Bedside Topline

What It Does: Runs blood through a hollow-fiber filter continuously, about 24 hours a day, to remove fluid and solutes in unstable ICU patients.
Key Settings & Targets: Effluent 20–25 mL/kg/hr
Post-filter iCa 0.2–0.4 mmol/L (citrate)
Net UF per order; start low if unstable
Check Every Hour: Access, return and filter pressures; air detector; lines for clots; MAP and vasopressor dose; catheter site and limb; net fluid balance.
Top Alarm → First Move: Access pressure too negative → check kinks, clamps and neck position first, then assess volume.
Never: Override an air alarm. Let a fluid bag run empty. Move the patient without checking every line.
Escalate Now If: MAP falls despite less UF; total:iCa ratio above the KDIGO-cited 2.1 cutoff (local protocol may act sooner); bleeding; or air that cannot be cleared.

Overview & How It Works

Continuous renal replacement therapy (CRRT) is blood purification outside the body, and it runs nonstop. Usually that means 24 hours a day. It stands in for kidney function in critically ill patients with acute kidney injury. The route is simple: blood leaves through a catheter, passes a hollow-fiber filter and goes back to the patient.

Key Components

Component	Where It Sits	What It Does
Dialysis catheter (double-lumen)	Vein: right internal jugular first; femoral, left jugular or subclavian as alternatives	Access lumen takes blood out; return lumen gives it back
Blood pump	Between the access line and the filter	Sets blood flow (Qb); typical 150–250 mL/min for a 70 kg adult
Anticoagulant port	Before the filter (citrate) or systemic (heparin)	Limits clotting in the circuit and filter
Hollow-fiber filter (hemofilter)	Central circuit	Membrane removes water and solutes by diffusion, convection or both
Effluent and replacement lines	Filter outlet and replacement port	Carry dialysate and replacement fluid; remove effluent
Pressure monitors, bubble trap and air detector	Access, pre-filter, effluent and return lines	Detect obstruction, clotting, leaks and air

Flow Path

Blood leaves the patient through the access lumen of the catheter.
The blood pump moves blood through the circuit. Citrate, if used, enters before the filter.
Blood enters the hollow-fiber filter. Dialysate runs on the other side of the membrane, and replacement fluid is added before (pre-dilution) or after (post-dilution) the filter.
Ultrafiltrate and dialysate leave the filter through the effluent line.
Blood passes the bubble trap and returns to the patient through the return lumen.

Key Point: CRRT replaces only part of kidney function. It is gentler on blood pressure than rapid intermittent dialysis, because it removes water and solutes slowly and all the time. Its benefit is steady control. Full replacement is not the point.

Physiology & Hemodynamic Effects

What It Does

Parameter	Effect	Why It Matters
Small solutes (urea, K⁺, phosphate)	↓ Continuous clearance	Smoother levels than intermittent dialysis; phosphate loss is a recurring problem
Water removal (net ultrafiltration)	↓ Slow, steady removal	Fewer rapid osmotic and volume shifts than intermittent hemodialysis
Blood pressure	↔ or ↑ tolerance	KDIGO 2012 suggests CRRT over intermittent therapy in hemodynamically unstable patients (2B)
Phosphate	↓ Serum phosphate	Hypophosphatemia was common in RENAL: 54% (lower intensity) and 65% (higher intensity)
Acid–base	↑ Bicarbonate	Bicarbonate-buffered fluids are preferred over lactate (KDIGO 2C); citrate is metabolized to bicarbonate
Core temperature	↓ Heat loss	The extracorporeal circuit cools blood; hypothermia worsens coagulopathy and arrhythmia risk
Drug levels	↑ Clearance of many drugs	Dose and interval changes are needed; pharmacy must review each new drug

What It Depends On

Access and blood flow: catheter position and Qb set both clearance and filter life.
Prescription: effluent rate, replacement and dialysate volumes, and net ultrafiltration
Anticoagulation: filter clotting is the main limit on delivered dose
Patient factors: volume status, perfusion, sepsis, liver function and drug therapy

Solute Transport Mechanisms

Diffusion: solutes slide down a concentration gradient across the membrane, against the dialysate flow. It works best for small solutes such as urea and K⁺.
Convection: transmembrane pressure pulls water across the membrane, and the water takes solutes along. It clears middle-sized molecules better than diffusion.
Adsorption: some solutes stick to the membrane. That capacity is limited, and it drops as the membrane fills up.

What CRRT Does Not Replace

CRRT does not replace the kidney's hormone jobs: erythropoietin, activation of vitamin D and renin. It cannot fine-tune tubular transport either. What it does is hold the patient steady while the native kidney recovers, or until another therapy is chosen.

Clinical Pearl: Diffusion is tea steeping. Solute moves down its concentration gradient. Convection is water pulled through coffee grounds, and the solvent drags solutes along with it.

Types, Modes & Configurations

Every mode mixes diffusion and convection in a different ratio. The fluid streams tell you which mix you're running.

Mode	Main Mechanism	Fluid Streams	Best For	Key Limitation
SCUF (slow continuous ultrafiltration)	Convection only	Ultrafiltrate; no dialysate or replacement	Fluid removal when solute clearance is not needed	Little solute clearance (urea clearance 1–5 mL/min, KDIGO Table 21)
CVVH (continuous venovenous hemofiltration)	Convection	Replacement fluid (pre- or post-filter) plus ultrafiltrate	Solute and fluid removal by convection	Large replacement volumes (about 1,500–2,000 mL/hr at 70 kg, KDIGO Table 21)
CVVHD (continuous venovenous hemodialysis)	Diffusion	Dialysate plus ultrafiltrate	Small-solute clearance such as K⁺ and urea	Less convective clearance than CVVH or CVVHDF
CVVHDF (continuous venovenous hemodiafiltration)	Diffusion plus convection	Dialysate, replacement and ultrafiltrate	Both small and middle-molecule clearance	Effluent about 36–72 L/day at 70 kg is the KDIGO Table 21 equipment range, not a dose target. Prescribe 20–25 mL/kg/hr (about 34–42 L/day at 70 kg); more complex fluid balance

Pre-Dilution and Post-Dilution

In pre-dilution, replacement fluid goes in before the filter. That lowers blood viscosity and cuts hemoconcentration, which helps the filter last longer (KDIGO 2012 lists predilution among strategies to prolong filter survival). In post-dilution, replacement goes in after the filter. It gets more out of each liter of replacement. The catch: the blood is more concentrated inside the filter. Follow the prescription your team has ordered.

CRRT vs Intermittent Hemodialysis vs SLED

Feature	CRRT	SLED (sustained low-efficiency dialysis)	IHD (intermittent hemodialysis)
Schedule	Continuous, about 24 hours a day	Extended session of several hours	Sessions of several hours, several times a week
Solute removal	Slow, steady	Slower than IHD	Rapid
Hemodynamic tolerance	Best tolerated in unstable patients	Comparable to CRRT in one small study	More hypotension with rapid fluid removal
Blood flow (70 kg, KDIGO Table 21)	150–250 mL/min	100–300 mL/min	200–300 mL/min
Dialysate flow (70 kg, KDIGO Table 21)	CVVHD 1,500–2,000 mL/hr; CVVHDF 1,000–1,500 mL/hr (KDIGO Table 21)	100–300 mL/min	300–500 mL/min

Note: KDIGO 2012 suggests CRRT over standard intermittent therapy for hemodynamically unstable patients (2B). Once the patient is stable, treatment may move to standard IHD. SLED is an option where CRRT is not available. The comparative data are thin, though.

Indications, Contraindications & Evidence

Guideline currency: this KDIGO AKI guideline is from 2012, so check for updates and your local protocol.

Indications

Life-threatening fluid, electrolyte or acid–base change: start emergently (KDIGO 5.1.1). Think refractory hyperkalemia, severe acidemia, pulmonary edema, or uremic complications such as pericarditis or bleeding.
Fluid overload not controlled by diuretics: Especially with hemodynamic instability, CRRT is the preferred choice (KDIGO 5.6.2, 2B).
Acute brain injury or raised intracranial pressure: For this, KDIGO suggests CRRT over intermittent therapy (5.6.3, 2B).
Uremia or solute control: Trend and clinical context matter more than the BUN number alone (KDIGO 5.1.2). AKIKI2 used a BUN above 112 mg/dL as a late threshold.
Selected poisonings: For dialyzable toxins such as lithium, salicylates and metformin-associated lactic acidosis, intermittent hemodialysis is preferred (EXTRIP workgroup). CRRT is an acceptable alternative when hemodialysis is unavailable. It is often the choice when the patient is too unstable for intermittent therapy. Decide with toxicology and nephrology.

Timing

No life-threatening indication? The timing trials disagree on the details, but they agree on one point. Waiting too long does not help. In AKIKI, the delayed strategy avoided RRT in 49% of patients, with no mortality penalty. In STARRT-AKI, starting early (within 12 hours of eligibility) did not lower 90-day mortality, and survivors were more often still dependent on RRT. In AKIKI2, postponing RRT beyond oliguria for more than 72 hours or a BUN above 112 mg/dL gave no benefit and possible harm.

Contraindications

No fixed absolute contraindication to CRRT itself is established. Three practical limits matter: access, bleeding risk and goals of care.

Relative Contraindications and Cautions

Access: inability to place a catheter safely, anatomic problems, or vascular injury
Bleeding: active uncontrolled bleeding, especially when systemic anticoagulation is also needed
Heparin: heparin is contraindicated in heparin-induced thrombocytopenia (HIT); use a non-heparin alternative
Goals of care: inconsistent with prolonged, resource-intensive support; discuss with the family and team

Citrate Contraindications (KDIGO)

Shock with poor muscle perfusion, where citrate metabolism is impaired
Severe liver failure or severe cirrhosis, where citrate accumulates
No established protocol: KDIGO recommends citrate only in centers with a protocol for it

Warning: Shock with poor perfusion, or severe liver failure, is where citrate turns dangerous. It can build up to toxic levels. Use heparin or another non-citrate strategy. Check the total:ionized calcium ratio closely.

Limitations

CRRT needs nursing intensity. It immobilizes the patient and prolongs anticoagulation exposure (KDIGO Table 22).
Continuous therapy brings more hypothermia risk and higher cost (KDIGO Table 22).
Higher doses did not improve survival in the ATN and RENAL trials. More effluent is not a goal in itself.

Key Evidence

Trial / Guideline (Year)	Population	Bottom Line
KDIGO 2012 AKI guideline	All AKI settings	Deliver 20–25 mL/kg/hr effluent (1A); CRRT for unstable patients (2B); citrate over heparin when not contraindicated (2B)
ATN (2008)	Critically ill AKI	Intensive (CVVHDF 35 mL/kg/hr or equivalent) vs less intensive (20 mL/kg/hr): 60-day death 53.6% vs 51.5%; no survival benefit
RENAL (2009)	1,508 critically ill AKI on CVVHDF	Effluent 40 vs 25 mL/kg/hr: 90-day death 44.7% in each group; more hypophosphatemia with the higher dose
AKIKI (2016)	Severe AKI, early vs delayed start	60-day death 48.5% vs 49.7%; 49% of the delayed group never needed RRT
STARRT-AKI (2020)	Severe AKI, accelerated vs standard start	90-day death 43.9% vs 43.7%; RRT dependence among survivors 10.4% vs 6.0%
AKIKI2 (2021)	Severe AKI with oliguria or high BUN	Postponing beyond oliguria over 72 hours or BUN above 112 mg/dL gave no benefit and possible harm
RICH (2020)	596 completed; citrate vs heparin	Citrate: median filter life 47 vs 26 hours; 90-day death 51.2% vs 53.6% unadjusted (underpowered); adjusted hazard ratio 0.79 (95% CI 0.63–1.004), borderline; bleeding 5.1% vs 16.9%; 34 of 38 secondary endpoints showed no difference

Setup, Settings & Targets

Targets, settings and limits must agree with the hero, the glance card, Alarms and Complications. Values marked typical depend on protocol. Follow institutional protocol and nephrology orders.

Parameter	Typical Target	If Below	If Above
Effluent dose	20–25 mL/kg/hr delivered (KDIGO 1A)	Under-dialysis: increase the prescription (KDIGO notes a higher prescription is usually needed)	Higher doses (35–40 mL/kg/hr in ATN and RENAL) did not improve survival; check the delivered dose and electrolytes
Net ultrafiltration (UF_net)	Per order, titrated to fluid balance and MAP	Positive balance: increase UF if hemodynamics allow	Hypotension or poor perfusion: reduce UF first
Post-filter iCa (citrate)	0.2–0.4 mmol/L (KDIGO); many protocols aim 0.25–0.35 mmol/L	Too much citrate: reduce citrate rate per protocol	Inadequate anticoagulation: increase citrate rate per protocol
Systemic iCa (citrate)	1.1–1.3 mmol/L (4.4–5.2 mg/dL), normal range (KDIGO)	Replace calcium per protocol (see calcium chloride)	Reduce calcium replacement per protocol
Total:ionized calcium ratio	Below 2.1 (KDIGO-cited detection cutoff; many protocols set a higher action level; follow local protocol)	—	Citrate accumulation: reduce citrate per protocol and reassess; check liver function and acid–base
aPTT (heparin)	45–60 seconds (RICH heparin arm)	Increase heparin per protocol	Reduce heparin per protocol; check for bleeding

Initial Settings

Blood flow (Qb): 150–250 mL/min for a 70 kg adult (KDIGO Table 21, typical; follow institutional protocol). Low flow means more clotting.
Dialysate and replacement: for CVVHDF at 70 kg, typically 1,000–1,500 mL/hr each (KDIGO Table 21). Bicarbonate is the preferred buffer (KDIGO 5.7.1, 2C)
Net UF: start low in unstable patients, then titrate upward as tolerated
Anticoagulation: Set per the anticoagulation section. Regional citrate is suggested over heparin when no citrate contraindication exists (KDIGO 5.3.2.2).
Temperature: use the circuit warmer per protocol and monitor core temperature

Sizing & Positioning

Ultrasound guidance for catheter insertion (KDIGO 5.4.3, 1A)
Site preference: right internal jugular first, then femoral, left internal jugular, and subclavian last (KDIGO 5.4.2, not graded)
Chest radiograph after internal jugular or subclavian placement and before first use (KDIGO 5.4.4, 1B)
Pediatric catheter size is weight-based: 7 Fr for 3–6 kg and 8 Fr double-lumen for 6–30 kg (KDIGO Table 20)

Effluent rate (check your machine's definition)

Effluent (mL/hr) = dialysate + replacement + UF_net

Calculations & Derived Values

Effluent dose

Effluent dose (mL/kg/hr) = effluent rate (mL/hr) ÷ weight (kg)

Net ultrafiltration

UF_net (mL/hr) = effluent rate − (dialysate + replacement)

Total:ionized calcium ratio

Ratio = total calcium (mmol/L) ÷ ionized calcium (mmol/L)

Variable	Formula	Target	Why You Care
Effluent dose	Effluent ÷ weight	20–25 mL/kg/hr (KDIGO 1A)	Delivered dose; check actual, not just ordered
Net UF	Effluent − (dialysate + replacement)	Per order	Sets the daily fluid balance
Total:iCa ratio	Total Ca ÷ ionized Ca	Below 2.1 (KDIGO-cited detection cutoff; protocol may set a different action level)	Rising value suggests citrate accumulation
Pressure drop (P-drop)	Pre-filter pressure − post-filter (return) pressure	Trend, not one number	A rising P-drop signals clotting in the filter

Clinical Pearl: Run the numbers on a 70 kg patient at 25 mL/kg/hr: that is 1,750 mL/hr of effluent. With dialysate at 1,000 mL/hr and replacement at 650 mL/hr, net UF comes to 100 mL/hr, about 2.4 L/day (arithmetic example, not a UF recommendation). Compare that with the daily I&O at the bedside.

Waveforms & Console Interpretation

Normal

Access pressure: negative, like suction. It moves with neck and body position.
Return pressure: positive. It rises when the return path meets resistance.
Pre-filter and effluent pressures: steady. The P-drop trend stays stable over hours.
Air detector and bubble trap: no air or blood in the air chamber

Abnormal Patterns

Pattern	What You See	Cause	Fix
Access pressure too negative	Access alarm; blood flow falls	Catheter malposition, kink, hypovolemia or a clot at the tip	Check kinks, clamps and neck position; reposition the patient; assess volume; flush per protocol
Return pressure high	Return alarm; resistance in the return line	Kink, clot in the venous chamber or filter, high central venous pressure	Inspect the line and chamber; review anticoagulation; reposition
Rising TMP and P-drop	P-drop climbs steadily; filter darkens; short filter life	Fibrin or protein clogging the membrane	Review anticoagulation and blood flow; avoid excess UF; plan a circuit change per protocol
Air detector alarm	Air in the line; pump stops	Empty bag, loose connection or air in the line	Stop per protocol; clamp; clear air; resume only after the cause is fixed
Blood leak alarm	Blood detected in the effluent line	Filter membrane breach or a connection leak	Stop the circuit; inspect the filter and lines; call the team

Warning: Never override the air detector. Air means stop, clamp and fix the cause. Restart only after that.

Monitoring & Ongoing Care

Frequency	What to Check	Expected / Action
Hourly	Access, return and filter pressures; P-drop trend; air detector; lines for clots; blood and effluent rates; MAP; vasopressor dose; catheter site and limb	Stable pressures and MAP. Act on any trend toward clotting, air or hypotension
Per protocol	Post-filter and systemic iCa; total calcium; K⁺, phosphate, Mg²⁺, sodium and bicarbonate	Within targets. Replace phosphate and potassium per protocol
Every 12–24 hours	CBC and platelets, aPTT, lactate, creatinine trend, liver tests (citrate risk)	A falling platelet count on heparin raises HIT concern; see Anticoagulation
Daily	Weight, net fluid balance, urine output, drug doses reviewed with pharmacy, mobility and skin	Balance matches the goal; doses adjusted for the current effluent rate

Positioning & Mobility

The circuit and the catheter limit movement. Secure the catheter and lines before you turn the patient. Check for kinks after every move. Immobility is a known downside of CRRT (KDIGO Table 22), so plan repositioning and early mobility with the team.

Clinical Pearl: The fluid balance on CRRT can look tidy. Totals alone can hide a slow positive balance. Track weight, the trend and the I&O together.

Anticoagulation & Hematology

Two things decide how much of the prescribed dose you deliver: filter life and anticoagulation. KDIGO 2012 suggests regional citrate over heparin when citrate is not contraindicated (2B). For patients at high bleeding risk, it suggests citrate over no anticoagulation (2C).

Strategy / Agent	Typical Target	Monitoring	Watch For
Regional citrate High-alert	Post-filter iCa 0.2–0.4 mmol/L; systemic iCa 1.1–1.3 mmol/L	Post-filter and systemic iCa; total:iCa ratio; acid–base	Citrate accumulation (ratio above the KDIGO-cited 2.1 cutoff or the protocol action level), hypocalcemia, metabolic alkalosis or acidosis; liver failure and shock raise risk
Unfractionated heparin High-alert	aPTT 45–60 seconds (RICH heparin arm)	aPTT per protocol (see the aPTT page)	Bleeding; HIT; shorter filter life than citrate
Argatroban or bivalirudin High-alert	Per pharmacy protocol	aPTT per protocol	Non-heparin alternatives in HIT; KDIGO suggests argatroban without severe liver failure (2C); argatroban is cleared by the liver
No anticoagulation	Not a target	Frequent circuit checks	Shorter filter life; reserved for very high bleeding risk

Citrate Data

In the RICH trial, filter life favored citrate: a median of 47 hours against 26 hours with heparin. Bleeding complications were 5.1% with citrate and 16.9% with heparin. New infections were more frequent with citrate (68.0% vs 55.4%). The trial was stopped early, and it was not powered for mortality.

Heparin-Induced Thrombocytopenia

Stop all heparin, including heparin lock solutions for other catheters, as KDIGO advises
Use a non-heparin anticoagulant. KDIGO recommends a direct thrombin or factor Xa inhibitor (1A) and suggests argatroban in HIT without severe liver failure (2C). With severe liver failure, choose another non-heparin agent with pharmacy. Dosing is set by pharmacy and the HIT protocol
Platelets: a fall in count during heparin exposure needs urgent review; see the platelets page

Bleeding & Filter Clotting

Anticoagulation is a balance between bleeding and clotting. Push it too far one way and the patient bleeds. Push it the other way and the filter clots. If filters clot early, check access, blood flow and anticoagulation before changing the modality.

Warning: Citrate accumulation can cause hypocalcemia and metabolic acidosis. Those can show up as arrhythmia or hypotension. Watch for a rising total:ionized ratio. When it climbs, check iCa and acid–base right away, and call the team.

Key Medications & Drug Considerations

Medication	Role Here	Typical Target / Dose	Device-Specific Notes
Heparin High-alert	Systemic anticoagulant (alternative to citrate)	aPTT 45–60 seconds (RICH); dose per protocol	Stop all heparin in HIT. See the heparin page
Trisodium citrate High-alert	Regional anticoagulant, infused before the filter	Post-filter iCa 0.2–0.4 mmol/L (KDIGO); rate per protocol	Accumulates in shock and severe liver failure; systemic calcium must be replaced
Calcium chloride High-alert	Replaces systemic calcium lost to citrate	Systemic iCa 1.1–1.3 mmol/L (KDIGO); rate per protocol	Concentrated. See the calcium chloride page
Phosphate replacement High-alert	Treats hypophosphatemia on CRRT	Per protocol and pharmacy	Phosphate-containing replacement solution was associated with less hypophosphatemia in one cohort
Sodium bicarbonate	Buffer in dialysate and replacement fluid	Per prescription; bicarbonate preferred over lactate (KDIGO 5.7.1)	Alkalosis risk with bicarbonate or citrate metabolism. See the sodium bicarbonate page
Vancomycin	Antibiotic	Dose set by pharmacy for CRRT	Clearance changes with effluent rate; antibiotic regimens need CRRT-specific dosing (see the vancomycin page)
Levetiracetam	Antiseizure drug	Dose set by pharmacy for CRRT	Cleared by CRRT; pharmacy sets the dose. See the levetiracetam page

Antibiotic dosing on CRRT is protocol-driven, and pharmacy should set it. The first (loading) dose goes in at full dose, and later doses are adjusted for kidney function and effluent rate. A 2025 Intensive Care Medicine study (see References) simulated a full initial loading dose in every CRRT scenario. The Surviving Sepsis Campaign recommends that loading dose before a prolonged beta-lactam infusion. Another 2025 Intensive Care Medicine paper covers optimized meropenem and piperacillin–tazobactam regimens in patients on renal replacement therapy (see References).

Note: Doses vary by protocol; follow local protocols and medical direction. Each drug's dose change depends on the modality and the effluent rate.

Alarms & Troubleshooting

Alarm / Problem	What You See	Likely Causes	First Actions
Access pressure too negative	Access alarm; falling blood flow	Kink, catheter malposition, hypovolemia, clot in the catheter	1) Check kinks, clamps and neck position. 2) Reposition. 3) Assess volume. 4) Flush per protocol. 5) Call nephrology if it persists
Return pressure high	Return alarm	Kink, clot in the venous chamber, high central venous pressure	1) Check the return line for kinks. 2) Inspect the chamber for clot. 3) Review anticoagulation. 4) Call the team
Filter pressure high or P-drop rising	Pressure alarm; darkening filter	Clot or protein in the filter; excess UF with low flow	1) Check anticoagulation and blood flow. 2) Reduce UF. 3) Plan the circuit change per protocol
Air detector alarm	Air in the line; pump stops	Empty bag, loose connection, air source	1) Stop per protocol and clamp. 2) Clear the air. 3) Resume only after the cause is fixed
Blood leak alarm	Blood in the effluent line	Filter membrane breach or connection leak	1) Stop the circuit per protocol. 2) Inspect filter and lines. 3) Call the team
Hypotension during therapy	MAP falling; patient looks unwell	UF too fast, sepsis, vasodilation, hypothermia	1) Reduce UF. 2) Assess volume and perfusion. 3) Give vasopressor per order. 4) Check temperature

Never: silence or override an air alarm. Never run the pump against a closed clamp. Never leave the circuit without a plan to stop or return blood. Never move the patient without checking every line.

Clinical Pearl: Patient first, then circuit. Start with perfusion and mental status. After that, follow the tubing, then the console, then the settings.

Complications & Red Flags

Complication	How You Recognize It	Immediate Action	Prevention
Insertion: pneumothorax or malposition	Dyspnea, falling oxygenation, abnormal chest film	Stop use; call the team; obtain a chest film	Ultrasound guidance and a chest radiograph before first use (KDIGO 5.4.3, 5.4.4)
Air embolism	Air alarm; sudden hypotension, arrhythmia or hypoxia	Stop and clamp; follow the institutional air-embolism protocol	Air detectors; secure connections; no open lines
Bleeding	Site or GI bleeding; falling hemoglobin; hypotension	Pressure to site; call the team; review anticoagulation	Use citrate when not contraindicated (RICH bleeding 5.1% vs 16.9%)
Hypotension	MAP falling with UF	Reduce UF; assess volume; give vasopressor per order	Start with low UF and titrate
Citrate accumulation	Total:iCa ratio above the KDIGO-cited 2.1 cutoff or protocol action level; hypocalcemia; acidosis; hypotension	Reduce citrate per protocol and reassess; replace calcium per protocol; check acid–base and liver	Avoid citrate in shock or severe liver failure
Hypophosphatemia, hypomagnesemia and hypokalemia	Low serum phosphate, Mg²⁺ or K⁺ on labs; weakness, arrhythmia	Replace per protocol; recheck	Check electrolytes per protocol; use phosphate-containing replacement fluid
Hypothermia	Falling core temperature	Warm the patient; check the circuit warmer	Monitor temperature; use circuit warmer per protocol
Catheter infection or thrombosis	Fever; site redness; arm or neck swelling	Culture; call the team; remove per protocol	Sterile technique; minimize line manipulation

Red Flags: Call Immediately

Sudden hypotension not relieved by reducing UF
Air that cannot be cleared from the circuit or the patient
Catheter dislodgement or uncontrolled bleeding
New arrhythmia with low calcium or high potassium
Rising total:iCa ratio above the KDIGO-cited cutoff with shock or severe liver disease

Emergencies: Arrest, Power Loss & Device Failure

Cardiac Arrest on CRRT

Start CPR and ACLS per current guidelines. The circuit does not change the resuscitation algorithm.
Pause the blood pump and clamp access and return lines per protocol. If on regional citrate, stop citrate and calcium infusions per protocol and recheck iCa when the circuit restarts. Return blood if the device protocol directs.
Check iCa and K⁺ early. Hypocalcemia from citrate and hyperkalemia are both reversible causes.
Call nephrology and the ICU team. Resume CRRT only on physician order after return of circulation.

Power or Console Failure

Confirm the alarm and the cause. Check the wall outlet, battery and console.
Clamp access and return lines per protocol. If on regional citrate, stop citrate and calcium infusions per protocol.
Return blood per the device manual or protocol. Do not leave blood static in the circuit beyond the protocol time.
Call the team and document the downtime.

Catheter Dislodgement or Bleeding

Apply firm direct pressure to the site and call for help.
Clamp both catheter lumens per protocol.
Do not reinsert the catheter unless trained and authorized (ICU or nephrology).
Monitor vital signs and the site; treat hypotension per order.

Air in the Circuit or Patient

Stop the pump and clamp lines per protocol.
Position the patient per the institutional air-embolism protocol.
Give oxygen and call for help. Treat arrest per ACLS if it occurs.
Clear the air from the circuit only after the cause is fixed.

Weaning & Discontinuation

Readiness Criteria

Hemodynamically stable with vasopressors weaned to low or no dose
Urine output and creatinine trend that suggest kidney recovery (per nephrology)
Acid–base and electrolytes controlled without CRRT
Underlying cause treated

Weaning Steps

Reduce net UF and effluent as hemodynamics allow, per the nephrology plan.
Once hemodynamically stable, switch to standard intermittent dialysis as KDIGO suggests.
Monitor urine output, creatinine, potassium and acid–base after each change.
Stop CRRT when kidney recovery is established and no further support is needed.

Failure Criteria: Step Back Up

Recurrent hypotension with fluid removal
Rising creatinine or falling urine output
Fluid overload, hyperkalemia or acidemia that returns

Removal & Post-Removal Care

Remove the catheter per protocol. Then check hemostasis and the site. Watch for bleeding, and for limb or site complications.

Protocol Varies: Each institution and each nephrology team sets its own timing and method for stopping CRRT. Follow the local protocol.

Transport Considerations

Before You Move

Confirm the transfer is safe with the ICU or nephrology team.
Check the device battery and backup power per the device protocol.
Secure all lines, bags and the catheter. Check that clamps are in place and labeled.
Know the blood-return procedure before you move.
Carry spare bags, clamps and the device manual.
Brief the receiving team on the modality, anticoagulant and recent alarms.

If You Are Not the Device Specialist

Watch: catheter position, line kinks, blood color in the lines, and the patient's MAP
Never touch: console settings, clamps or connections outside your training
Call: the CRRT nurse or nephrology for any alarm
Air alarm: stop the transport if safe, and call for help
Cardiac arrest: start CPR and ACLS; the circuit is paused per protocol

During Transport

Keep CRRT running when the transport team and the device allow it. If it pauses, document the time and the plan to restart. On regional citrate, stop citrate and calcium infusions per protocol, and recheck iCa before restart. Kinks are the enemy: prevent them and keep the catheter secured.

Air Medical & Altitude

Air transport needs a CRRT device cleared for flight by both the manufacturer and the transport service. Gas in a closed system expands as altitude rises (Boyle's law). That is why you check the air traps and bag fill per protocol.

Handoff

Modality and prescription: effluent, net UF, dialysate and replacement rates
Anticoagulant and the latest iCa or aPTT results
Recent alarms, clots, air or downtime
Catheter site, limb checks and bleeding
Hemodynamics, vasopressor dose and net fluid balance
Goals of care and the plan for CRRT

Transport Pearl: Before you move, confirm the modality and the fluids running. The receiving team needs two things: which streams are on, and what the last iCa was.

Special Populations

Pediatric & Neonatal

Pediatric nephrology sets CRRT settings, anticoagulation and catheter size. All three are based on weight or body-surface area. KDIGO notes that standardized heparin and citrate protocols are well established in children. Catheter size follows weight: 7 Fr for 3–6 kg, and 8 Fr double-lumen for 6–30 kg (KDIGO Table 20).

Pediatric drug doses run on weight. Start with weight-based dosing, and for pediatric shock, see pediatric shock.

Liver Failure & Shock

Citrate is not recommended in shock or severe liver failure, because it builds up there. When citrate is contraindicated, KDIGO suggests unfractionated or low-molecular-weight heparin (5.3.2.3, 2C).

Pregnancy

This page does not cover pregnancy-specific CRRT guidance. Nephrology and obstetric teams make those decisions together.

Note: Confirm every pediatric catheter and dose with the pediatric nephrology protocol and pharmacy before use.

Bedside Pearls & Teaching Script

Systematic Walk-Through

Indication: why CRRT rather than intermittent therapy: instability, fluid, potassium, acid–base or uremia?
Modality: SCUF, CVVH, CVVHD or CVVHDF? Which fluids are dialysate, replacement or ultrafiltrate?
Prescription: effluent dose in mL/kg/hr; net UF in mL/hr; actual delivered dose
Anticoagulation: citrate or heparin? Which labs are being watched?
Circuit: access, return and filter pressures, the P-drop trend, and the air detector
Patient: MAP, perfusion, electrolytes, acid–base and today's goal

Pearls

Higher doses in ATN and RENAL did not improve survival. Target 20–25 mL/kg/hr, not the maximum.
Phosphate washes out on CRRT. Ask about phosphate replacement at every lab check.
Citrate needs a total:ionized calcium check. A rising ratio is the earliest warning.
Anticoagulation, blood flow and access matter most for filter life.
Ask pharmacy for a CRRT dose on every new drug

Teaching Tip: Walk the circuit from the patient's catheter. Follow the blood through the pump, the filter and back to the return. Then trace the dialysate and replacement fluids. Learners find the whole system easier to grasp this way.

References

Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group. (2012). KDIGO clinical practice guideline for acute kidney injury. Kidney International Supplements, 2(1), 1–138. https://kdigo.org/wp-content/uploads/2016/10/KDIGO-2012-AKI-Guideline-English.pdf
VA/NIH Acute Renal Failure Trial Network. (2008). Intensity of renal support in critically ill patients with acute kidney injury (ATN trial). New England Journal of Medicine, 359, 7–20. https://doi.org/10.1056/NEJMoa0802639
RENAL Replacement Therapy Study Investigators. (2009). Intensity of continuous renal-replacement therapy in critically ill patients (RENAL trial). New England Journal of Medicine, 361, 1627–1638. https://doi.org/10.1056/NEJMoa0902413
Gaudry, S., Hajage, D., Schortgen, F., et al. (2016). Initiation strategies for renal-replacement therapy in the intensive care unit (AKIKI trial). New England Journal of Medicine, 375, 122–133. https://doi.org/10.1056/NEJMoa1603017
STARRT-AKI Investigators. (2020). Timing of initiation of renal-replacement therapy in acute kidney injury. New England Journal of Medicine, 383, 240–251. https://doi.org/10.1056/NEJMoa2000741
Gaudry, S., Hajage, D., Martin-Lefevre, L., et al. (2021). Comparison of two delayed strategies for renal replacement therapy initiation for severe acute kidney injury (AKIKI 2). The Lancet, 397, 1293–1300. https://doi.org/10.1016/S0140-6736(21)00350-0
Zarbock, A., Küllmar, M., Kindgen-Milles, D., et al. (2020). Effect of regional citrate anticoagulation vs systemic heparin anticoagulation during continuous kidney replacement therapy on dialysis filter life span and mortality among critically ill patients with acute kidney injury (RICH trial). JAMA, 324(16), 1629–1639. https://doi.org/10.1001/jama.2020.18618
Thompson Bastin, M. L., Adams, P. M., Nerusu, S., Morris, P. E., Mayer, K. P., & Neyra, J. A. (2022). Association of phosphate containing solutions with incident hypophosphatemia in critically ill patients requiring continuous renal replacement therapy. Blood Purification, 51(2), 122–129. https://doi.org/10.1159/000514418
Roberts, J. A., Ulldemolins, M., Liu, X., et al. (2025). Meropenem and piperacillin/tazobactam optimised dosing regimens for critically ill patients receiving renal replacement therapy. Intensive Care Medicine, 51, 1628–1640. https://doi.org/10.1007/s00134-025-08067-w
Decker, B. S., Goldfarb, D. S., Dargan, P. I., et al. (2015). Extracorporeal treatment for lithium poisoning: Systematic review and recommendations from the EXTRIP workgroup. Clinical Journal of the American Society of Nephrology, 10(5), 875–887. https://doi.org/10.2215/CJN.10021014
Juurlink, D. N., Gosselin, S., Kielstein, J. T., et al. (2015). Extracorporeal treatment for salicylate poisoning: Systematic review and recommendations from the EXTRIP workgroup. Annals of Emergency Medicine, 66(2), 165–181. https://doi.org/10.1016/j.annemergmed.2015.03.031
Calello, D. P., Liu, K. D., Wiegand, T. J., et al. (2015). Extracorporeal treatment for metformin poisoning: Systematic review and recommendations from the Extracorporeal Treatments in Poisoning Workgroup. Critical Care Medicine, 43(8), 1716–1730. https://doi.org/10.1097/CCM.0000000000001002

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For Educational Purposes Only: This content is intended for educational reference and should not be used for clinical decision-making.
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Continuous Renal Replacement Therapy (CRRT)