The effect of preoperative magnesium supplementation on blood catecholamine concentrations in patients undergoing CABG
It is well known that magnesium (Mg) plays an important role in many physiological processes such as regulation of blood catecholamine concentrations, particularly epinephrine (E) and norepinephrine (NE). The complex character of extracorporeal circulation (ECC) with intraoperative normovolemic haemodilution (NH) may alter blood Mg levels, which is likely to result in disorders of E and NE. The aim of this study was to analyze the influence of preoperative Mg supplementation on E and NE in patients undergoing CABG.
Forty male patients undergoing CABG under general anaesthesia were included. Patients were randomly divided into two groups: A--the patients receiving pre-operative magnesium supplementation and B--patients without pre-operative magnesium supplementation. The Mg, E and NE blood concentrations were measured in five stages: 1) before anesthesia after the radial artery cannulation, 2) during NH and ECC, 3) immediately after surgery, 4) in the morning of the 1st postoperative day, 5) in the morning of the 2nd postoperative day. The Mg levels were determined by spectrophotometric methods, E and NE were measured by radioimmunoassay methods.
The CABG caused a decrease of Mg and an increase of E and NE in both groups, but the changes were significantly higher in group B.
1) CABG causes a decrease of Mg and an increase of E and NE; 2) Preoperative, oral supplementation of Mg substantially reduces intra- and postoperative disorders.
Available from: William L Baker
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ABSTRACT: To review the available literature addressing preventive strategies of post-cardiothoracic surgery atrial fibrillation (post-CTS atrial fibrillation).
Pertinent articles related to the etiology, risk factors, and preventive strategies were identified through a MEDLINE search (1966-March 2007) using the MeSH terms atrial fibrillation, cardiothoracic surgery, cardiac surgery, etiology, neurohormonal, sympathetic, volume, fluid, inflammation, risk factors, operative, pacing, beta-adrenergic blockers, amiodarone, sotalol, calcium-channel blockers, magnesium, HMG-CoA reductase inhibitors, statins, fatty acids, PUFA, steroids, and nonsteroidal antiinflammatory drugs.
Articles evaluated were limited to human studies, published in the English language, with a Jadad score greater than 3. References of identified articles were reviewed for additional pertinent articles.
Post-CTS atrial fibrillation most commonly occurs on the second or third postoperative day, with an incidence of 20-50%. Etiology theories include neurohormonal activation, volume overload, and inflammation. Studies examining nonpharmacologic therapies have shown that maintenance of the anterior epicardial fat pad is not a viable prophylactic strategy. Biatrial cardiac pacing, especially in combination with amiodarone, is a viable preventive option. Withdrawal of preoperative beta-blockers places patients at higher risk for atrial fibrillation; these drugs should be continued postoperatively. Evidence exists supporting the use of amiodarone, sotalol, and magnesium in addition to beta-blockers. Since most of these strategies work by attenuating neurohormonal activation, adverse events, including hypotension and bradycardia, are of concern. Adding agents with antiinflammatory properties, including hydroxymethylglutaryl coenzyme A reductase inhibitors or corticosteroids, may prove to be of benefit. Additional studies using novel therapies are needed in addition to established preventive strategies.
Available evidence supports the continuation of preoperative beta-blockers, as well as prophylactic amiodarone, sotalol, and magnesium. Other novel therapies, mostly targeting inflammation, are under investigation and may provide additional strategies.
Available from: umich.edu
Available from: Silvia Izquierdo Alvarez
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