Ultrasound Guided Erector Spinae Plane Block for Postoperative Analgesia in Patients undergoing Percutaneous Nephrolithotomy – A Double-blinded, Randomized Controlled Trial

Percutaneousnephrolithotomy (PCNL), a minimally invasive surgical procedure used to treatpatients with large kidney stones(1),is usually associated with significant pain in the perioperative period. PCNLis performed in the prone position and although neuraxial anaesthesia has beensuccessfully employed for the procedure, most patients and physicians prefergeneral anaesthesia for the same (2).

Intravenousanalgesics such as opioids are routinely employed for the management ofintraoperative and postoperative pain in these patients. These are oftenassociated with significant adverse effects such as nausea and vomiting,pruritis and respiratory depression which may affect the postoperative coursein these patients (3). Nonsteroidal anti-inflammatory (NSAID) drugs are oflimited use in these patients as they are likely to have deranged kidneyfunction tests (4).

In order tominimize the adverse effects of intravenous analgesics and to optimizeperioperative analgesia, supplemental regional analgesia techniques such asepidural block, paravertebral block and intercostal nerve block have been usedfor the management of pain (5),(6). Epidural anaesthesia may be associated withcomplications like paraplegia, cauda equina syndrome, epidural hematoma,infection, intravascular injection, urinary retention etc. Although thesecomplications are rare, they are severe enough to pose high morbidity to thepatient (3). Thoracic paravertebral block is also as effective as epiduralanaesthesia but is more technically demanding and requires multilevelinjections to achieve large dermatomal coverage (7).

Theultrasound-guided erector spinae plane (ESP) block is a recently describedtechnique which involvesinjection of local anaesthetic in plane deep to erector spinae muscle.Cadaveric investigation indicates that injection of 20-mLsolutioninto the fascial plane deep to the erector spinae muscle at the levelofthe T5 transverse process can result in injectate spread betweenthe C7 and T8vertebral levels. Given that the erector spinae muscleextends inferiorly to thelumbar spine, injection into the ESP ata lower vertebral level (e.g, T7 or T8)should result in spread to thelower thoracoabdominal nerves as well. Inaddition, because the mechanism of action of the ESP block involvespenetrationof local anaesthetic into the thoracic paravertebralspace, it anaesthetizes notonly the ventral rami of spinal nerves but also the rami communicantes thatcontain sympathetic nervefibers. The ESP block thus has the potential toprovide both somaticand visceral sensory blockade (8), (9).

The main sourcesof acute pain after PCNL are visceral pain originating from the kidneys andureters and somatic pain from the incision site. Visceral pain is conductedlargely through T10–L2 spinal nerves whereas the cutaneous innervation of theincision site is by the T8–T12 nerves. Thus, ESPBwould likely be a good regional anaesthetic technique for PCNL (3), (10).

Also, the literature suggests that it iseasier to perform as landmarks for the identification of the site of block arereadily identifiable and good dermatomal coverage with a single puncture.Another important advantage lies in that the block site is away from majorvascular structures and pleura and therefore is associated with less incidenceof complications as compared to PVB (8).

We hypothesized that ESPB would be agood adjunct for providing perioperative analgesia and lead to reduction intotal opioid consumption in the perioperative period following PCNL. Although ESPB has been used for many procedures, there isno data till date for its use for the management of pain in patients undergoingpercutaneous nephrolithotomy. Hence, we aim to assess the efficacy ofESPB in providing perioperative analgesia in patients undergoing PCNL.

References

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5.           5.  Li C, Song C, Wang W, Song C, Kong X.Thoracic Paravertebral Block versus Epidural Anesthesia Combined with ModerateSedation for Percutaneous Nephrolithotomy.Med Princ Pract. 2016Aug; 25(5): 417–422.

6.     6. Ozkan, D., Akkaya, T., Karakoyunlu, N. et al.Effect of ultrasound-guided intercostal nerve block on postoperative pain afterpercutaneous nephrolithotomy.Anaesthesist. 2013 Dec;62(12):988-94.

7.       7. El-Boghdadly, K., Madjdpour, C., &Chin, K. J. (2016). Thoracic paravertebral blocks in abdominal surgery – asystematic review of randomized controlled trials.Br J Anaesth. 2016Sep;117(3):297-308.

8.            8. Forero M, AdhikarySD, Lopez H, Tsui C, Chin KJ. The erector spinae plane block: anovel analgesictechnique in thoracic neuropathic pain. RegAnesth Pain Med2016;41:621–7.