11.3 Continuous Renal Replacement Therapy (CRRT) & Peritoneal Dialysis in Pediatric Critical Care

Continuous kidney replacement therapy and acute peritoneal dialysis

Decide when and how to start

Start kidney replacement therapy (KRT) urgently for life-threatening derangements that cannot be controlled promptly, such as refractory hyperkalemia, severe acidemia, pulmonary edema with impaired oxygenation, or a uremic complication such as pericarditis. Treat immediately reversible threats while arranging access and support. Consider trajectory, urine output, perfusion, fluid balance and the ability to provide nutrition or essential infusions. An isolated BUN, creatinine, pH or fluid percentage cannot make the decision.

Estimate cumulative fluid accumulation as $100\times(\text{intake in L}-\text{output in L})/\text{baseline weight in kg}$, approximating 1 L as 1 kg of water. A 20 kg child with a positive balance of 2.4 L has 12% accumulation. Check the time window, the reliability of fluid records and the weight trend. The original ppCRRT registry associated greater accumulation at initiation with mortality. In a newer WE-ROCK analysis the adjusted association was with fewer ventilator- and ICU-free days, without a demonstrated independent ICU mortality association. A separate WE-ROCK timing analysis linked later initiation with worse 90-day kidney outcomes. Observational findings support early planning and close reassessment. They cannot establish that starting therapy at a fixed percentage or hour improves survival. KDIGO issued AKI guideline · ppCRRT registry · WE-ROCK fluid study · WE-ROCK timing study

Use CRRT when gradual, sustained fluid or solute removal suits a child with hemodynamic instability or cerebral edema risk. Intermittent hemodialysis can clear some solutes more quickly when tolerated. Use toxin-specific criteria and consult toxicology, for example for severe salicylate poisoning. Peritoneal dialysis (PD) is an option in selected small infants and when vascular access is difficult. Check whether abdominal surgery, abdominal disease or respiratory mechanics limit fills. If a toxin or metabolite requires rapid clearance, choose a modality that can deliver that clearance. The 2026 pediatric Surviving Sepsis Campaign conditionally favors high-volume hemofiltration above 35 mL/kg/h over standard volume in children with sepsis already requiring KRT. The recommendation has low certainty. The guideline gives no recommendation for extracorporeal blood purification as a general sepsis treatment. EXTRIP salicylate guidance · ISPD pediatric acute PD · Pediatric SSC 2026

Hyperammonemia: In a suspected inborn error, activate metabolic and nephrology teams early and treat alongside dialysis preparation. The PCRRT consensus describes urgent extracorporeal clearance for levels above 500 µmol/L, and earlier escalation for significant encephalopathy, a rapid rise or inadequate medical response. It favors high-dose continuous venovenous hemodialysis when feasible. Intermittent hemodialysis or a sequential approach can be used by experienced teams, with surveillance for rebound. Acquired pediatric acute liver failure has separate indications. With worsening encephalopathy and rising ammonia, discuss continuous clearance early with a transplant center. The PALF position paper emphasizes clinical trajectory and associates values above 200 µmol/L with herniation risk. This is a risk marker and should not be used as a universal starting threshold. PCRRT hyperammonemia consensus · NASPGHAN acute liver failure · PCRRT pediatric acute liver failure

Match modality, filter and delivered dose to the problem

Membrane properties, molecular size, binding, circuit flows and downtime affect clearance. Myoglobin clearance cannot be inferred from the modality alone. An adult trial found greater myoglobin clearance with a high-cutoff CVVHD membrane than with high-flux CVVHDF. That comparison changed both membrane and mode and did not establish a pediatric clinical benefit. Use conventional KRT indications in crush-associated AKI. KRT nomenclature consensus · Myoglobin clearance trial · AAST rhabdomyolysis consensus

Worked dose example. For a 20 kg child on CVVHDF, dialysate at 300 mL/h, postfilter replacement at 200 mL/h and net patient removal at 40 mL/h yield 540 mL/h effluent, or 27 mL/kg/h, ignoring other circuit infusions. Net machine fluid removal is 2 mL/kg/h. If the circuit runs 20 of 24 hours, average effluent is 22.5 mL/kg/h. If the waste-fluid concentration is 0.9 times the systemic concentration for a marker absent from incoming fluids, estimated average clearance is about 20.25 mL/kg/h. The issued KDIGO guideline uses a delivered effluent benchmark of 20–25 mL/kg/h for AKI. Tailor the prescription to the indication, downtime and solute response. Verify the actual delivered dose. KDIGO AKI guideline Net machine removal and the child's total fluid balance differ because the patient also receives fluids and has other output.

Worked filtration example. At blood flow 60 mL/min and hematocrit 0.30, plasma flow is about 42 mL/min. At a total filtration rate of 12 mL/min, filtration fraction is 12/42, about 29%, without predilution. With 10 mL/min of prefilter replacement and the same total filtration, it is 12/(42 + 10), about 23%. Prefilter dilution reduces hemoconcentration and lowers concentration at the membrane, reducing clearance per liter filtered. Postfilter replacement preserves inlet concentration. Recalculate using the machine's definitions and actual inputs when changing the prescription.

Choose an ultrasound-guided dialysis catheter sized to the child, vessel and needed flow. Right internal jugular access often gives a direct route. Femoral access is an alternative. Preserve future access and avoid the subclavian route when feasible. In a small infant, compare circuit volume with estimated blood volume and plan priming and connection. Blood priming or a low-volume pediatric circuit can change the risk. Coordinate monitoring of pressure, electrolytes, phosphate, temperature, fluid balance and medication exposure. KDIGO AKI guideline · Small-child WE-ROCK study · Infant circuit comparison

Monitor regional citrate anticoagulation

Citrate enters before the filter and binds ionized calcium. Some complexes leave in the effluent. Replace calcium according to the circuit protocol and systemic ionized calcium. Check postfilter ionized calcium for circuit anticoagulation and systemic values for patient safety. The target ranges and calcium infusion site depend on the device and protocol. Citrate can prolong circuit life compared with systemic heparin. Weigh citrate handling, heparin-related bleeding and HIT risk and the feasibility of therapy without anticoagulation.

During shock or liver dysfunction, falling systemic ionized calcium despite more calcium, a rising total-to-ionized calcium ratio above about 2.5 (both in mmol/L), and worsening acidosis together raise concern for citrate accumulation. Check other contributors to acidosis. For total calcium 11.8 mg/dL and ionized calcium 0.92 mmol/L, convert total calcium to about 2.95 mmol/L and divide to obtain about 3.2. Promptly involve the dialysis team, correct systemic calcium and address perfusion. Reduce or stop citrate and change clearance or anticoagulation according to protocol and severity. Excess metabolized citrate can instead contribute to alkalosis. Interpret the ratio with the calcium requirement and acid-base trend. Pediatric citrate versus heparin trial · Pediatric citrate in liver injury

Prescribe and monitor acute peritoneal dialysis

PD uses a peritoneal membrane and osmotic gradient and avoids an extracorporeal blood circuit. ISPD suggests starting with fills of 10–20 mL/kg and total cycles of 60–90 minutes, including fill, dwell and drain, with adjustment for small infants, leaks or ventilation effects. Acute treatment usually runs continuously for the first 1–3 days. A 3.1 kg infant starting at 10 mL/kg receives 31 mL per fill. Record fill and drain volumes. Draining 38 mL after a 31 mL fill gives 7 mL net removal for that exchange, assuming complete drainage. Adjust dwell, fill and glucose concentration to solute and fluid goals, with close glucose, electrolyte and hemodynamic monitoring. Use prescribed commercial solution and monitor potassium losses. Reduce fills or reassess modality if leaks or worsening respiratory mechanics develop. ISPD pediatric acute PD guideline · Infant cardiac surgery PD trial

For suspected peritonitis, send effluent cell count, differential, Gram stain and culture. The 2024 pediatric ISPD framework uses two of three findings: compatible symptoms, effluent white cell count above 100/µL with at least 50% neutrophils, or a positive effluent culture. The count is most interpretable after at least a 2-hour dwell. In short cycles, a neutrophil fraction of at least 50% can still be suggestive at a lower total count. Obtain cultures promptly and start gram-positive and gram-negative coverage per local guidance. Intraperitoneal delivery is preferred when feasible. Systemic sepsis requires urgent systemic management. ISPD pediatric PD infection guideline