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During carotid endarterectomy, the use of locoregional anesthesia to achieve a combined superficial and deep cervical plexus block can cause cardiovascular, respiratory, and neurologic complications. Seeking to reduce risk and find an easier procedure, we applied locoregional anesthesia and an intermediate cervical plexus block in a series of patients who underwent carotid endarterectomy.
From 2006 through 2007, 183 patients underwent primary carotid endarterectomy at our hospital. Mean age was 75.9 ± 9.9 yr; mean body mass index, 27.3 ± 6.7 kg/m2; and median American Society of Anesthesiologists physical status classification, P3 (range, P2–P4). All procedures combined an intermediate cervical plexus block with subcutaneous infiltration of the incision line. We inserted a 15-mm, 25G needle to its full length, perpendicular to the skin along the posterior border of the sternocleidomastoid muscle, midway between the mastoid process and the clavicle. We injected 10 mL of 0.75% ropivacaine solution for 3 to 5 minutes. This block was systematically combined with subcutaneous infiltration of the incision line with the ropivacaine (0.75%, 10 mL), and sometimes also with 2% topical lidocaine intraoperatively. If necessary, intraoperative sedation, analgesia, or both were given to patients to improve their compliance.
Intraoperative topical lidocaine was required in 59 patients (32.2%), and intravenous midazolam, fentanyl, or both were required in 29 patients (15.8%). Two procedures were converted to general anesthesia (1.1%). No perioperative deaths or complications occurred. Postoperatively, 2 patients experienced strokes and 1 sustained a myocardial infarction (total rate, 1.6%).
We found the intermediate cervical plexus block to be feasible, effective, and safe, with low perioperative and postoperative complication rates. Herein, we report our findings.
General anesthesia and locoregional anesthesia (LRA) are both suitable choices in carotid endarterectomy (CEA). Although today most surgeons use general anesthesia, the potential benefits of LRA techniques are well described.1,2 If LRA is the choice, CEA is typically approached via a combined superficial and deep cervical plexus block. This technique requires specific skills and expertise, and it can potentially cause complications, such as respiratory depression, cardiac arrest, and vertebral artery or nerve injury.3 In 2003, experimenting on human cadavers, Pandit and colleagues4 showed that the deep cervical fascia is permeable, giving a possible explanation for the clinical efficacy of a purely superficial cervical plexus block in comparison with a deep or combined cervical plexus block. In 2004, Telford and Stoneham5 systematized the nomenclature of cervical plexus block, classifying “intermediate” block as the injection of local anesthetic between the superficial and deep cervical fascia. We contend that there is some confusion and misunderstanding in the literature regarding cervical plexus block: some authors define superficial block as a block deep in the investing layer of the deep cervical fascia that can spread to the deep areas of the neck. Moreover, there is no consensus in regard to the preferable LRA approach, and no clinical series appear to have dealt with intermediate cervical plexus block.
To overcome the risks and technical difficulties of the combined cervical plexus block, we began in 2006 to approach CEA with an intermediate block. In our observational study, we sought to investigate this technique's feasibility, efficacy, and safety for the patient. Herein, we report our findings.
After years of performing combined cervical plexus block as described by Moore,6 we began approaching CEA by implementing an intermediate cervical plexus block. From January 2006 through December 2007, our observational study involved 183 patients who underwent primary CEA at our hospital. Their mean age was 75.9 ± 9.9 years; their mean body mass index was 27.3 ± 6.7 kg/m2; and their median American Society of Anesthesiologists physical status classification was P3 (range, P2–P4). Our Institutional Review Board approved the study.
All CEAs were performed by the same 3 senior vascular surgeons, and all anesthesiologic procedures were conducted by staff anesthesiologists. After each patient was premedicated with intramuscular morphine (0.1 mg/kg of body weight), a 15-mm, 25G needle was inserted to its full length, perpendicular to the skin along the posterior border of the sternocleidomastoid muscle, midway between the mastoid process and the clavicle (Fig. 1). Ten mL of 0.75% ropivacaine solution was injected for 3 to 5 minutes. Injection into the sternocleidomastoid muscle was carefully avoided, as was risking paresthesia or contact with the vertebrae. The block was systematically combined with subcutaneous infiltration of the incision line with 10 mL of 0.75% ropivacaine. As necessary, the block was supplemented intraoperatively with topical lidocaine (2%), in 3-mL increments. In a few instances of poor patient compliance, we added midazolam (1–2 mg) or fentanyl (25–50 μg) intravenously.
We recorded data that included the characteristics of the patients; the intraoperative administration of topical anesthesia, sedation, and intravenous analgesia; instances of conversion to general anesthesia if LRA failed; and the occurrence of procedure-related complications during the perioperative period (for example, respiratory problems, intrathecal injection, intravascular injection with convulsions, cardiac arrest, or unscheduled admission to the intensive care unit).
Table I shows the data on the patients and the procedures. Intraoperative topical supplementation was required in 59 patients (32.2%), with the median use of two 3-mL increments of 2% lidocaine (range, 1–5 increments). Intraoperative systemic sedation, analgesia, or both were required in 29 patients (15.8%). Two LRA procedures were converted to general anesthesia (1.1%). There were no perioperative deaths or intraoperative complications. During the 1st postoperative week, 2 patients experienced a stroke and 1 sustained a myocardial infarction (total rate, 1.6%).
We found that the intermediate cervical plexus block overcomes the practical difficulties of Moore's deep block, reducing the risk of life-threatening complications and achieving the criteria of technical feasibility, efficacy, and safety.
The concept of intermediate cervical plexus block arises from the cadaver study by Pandit and colleagues.4 The investigators injected methylene blue deeply into the superficial cervical fascia. The solution spread to the deep cervical space across the deep cervical fascia, which suggested fascial permeability. Conversely, methylene blue that was injected above the superficial cervical fascia did not travel to the deeper tissues. On the basis of these observations, we realized that intermediate cervical plexus block, as a modification of the single-injection technique described by Winnie and associates in 1975,7 changes the surface landmark and reduces the injection depth to 15 mm (the length of the needle). We contend that this distance from the skin is sufficient to pass the superficial fascia. However, inserting the needle to this depth would not be feasible in morbidly obese patients (body mass index, approximately 40 kg/m2 or greater) or in patients with localized obesity in the neck (neck circumference, approximately 60 cm or greater).
Efficacy. During a deep block, the delicate anatomic structures near the needle route may be seriously injured. Our technique involves only 1 injection (rather than the multiple injections in Moore's deep block) and does not cause paresthesia or require vertebral contact.6 The intermediate approach is less invasive than a deep block.
Only 2 patients required conversion to general anesthesia after block placement. One instance was due to a block failure, the other to a sudden lack of cooperation from the patient. These results are encouraging when they are compared with the data published in a complete systematic review by Pandit and colleagues,3 who reported a conversion rate of 2.08% after purely deep cervical plexus blocks. Our low conversion rate when using an intermediate approach seems to contradict the conventional belief that a deep cervical plexus block produces a complete block and improves intraoperative muscle relaxation, therefore resulting in a greater success rate than that of a purely superficial cervical plexus block.8 In terms of surgical conditions, Stoneham and co-authors9 concluded that purely superficial block and purely deep block were of similar efficacy.
Under the assumption that anesthesia of the carotid wall could not be completely achieved in some patients, we administered intraoperative topical supplementation in 32.2% of the procedures. This incidence of block supplementation should be interpreted not as a high failure rate, but rather as a routine (often unnecessary) addition—one that is also commonly performed in deep cervical plexus block. Otherwise, we used complementary systemic sedation, analgesia, or both in patients who exhibited poor intraoperative compliance.
Safety. Postoperatively, we observed no deaths and a very low incidence of individual sequelae. In deep cervical plexus block, others have described risks such as phrenic nerve block, vocal cord dysfunction (paresis), and 12th-cranial-nerve block, with consequent respiratory distress or failure.10-12 In particular, diaphragmatic dysfunction—most likely due to phrenic nerve block—has been reported in approximately 60% of patients who have undergone deep cervical plexus block.12 Deep block (particularly with the multiple-injection technique) increases the risk of intrathecal injection or vertebral arterial injection, whereas our intermediate-block technique does not. Despite the higher complication rate that is associated with deep cervical plexus block, many anesthesiologists continue to use it. In a survey of British anesthesiologists, 71% reported that they would choose a combined cervical plexus block when undertaking CEA.13
During the study period, we realized that the intermediate cervical plexus block took less time to perform, on average, than did Moore's deep block. We also noted that the intermediate approach resulted in improved intraoperative compliance and cooperation on the part of patients, which we attribute to the less invasive nature of the intermediate procedure. These observations were incidental and were not measured as part of the study design.
Our findings are limited by a “hypothetical” intermediate block: the 15-mm depth is not valid in obese patients, as is stated above. This study is also characteristic of a case series, with possible bias due to a lack of randomization and blinding. However, our chief aim was not to evaluate the LRA technique in general, but to investigate the feasibility, efficacy, and safety of the intermediate cervical plexus block.
We conclude that our intermediate cervical plexus block technique is feasible, effective, and safe. To confirm our observations, randomized controlled trials could be conducted in order to compare the intermediate block with the other methods (superficial, deep, and combined block). Meanwhile, in consideration of the potential sequelae that are associated with deep cervical plexus block, studies using ultrasonographic imaging could validate the superiority of an intermediate block in comparison with a deep block.
Address for reprints: Marco Barone, MD, Department of Anesthesia & Perioperative Medicine, “Umberto Parini” Hospital, Viale Ginevra, 11100 Aosta/Aoste, Italy