Thoracic epidural analgesia (TEA) and paravertebral block (PVB) were still the gold standards for postoperative analgesia after thoracic and abdominal surgeries. Techniques of TEA and PVB changed to become safer with less failures thanks to ultrasounds. the increased of ultrasound use, permitted the anesthesiologists to explore the paraspinal anatomy. Since a couple of years, appeared new paraspinal techniques. It involves injections into the musculofascial plane. All these interfascial plane blocks have shown promise as an alternative to neuraxial blockade for a variety of surgeries with good effects. In addition, these blocks have a reduced risk of direct spinal cord injury, epidural hematoma, and central infection. the site of injection is distant from neuraxis and pleura. These new paraspinal blocks become more and more popular because they are easy to perform. This short review will explore all these new paraspinal techniques.

Between the transverse process and the paravertebral space, the costovertebral ligament do not performed a closed border. Costache and al. aimed to place the needle tip at the mid-point between the transverse process and pleura.¹ on cadavers, the presence of methylene blue dye in the paravertebral space was examined because of the presence of a gap between the medial and lateral portions of the costovertebral ligament. Case reports confirmed the analgesic effect of this injection. the name of this regional analgesia is the mid-point transverse process to pleura (MTP) block. the injection posterior to the costovertebral ligament will result in solution passing through gaps and fenestrations, and reaching the nerve root in the paravertebral space. So pleural displacement may not always be necessary for paravertebral spread, as evident with other paraspinal blocks: the retrolaminar (RLB), the erector spinae plane (ESP) and the paraspinal blocks. the injectate distribution from these paraspinal blocks to the paravertebral space is volume dependent, suggesting that high volumes would be required to achieve effective regional anesthesia and analgesia that would be consistent with PVB.² Thoracic paravertebral block has complications: epidural spread (2.1%), Horner’s syndrome (1.8%), vascular puncture (0.5%), convulsions (0.2%) and pneumothorax (0.1%).³ These paraspinal blocks seem to be safer because of the placement of the needle tip within a few millimetres or centimeters of the pleura and the intervertebral foramen.

The retrolaminar block is the most posterior and medial block. the injection of local anesthetic is performing just behind the lamina. the indication of this block has to be specified. a retrolaminar block has been reported to be an effective analgesic method for breast cancer surgery: 15 ml of 0.5% ropivacaine for each lamina of the T2 and T4 vertebrae versus placebo reduce pain score immediatly after surgery⁴ or 20mL of 0.375% levobupivacaine at T4 lamina and a continuous infusion with 4 ml/h of 0.25% levobupivacaine for 72h.⁵ the other surgeries reported for this block were at the thoracic level or on vertebra: thoracic lobectomy,⁶ transapical transcatheter aortic valve implantation,⁷ and acute lumbar trauma.⁸ However, the use of a bilateral retrolaminar block for lumbar vertebral surgery has been successfully reported in 2017.⁹ Lumbar laminoplasty of L2 to L4 with a bilateral retrolaminar block performed with 0.375% levobupivacaine (20 mL injected into each side, 40 mL total) injected into the bilateral dorsal space of the fourth thoracic spinous process. No additional analgesics were administered during the perioperative period. This study suggests that a retrolaminar block can block the posterior rami of the lumbar nerves. a bilateral retrolaminar block was an effective analgesic for lumbar vertebral surgery.⁹ Bilateral block seems to be necessary despite unilateral surgery because of the existence of cross over innervation near the midline.¹⁰

Currently, the most popular paraspinal block is the ESP block. More than 242 case reports were actually published.¹¹ Forero M et al described this novel technique in 2016.¹² the ultrasound-guided ESP block is a recently developed procedure for providing extensive truncal analgesia.¹² the procedure is relatively easier to perform and noninvasive, compared to thoracic paravertebral block and thoracic epidural analgesia. the patient is placed in a sitting position and ultrasound is used to identify the chosen transverse process by counting down from the first rib. the transducer is placed in a longitudinal parasagittal orientation to identify the tip of the transverse process deep to the overlying muscles. a needle is inserted in plane to the US beam in a caudal-to-cranial direction to place the needle tip between the posterior fascia of the erector spinae muscle and the chosen transverse process. This is verified by hydrodissection with 0.5–1 mL of normal saline and visualization of linear fluid spread deep to the erector spinae muscle following which local anesthesics can be injected. the ESP block is a recently described, easy and reliable superficial block that targets the posterior part of the transverse process and the erector spinae muscle.¹² the ESP block seems to be a simple alternative to the conventional paravertebral and neuraxial blocks. the easily identifiable landmarks make this block a good novel regional anesthetic technique. a catheter can be insert easily in this interfascial space. ESP was described and used for several adult and pediatric indications: thoracic neuropathic pain,¹² analgesia for thoracic surgery,^{13 14} analgesia for rib fractures,¹⁵ vertebra surgery,^{16 17} breast surgery,^18–20 analgesia for chronic shoulder pain,²¹ major open abdominal surgery (open radical cystoprostatectomy with ureter and neobladder reconstruction),²² bariatric surgery,²³ laparoscopic ventral hernia repair²⁴ and hip analgesia: total hip arthroplasty.²⁵

More laterally of the paravertebral space, a paraspinal block can be performed.²⁶ the injection of local anesthetics is perform between the extrathoracic fascia and paraspinal muscles near the T3/T4 spinous process. the needle advanced cranio-caudally towards the lower ribs to provide maximal diffusion.²⁶ Paraspinal block do not have lots of evaluation but this block could be comparable as a lateral ESP block. More lateraly on the body, limit between a para-spinal and a thoracic block, the rhomboid intercostal block can be performed by an injection between the rhomboid major and intercostal muscles at the T6-7 level.²⁷

At last, an injection of local anesthetic in the fascial plane between the multifidus and longissimus muscles of the thoracolumbar spine can be performed: the thoraco-lumbar interfascial plane (TLIP) block.²⁸ For memory, erector spinae muscules are composed from median to lateral by 3 parts: multifidus, longissimus thoracis, and iliocostalis. the dorsal ramus emerges at junction between superior articular process and transverse process and splits into 3 branches (medial, intermediate, and lateral). TLIP block targets the sensory component of the dorsal rami of the thoracolumbar nerves. TLIP is reported for the treatment of postoperative pain after spine surgery. Some modified technique can be described with an other injection between the longissimus and iliocostalis muscles.²⁹ An injection superficial to the posterior thoracolumbar fascia (investing the paraspinal muscles) will probably ensure subcutaneous blockade. Randomized controlled trials are needed to valid the indications. At the cervical level, different para-spinous blocks are described. They are performed for cervical spinal surgery because of blocking the dorsal rami of the cervical spinal nerves. the inter-semispinal plane (ISP) block involves injection of local anesthetic into the fascial plane between the semispinalis cervicis and semispinalis capitis muscles.³⁰ the multifidus cervicis plane (MCP) is the fascial plane block between the multifidus cervicis and semispinalis cervicis muscles.³¹ the cervical interfascial plane (CIP) block need an anesthetic injection between the multifidus and longissimus muscles.³²

In conclusion, it is well kown that TEA and PVB are technically challenging procedures and are associated with a significant failure rate. In contrast, the para-spinal blocks are novel alternatives. They are simpler and safer to perform. But there is a paucity of controlled clinical trials, yet an abundance of case reports. Randomized controlled trials are needed to valid all these good experiences described in case reports. ESP still actually the most described para-spinal block.

References

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