The cardioprotective effect of dexmedetomidine on global ischaemia in isolated rat heartsick

Aim: Dexmedetomidine is a highly specific and selective alpha-2 adrenergic agonist that is now widely used in the intensive care setting. Many intensive care unit (ICU) patients are at risk of respiratory or cardiac arrest. This study was conducted to determine whether dexmedetomidine exhibits a cardioprotective effect on global ischaemia and subsequent myocardial infarction. Methods: Isolated rat hearts were subjected to 30 min of global ischaemia followed by 120 min reperfusion, with administration of 0, 1 and 10 nM dexmedetomidine during the pre-ischaemic period (n=7 each group). Secondly, 1 mu M yohimbine, an a-2 antagonist, was given during the pre-ischaemic period, atone or in combination with 10 nM dexmedetomidine (n = 7 each group). Results: Dexmedetomidine administration reduced coronary flow significantly (103.6 +/- 4.7%, 77.9 +/- 3.7, 63.7 +/- 6. 1 %, of the baseline values for 0, 1 and 10 nM dexmedetomidine, respectively), and yohimbine administration reversed this effect (88.0 +/- 12.2%). Dexmedetomidine improved the infarct size at each concentration (45.3 +/- 3.6, 30.2 +/- 3.3, and 21.2 +/- 2.3% of the total left ventricular mass for 0, 1, and 10 nM dexmedetomidine, respectively), which was also reversed by yohimbine (43.6 +/- 1.4%). Conclusion: Dexmedetomidine exhibited a cardioprotective effect on global ischaemia in the isolated rat heart model, which was mediated by alpha-2 adrenergic stimulation. (c) 2007 Elsevier Ireland Ltd. All rights reserved.