nitroarginine and Postoperative-Complications

Postoperative hypomagnesemia is common in patients who have undergone cardiac operations and is associated with clinically significant morbidity resulting from atrial and ventricular dysrhythmias. Magnesium supplementation may increase the cardiac index in the early postoperative period.. The action of the magnesium cation on coronary vascular reactivity was studied. Segments of canine epicardial coronary artery were suspended in organ chambers to measure isometric force (95% O2/5% CO2, 37 degrees C).. In coronary segments constricted with prostaglandin F2alpha (2 x 10[-6] mol/L), acetylcholine and adenosine diphosphate (10[-9] to 10[-4] mol/L) induced vasodilation in arteries with endothelium (n=10, each group; p < 0.05). Acetylcholine-mediated vasodilation was blocked by NG-monomethyl-L-arginine (10[-4] mol/L) and NG-nitro-L-arginine (10[-4] mol/L), two inhibitors of nitric oxide synthesis from L-arginine (n=10, p < 0.05). The removal of magnesium from the organ chamber solution impaired vasodilation in response to acetylcholine and adenosine diphosphate. However, normal endothelium-dependent vasodilation could be restored by return of magnesium to the bathing solution. Vascular relaxation in response to bradykinin (10[-9] to 10[-6] mol/L), which was found to induce endothelium-dependent vasodilation independent of nitric oxide production, was unaffected by magnesium removal (n=10).. Hypomagnesemia selectively impaired the release of nitric oxide from the coronary endothelium. Because nitric oxide is a potent endogenous nitro-vasodilator and inhibitor of platelet aggregation and adhesion, hypomagnesemia could promote vasoconstriction and coronary thrombosis in the early postoperative period.

Topics: Acetylcholine; Adenosine Diphosphate; Animals; Arrhythmias, Cardiac; Bradykinin; Cardiac Output; Cardiac Surgical Procedures; Coronary Thrombosis; Coronary Vessels; Dinoprost; Dogs; Endothelium, Vascular; Enzyme Inhibitors; Female; Infusions, Intravenous; Magnesium; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; omega-N-Methylarginine; Pericardium; Platelet Aggregation Inhibitors; Postoperative Complications; Vasoconstriction; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

The effect of two prostaglandin biosynthesis inhibitors and their interaction with the L-arginine/nitric oxide (NO) pathway was investigated in a rat model of experimental ileus. The gastrointestinal transit was measured as the migration of Evans blue after three different operations. Indomethacin completely reversed the additional inhibition of the transit induced by mechanical stimulation of the gut. Ketorolac completely reversed the inhibition of the transit induced by the laparotomy, but had no additional effect on the inhibition induced by mechanical stimulation of the gut. Administration of indomethacin plus L-nitroarginine or L-arginine could not enhance or prevent the effect of indomethacin alone. Administration of ketorolac and L-nitroarginine completely reversed the transit after the laparotomy plus manipulation whereas ketorolac plus L-arginine had no additional effect as compared to ketorolac alone. From these findings we conclude that in addition to NO, prostaglandins are involved in the pathogenesis of postoperative ileus in the rat. However, indomethacin and ketorolac differentially affect postoperative ileus suggesting that prostaglandins are involved in different pathogenic mechanisms leading to postoperative ileus.

Topics: Animals; Disease Models, Animal; Indomethacin; Intestinal Obstruction; Ketorolac; Nitric Oxide; Nitroarginine; Postoperative Complications; Prostaglandin Antagonists; Rats; Tolmetin