 23 mL/kg/hour
Adjustments	Increase dose (to 25-35 mL/kg/hour) if: Sepsis, hypercatabolic state, persistent azotemia (BUN >100 mg/dL), hyperkalemia (K+ > 5.5 mEq/L). Decrease duration/dose if: Hemodynamic instability, improving renal function, transitioning to IHD
Transition strategy	From CRRT to PIRRT: Start with 12 hours sessions, assess tolerance from PIRRT to IHD: Gradually reduce session length (12 hours to 8 hours to 6 hours), then transition to 4 hours IHD alternate days criteria for transition: Hemodynamic stability for 24 hours, improving urine output, stable electrolytes

PIRRT: Prolonged intermittent renal replacement therapy; PBP: Pre blood pump; TMP: Transmembrane pressure; BUN: Blood urea nitrogen; CRRT: Continuous renal replacement therapy; IHD: Intermittent hemodialysis.