Intermediate cervical plexus block in the management of persistent postoperative pain post carotid endarterectomy: A prospective, randomized, controlled, clinical trial

Background: The mechanisms of persistent postoperative pain (PPP) with neuropathic features after carotid endarterectomy (CEA) are multifaceted and are incompletely understood. Objectives: The aim of this research was to assess whether the ultrasound-guided (USG) intermediate cervical plexus block (ICPB) could provide better control of PPP and neuropathic disturbances (NPDs) after CEA than the USG superficial cervical plexus block (SCPB). Study Design: Prospective, randomized, controlled, clinical trial. Setting: This clinical trial was conducted at the SS Filippo and Nicola Academic Hospital of Avezzano (L’Aquila, Italy). Methods: Patients who were scheduled for primary CEA were chosen. In the experimental group, the USG-ICPB was performed unilaterally, at the level of the third cervical vertebra. The needle was inserted into the deep lamina of the deep fascia of the neck, between the posterior border of the middle scalene muscle and the anterior border of the posterior scalene muscle. Three milliliters saline solution was injected into the opening of the deep lamina, and 20 mL 0.375% levobupivacaine was injected. In the control group, the anesthetic target was located at the inferior border of the sternocleidomastoid muscle at the level of the third cervical vertebra. The needle was superficially inserted below the skin, and 2 to 3 mL saline solution was injected into the opening of the superficial lamina of the deep fascia of the neck. A total of 20 mL 0.375% isobaric levobupivacaine was subsequently injected. The primary outcome measure was the proportion of patients with PPP on movement and at rest 3 months after surgery. The secondary outcome measures were NPD assessment scores using the von Frey hair test and the Lindblom test, opioid and pregabalin consumption. Adverse effects were also recorded. Results: A total of 98 consecutive patients were enrolled and randomized to receive either a USG-SCPB (control group, n = 49) or a USG-ICPB (experimental group, n = 49). The sensory blockade was longer in the experimental group. Three months after surgery, the proportions of patients with PPP on movement were significantly different between the experimental and control groups (33%, 95% confidence intervals [CI], 20%-47% vs. 71%, 95% CI, 57%-83%; P < 0.001), whereas there were no differences in the proportions of patients with pain at rest between groups (31%, 95% CI, 18%-45% vs. 49%, 95% CI, 34%-64%; P = 0.063). The proportions of patients with NPDs were not different between the groups, whereas the sizes of the areas of interest (cm2) were significantly different. Limitations: A limitation of this study is that we assessed NPDs for only 3 months using the von Frey hair test and the Lindblom test without additional instrumental techniques. Additionally, there are many risk factors for NPDs after CEA. For this reason, another limitation of this research is that we neglected to consider the relationship between the choice of anesthetic block and the presence of these risk factors. Conclusions: The USG-ICPB provided long-lasting analgesia during the postoperative period and might mitigate the development of NPDs, thereby decreasing the analgesic drug requirement.