The analgesic efficacy of pre-operative bilateral erector spinae plane (ESP) blocks in patients
having ventral hernia repair.
Sanjib Adhikary, Ki Jinn Chin, Mauricio Forero, Nabeel Sarwani
•The ultrasound-guided erector spinae plane (ESP) block at the T5 transverse process is a recently-described technique for providing thoracic analgesia .
•Based on its mechanism of action, we hypothesised that if performed at a lower vertebral level, it would provide effective truncal analgesia for abdominal surgery.
•Here we describe our experience with the ultrasound-guided ESP block performed at the T7 transverse process in a pilot study of four patients undergoing laparoscopic ventral hernia repair together with radiological data from injection in a fresh cadaver.
•We performed the block in a fresh cadaver and assessed the extent of injectate spread using computerised tomography. There was radiographic evidence of spread extending cranially to the upper thoracic levels and caudally as far as the L2-L3 transverse processes.
•We performed pre-operative bilateral ESP blocks with 20-30 ml 0.5% ropivacaine at the level of the T7 transverse process in four patients undergoing laparoscopic ventral hernia repair.
•We detected spread of injectate as far caudad as the L2-L3 transverse process in a fresh cadaver model
•The patients in our case series had NRS pain scores in the recovery area that ranged from 0 to 5/10 despite minimal doses of intraoperative opioid
•Median (range) 24 hour opioid consumption was 18.7 mg (0.0 to 43.0 mg) oral morphine. The highest and lowest median (range) pain scores in the first 24 h were 3.5 (3 to 5) and 2.5 (0 to 3) on an 11-point numerical rating scale.
•In our initial report, we demonstrated that injection into the fascial plane deep to erector spinae muscle (the erector spinae plane, ESP) at the level of the T5 transverse process can produce profound analgesia of the ipsilateral hemithorax.
•Anatomical dissection indicates that the likely mechanism of action is diffusion of local anaesthetic anteriorly through the connective tissues and ligaments spanning the adjacent transverse processes and into the vicinity of the spinal nerve roots.
•The erector spinae muscle is a complex composite of three muscles: iliocostalis, longissimus and spinalis. It originates from the sacrum and the lumbar spinous processes, and extends upwards as a gradually tapering column of muscle in the paravertebral groove on either side of the spinous processes, with insertions on the thoracic and cervical vertebrae as high as C2.
•The columnar arrangement of erector spinae muscle and its associated retinaculum provides an anatomical basis for fluid injected in the ESP to spread extensively in a cephalad-caudad direction and, furthermore, implies that injection at levels caudad to T5 should result in spread to the lower thoracic nerve roots supplying the abdomen.
•The patients in our case series had NRS pain scores in the recovery area that ranged from 0 to 5/10 despite minimal doses of intraoperative opioid, and the median 24-hour opioid requirement was 18.7 mg. This compares favourably with the results of Fields et al  whose average 24-hour oral morphine consumption was 64.0 mg in the group who received surgical TAP blocks compared with 106.5 mg in their control group. Average NRS pain scores in recovery were 5.2 vs 6.5 at rest in the TAP and control groups respectively, and 6.2 vs 7.3 with movement.
•In this pilot study we have demonstrated that the ESP block can indeed provide effective abdominal analgesia following injection at the T7 transverse process. We detected spread of injectate as far caudad as the L2-L3 transverse process in a fresh cadaver model, and documented a sensory block from T6 to T12 in one of our patients.
•We conclude that the ESP block is a promising regional anaesthetic technique for laparoscopic ventral hernia repair and other abdominal surgery when performed at the level of the T7 transverse process. Its advantages are the ability to block both supra-umbilical and infra-umbilical dermatomes with a single-level injection and its relative simplicity.