The coagulation changes induced by rapid in vivo crystalloid infusion are attenuated when magnesium is kept at the upper limit of normal

BACKGROUND: Rapid crystalloid infusion enhances coagulation, regardless of electrolytes, pH or osmolality, an effect thought to be related to deep vein thrombosis and other clot formations. Altered serum magnesium may play a role in the balance of coagulation. In this in vivo study we investigated the coagulation response to rapid hemodilution when serum magnesium is maintained or partially increased. METHODS: Twenty-five healthy volunteers were investigated on three occasions, randomly receiving normal saline, Balsol (magnesium 1.5 g/L), and Balsol plus additional magnesium (magnesium 3.0 g/L). Investigators were blinded to the solution's identity. Baseline blood samples were taken measuring hematocrit, serum magnesium, and thrombelastography (TEG), whereafter 14 mL/kg (20% blood volume) was infused over 30 min, followed by a second blood sample. All results were compared to their own baseline values using ANOVA with LSD post hoc significance testing. RESULTS: All groups had a similar postdilutional hematocrit decrease, with significant magnesium reduction in the saline group (0.81 ± 0.07 to 0.74 ± 0.07 (approximately -8.6%) (P < 0.003)), no change in the Balsol group and significant increase in the Balsol + magnesium group (0.84 ± 0.07 to 0.99 ± 0.06 (approximately 17.9%) (P < 0.001)). Postdilutional TEG results reflected no significant change from control in the Balsol + magnesium group. Both of the other two groups had statistically significant increased clot formation (reaction time to onset of clotting and clotting time shortened; α-angle increased). CONCLUSIONS: Rapid hemodilution-induced coagulation may be partially due to decreased magnesium, and the effect is attenuated by maintaining magnesium at the upper limit of normal. Crystalloid resuscitation fluids should possibly contain higher magnesium levels, around 3 mmol/L. © 2007 by International Anesthesia Research Society.