Monitoring regional myocardial function after myocardial revascularization

High thoracic epidural blockade increases myocardial oxygen availability in coronary surgery patients

BACKGROUND

High thoracic epidural techniques are increasingly being used in patients scheduled for cardiothoracic surgery, including coronary artery bypass grafting. In the present study, we evaluated the acute effects of the epidural blockade on myocardial oxygen availability by means of tissue oxygen pressure monitoring in patients submitted for surgical revascularization.

METHODS

Fifty adult patients were included in a prospective, randomized, double-blind study. After placement of an epidural catheter in thoracic space T1-T2, and under general anesthesia, 5-10 ml of either normal saline or 0.3% ropivacaine was injected through the epidural catheter. Hemodynamic parameters and the intramyocardial oxygen partial pressure were recorded before and 20 min after the epidural injection.

RESULTS

There were no demographic or hemodynamic differences between the groups before intervention. A significant increase in intramyocardial partial oxygen pressure was observed in the ropivacaine group (14.6 mmHg vs. 25.1 mmHg, P < 0.0005).

CONCLUSION

High thoracic epidural blockade with 5-10 ml of 0.3% ropivacaine increases myocardial oxygen availability in coronary diseased patients prior to surgical revascularization without deleterious hemodynamic disturbances.

A computerized bioelectrical cardiac monitor

The use of a micro-computer improves the performance of an impedance cardiograph. The impedance signals and the ECG are real-time processed and four analog signals are displayed on the screen. A beat-to-beat estimation of cardiac output and several indexes are computed and displayed. User's interface is by interactive screen menus. Some facilities permit data identification, storage and post-processing. The software has been designed in such a way as to be adaptable to each specific application and to enable the development of new routines for cardiac signal processing. The signals recorded in healthy patients are in agreement with the results of other similar studies.