Does CRRT Remove Lactate?
Yes, CRRT does remove lactate through both convective and diffusive mechanisms, but the clinical significance of this removal is limited because the rate of lactate clearance by the filter is typically negligible compared to the rate of lactate production in critically ill patients with lactic acidosis.
Mechanisms of Lactate Removal
CRRT removes lactate through two primary mechanisms depending on the modality used:
- Convective clearance occurs during continuous venovenous hemofiltration (CVVH), where lactate is removed with ultrafiltrate production 1
- Diffusive clearance occurs during continuous venovenous hemodialysis (CVVHD), where lactate moves across the membrane down a concentration gradient 1
- Combined clearance occurs during continuous venovenous hemodiafiltration (CVVHDF), utilizing both mechanisms 1
Quantitative Evidence of Lactate Clearance
The actual amount of lactate removed by CRRT is measurable but clinically modest:
- Filter lactate clearance increases with higher CVVH doses (from 9.36 mmol/h at 20 ml/kg/h to 16.52 mmol/h at 45 ml/kg/h), and also increases with higher initial lactate levels 2
- In one case report using high-volume hemofiltration at 7 L/h (58 mL/kg/h), lactate clearance was calculated at only 79 mL/min—a rate considered quite small compared to lactate overproduction rates in septic shock 3
- The lactate sieving coefficient remains consistent across different CVVH doses and initial lactate levels, indicating predictable removal characteristics 2
Clinical Implications and Limitations
The critical limitation is that CRRT-mediated lactate removal is insufficient to treat severe lactic acidosis as a primary mechanism:
- High-volume hemofiltration is not effective for severe lactic acidosis, and lactic acidosis alone should not be considered a nonrenal indication for CRRT 3
- Treatment of lactic acidosis must focus on correcting underlying causes and optimizing oxygen delivery to tissues, not on extracorporeal removal 3
Buffer Solution Considerations
An important caveat when using lactate-buffered replacement fluids:
- Bicarbonate is preferred over lactate as a buffer in patients with lactic acidosis and/or liver failure because lactate-buffered fluids can worsen acidosis in these populations 1
- Either lactate or bicarbonate can be used as buffer in most CRRT patients without lactic acidosis 1
- Bicarbonate is also preferred in high-volume hemofiltration 1
- The KDIGO guidelines recommend bicarbonate over lactate as a buffer in dialysate and replacement fluid for CRRT in patients with acute kidney injury 4, 5
Practical Recommendation
While CRRT does technically remove lactate from the circulation, do not initiate or escalate CRRT with the expectation of meaningfully treating lactic acidosis through lactate removal alone. Focus instead on addressing the underlying cause of lactate production and ensuring adequate tissue perfusion 3.