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A 65-year-old man is undergoing an awake carotid endarterectomy. You plan to perform a cervical plexus block with mild sedation, and the surgeon agrees to supplementation with local anesthetic if needed. According to a recent study, which of the following perioperative outcomes is MOST likely to be increased if you were to perform a superficial cervical plexus block instead of a deep cervical plexus block?
(A) Conversion to general anesthesia X
(B) Desaturation in the postanesthesia care unit X
(C) Preserved movement of the ipsilateral diaphragm ✔Gain insight on this topic, and many others, with Summaries of Emerging Evidence (SEE) 2023 – now available. The content is aggregated from 30 international medical journals to streamline your learning and improve your practice.
Cervical plexus block is a widely used technique as part of an anesthetic plan for various neck procedures. The plexus can be blocked by depositing local anesthetic at various depths. In the superficial block technique, local anesthetic is placed superficial to the deep cervical fascia; in the intermediate block technique, local anesthetic is deposited between the deep cervical fascia and prevertebral fascia; and in the deep plexus block technique, the anesthetic is deposited deep to the prevertebral fascia. The rate of phrenic nerve dysfunction as well as the spread of the injectate associated with the 3 depths of the cervical plexus block has not been previously studied.
A recent randomized controlled, observer-blinded study evaluated the rate of ipsilateral diaphragmatic dysfunction and the spread of the injectate across facial planes when the plexus is blocked at various depths. The study enrolled 45 patients scheduled to undergo awake elective extracranial internal carotid endarterectomy under regional anesthesia. On the day of surgery, the patients were randomly assigned to 1 of 3 block groups: superficial, intermediate, or deep. Each block was performed by injecting 20 mL of 0.5% ropivacaine using the in-plane approach under ultrasound guidance at the C4 level. Baseline data were collected and included ipsilateral and contralateral diaphragm excursion using ultrasound at normal inspiration and with forced inspiration, as well as lung function tests, specifically, forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). After the block, a magnetic resonance imaging (MRI) scan of the neck area was performed to evaluate the spread of local anesthetic. Lung function tests were repeated before and after surgery.
The primary outcome of the study was the difference in ipsilateral diaphragmatic movement (measured in centimeters during forced inspiration) between the study groups. The secondary outcomes included the amount of supplemental local anesthetic used by the surgeon during surgery, intravenous analgesics, conversion rates to general anesthesia, pain levels postprocedure, narcotic consumption in the recovery area, complication rates, hemodynamic changes, oxygen saturation, postoperative hoarseness, and paresis of the recurrent laryngeal nerve.
A noticeable difference was observed between the 3 groups in diaphragmatic movement during forced inspiration favoring the superficial plexus block in preserving phrenic nerve function (deep group, 2.04 ± 1.20 cm; intermediate group, 3.86 ± 1.24 cm; superficial group, 4.34 ± 1.06 cm). Post hoc analysis demonstrated a mean difference of −1.82 cm (95% CI, −2.79 to –0.85) between the deep and intermediate blocks, a mean difference of −2.30 cm (95% CI, −3.27 to –1.33) between the deep and superficial blocks, and a mean difference of −0.48 cm (95% CI, −1.45 to 0.50) between the intermediate and superficial blocks. The difference in diaphragmatic movement was also present during normal inspiration after the block (deep group, 1.00 ± 0.93 cm; intermediate group, 1.60 ± 0.75 cm; and superficial group, 1.62 ± 0.50 cm).
No major difference in hoarseness was observed between the 3 groups, although it was more commonly noted in those who received a deep cervical plexus block. Lung function values decreased marginally before and after block only in the deep group (FEV1 by 0.46 L and FVC by 0.66 L). Conversion to general anesthesia, intraoperative local anesthetic use, intravenous opioid use, rate of desaturation, complication rates, pain score in the postanesthesia care unit, and patient satisfaction were similar between the 3 groups.
Analysis of the MRI scans revealed that the most extensive cranio-caudal spread occurred in the deep group while there was similar lateral spread in all groups. Contrast spread below the superficial cervical fascia but did not extend beyond the deep fascia in both the superficial and intermediate groups. In most of the patients in the deep group, local anesthetic spread below the deep fascia.
In conclusion, this is the first randomized study to evaluate the association between diaphragmatic dysfunction and depth of local anesthetic deposition administered for various depths of cervical plexus block. Cervical plexus block is a safe anesthetic technique that can result in patient satisfaction, if certain exclusion criteria are followed. In this study, which excluded patients with severe lung dysfunction, no clinically relevant differences in patient outcomes were found despite the differences in diaphragmatic dysfunction between the superficial, intermediate, and deep cervical plexus blocks. The clinical relevance of this diaphragmatic dysfunction has yet to be determined in patients with severe lung dysfunction.
Reference
Date of last update: June 28, 2023
