A comparison of two citrate anticoagulation regimens for continuous veno-venous hemofiltration

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.

Non anti-coagulant factors associated with filter life in continuous renal replacement therapy (CRRT): a systematic review and meta-analysis

BACKGROUND

Optimising filter life and performance efficiency in continuous renal replacement therapy has been a focus of considerable recent research. Larger high quality studies have predominantly focussed on optimal anticoagulation however CRRT is complex and filter life is also affected by vascular access, circuit and management factors. We performed a systematic search of the literature to identify and quantify the effect of vascular access, circuit and patient factors that affect filter life and presented the results as a meta-analysis.

METHODS

A systematic review and meta-analysis was performed by searching Pubmed (MEDLINE) and Ovid EMBASE libraries from inception to 29th February 2016 for all studies with a comparator or independent variable relating to CRRT circuits and reporting filter life. Included studies documented filter life in hours with a comparator other than anti-coagulation intervention. All studies comparing anticoagulation interventions were searched for regression or hazard models pertaining to other sources of variation in filter life.

RESULTS

Eight hundred nineteen abstracts were identified of which 364 were selected for full text analysis. 24 presented data on patient modifiers of circuit life, 14 on vascular access modifiers and 34 on circuit related factors. Risk of bias was high and findings are hypothesis generating. Ranking of vascular access site by filter longevity favours: tunnelled semi-permanent catheters, femoral, internal jugular and subclavian last. There is inconsistency in the difference reported between femoral and jugular catheters. Amongst published literature, modality of CRRT consistently favoured continuous veno-venous haemodiafiltration (CVVHD-F) with an associated 44% lower failure rate compared to CVVH. There was a trend favouring higher blood flow rates. There is insufficient data to determine advantages of haemofilter membranes. Patient factors associated with a statistically significant worsening of filter life included mechanical ventilation, elevated SOFA or LOD score, elevations in ionized calcium, elevated platelet count, red cell transfusion, platelet factor 4 (PF-4) antibodies, and elevated fibrinogen. Majority of studies are observational or report circuit factors in sub-analysis. Risk of bias is high and findings require targeted investigations to confirm.

CONCLUSION

The interaction of patient, pathology, anticoagulation, vascular access, circuit and staff factors contribute to CRRT filter life. There remains an ambiguity from published data as to which site and side should be the first choice for vascular access placement and what interaction this has with patient factors and timing. Early consideration of tunnelled semi-permanent access may provide optimal filter life if longer periods of CRRT are anticipated. There remains an absence of robust evidence outside of anti-coagulation strategies despite over 20 years of therapy delivery however trends favour CVVHD-F over CVVH.

Bicarbonate- versus lactate-buffered solutions for acute continuous haemodiafiltration or haemofiltration

BACKGROUND

Acute kidney injury (AKI) is a severe loss of kidney function that results in patients' inability to appropriately excrete nitrogenous wastes and creatinine. Continuous haemodiafiltration (HDF) or haemofiltration (HF) are commonly used renal replacement therapies for people with AKI. Buffered dialysates and solutions used in HDF or HF have varying effects on acid-base physiology and several electrolytes. The benefits and harms of bicarbonate- versus lactate-buffered HDF or HF solutions for treating patients with AKI remain unclear.

OBJECTIVES

To assess the benefits and harms of bicarbonate- versus lactate-buffered solutions for HDF or HF for treating people with AKI.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register to 6 January 2015 through contact with the Trials' Search Co-ordinator using search terms relevant to this review. We also searched the Chinese Biomedical Literature Database.

SELECTION CRITERIA

All randomised controlled trials (RCT) and quasi-RCTs that reported comparisons of bicarbonate-buffered solutions with lactate-buffered solutions for AKI were selected for inclusion irrespective of publication status or language.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed titles and abstracts, and where necessary the full text of studies, to determine which satisfied our inclusion criteria. Data were extracted by two authors who independently assessed studies for eligibility and quality using a standardised data extraction form. Methodological quality was assessed using the Cochrane risk of bias tool. Results were expressed as risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI).

MAIN RESULTS

We identified four studies (171 patients) that met our inclusion criteria. Overall, study quality was suboptimal. There were significant reporting omissions related to methodological issues and potential harms. Outcome measures were not defined or reported adequately. The studies were small and lacked follow-up phases.Serum lactate levels were significantly lower in patients treated with bicarbonate-buffered solutions (4 studies, 171 participants: MD -1.09 mmol/L, 95% CI -1.30 to -0.87; I(2) = 0%). There were no differences in mortality (3 studies, 163 participants: RR 0.76, 95% CI 0.50 to 1.15; I(2) = 0%); serum bicarbonate levels (3 studies, 163 participants: MD 0.27 mmol/L, 95% CI -1.45 to 1.99; I(2) = 78%), serum creatinine (2 studies, 137 participants: MD -22.81 µmol/L, 95% CI -129.61 to 83.99; I(2) = 73%), serum base excess (3 studies, 145 participants: MD 0.80, 95% CI -0.91 to 2.50; I(2) = 38%), serum pH (4 studies, 171 participants: MD 0.01, 95% CI -0.02 to 0.03; I(2) = 70%) or carbon dioxide partial pressure (3 studies, 151 participants: MD -1.04, 95% CI -3.84 to 1.76; I(2) = 83%). A single study reported fewer cardiovascular events (RR 0.39, 95% CI 0.20 to 0.79), higher mean arterial pressure (10.25 mm Hg, 95% CI 6.68 to 13.82) and less hypotensive events (RR 0.44, 95% CI 0.26 to 0.75) in patients receiving bicarbonate-buffered solutions. One study reported no significant difference in central venous pressure (MD 2.00 cm H2O, 95% CI -0.7 to, 4.77). Total length of hospital and ICU stay and relapse were not reported by any of the included studies.

AUTHORS' CONCLUSIONS

There were no significant different between bicarbonate- and lactate-buffered solutions for mortality, serum bicarbonate levels, serum creatinine, serum base excess, serum pH, carbon dioxide partial pressure, central venous pressure and serum electrolytes. Patients treated with bicarbonate-buffered solutions may experience fewer cardiovascular events, lower serum lactate levels, higher mean arterial pressure and less hypotensive events. With the exception of mortality, we were not able to assess the main primary outcomes of this review - length of time in ICU, total length of hospital stay and relapse.

A retrospective review of the use of regional citrate anticoagulation in continuous venovenous hemofiltration for critically ill patients

Background. The emergence of a commercially prepared citrate solution has revolutionized the use of RCA in the intensive care unit (ICU). The aim of this study was to evaluate the safety profile of a commercially prepared citrate solution. Method. Predilution continuous venovenous hemofiltration (CVVH) was performed using Prismocitrate 10/2 at 2500 mL/h and a blood flow rate of 150 mL/min. Calcium chloride solution was infused to maintain ionized calcium within 1.0–1.2 mmol/L. An 8.4% sodium bicarbonate solution was infused separately. Treatment was stopped when the predefined clinical target was reached or the filter clotted. Result. 58 sessions of citrate RCA were analyzed. The median circuit lifetime was 26.0 h (interquartile range IQR 21.2–44.3). The percentage of circuits lasting more than 12 h, 24 h, and 48 h was 94.6%, 58.9%, and 16.1%, respectively. There was no incidence of hypernatremia and median pH was <7.5. Hypomagnesemia and hypophosphatemia were detected in 41.6% and 17.6% of blood samples taken, respectively. Although 16 episodes had a total calcium/ionized calcium (total Ca/iCa) >2.5, only four patients had evidence of citrate accumulation. Conclusion. The commercially prepared citrate solution could be used safely in critically ill patients who required CVVH with no major adverse events.

Ionized calcium concentration and outcome in critical illness

OBJECTIVE

To assess the association of abnormalities of ionized calcium levels with mortality in a heterogeneous cohort of critically ill patients.

DESIGN

Retrospective, combined clinical and biochemical study.

SETTING

Four combined medical/surgical intensive care units.

PATIENTS

Cohort of 7,024 adult critically ill patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We studied 177,578 ionized calcium measurements, from 7024 patients, with a mean value of 1.11 mmol/L (ionized calcium measured every 4.5 hrs on average). The unadjusted lowest and highest ionized calcium reported during intensive care unit stay were significantly different between intensive care unit survivors and nonsurvivors (p < .001). If hypocalcemia occurred at least once during the intensive care unit stay, the probability of intensive care unit mortality increased by 46%, 108%, and 150% for ionized calcium levels <1.15, 0.90, and 0.80 mmol/L, respectively. If hypercalcemia occurred at least once during the intensive care unit stay, the probability of intensive care unit mortality increased by 100%, 162%, and 190% for ionized calcium levels >1.25, 1.35, and 1.45 mmol/L, respectively. Similar trends were seen for hospital mortality. However, from multivariate logistic regression analysis, only an ionized calcium <0.8 mmol/L or an ionized calcium >1.4 mmol/L were independently associated with intensive care unit and hospital mortality.

CONCLUSIONS

Within a broad range of values, ionized calcium concentration has no independent association with hospital or intensive care unit mortality. Only extreme abnormalities of ionized calcium concentrations are independent predictors of mortality.

Clinical review: anticoagulation for continuous renal replacement therapy--heparin or citrate?

Heparin is the most commonly prescribed anticoagulant for continuous renal replacement therapy. There is, however, increasing evidence questioning its safety, particularly in the critically ill. Heparin mainly confers its anticoagulant effect by binding to antithrombin. Heparin binds to numerous other proteins and cells as well, however, compromising its efficacy and safety. Owing to antithrombin consumption and degradation, and to the binding of heparin to acute phase proteins, and to apoptotic and necrotic cells, critical illness confers heparin resistance. The nonspecific binding of heparin further leads to an unpredictable interference with inflammation pathways, microcirculation and phagocytotic clearance of dead cells, with possible deleterious consequences for patients with sepsis and systemic inflammation. Regional anticoagulation with citrate does not increase the patient's risk of bleeding. The benefits of citrate further include a longer or similar circuit life, and possibly better patient and kidney survival. This needs to be confirmed in larger randomized controlled multicenter trials. The use of citrate might be associated with less inflammation and has useful bio-energetic implications. Citrate can, however, with inadequate use cause metabolic derangements. Full advantages of citrate can only be realized if its risks are well controlled. These observations suggest a greater role for citrate.

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.

Clinical review: Patency of the circuit in continuous renal replacement therapy

Premature circuit clotting is a major problem in daily practice of continuous renal replacement therapy (CRRT), increasing blood loss, workload, and costs. Early clotting is related to bioincompatibility, critical illness, vascular access, CRRT circuit, and modality. This review discusses non-anticoagulant and anticoagulant measures to prevent circuit failure. These measures include optimization of the catheter (inner diameter, pattern of flow, and position), the settings of CRRT (partial predilution and individualized control of filtration fraction), and the training of nurses. In addition, anticoagulation is generally required. Systemic anticoagulation interferes with plasmatic coagulation, platelet activation, or both and should be kept at a low dose to mitigate bleeding complications. Regional anticoagulation with citrate emerges as the most promising method.