High dose magnesium infusions are not associated with increased pressor requirements after carotid endarterectomy.
BACKGROUND
Although magnesium provides cerebral protection in animal stroke models, magnesium therapy has significant side effects in humans. Therefore, we sought to examine the incidence of alpha-agonist treated hypotension in our ongoing, prospective, randomized, double-blind, placebo-controlled Phase I/IIa dose escalation study of magnesium therapy in patients undergoing carotid endarterectomy.


METHODS
Eighty patients undergoing elective carotid endarterectomy were randomly assigned to a placebo control group (n = 38) or to one of the three intravenous magnesium groups. Magnesium levels were obtained before induction, and then 15 minutes, 1 hour, 2 hours, 6 hours, 12 hours, and 24 hours after a loading dose and infusion. After surgery, a target systolic blood pressure range was chosen, and the amount and duration of phenylephrine needed to maintain that pressure was compared across treatment groups.


RESULTS
All treatment groups achieved levels significantly different from baseline at 12 and 24 hours (P < 0.01). Magnesium treatment did not significantly increase the proportion of patients requiring pressure support. For those requiring pressure support, the amount and average duration of phenylephrine required was not different between control patients and those receiving magnesium, even when the individual minimum systolic blood pressures required were subdivided on the basis of dose of magnesium administered.


CONCLUSIONS
There were no significant differences detected in the 1) percentage of patients requiring pressor support, 2) the duration of postoperative pressor support, or 3) the amount of phenylephrine support needed between controls and magnesium treated patients. The percentage of patients requiring pressure support depended on the minimum systolic blood pressure ordered after surgery.
Chiu
Camay
C
Department of Anesthesiology, Columbia University College of Physicians and Surgeons, New York, New York, USA.
Heyer
Eric J
EJ
Rampersad
Anita D
AD
Zurica
Joseph
J
Ornstein
Eugene
E
Sahlein
Daniel H
DH
Sciacca
Robert R
RR
Connolly
E Sander
ES
D000316:Adrenergic alpha-Agonists / Q000627:therapeutic use; D000368:Aged; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D016894:Endarterectomy, Carotid; D005260:Female; D006801:Humans; D007022:Hypotension / Q000139:chemically induced* / Q000188:drug therapy / Q000453:epidemiology; D015994:Incidence; D007262:Infusions, Intravenous; D008274:Magnesium / Q000008:administration & dosage* / Q000009:adverse effects* / Q000627:therapeutic use; D008297:Male; D018696:Neuroprotective Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D010656:Phenylephrine / Q000627:therapeutic use; D011182:Postoperative Care
D000316:Adrenergic alpha-Agonists; D018696:Neuroprotective Agents; D010656:Phenylephrine; D008274:Magnesium