Importance of ionized magnesium measurement for monitoring of citrate-anticoagulated plateletpheresis.

BACKGROUND

The infusion of citrate during apheresis may affect the levels of ionized magnesium in the blood. Hypomagnesemia and concomitant hypocalcemia could influence the parathormone response and could be responsible for some of the symptoms observed during apheresis.

STUDY DESIGN AND METHODS

The study reports measurement of ionized magnesium by the new ion-selective electrode technique in response to citrate infusion in 15 donors undergoing continuous flow high-yield plateletpheresis. The monitoring included measurement of ionized calcium and parathormone every 30 minutes during the 120-minute apheresis (plus the next 30 minutes to assess recovery).

RESULTS

Ionized magnesium fell by 30 +/- 4 percent (mean +/- SD, p<0.01), which contrasts with minor changes in total concentrations. Comparison of variations in the levels of ionized and total magnesium found major formation of complexes during citrate infusion. Ionized calcium fell by 15 +/- 3 percent (p<0.01), while parathormone peaked at 356 +/- 114 percent (p<0.01) of initial value after 30 minutes. Ionized cations and parathormone recovered by more than 50 percent within 30 minutes of the end of apheresis.

CONCLUSION

An acute and steep drop in ionized magnesium occurs during citrate administration. The measurement of ionized magnesium should be included in future prospective studies of donor safety and parathormone regulation during apheresis.