Risk factors of perioperative myocardial infarction in adult non-cardiac operation, 2002-2004 : a case-control study

Background : Eventhough an international standard of preoperative risk assessment of cardiac events in perioperative period has been implemented at Siriraj Hospital, there were still reports of peri-operative myocardial infarction, about 20-30 cases a year. We would like to identify preventable and modifiable risk factors. Objective: To determine the risk factors of peri-operative myocardial infarction in adult non-cardiac operations during 2002-2004 at Siriraj Hospital. Study design: a case-control study. Material and Methods: Seventy-four cases of peri-operative myocardial infarction were matched with 222 cases of control cases (ratio 1:3) on the basis of same sex, same operational risks andthe same year of operation. The underlying cardiovascular disease, age of more than 55 years, emergency operations, ASA-classification and the duration of anesthesia for more than 90 minutes were compared between cases and controls. The crude odds ratio and adjusted odds ratio were analyzed by multiple logistic regressions. Result: The patients who developed peri-operative myocardial infarction were older, in a higher ASA-classification, were operated on in emergency situations, had more underlying cardiovascular diseases and were operated on for a longer time. An increasing duration of anesthesia every 90 minutes would progressively increase the risk of peri-operative myocardial infarction (adjusted odds ratio increases fro 2.95 to 5.23). Conclusion: All parameters of underlying cardiovascular diseases, age, ASA-classification and emergency operations increased the risk of peri-operative myocardial infarction, the same as in other studies. From this study, we demonstrated that increasing the anesthetic duration every 90 minutes also increased the risk of peri-operative myocardial infarction.