Background: The regional citrate anticoagulation (RCA) induces changes in total (Ca^tot) and ionized (Ca²⁺) calcium. As of now, we do not have much information about parallel changes of total (Mg^tot) and ionized (Mg²⁺) magnesium. Methods: The authors compared changes of Mg²⁺ and Mg^tot with changes of Ca²⁺ and Ca^tot in 32 critically ill patients on 4% trisodium citrate (4% TSC) with calcium-free fluids. Results: The median continuous venovenous hemodiafiltration balance of Mg^tot was -0.91 (-1.18 to -0.53) mmol/h compared to the median balance of Ca^tot 0.86 (0.08-1.55) mmol/h. Postfilter Mg²⁺ decreased by 68.3% (70.8-65.6) in parallel (r = 0.41, p = 0.03) to decrease of postfilter Ca²⁺ (by 70.2% (73.0-66.1)) and was significantly related to the postfilter Ca²⁺ (r = 0.50, p < 0.001). The decrease of prefilter to postfilter Ca²⁺ correlated to a dosage of 4% TSC per blood flow (r = 0.37, p = 0.04). Conclusions: The loss of Mg^tot during RCA is not covered by magnesium concentration in ordinary dialysis/substitution fluid and may lead to the depletion of total body magnesium. The postfilter Mg²⁺ is significantly related to the postfilter Ca²⁺. Video Journal Club “Cappuccino with Claudio Ronco” at http://www.karger.com/?doi = 440972.

BackgroundThe requirements for magnesium (Mg) supplementation increase under regional citrate anticoagulation (RCA) because citrate acts by chelation of bivalent cations within the blood circuit. The level of magnesium in commercially available fluids for continuous renal replacement therapy (CRRT) may not be sufficient to prevent hypomagnesemia.MethodsPatients (n = 45) on CRRT (2,000 ml/h, blood flow (Qb) 100 ml/min) with RCA modality (4% trisodium citrate) using calcium free fluid with 0.75 mmol/l of Mg with additional magnesium substitution were observed after switch to the calcium-free fluid with magnesium concentration of 1.50 mmol/l (n = 42) and no extra magnesium replenishment. All patients had renal indications for CRRT, were treated with the same devices, filters and the same postfilter ionized calcium endpoint (<0.4 mmol/l) of prefilter citrate dosage. Under the high level Mg fluid the Qb, dosages of citrate and CRRT were consequently escalated in 9h steps to test various settings.ResultsMedian balance of Mg was -0.91 (-1.18 to -0.53) mmol/h with Mg 0.75 mmol/l and 0.2 (0.06–0.35) mmol/h when fluid with Mg 1.50 mmol/l was used. It was close to zero (0.02 (-0.12–0.18) mmol/h) with higher blood flow and dosage of citrate, increased again to 0.15 (-0.11–0.25) mmol/h with 3,000 ml/h of high magnesium containing fluid (p<0.001). The arterial levels of Mg were mildly increased after the change for high level magnesium containing fluid (p<0.01).ConclusionsCompared to ordinary dialysis fluid the mildly hypermagnesemic fluid provided even balances and adequate levels within ordinary configurations of CRRT with RCA and without a need for extra magnesium replenishment.Trial RegistrationClinicalTrials.gov Identifier: NCT01361581

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