Effect of magnesium on coagulation as measured by thrombelastography.

Magnesium has long been assumed to have anticoagulant properties, but the effect has been poorly quantified. The thrombelastograph (TEG) was used to evaluate the effect of magnesium using blood from volunteers. Magnesium sulphate was added to one blood sample and another sample was used as a control. Both samples were tested simultaneously and the results evaluated against the magnesium concentration measured in each sample. At serum magnesium concentrations < 3 mmol litre-1, there were no significant effects of magnesium. With increasing magnesium concentrations there was a statistically significant but small prolongation of the r time, k time and r + k time. Maximum amplitude was affected only at magnesium concentrations > 7 mmol litre-1. Magnesium has only minimal effects on coagulation which are unlikely to be clinically important.