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ORIGINAL ARTICLE

A Randomized Comparison Between Ultrasound-Guided and Landmark-Based Superficial Cervical Plexus Block De Q.H. Tran, MD, FRCPC, Shubada Dugani, MBBS, FRCA, and Roderick J. Finlayson, MD, FRCPC

Background: This prospective, randomized, observer-blinded study compared ultrasound guidance and the conventional landmark-based technique for superficial cervical plexus blockade. Methods: Forty patients were randomly allocated to receive a block of the superficial cervical plexus using ultrasound guidance (n = 20) or the traditional landmark-based technique (n = 20). The main outcome, success, was defined as the absence of cold sensation for all 4 branches of the superficial cervical plexus at 15 mins. A blinded observer recorded success rate, onset time, block-related pain scores, and the incidence of complications. Performance time and the number of needle passes were also recorded during the performance of the block. Total anesthesiarelated time was defined as the sum of performance and onset times. Results: Success rate (80%Y85%) was similar between the 2 groups. Performance time was slightly longer with ultrasonography (119 versus 61 sec, P G 0.001); however, no differences in onset and total anesthesiaY related times were found. There were also no differences in the number of passes and procedural discomfort. Conclusions: Ultrasound guidance does not increase the success rate of superficial cervical plexus block compared with a landmark-based technique. Additional confirmatory trials are required. (Reg Anesth Pain Med 2010;35: 539Y543)

U

ltrasound (US) guidance has become a reliable adjunct for brachial plexus, femoral, and sciatic nerve blocks.1 Furthermore, US can also be used to anesthetize purely sensory nerves such as the lateral femoral cutaneous and saphenous nerves.2,3 The superficial cervical plexus (SCP), a sensory neural plexus, supplies the skin overlying the ear, neck, angle of the mandible, shoulder, and clavicle.4,5 The SCP originates from the anterior rami of the C1 to C4 spinal nerves and gives rise to 4 terminal branches: the great auricular, lesser occipital, transverse cervical, and supraclavicular nerves. Traditionally, the SCP is blocked using a subcutaneous infiltration of local anesthetics along the posterior border of the sternocleidomastoid muscle.4,5 Recently, US has been used to identify intermuscular planes to carry out transversus abdominis plane and obturator nerve blocks.6,7 In our practice, we have observed that the SCP can also be scanned and anesthetized between the sternocleidomastoid and scalene muscles. Thus, to validate this new method, we conducted a prospective, randomized, observer-blinded trial comparing US and the conventional landmark-based technique. Our research hypothesis was that US results in a higher success From the Montreal General Hospital, Department of Anesthesia, McGill University, Montreal, Quebec, Canada. Accepted for publication August 27, 2010. Address correspondence to: De Q.H. Tran, MD, FRCPC, Montreal General Hospital, Department of Anesthesia, 1650 Ave Cedar, D10-144, Montreal, Quebec, Canada H3G 1A4 (e-mail: de_tran@hotmail.com). Copyright * 2010 by American Society of Regional Anesthesia and Pain Medicine ISSN: 1098-7339 DOI: 10.1097/AAP.0b013e3181faa11c

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rate. The latter was defined as the absence of cold sensation for all 4 branches of the SCP at 15 mins.

MATERIALS AND METHODS After obtaining ethics committee approval (McGill University Health Center, Montreal, Canada) and written informed consent, 40 patients undergoing surgery of the shoulder and clavicle were prospectively enrolled. Inclusion criteria were age between 18 and 70 years, American Society of Anesthesiologists (ASA) status I to III, and body mass index between 20 and 35 kg/m2. Exclusion criteria were inability to consent to the study, coagulopathy, hepatic or renal failure, and allergy to local anesthetic agents. After arrival in the induction room, an 18- or 20-gauge intravenous catheter was placed in the upper limb contralateral to the surgical site. Standard ASA monitoring was applied throughout the procedure. Sedation was not provided for the performance of the block. Using a computer-generated sequence of random numbers and a sealed envelope technique, 40 patients were randomly allocated to US or the traditional landmark-based technique (LM) for SCP blockade. All blocks were performed by 2 operators (D.Q.H.T and R.J.F.) who possess experience with both techniques. In the LM group, patients were positioned supine with the head turned toward the nonoperative side. The puncture site was located at the midpoint of the posterior border of the sternocleidomastoid muscle.5 After negative aspiration, using a 1.5-in, 25-gauge needle (Precision Glide; Becton Dickinson, Franklin Lakes, NJ), 5 mL of lidocaine 1.5% with 5 Kg/mL of epinephrine was injected subcutaneously in a cephalad direction. Another 5 mL was deposited in a caudad direction.5 In the US group, patients were placed in the lateral decubitus position with the operative side uppermost (Fig. 1A). Using a US machine (SonoSite Turbo; SonoSite Inc, Bothell, Wash) and a 6- to 13-MHz linear probe, the midpoint of the sternocleidomastoid muscle was scanned in a coronal section (Fig. 1B) to reveal the intermuscular plane between the sternocleidomastoid and scalene muscles (Fig. 2). Although neural structures (hypoechoic nodules) could often be visualized, we did not systematically search for them because the technique relied on injection of local anesthetic agents in the intermuscular plane (Fig. 3). Using a lateral to medial in-plane technique and a similar needle to that in the LM group, 10 mL of lidocaine 1.5% with 5 Kg/mL of epinephrine was deposited in the intermuscular plane. The imaging time (defined as the time interval between contact of the US probe with the patient and the acquisition of a satisfactory picture) was recorded in the US group, whereas the needling time (defined as the time interval between needle puncture and the end of local anesthetic injection) was recorded for both groups. Thus, performance time was defined as the sum of the imaging and needling times in the US group; in the LM group, performance and needling times were equivalent. The number of needle passes was also recorded. The initial needle insertion counted as the first pass. Any subsequent needle

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FIGURE 1. A, Identification of the posterior border (line) and the midpoint (arrow) of the sternocleidomastoid muscle. B, Position of the US probe.

elbow flexion (musculocutaneous), thumb abduction (radial), thumb opposition (median), and thumb adduction (ulnar). After the 15-min evaluation period, patients could receive interscalene blocks (to anesthetize the axillary, suprascapular, and subclavian nerves) and general anesthesia (for the beach chair position). This was left to the discretion of the treating anesthesiologist and was not recorded for the purpose of the study. Thus, surgical anesthesia and postoperative pain were not studied. One week after the surgery, patients were contacted by the blinded investigator to inquire about complications such as persistent paresthesiae.

advancement that was preceded by a retraction of at least 10 mm counted as an additional pass.8 Furthermore, the incidence of vascular puncture and paresthesiae was also noted. Subsequently, measurements of SCP blockade were carried out every 5 mins until 15 mins by a single, blinded observer. Sensory blockade of the lesser occipital, greater auricular, transverse cervical, and supraclavicular nerves was graded according to a 3-point scale using a cold test: 0 = no block, 1 = analgesia (patient can feel touch, not cold), 2 = anesthesia (patient cannot feel touch). The lesser occipital, greater auricular, transverse cervical, and supraclavicular nerves were tested on the skin overlying the mastoid process, the anterior surface of the ear lobe, the cricoid cartilage, and the clavicle, respectively.5 We considered a block to be successful if, at 15 mins, a score equal or superior to 1 was achieved for each of the 4 nerves. In successful blocks, the onset time was defined as the time required to obtain these scores. The blinded observer also recorded the patient’s anthropometric data as well as the level of procedural pain immediately after block placement using a 10-cm visual analog scale (0 cm = no pain, 10 cm = worst, imaginable pain). The incidence of Horner syndrome, hoarseness, dyspnea, and symptoms suggestive of local anesthetic toxicity was also noted. Furthermore, at 15 mins, sensory and motor testing of the upper extremity were also carried out by the same blinded observer to detect an unintentional brachial plexus block. Sensory blockade of the axillary, musculocutaneous, median, radial, and ulnar nerves were assessed on the lateral aspect of the deltoid, the lateral aspect of the forearm, the volar aspect of the thumb, the lateral aspect of the dorsum of the hand, and the volar aspect of the fifth finger, respectively. Motor blockade of the axillary, musculocutaneous, radial, median and ulnar nerves were evaluated by shoulder abduction (axillary),

Our working hypothesis was that, compared with the LMbased technique, US yields a higher success rate. Unfortunately, the success rate of the conventional technique is poorly quantified in the literature. However, using a volume of local anesthetic similar to ours, Dieudonne et al9 have previously reported that, after thyroid surgery, 45% of patients who received a SCP block did not require opioids in the recovery room. Thus, we expected the success rate in the LM group to be 45%. In our experience, we have observed that US yields a 90% success rate. To show such a difference, using a Student t test, a calculated sample size of 19 patients per group was required to provide a statistical power of 0.8 and a type 1 error of 0.05. We recruited 20 patients per group to account for potential patient dropouts. Statistical analysis was performed using SPSS version 16 statistical software (SPSS, Chicago, IL). For continuous data, normality was first assessed with the Kolmogorov-Smirnov test and then analyzed with the Student t test. Categorical data were

FIGURE 2. Identification of the sternocleidomastoid-scalene intermuscular plane (asterisk). Arrow indicates the needle. SAM indicates scalenus anterior muscle; SCM, sternocleidomastoid muscle; SMM, scalenus medius muscle.

FIGURE 3. Sternocleidomastoid-scalene intermuscular plane (asterisk) after local anesthetic injection. SAM indicates scalenus anterior muscle; SCM, sternocleidomastoid muscle; SMM, scalenus medius muscle.

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Statistical Analysis

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Volume 35, Number 6, November-December 2010 US-Guided Superficial Cervical Plexus Block

TABLE 1. Patient Characteristics Landmark (n = 20) US (n = 20) Age, yrs Sex (male/female) Body mass index, kg/m2 ASA physical status (I/II/III)

46 T 17 13/7 27 T 5 11/4/5

47 T 18 11/9 26 T 5 10/8/2

P 0.782 0.519 0.506 0.264

Continuous variables are presented as means T SDs; categorical variables are presented as counts. ASA indicates American Society of Anesthesiologists.

analyzed using the W2 test or Mann-Whitney U test as appropriate. Because of the extremely low incidence of complications, the latter were documented but not included in the statistical analysis. P e 0.05 was considered significant.

RESULTS No differences in anthropometric data were observed between the 2 groups (Table 1). Success rate (80%Y85%) was similar between the 2 groups. Performance time was slightly longer with US (119 versus 61 sec; P G 0.001), but no differences in needling, onset, and total anesthesiaYrelated times were found. The number of passes and procedural discomfort was also similar (Table 2). At 15 mins, patients in the US group presented a higher rate of sensory analgesia in the territory of the supraclavicular nerves. No differences were found for the other terminal branches of the SCP (Fig. 4). No instances of brachial plexus block, vascular puncture, or Horner syndrome were observed. No patient reported symptoms suggestive of local anesthetic toxicity. Dyspnea or decrease in peripheral oxygen saturation (measured by pulse oxymetry) did not occur. The 95% confidence interval (CI) for all these complications is 0% to 8.6%. With US, 1 patient experienced hoarseness (95% CI, 0.5%Y12.9%) and another reported difficulty swallowing (95% CI, 0.5%Y12.9%). In the US group, patient follow-up revealed 1 case of transient (1 week) and selfresolving paresthesiae in the territory of the cervical plexus (95% CI, 0.5%Y12.9%). In the LM group, 1 patient undergoing clavicular fracture repair experienced complete brachial palsy postoperatively. Magnetic resonance imaging revealed an injury of the brachial plexus at the surgical site.

DISCUSSION Superficial cervical plexus block is commonly used to provide postoperative analgesia for thyroidectomy,9,10 parathyroidectomy,11 carotid endarterectomy,12,13 as well as shoulder and clavicle surgery.14 In our practice, we rely on US to identify the sternocleidomastoid-scalene intermuscular plane where the 4 terminal branches of the SCP can be found before they branch out along the posterior border of the sternocleidomastoid muscle. Initial experience in shoulder and clavicular surgery (unpublished data) suggests that this technique is easy to perform, safe, and reliable. Thus, in this prospective, observer-blinded, randomized trial, we set out to validate US by comparing it to the conventional LM-based technique. Our results show no difference in success rates. We hypothesize that this lack of difference could be explained by the * 2010 American Society of Regional Anesthesia and Pain Medicine

fact the terminal branches of the SCP travel superficially under the skin and can be readily anesthetized with a blind, subcutaneous infiltration of local anesthetics. This echoes the results of a previous study by Antonakakis et al,15 who compared US to LM for deep peroneal nerve block and found similar success rates in both groups. Another explanation stems from the fact the socalled investing fascia, traditionally thought to be located underneath the sternocleidomastoid muscle, may not exist.16,17 Thus, local anesthetics injected subcutaneously (LM group) can potentially diffuse freely into the sternocleidomastoid-scalene intermuscular plane (injection site of US group).17 However, because of the small sample size, we cannot exclude the possibility that our study was underpowered to detect a small difference between the 2 techniques. Interestingly, subgroup analysis reveals different etiologies for failure. With US, all failed blocks (n = 3) were due to inadequate blockade of the greater auricular and lesser occipital nerves. In contrast, with LM, failure (n = 4) was caused by an inadequate block of the transverse cervical and/or supraclavicular nerves. Although further confirmatory trials are needed, these findings suggest that, for shoulder and clavicular surgery, US provides better coverage of skin incision than LM. With US, performance time was statistically longer. However, the 1-min difference seemed to be of limited clinical relevance as the total anesthesiaYrelated time and procedural discomfort were similar between the 2 groups. Both techniques appear to be safe as no major adverse effects were observed. In the LM group, 1 case of transient and self-resolving paresthesiae of the SCP was noted. Interestingly, this patient did not report paresthesiae during the performance of the block itself. However, because he subsequently underwent a single-injection interscalene block, we cannot rule out the possibility that the paresthesiae were caused by the brachial plexus block.18 In the US group, despite depositing local anesthetics along the scalene muscles, we observed no instances of unintentional brachial plexus block. This can be explained by the fact that the injection was carried out at the midpoint of the sternocleidomastoid muscle (approximately the upper pole of the thyroid cartilage), whereas (interscalene) brachial plexus block is typically performed at the level of the cricoid cartilage. Although dyspnea and desaturation did not occur in subjects receiving US, we cannot rule out the possibility that injection in the sternocleidomastoid-scalene intermuscular plane can lead to

TABLE 2. Block Performance Data

Imaging time, sec Needling time, sec Performance time, sec Onset time, min Total anesthesiaYrelated time, min Success No. Passes Block-related pain (scale 0Y10)

Landmark (n = 20)

US (n = 20)

P

NA 61 T 19 61 T 19 6.3 T 2.2 7.3 T 2.1

20 T 11 99 T 65 119 T 67 7.1 T 3.6 9.0 T 3.5

NA 0.060 G0.001 0.736 0.053

16 (80%) 2T0 3T2

17 (85%) 2T1 4T2

0.681 0.289 0.119

Continuous variables are presented as means T SDs; categorical variables are presented as count and percentage. Onset and total anesthesiaY related times are calculated only for patients with successful blocks. NA indicates not applicable.

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FIGURE 4. Percentage of patients with sensory analgesia (score of 1) according to time in the distributions of the lesser occipital, greater auricular, transverse cervical, and supraclavicular nerves.

ipsilateral phrenic nerve block. Thus, caution should be exercised in patients with preexisting respiratory compromise. With US, hoarseness or difficulty swallowing occurred in 2 patients. These symptoms suggest diffusion of local anesthetics to the superior laryngeal nerve. The main limitation of our study stems from the small sample size (n = 40). Our sample size was predicated on the assumption that LM and US would yield success rates of 45% and 90%, respectively. Although our results (85%) support this initial assumption for US, LM (80%) was more successful than expected. In the literature, the success rate of the conventional technique is poorly documented. Using a volume of local anesthetic similar to ours, Dieudonne et al9 have previously reported that, after thyroid surgery, 45% of patients who received a SCP block did not require opioids in the recovery room. In hindsight, we speculate that this figure underestimated the true success of SCP block because patients could have received narcotics for pain unrelated to surgery (such as pharyngeal discomfort after endotracheal intubation). Furthermore, postoperative pain could have originated from muscular layers innervated by the deep cervical plexus. Thus, we suggest that future trials comparing US and LM be carried out as equivalence studies with an expected success rate of 80% for LM. Another limitation of our protocol pertains to the absence of novice operators. However, despite the fact that experienced anesthesiologists performed all the blocks, we expect our results to be widely applicable because of the simplicity of the techniques and end points. Finally, in our study, the number of injections differs between the 2 groups. In contrast to the LM-guided doubleinjection technique, we elected to use a single injection with US because the latter allows the precise targeting of nerves (or intermuscular planes), thus eliminating the need for blind fanning of local anesthetic agents.2 However, we cannot rule out the possibility that, with US, a multiple-injection technique might have produced superior results and led to a statistically significant difference between the 2 study groups. In conclusion, despite providing a better block of the supraclavicular nerves, US guidance does not increase the success of SCP block compared with an LM-based technique. Additional confirmatory studies are required. The role of multiple injections for US also requires further investigation.

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REFERENCES 1. Liu SS, Ngeow J, John RS. Evidence basis for ultrasound-block characteristics: onset, quality, and duration. Reg Anesth Pain Med. 2010;35:S26YS35. 2. Bodner G, Bernathova M, Galiano K, Putz D, Martinoli C, Felfernig M. Ultrasound of the lateral femoral cutaneous nerve. Reg Anesth Pain Med. 2009;34:265Y268. 3. Manickam B, Perlas A, Duggan E, Brull R, Chan VWS, Ramlogan R. Feasibility and efficacy of ultrasound-guided block of the saphenous nerve in the adductor canal. Reg Anesth Pain Med. 2009;34:578Y580. 4. Moore DC. Block of the cervical plexus. In: Moore DC, ed. Regional Block. 4th ed. Fort Lauderdale, FL: Thomas Books; 1965. 5. Murphy TM. Somatic blockade of the head and neck. In: Cousins MJ, Bridenbaugh PO, eds. Neural Blockade in Clinical Anesthesia and Management of Pain. 3rd ed. Philadelphia, PA: Lippincott Raven; 1998. 6. Shibata Y, Sato Y, Fujiwara Y, Komatsu T. Transversus abdominis plane block. Anesth Analg. 2007;105:883. 7. Sinha SK, Abrams JH, Houle TT, Weller RS. Ultrasound-guided obturator nerve block. An interfascial injection approach without nerve stimulation. Reg Anesth Pain Med. 2009;34:261Y264. 8. Casati A, Danelli G, Baciarello M, et al. A prospective, randomized comparison between ultrasound and nerve stimulation guidance for multiple injection axillary brachial plexus block. Anesthesiology. 2007;106:992Y996. 9. Dieudonne N, Gomola A, Bonnichon P, Ozier Y. Prevention of postoperative pain after thyroid surgery: a double-blind randomized study of bilateral superficial cervical plexus blocks. Anesth Analg. 2001;92:1538Y1542. 10. Andrieu G, Amrouni H, Robin E, et al. Analgesic efficacy of bilateral superficial cervical plexus block administered before thyroid surgery under general anesthesia. Br J Anaesth. 2007;99:561Y566. 11. Pintaric S, Hocevar M, Jereb S, Casati A, Jankovic VN. A prospective, randomized comparison between combined (deep and superficial) and superficial cervical plexus block with levobupivacaine for minimally invasive parathyroidectomy. Anesth Analg. 2007;105: 1160Y1163. 12. Stoneham MD, Doyle AR, Knighton JD, Dorje P, Stanley JC. Prospective, randomized comparison of deep or superficial cervical

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plexus block for carotid endarterectomy surgery. Anesthesiology. 1998;89:907Y912. 13. Pandit JJ, Bree S, Dillon P, Elcock D, McLaren ID, Crider B. A comparison of superficial versus combined (superficial and deep) cervical plexus block for carotid endarterectomy: a prospective, randomized study. Anesth Analg. 2000;91:781Y786. 14. Choi D, Atchabahian A, Brown AR. Cervical plexus block provides postoperative analgesia after clavicle surgery. Anesthesiology. 2005;100:1542Y1543. 15. Antonakakis JG, Scalzo DC, Jorgenson SA, et al. Ultrasound does

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not improve the success rate of a deep peroneal nerve block at the ankle. Reg Anesth Pain Med. 2010;35:217Y221. 16. Nash L, Nicholson HD, Zhang M. Does the investing layer of the deep cervical fascia exist? Anesthesiology. 2005;103:962Y968. 17. Pandit JJ, Dorje P, Satya-Krishna R. Investing layer of the cervical fascia of the neck may not exist. Anesthesiology. 2006;104:1344. 18. Christ S, Rindfleisch F, Friederich P. Superficial cervical plexus neuropathy after single-injection interscalene brachial plexus block. Anesth Analg. 2009;109:2008Y2111.

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US v landmark Cerv plex  

rate.Thelatterwasdefinedastheabsenceofcoldsensationfor all4branchesoftheSCPat15mins. RegionalAnesthesiaandPainMedicine & Volume35,Number6...

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