Anatomical basis of fascial plane blocks

Abstract

Fascial plane blocks (FPBs) are regional anesthesia techniques in which the space (“plane”) between two discrete fascial layers is the target of needle insertion and injection. Analgesia is primarily achieved by local anesthetic spread to nerves traveling within this plane and adjacent tissues. This narrative review discusses key fundamental anatomical concepts relevant to FPBs, with a focus on blocks of the torso. Fascia, in this context, refers to any sheet of connective tissue that encloses or separates muscles and internal organs. The basic composition of fascia is a latticework of collagen fibers filled with a hydrated glycosaminoglycan matrix and infiltrated by adipocytes and fibroblasts; fluid can cross this by diffusion but not bulk flow. The plane between fascial layers is filled with a similar fat-glycosaminoglycan matric and provides gliding and cushioning between structures, as well as a pathway for nerves and vessels. The planes between the various muscle layers of the thorax, abdomen, and paraspinal area close to the thoracic paravertebral space and vertebral canal, are popular targets for ultrasound-guided local anesthetic injection. The pertinent musculofascial anatomy of these regions, together with the nerves involved in somatic and visceral innervation, are summarized. This knowledge will aid not only sonographic identification of landmarks and block performance, but also understanding of the potential pathways and barriers for spread of local anesthetic. It is also critical as the basis for further exploration and refinement of FPBs, with an emphasis on improving their clinical utility, efficacy, and safety.

Transverse abdominis plane injection of bupivacaine with dexmedetomidine or a bupivacaine liposomal suspension yielded lower pain scores and requirement for rescue analgesia in a controlled, randomized trial in dogs undergoing elective ovariohysterectomy

“…10,17 The reality is that we still do not fully understand how fascial anatomy interacts with local anesthetic and its subsequent migration after injection. [4][5][6][7] The longer duration of action (72 hours) 18 claimed by the manufacturer of the commercial preparation of a BLS used in this study and approved to use in dogs and cats in the United States (Nocita; Elanco) did not appear to further the benefit that the TAP block provided. This could have been due to a lack of sensitivity of our scoring system at picking up subtle signs of pain beyond 24 hours, and therefore, our BLS could have outlasted the duration of the immediate and acute postoperative pain, beyond which, prolonged local anesthetic duration did not provide any extra benefit.…”

“…These infiltrations, however, may behave in an unpredictable way, 4 and therefore, investigations of the interaction between the anatomy and the infiltration itself may provide a better understanding of the technique and thus increase their reliability, repeatability, and the overall success of these blocks. [5][6][7] The transverse abdominis plane (TAP) block relies on the infiltration of local anesthetic in between…”

Erector Spinae Plane Catheter Analgesia in Minimally Invasive Mitral Valve Surgery: A Retrospective Case–Control Study for Inclusion in an Enhanced Recovery Program

“…4 Fascial plane blocks, in general, are not capable of producing as complete and dense blockade compared to neuraxial blocks, in part due to their lack of visceral analgesic potential. 5 Neuraxial blocks, conversely, provide both somatic and visceral analgesia and are even capable of providing surgical anesthesia in some cases. 6-8…”

Development of Enhanced Recovery After Surgery (ERAS) protocols in veterinary medicine through a one-health approach: the role of anesthesia and locoregional techniques

“…17 The incidence of associated observed side effects with neuraxial techniques such as intraoperative hypotension, postoperative residual motor paralysis, or urinary retention is significantly decreased in the dog, 18 making peripheral nerve blocks preferred. More recently, ultrasound-guided fascial plane blocks (injection of local anesthetic within a selected fascial plane to target nerves that run through that plane) are gaining popularity, [19][20][21][22][23] and a number of injection techniques are being described and successfully adapted from human anesthesia to be used in the dog. [24][25][26][27] Currently, there are no standards in veterinary anesthesia regarding ERAS protocols and locoregional anesthesia for individual surgical procedures; however, there is enough published literature and clinical information to make some informed recommendations.…”