Abstract
Rectus sheath blocks can provide analgesia for upper abdominal midline incisions. These blocks can be placed on patients who are anticoagulated, supine, and under general anesthesia. However, block success rates remain low, presumably because of the difficulty of placing local anesthetic between the correct fascial layers. Here we characterize a hypoechoic triangle with sonography, an anatomic space between adjacent rectus abdominis segments that can be accessed for easier needle tip and catheter placement. This approach could reduce reliance on hydrodissection to correctly identify the potential space and instead improve block efficacy by offering providers a discrete target for local anesthesia.