The acid-base effect of changing citrate solution for regional anticoagulation during continuous veno-venous hemofiltration

Regional Citrate Anticoagulation in Continuous Renal Replacement Therapy: Is Metabolic Fear the Enemy of Logic? A Systematic Review and Meta-Analysis of Randomised Controlled Trials

BACKGROUND

Anticoagulation is recommended to maintain the patency of the circuit in continuous renal replacement therapy (CRRT). However, anticoagulation-associated complications can occur. We performed a systematic review and meta-analysis to compare the efficacy and safety of citrate anticoagulation to heparin anticoagulation in critically ill patients treated with CRRT.

METHODS

Randomised controlled trials (RCTs) evaluating the safety and efficacy of citrate anticoagulation and heparin in CRRT were included. Articles not describing the incidence of metabolic and/or electrolyte disturbances induced by the anticoagulation strategy were excluded. The PubMed, Embase, and MEDLINE electronic databases were searched. The last search was performed on 18 February 2022.

RESULTS

Twelve articles comprising 1592 patients met the inclusion criteria. There was no significant difference between the groups in the development of metabolic alkalosis (RR = 1.46; (95% CI (0.52-4.11); p = 0.470)) or metabolic acidosis (RR = 1.71, (95% CI (0.99-2.93); p = 0.054)). Patients in the citrate group developed hypocalcaemia more frequently (RR = 3.81; 95% CI (1.67-8.66); p = 0.001). Bleeding complications in patients randomised to the citrate group were significantly lower than those in the heparin group (RR 0.32 (95% CI (0.22-0.47); p < 0.0001)). Citrate showed a significantly longer filter lifespan of 14.52 h (95% CI (7.22-21.83); p < 0.0001), compared to heparin. There was no significant difference between the groups for 28-day mortality (RR = 1.08 (95% CI (0.89-1.31); p = 0.424) or 90-day mortality (RR 0.9 (95% CI (0.8-1.02); p = 0.110).

CONCLUSION

regional citrate anticoagulation is a safe anticoagulant for critically ill patients who require CRRT, as no significant differences were found in metabolic complications between the groups. Additionally, citrate has a lower risk of bleeding and circuit loss than heparin.

Comparison of two regional citrate anticoagulation modalities for continuous renal replacement therapy by a prospective analysis of safety, workload, effectiveness, and cost

BACKGROUND

Currently, regional citrate anticoagulation (RCA) is the preferred approach for continuous renal replacement therapy (CRRT), and several RCA protocols are commercially available. This study was aimed at comparing two RCA modalities for CRRT in terms of safety, workload, effectiveness, and costs.

METHODS

We prospectively evaluated two different RCA approaches in patients admitted to our intensive care unit (ICU) who needed CRRT. Patients with acute liver failure were excluded. We compared a hypertonic sodium-citrate solution 136 mmol/L added before the filter as anticoagulant during bicarbonate continuous hemodialysis (RCA-CVVHD) versus citrate-buffered replacement fluid 13.3 mmol/L infused by predilution setting in continuous venovenous hemofiltration (RCA-CVVH). Alkalosis, calcium homeostasis, nursing workload, filter lifespan, urea-creatinine metabolic control, and costs were recorded.

RESULTS

Forty-five and 31 patients who underwent RCA-CVVH and RCA-CVVHD, respectively, were included. Alkalosis-free time distributions were significantly different in favor of a higher alkalosis incidence in the RCA-CVVHD group (log-rank test χ²(1)=8.18, P=0.004). Multivariable analysis showed that RCA-CVVHD was associated with a longer filter lifespan (HR=0.47; 95% CI: 0.28-0.78), higher total cost (1362 CHF [782-1901] vs. 976 CHF [671-1353], P<0.001), and higher number of anticoagulation adjustments (9 [IQR, 4-14] vs. 2 [IQR, 1-4]). The mean urea and creatinine reduction ratios at the first 24 hours were significantly higher in the RCA-CVVHD group. Calcium homeostasis and filter downtime were similar in the two groups.

CONCLUSIONS

Pre-filter hypertonic sodium-citrate solution (136 mmol/L) results in longer filter patency and improves depuration effectiveness. However, compared to RCA-CVVHF, it causes metabolic alkalosis and increases nursing interventions and cost.

Strong ion difference and CVVH: Different response during nadroparin versus citrate anticoagulation

PURPOSE

To determine the effect on strong ion difference of citrate as an anticoagulant during continuous veno-venous hemofiltration (CVVH).

MATERIALS AND METHODS

ICU patients with renal failure and CVVH were included. Patients were treated with either nadroparin (N) or sodium citrate (C) as an anticoagulant. Strong ion difference (SID) apparent (SIDa) and SID effective (SIDe) and strong ion gap (SIG) were calculated at t = 0 and t = 24 h. Citrate concentration was measured in the citrate treated patients.

RESULTS

Ten patients with N and nine with C were included. In both groups the SIDa did not change significantly. SIG decreased significantly with N (11.4 ± 4.2 to 4.0 ± 3.1 meq/l; p = 0.005) but not with C (9.3 ± 1.9 to 8.1 ± 2.4 meq/l; p = 0.097). The decrease was significantly greater for N compared to C; p = 0.014. This is reflected by the SIDe which increased significantly (p = 0.022) more from 24.7 ± 4.5 to 32.9 ± 3.9 (p = 0.005) for N and from 26.3 ± 5.8 to 29.6 ± 1.6 for C (p = 0.058).

CONCLUSION

Citrate anticoagulation results in a persistently high SIG during CVVH compared to nadroparin. This is associated with the presence of unmeasured anions such as citrate in the systemic circulation.

Chloride content of solutions used for regional citrate anticoagulation might be responsible for blunting correction of metabolic acidosis during continuous veno-venous hemofiltration

Background

Citrate, the currently preferred anticoagulant for continuous veno-venous hemofiltration (CVVH), may influence acid-base equilibrium.

Methods

The effect of 2 different citrate solutions on acid-base status was assessed according to the Stewart-Figge approach in two consecutive cohorts of critically ill adult patients. The first group received Prismocitrate 10/2 (PC10/2; 10 mmol citrate/L). The next group was treated with Prismocitrate 18/0 (PC18; 18 mmol citrate/L). Both groups received bicarbonate-buffered fluids in post-dilution.

Results

At similar citrate flow, the metabolic acidosis present at baseline in both groups was significantly attenuated in PC18 patients but persisted in PC10/2 patients after 24 h of treatment (median pH 7,42 vs 7,28; p = 0.0001). Acidosis in the PC10/2 group was associated with a decreased strong ion difference and an increased strong ion gap (respectively 43 vs. 51 mmol/L and 17 vs. 12 mmol/L, PC10/2 vs. PC18; both p = 0.001). Chloride flow was higher in PC10/2 than in PC18 subjects (25.9 vs 14.3 mmol/L blood; p < 0.05).

Conclusion

Correction of acidosis was blunted in patients who received 10 mmol citrate/L as regional anticoagulation during CVVH. This could be explained by differences in chloride flow between the applied citrate solutions inducing hyperchloremic acidosis.

Bench-to-bedside review: Citrate for continuous renal replacement therapy, from science to practice

To prevent clotting in the extracorporeal circuit during continuous renal replacement therapy (CRRT) anticoagulation is required. Heparin is still the most commonly used anticoagulant. However, heparins increase the risk of bleeding, especially in critically ill patients. Evidence has accumulated that regional anticoagulation of the CRRT circuit with citrate is feasible and safe. Compared to heparin, citrate anticoagulation reduces the risk of bleeding and requirement for blood products, not only in patients with coagulopathy, but also in those without. Metabolic complications are largely prevented by the use of a strict protocol, comprehensive training and integrated citrate software. Recent studies indicate that citrate can even be used in patients with significant liver disease provided that monitoring is intensified and the dose is carefully adjusted. Since the citric acid cycle is oxygen dependent, patients at greatest risk of accumulation seem to be those with persistent lactic acidosis due to poor tissue perfusion. The use of citrate may also be associated with less inflammation due to hypocalcemia-induced suppression of intracellular signaling at the membrane and avoidance of heparin, which may have proinflammatory properties. Whether these beneficial effects increase patient survival needs to be confirmed. However, other benefits are the reason that citrate should become the first choice anticoagulant for CRRT provided that its safe use can be guaranteed.

Continuous renal replacement therapy: cause and treatment of electrolyte complications

Continuous renal replacement therapy (CRRT) has become the modality of choice for critically ill patients. Although often hemodynamically better tolerated than intermittent dialysis, the continuous nature of this therapy may cause significant electrolyte complications. These complications commonly result from removal of electrolytes from the body without adequate replacement or because of the use of trisodium citrate as the anticoagulant. Both hypophosphatemia and hypokalemia frequently complicate prolonged treatment. These complications can be avoided by adding these electrolytes to the dialysate or replacement fluid. The use of citrate, especially if this anticoagulant is not used routinely following established protocols, can also result in several electrolyte abnormalities. Because citrate works by chelating calcium, hypo- and hypercalcemia occur because of under- or overreplacement of calcium. Because citrate is a base equivalent, if the bicarbonate concentration of the dialysate or replacement fluid is not decreased, a metabolic alkalosis may develop. Less commonly, in patients with severe liver dysfunction who cannot metabolize citrate back to bicarbonate, a metabolic acidosis may develop. Although CRRT may cause electrolyte complication it also can be the treatment of choice for the correction of certain electrolyte complications. In patients with acute or chronic renal failure who present with significant dysnatremias, intermittent hemodialysis may cause overly rapid correction of the serum sodium with serious neurologic sequelae. The ability to manipulate the sodium concentration of the dialysate or replacement fluid and the more sustained nature of the treatment allows for a slower correction thus avoiding complications.