1. To analyze the association of different doses of opioids on myocardial injury/protection through BMP-6/SMAD pathway.
2. To observe the effect of different doses of opioids on the expression of BMP-6 in bone marrow.
3. To investigate the relationship between different doses of opioids and BMP-6 and perioperative cardiovascular adverse events in patients with lower extremity fracture surgery.

This study explored the important role of BMP6/SMAD pathway in myocardial/injury protection by observing the effects of different doses of opioids on myocardial injury indexes hs-cTnI and BMP-6 related indexes in patients undergoing lower extremity fracture surgery, as well as the changes of BMP6 expression in bone marrow tissue of fracture end. The relationship between different doses of opioids and BMP6 and cardiac adverse events provides a theoretical basis for clinical rational drug use.

Inclusion Criteria:

• There were 160 patients aged 18-65 years and older who needed surgery for lower extremity fracture.
• ASA grades I to III, gender is not limited.

Exclusion Criteria:

• Patients with acute myocardial infarction in the last 6 months, those with a history of heart failure, and those with elevated troponin levels before injury.
• Old fracture
• Stroke patients
• Liver cirrhosis, kidney failure
• Serious systemic infections, alcoholism, drug dependence
• Pathological fracture
• Use of glucocorticoids in the past one month
• Diabetic