Reference — Critical Care
CRRT Reference
Quick-access CRRT reference for ICU nurses — modalities, anticoagulation, monitoring intervals, fluid balance, and alarm response.
Educational use only. CRRT prescriptions, anticoagulation, and circuit management are provider- and protocol-driven; this overview supports concept review only. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
CRRT Modalities at a Glance
| Feature | CVVH | CVVHD | CVVHDF |
|---|---|---|---|
| Mechanism | Convection only | Diffusion only | Convection + Diffusion |
| Dialysate | No | Yes | Yes |
| Replacement Fluid | Yes | No | Yes |
| Small Molecule Clearance | Moderate | High | High |
| Middle Molecule Clearance | High | Low | High |
| Best For | Fluid removal; cytokines | Uremia; hyperkalemia | General ICU AKI (most common) |
Anticoagulation Quick Reference
| Agent | Monitoring Parameter | Target | Use When |
|---|---|---|---|
| Heparin (systemic) | aPTT | 45–60 seconds (or per protocol) | Standard first-line; no HIT; acceptable bleeding risk |
| Regional Citrate | Ionized Ca²⁺ (circuit + systemic) | Circuit iCa: 0.25–0.35 mmol/L; Systemic iCa: 1.12–1.35 mmol/L | High bleeding risk; preferred for prolonged filter life; requires Ca²⁺ replacement |
| Argatroban | aPTT or ACT per protocol | 1.5–3× baseline aPTT | Confirmed or suspected HIT (heparin-induced thrombocytopenia) |
| No anticoagulation | Visual circuit inspection; circuit pressures | TMP < threshold; no visible clot | Unacceptably high bleeding risk (recent surgery, active hemorrhage) |
Nursing Monitoring Intervals
| Parameter | Frequency | Clinical Significance |
|---|---|---|
| Circuit pressures (access, return, TMP) | Continuous (alarm-monitored) | Rising TMP = filter clotting; falling access pressure = catheter kink/positional |
| Fluid balance / net UF | Hourly | Cumulative balance must match prescribed net removal goal |
| Blood pressure / MAP | Continuous (art-line) or q15–30 min | Hypotension = too aggressive net removal; reduce UF rate and notify provider |
| Temperature | Every 1–2 hours | CRRT causes blood cooling; hypothermia common without active warming |
| Potassium (K⁺) | Every 4–6 hours | CRRT clears K⁺ efficiently; hypokalemia is a common complication |
| Ionized Calcium (iCa) | Every 1–2 hours (citrate protocol) | Low systemic iCa = citrate toxicity or insufficient replacement; hypocalcemia risk |
| Phosphorus | Every 6–12 hours | CRRT clears phosphorus; hypophosphatemia can cause weakness, respiratory failure |
| Magnesium | Every 6–12 hours | Cleared by CRRT; hypomagnesemia may cause dysrhythmias and neuromuscular signs |
Common CRRT Alarms and Actions
| Alarm | Common Cause | Nursing Action |
|---|---|---|
| High TMP | Filter clotting from inadequate anticoagulation | Check anticoagulation levels; notify provider; prepare for filter change |
| Low access pressure | Catheter kink, patient position, hypotension | Reposition patient/catheter; check for kinking; assess BP |
| High return pressure | Circuit kink, clot in return line | Inspect return tubing; check for clot; notify RT/provider |
| Air detector alarm | Air in circuit | Immediately clamp circuit; do NOT return blood until air cleared; call provider |
| Blood leak | Filter membrane rupture | Clamp circuit; do not return blood to patient; change circuit; notify provider |
| Low flow / high pressure differential | Catheter dysfunction or clot | Flush catheter per protocol; reposition; consider catheter exchange |
Related Resources
Standards & sources
Fact-checked Jun 20, 2026This page is written to align with Society of Critical Care Medicine (SCCM) · Surviving Sepsis Campaign · American Association of Critical-Care Nurses (AACN). It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →