The effect of intravenously administered magnesium on platelet function in patients after cardiac surgery.
After cardiac surgery, magnesium is often administered for prophylaxis and treatment of cardiac arrhythmias. Magnesium, however, inhibits platelet function in vitro and in healthy volunteers. We performed a randomized, blinded, and placebo-controlled study to investigate the effect of magnesium on platelet function in patients after cardiac surgery. We studied patients who underwent uneventful coronary revascularization with cardiopulmonary bypass on the first postoperative day. Before and after an infusion of either 5.4 mmol magnesium (n = 19) or saline (n = 20), platelet function was investigated by means of in vitro bleeding time, platelet aggregation, and flow-cytometric assays. In addition, to investigate platelet function in vitro, 1, 5, and 10 mM magnesium were added to platelet-rich plasma before and 24 h after surgery in 30 patients. Compared with the control group, magnesium prolonged the in vitro bleeding time (22%) and inhibited ADP- and collagen-induced platelet aggregation (13% and 17%), platelet P-selectin expression (18%), and the binding of fibrinogen to the platelet glycoprotein IIb/IIIa receptor (10%). Magnesium also led to significant dose-dependent inhibition of platelet aggregation (19%), P-selectin expression (14%), and fibrinogen binding (11%) before and after surgery in vitro. Although the antithrombotic effect of magnesium may be beneficial in patients after coronary revascularization, large-dose magnesium therapy should be carefully considered in patients with impaired platelet function and co-existing bleeding disorders.


CONCLUSIONS
In a randomized, blinded, placebo-controlled study of patients 24 h after coronary artery bypass grafting, IV administered magnesium inhibited platelet function in vitro and in vivo.
Gries
A
A
Department of Anesthesiology, University of Heidelberg, Germany. ANDREvGRIES@med.uni-heidelberg.de
Bode
C
C
Gross
S
S
Peter
K
K
Böhrer
H
H
Martin
E
E
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000368:Aged; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D003094:Collagen / Q000494:pharmacology; D001026:Coronary Artery Bypass; D004311:Double-Blind Method; D005340:Fibrinogen / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D066298:In Vitro Techniques; D007262:Infusions, Intravenous; D008274:Magnesium / Q000008:administration & dosage / Q000009:adverse effects* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D019007:P-Selectin / Q000096:biosynthesis; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use; D010979:Platelet Function Tests; D011184:Postoperative Period
D019007:P-Selectin; D010975:Platelet Aggregation Inhibitors; D000244:Adenosine Diphosphate; D005340:Fibrinogen; D003094:Collagen; D008274:Magnesium