Regional Citrate Anticoagulation for Continuous Renal Replacement Therapy in Critically Ill Patients after Cardiac Surgery—A safe Option?

Objectives: Regional citrate anticoagulation continuous renal replacement therapy (RCA-CRRT) has become a cornerstone of modern intensive care medicine. However, recent concern has arisen about its negative side effects, especially in critically ill patients, that is, after cardiac surgery. Citrate accumulation may lead to metabolic acidosis and severe hypocalcemia with consecutive low cardiac output syndrome.

Methods: We conducted a retrospective analysis of all patients who had undergone postoperative CRRT strictly within 24 hours of cardiac surgery (n = 22) at our department from June 1, 2017, to June 30, 2018. Patients who had already been on CRRT before surgery were excluded from analysis. We compared RCA-CRRT (n = 11) and classic heparin-based anticoagulation CRRT (HA-CRRT, n = 11) on an intention-to-treat basis. Lactate elimination, calcium level stability, vasopressor requirements, and blood loss within 48 hours as well as ventilation time, intensive care unit (ICU) and total hospital stay and survival to discharge were analyzed.

Results: Patients were admitted to CRRT within 5.9 ± 6.3 hours upon ICU arrival and received treatment for 178.6 ± 223.6 hours. While most baseline characteristics did not differ among groups, total operation and extracorporeal circulation time were significantly longer in the RCA-CRRT group (p = 0.004 and 0.006, respectively). Though the initially higher noradrenaline load in this group was leveled within 12 hours, repeated measures tests revealed this to be independent of the type of CRRT. While calcium levels had been significantly lowered after 12 hours in the RCA-CRRT group (p = 0.007), no differences were detectable after 24 hours. Serum lactate levels were reduced significantly (p < 0.001) upon CRRT implementation in both groups. There were no differences regarding drainage volume, transfusion requirements, and need for surgical bleeding control. In this high-risk collective, 50% of patients required postoperative extracorporeal circulatory support, overall survival was 59.1%. Neither survival nor hospital or ICU stay were influenced by CRRT group affiliation.

Conclusions RCA-CRRT was not inferior to HA-CRRT in terms of metabolic control and vasopressor requirements among critically ill patients after cardiac surgery. Though we did not find any lasting effects of transient calcium level depletion on RCA-CRRT, further studies are mandatory to confirm our findings in this clinically unstable patient group.