Blood Products, Crystalloids, and Rapid Infusion: An Experimental Study With Magnesium.

OBJECTIVES

Calcium and magnesium are concentration-dependent pro- and anticoagulant cofactors, and magnesium behaves similarly to calcium in the presence of citrate. The authors hypothesized that magnesium can cause clot formation (primary objective) when mixed with coagulation factor-containing blood products diluted with different crystalloids in a rapid- infuser reservoir. A secondary objective was the observation of any infuser alarms and stops in the event of clotting.

DESIGN

An experimental in vitro study with blood products, crystalloids, magnesium, and calcium in a rapid infuser with a reservoir using a closed-loop system.

SETTING

Anesthesia research laboratory at an urban academic tertiary medical center PARTICIPANTS: Not applicable.

INTERVENTIONS

Exposure of fresh frozen plasma (FFP) and packed red blood cells alone (control) or in combination with either normal saline (NS), lactated Ringer's solution (LR), or Plasma-Lyte A (PL) to increasing concentrations of magnesium sulphate (MgSO) up to 1 g. After each incremental MgSO change, the authors applied a specific pump-flow sequence in a closed-loop system with a rapid-infuser reservoir, and if no clot was observed, the authors incrementally added calcium chloride (CaCl) up to 1 g.

MEASUREMENTS AND MAIN RESULTS

Observation of macroscopic clot and time to event, as well as occurrence and type of any pump alarms or stops. LR experiments resulted in clot observation in the reservoir by a dedicated observer after MgSO 275 ± 206 mg (95% confidence interval [CI], 9-541). Adding MgSO 1 g in the NS, PL, or the control experiments did not result in clot observation. Only when CaCl 166.7 ± 51.64 mg (95% CI, 112.0-22.01) was added to the combination of blood products alone or mixed with NS and PL, clotting occurred. The mean FFP volume was 281 ± 48.6 mL (range, 204-340 mL) and was not different between groups (p = 0.44). Pump alarms and stops were inconsistent.

CONCLUSIONS

The addition of magnesium to a combination of LR with coagulation factor- containing blood products consistently resulted in a visible blood clot in the rapid-infuser reservoir in the authors' experimental setup. In addition to MgSO 1 g in the control, NS, and PL experiments, CaCl is needed before a clot can be observed.