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Ionized calcium measurements during regional citrate anticoagulation in CRRT: we need better blood gas analyzers
Critical Care volume 19, Article number: 427 (2015)
Schwarzer et al.  showed discrepant postfilter ionized calcium concentrations [iCa] when using different blood gas analyzers (BGAs) and called for a change of the Fresenius regional citrate anticoagulation (RCA) protocol to ensure patient safety. Of note, precision of the BGAs was not tested.
In our opinion, the key message of their study is that commercially available BGAs are not accurate when measuring [iCa] outside the reference range and therefore clinicians should avoid using multiple BGAs to guide RCA in individual patients. However, there is no indication to change a RCA protocol which has been proven safe and effective in >10 studies including >2000 patients from different countries regardless of the BGA used [2–5].
Schwarzer et al. also raise concern about the potential risk of life-threatening citrate intoxication. Whether raised citrate levels are toxic or merely indicative of impaired cellular metabolism remains unclear, but excess citrate can cause metabolic alkalosis. The Fresenius RCA protocol and the technical specifications of the multifiltrate machine both include safety mechanisms to detect potential citrate accumulation early. The risk of citrate toxicity is low (<3 %), even in high-risk patients with liver failure [3, 5].
Given the proven advantages of RCA and the Kidney Disease Improving Global Outcomes (KDIGO) recommendation to use citrate as the first-line anticoagulant during continuous renal replacement therapy, the accuracy of commercially available BGA devices should be improved. In our opinion, there is no need to change a safe and effective protocol.
Ionized calcium concentration
Blood gas analyzer
Kidney Disease Improving Global Outcomes
Regional citrate anticoagulation
Schwarzer P, Kuhn S-O, Stracke S, Grundling M, Knigge S, et al. Discrepant post filter ionized calcium concentrations by common blood gas analyzers in CRRT using regional citrate anticoagulation. Crit Care. 2015;19:321.
Kalb R, Kram R, Morgera S, Slowinski T, Kindgen-Milles D. Regional citrate anticoagulation for high volume continuous venovenous hemodialysis in surgical patients with high bleeding risk. Ther Apher Dial. 2013;17:202–12.
Khadzhynov D, Schelter C, Lieker I, Mika A, Staeck O, et al. Incidence and outcome of metabolic disarrangements consistent with citrate accumulation in critically ill patients undergoing continuous venovenous hemodialysis with regional citrate anticoagulation. J Crit Care. 2014;29:265–71.
Morgera S, Schneider M, Slowinski T, Vargas-Hein O, Zuckermann-Becker H, et al. A safe citrate anticoagulation protocol with variable treatment efficacy and excellent control of the acid-base status. Crit Care Med. 2009;37:2018–24.
Slowinski T, Morgera S, Joannidis M, Henneberg T, Stocker R, et al. Safety and efficacy of regional citrate anticoagulation in continuous veno-venous hemodialysis in the presence of liver failure: The Liver Citrate Anticoagulation Threshold (L-CAT)—an observational study. Crit Care. 2015;19:349.
DKM, MO, and TS have received research grants and funds for speaking at symposia organized on behalf of Fresenius Medical Care, Germany.
All authors were responsible for analysis and interpretation of data, manuscript writing, and final approval of the manuscript.
See related research by Schwarzer et al., http://www.ccforum.com/content/19/1/321
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Kindgen-Milles, D., Ostermann, M. & Slowinski, T. Ionized calcium measurements during regional citrate anticoagulation in CRRT: we need better blood gas analyzers. Crit Care 19, 427 (2015). https://doi.org/10.1186/s13054-015-1143-y
- Renal Replacement Therapy
- Continuous Renal Replacement Therapy
- Metabolic Alkalosis
- Kidney Disease Improve Global Outcome
- Ionize Calcium Concentration