Background and Aims Internal thoracic artery (ITA) is the gold-standard conduit in coronary artery bypass graft surgery (CABG). Therefore, ITA injury should be avoided during the pre-incision transversus thoracic muscle plane block (TTPB) in CABG. Hence, some anesthesiologists prefer to perform TTPB postoperatively. However, pre-incisional TTPB has potential advantages in reducing the requirement for intraoperative opioids and decreasing pain sensitization. We describe a sequence of steps in performing pre-incision TTPB to avoid ITA injury.

Methods We performed a pre-block scan by placing a high-frequency linear ultrasound probe transversely at desired intercostal space (ICS), applied color Doppler to identify ITA (figure 1), and marked the skin above ITA. After aseptic skin preparation, we put the ultrasound probe in sagittal orientation on the skin mark and then moved laterally until the lateral edge of transversus thoracic muscle (TTM) is visible. We target the plane between internal intercostal muscle and TTM, lateral to ITA.

Results TTPB can be performed at the 3^rd or 4^th ICS, using a transverse or sagittal approach. A sagittal approach at the 4^th ICS is recommended due to the wider LA spread. We may encounter several challenges during TTPB performance: ITA location is in the same plane as the target of TTPB, ITA varies in size, identification of ITA is not always easy, and ITA might mimic TTM (figure 2), which prone to accidental puncture.

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Abstract 137 Figure 1

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Abstract 137 Figure 2

Conclusions We have developed a sequence of steps that may guide anesthesiologists to perform the safe and effective TTPB, particularly when the block is performed before the incision in CABG.