PRE-ISCHEMIC MYOCARDIAL EVALUATION THROUGH INDUCED INTERMITTENT HYPOXEMIA IN RABBITS

• Grant number: 09/14323-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2009
• End date: May 31, 2010
• Field of knowledge: Health Sciences - Medicine - Surgery
• Principal Investigator: Luiz Antonio Rivetti
• Grantee: Caio César Cardoso
• Host Institution: Faculdade de Ciências Médicas da Santa Casa de São Paulo (FCMSCSP). Fundação Arnaldo Vieira de Carvalho. São Paulo , SP, Brazil

Abstract

Introduction: The ischemic preconditioning consists in a hypoxic/ischemic intervention, in which protection is given against subsequent ischemic insults. The following study pretends to evaluate the myocardial protection promoted by a mild and intermittent hypoxia through mechanical ventilation. Methods:Male adult New Zeland rabbits will be divided in two groups of study (n=10). All animals will be anesthetized (induction with ketamine and xilazine, and maintained with propofol), intubated, instrumented for hemodynamic measurement, and will be obtained blood samples for measurement of arterial blood gas tensions and acid-base status, creatinofosfocinase (CPK), creatinocinase MB (CK-MB) e troponin I (TI) in order to evaluate the myocardial damage trough laboratorial parameters. In group 1, mechanical ventilation will be proceeded with FiO2=15% alternated with FiO2=30% each 5 minutes, for 3 cycles, totalizing 30 minutes. Afterwards, the anticoagulation with heparin will be realized. Then the animals will be subjected to a 30-minute left anterior coronary artery occlusion, and then a 60-minute reperfusion. In group 2, the procedures will be the same, apart from the mechanical ventilation that will be performed with FiO2=30%, what means that there will not be periods of hypoxia in this group. After sacrifice, hearts will be prepared for both ischemia and infarct areas detection and quantification by 2,3,5-triphenyltetrazolium chloride, and following quantitative histopathological study.Results:It is hoped that mild and intermittent hypoxia through mechanical ventilation provides myocardial protection, resulting in smaller infarction areas and lower measures of cardiac enzymes. Conclusions:It is concluded, if the expected results be confirmed, that mild and intermittent hypoxia is also a myocardial protection factor in rabbits, taking in consideration the proposed methodology.