Ionized Magnesium and Regional Citrate Anticoagulation for Continuous Renal Replacement Therapy.

Background: The regional citrate anticoagulation (RCA) induces changes in total (Catot) and ionized (Ca2+) calcium. As of now, we do not have much information about parallel changes of total (Mgtot) and ionized (Mg2+) magnesium.

Methods: The authors compared changes of Mg2+ and Mgtot with changes of Ca2+ and Catot in 32 critically ill patients on 4% trisodium citrate (4% TSC) with calcium-free fluids.

Results: The median continuous venovenous hemodiafiltration balance of Mgtot was -0.91 (-1.18 to -0.53) mmol/h compared to the median balance of Catot 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 Mgtot 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.