Evaluation of the Spread and Effect of Local Anesthetic Administered Using Thoracic Muscle Plane Block on Internal Thoracic Artery Grafts.

Objectives: To evaluate the spread and effect of local anesthetic administered using transverse thoracic muscle plane block (TTPB) in the tissue surrounding the internal thoracic artery (ITA) during ITA graft harvesting.

Design: Cross-sectional study.

Setting: Single hospital.

Participants: This study included 60 adult patients undergoing cardiac surgery with a median sternotomy.

Interventions: The change in peri-ITA tissue properties before and after TTPB with 20 mL local anesthetics on each side at the T4-T5 intercostal level was evaluated using transthoracic echocardiography in 47 patients. The peri-ITA tissue properties were evaluated from the internal side of sternum using a T-shaped ultrasound probe at the T4-T5 intercostal level after median sternotomy and the dissection of the sternal back side tissue to the ITA region in 30 patients. Seventeen patients underwent both evaluations.

Measurements and main results: The ITA identifying rate using transthoracic echocardiography was 90.4%. A weak correlation was observed between the distance from the sternum to ITA and patient height. The 20 mL local anesthetics administered using TTPB spread laterally to the ITA area in all identified ITAs. However, the evaluation from the internal side of the sternum using a T-shaped ultrasound probe revealed that the property changes in the peri-ITA tissue had completely disappeared in all cases. The minimum time from TTPB implementation to this observation was 50 minutes.

Conclusions: TTPB can be performed safely on patients undergoing coronary artery bypass grafting using ITAs without affecting the ITA graft properties and patency.