Low-dose Citrate Continuous Veno-venous Hemofiltration (CVVH) and Acid-base Balance

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.

Continuous venovenous haemofiltration with citrate-buffered replacement solution is safe and efficacious in patients with a bleeding tendency: a prospective observational study

Background

There is ongoing controversy concerning optimum anticoagulation and buffering in continuous venovenous haemofiltration (CVVH). Regional anticoagulation with trisodium citrate also acting as a buffer in the replacement fluid has several advantages and disadvantages over prefilter citrate administration alone. We analysed a large cohort of patients with acute kidney injury (AKI) treated by the former method and hypothesized that it is safe and efficacious.

Methods

Patients admitted at the intensive care unit with AKI and a high bleeding risk, without exclusion of liver disease, treated by CVVH with citrate in a custom-made replacement solution were prospectively included. Patient and CVVH characteristics, including citrate accumulation, were evaluated in outcome groups. A standardized mortality rate (SMR) was calculated using the simplified acute physiology score II.

Results

Ninety-seven patients were included; metabolic control was adequate and did not differ between outcome groups, apart from lower pH/bicarbonate in non-survivors. Citrate accumulation was proven in 9% and was timely identified. These patients had about threefold higher plasma transaminases and higher CVVH dose and mortality. The hospital mortality was 60% with a SMR of 1.1 (95% confidence interval 0.90-1.40): age and hyperlactatemia, rather than CVVH-characteristics and citrate accumulation, predicted mortality in multivariable analysis.

Conclusion

In critically ill, patients with AKI at high risk of bleeding, CVVH with citrate-containing replacement solution is safe and efficacious. The risk for citrate accumulation is 9% and best predicted by levels of transaminases. It carries, when citrate is discontinued, no attributable mortality.

Pharmacologically-induced metabolic acidosis: a review

Metabolic acidosis may occasionally develop in the course of treatment with drugs used in everyday clinical practice, as well as with the exposure to certain chemicals. Drug-induced metabolic acidosis, although usually mild, may well be life-threatening, as in cases of lactic acidosis complicating antiretroviral therapy or treatment with biguanides. Therefore, a detailed medical history, with special attention to the recent use of culprit medications, is essential in patients with acid-base derangements. Effective clinical management can be handled through awareness of the adverse effect of certain pharmaceutical compounds on the acid-base status. In this review, we evaluate relevant literature with regard to metabolic acidosis associated with specific drug treatment, and discuss the clinical setting and underlying pathophysiological mechanisms. These mechanisms involve renal inability to excrete the dietary H+ load (including types I and IV renal tubular acidoses), metabolic acidosis owing to increased H+ load (including lactic acidosis, ketoacidosis, ingestion of various substances, administration of hyperalimentation solutions and massive rhabdomyolysis) and metabolic acidosis due to HCO3- loss (including gastrointestinal loss and type II renal tubular acidosis). Determinations of arterial blood gases, the serum anion gap and, in some circumstances, the serum osmolar gap are helpful in delineating the pathogenesis of the acid-base disorder. In all cases of drug-related metabolic acidosis, discontinuation of the culprit medications and avoidance of readministration is advised.

Metabolic effects of citrate- vs bicarbonate-based substitution fluid in continuous venovenous hemofiltration: a prospective sequential cohort study

BACKGROUND

Studies investigating the metabolic effects of citrate-based substitution fluids are lacking. This study aims to compare the effect of citrate- vs bicarbonate-based substitution fluid used during continuous venovenous hemofiltration (CVVH) for acute kidney injury on acid-base balance and electrolytes in critically ill patients.

METHODS

This was a prospective sequential cohort study in patients with a contraindication for systemic anticoagulation. The first cohort was treated by bicarbonate-based CVVH (n = 10) and the second cohort was treated by CVVH with citrate-based substitution fluid (n = 19). Flow of the latter was coupled to blood flow, and ionized calcium concentrations were monitored and kept constant by calcium-glubionate infusion.

RESULTS

No major differences between the 2 groups were found in baseline acid-base parameters. In both groups, arterial pH increased after initiation of treatment and normalized on the average within 18 hours in either group. No differences were found in bicarbonate concentrations. Electrolyte control was comparable for the groups.

CONCLUSION

Citrate-based substitution fluid is comparable to bicarbonate-based substitution fluid during CVVH in critically ill patients with acute kidney injury, concerning acid-base balance and electrolyte control. This implies complete conversion of citrate to bicarbonate in the patients studied.

Is there a role for sodium bicarbonate in treating lactic acidosis from shock?

PURPOSE OF REVIEW

Bicarbonate therapy for severe lactic acidosis remains a controversial therapy.

RECENT FINDINGS

The most recent 2008 Surviving Sepsis guidelines strongly recommend against the use of bicarbonate in patients with pH at least 7.15, while deferring judgment in more severe acidemia. We review the mechanisms causing lactic acidosis in the critically ill and the scientific rationale behind treatment with bicarbonate.

SUMMARY

There is little rationale or evidence for the use of bicarbonate therapy for lactic acidosis due to shock. We agree with the Surviving Sepsis guidelines recommendation against the use of bicarbonate for lactic acidosis for pH at least 7.15 and we further recommend a lower target pH of 7.00 or less. If bicarbonate is used, consideration must be given to slow infusion and a plan for clearing the CO2 that is produced and measuring and correcting ionized calcium as the resultant 10% drop may decrease cardiac and vascular contractility and responsiveness to catecholamines. When continuous renal replacement therapy is used during severe acidosis, we recommend bicarbonate-based replacement fluid over citrate as citrate may increase the strong ion gap. Effective therapy of lactic acidosis due to shock is to reverse the cause.

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

PURPOSE

To compare the acid-base balance effects of two different citrate doses for regional citrate anticoagulant (RCA) for continuous veno-venous hemofiltration (CVVH).

METHODS

We used a commercial citrate fluid (citrate concentration: 11 mmol/L) from July 2003 to July 2004 (period A) in 22 patients; then changed to a new citrate fluid (citrate concentration: 14 mmol/L) from July 2004 to Feb 2005 (Period B) in 21 patients. Replacement fluid rate was fixed at 2,000 ml/h. We measured all relevant variables for acid-base analysis according to the Stewart-Figge methodology.

RESULTS

After commencement of RCA-CVVH, there was a change in bicarbonate and base excess (BE) toward acidosis for both fluids. This change was significantly different between period A and B at 6 and 12 hours (pH: p<0.01, BE: p<0.05) with greater decreases with the 11 mmol/L citrate fluid. These changes were mostly secondary to an increase in the strong ion difference (SID) and occurred despite an increased strong ion gap (SIG) (+0.5 mEq/L vs. +1.5 mEq/L; p<0.01) in the higher citrate concentration fluid. Cessation of RCA-CVVH was associated with short-lived differences in bicarbonate and SIG which were similar to those seen on initiation of RCA-CVVH but in the opposite direction.

CONCLUSIONS

A small increase This was partly offset by an increase in SIG, consistent with increased citratemia. Cessation of treatment showed a differential improvement in SIG also consistent with disposal of therapy-associated citrate. These observations might assist clinicians in interpreting acidbase changes during RCA-CVVH.in citrate infusion rate caused an alkalinizing increase in SID.