Background This randomized trial compared ultrasound-guided interscalene block (ISB) and costoclavicular brachial plexus block (CCB) for arthroscopic shoulder surgery. We hypothesized that CCB would provide equivalent analgesia to ISB 30 min after surgery without the risk of hemidiaphragmatic paralysis.
Methods All 44 patients received an ultrasound-guided block of the intermediate cervical plexus. Subsequently, they were randomized to ISB or CCB. The local anesthetic agent (20 mL of levobupivacaine 0.5% and epinephrine 5 µg/mL) and pharmacological block adjunct (4 mg of intravenous dexamethasone) were identical for all study participants. After the block performance, a blinded investigator assessed ISBs and CCBs every 5 min until 30 min using a composite scale that encompassed the sensory function of the supraclavicular nerves, the sensorimotor function of the axillary nerve and the motor function of the suprascapular nerve. A complete block was defined as one displaying a minimal score of six points (out of a maximum of eight points) at 30 min. Onset time was defined as the time required to reach the six-point minimal composite score. The blinded investigator also assessed the presence of hemidiaphragmatic paralysis at 30 min with ultrasonography.
Subsequently, all patients underwent general anesthesia. Postoperatively, a blinded investigator recorded pain scores at rest at 0.5, 1, 2, 3, 6, 12, and 24 hours. Patient satisfaction at 24 hours, consumption of intraoperative and postoperative narcotics, and opioid-related side effects (eg, nausea/vomiting, pruritus) were also tabulated.
Results Both groups displayed equivalent postoperative pain scores at 0.5, 1, 2, 3, 6, 12, and 24 hours. ISB resulted in a higher incidence of hemidiaphragmatic paralysis (100% vs 0%; P < 0.001) as well as a shorter onset time (14.0 (5.0) vs 21.6 (6.4) minutes; p<0.001). However, no intergroup differences were found in terms of proportion of patients with minimal composite scores of 6 points at 30 min, intraoperative/postoperative opioid consumption, side effects, and patient satisfaction at 24 hours.
Conclusion Compared to ISB, CCB results in equivalent postoperative analgesia while circumventing the risk of hemidiaphragmatic paralysis. Further confirmatory trials are required. Future studies should also investigate if CCB can provide surgical anesthesia for arthroscopic shoulder surgery.
Clinical Trials Registration NCT03411343.
- acute pain
- brachial plexus
- upper extremity
- postoperative pain
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Postoperative analgesia after shoulder surgery remains a challenge in patients with pre-existing pulmonary pathology, as interscalene brachial plexus block (ISB), the standard nerve block for shoulder surgery, carries a prohibitive risk of hemidiaphragmatic paralysis (HDP).1 Although several diaphragm-sparing nerve blocks have been proposed, to date, none seems to offer equivalent analgesia to ISB while avoiding HDP. For instance, the analgesic benefits of isolated suprascapular blocks remain controversial.2–5 Furthermore, combining suprascapular nerve blocks with targeted axillary nerve blocks or infraclavicular brachial plexus blocks still results in inferior analgesia compared with ISB in the immediate postoperative period.6–9 Although small-volume supraclavicular brachial plexus block does provide equivalent analgesia to ISB during the first 24 hours, it is unfortunately afflicted with a non-negligible 9% incidence of HDP.10
First described in 2015,11 the costoclavicular block (CCB) targets the brachial plexus in the costoclavicular space where its three cords are tightly clustered together. The costoclavicular space is bound ventrally by the subclavius and pectoralis major (clavicular head) muscles, and dorsally by the anterior chest wall.11 Recently, Garcia-Vittoria et al 12 have suggested that the costoclavicular space could also serve as a retrograde channel to supraclavicular brachial plexus blocks. This led our team to speculate that, if local anesthetic (LA) injected in the costoclavicular space can reliably reach the supraclavicular brachial plexus, one could achieve analgesic parity with small-volume supraclavicular block (and ISB) while retaining the 0% incidence of HDP seen with infraclavicular blocks.9
Thus, in this randomized trial, we set out to compare ISB and CCB for patients undergoing arthroscopic shoulder surgery. We hypothesized that CCB would provide equivalent postoperative analgesia to ISB 30 min after shoulder surgery (without the risk of HDP) and therefore designed the current study as an equivalence trial.
The current trial was registered on 26 January 2018, at www.clinicaltrials.gov (NCT03411343) prior to patient recruitment. After obtaining ethics committee approval, we enrolled 44 patients undergoing arthroscopic shoulder surgery. Written informed consent was obtained from all participants. Inclusion criteria were: age between 18 and 80 years, American Society of Anesthesiologists (ASA) physical status I–III and body mass index between 20 and 35 kg/m2. Exclusion criteria were: inability to consent to the study, pre-existing (obstructive or restrictive) pulmonary disease, coagulopathy, sepsis, hepatic or renal failure, pregnancy, allergy to LA, chronic pain condition require the intake of opioids at home, and prior surgery in the neck or infraclavicular region.
The protocol employed in the current study was similar to the ones used in our two previous trials, which investigated combined infraclavicular–suprascapular blocks9 and small-volume supraclavicular blocks10 as diaphragm-sparing alternatives to ISB. After arrival in the induction room, an 18-gauge or 20-gauge intravenous catheter was placed in the upper limb contralateral to the surgical site and intravenous premedication (2 mg of midazolam and 50 µg of fentanyl) was administered to all patients. Supplemental oxygen (nasal cannulae at 4 L/min) and standard ASA monitoring were applied throughout the procedure. The 5–13 MHz linear ultrasound (US) transducer (General Electric LOGIC E, General Electric Healthcare, Wauwatosa, Wisconsin, USA), LA (levobupivacaine 0.5% with epinephrine 5 µg/mL) and pharmacological adjunct (4 mg of intravenous dexamethasone) were identical in all patients. Stimuplex Ultra 360 22-gauge block needles (B. Braun Medical AG, Melsungen, Germany) of varying lengths were employed in both groups: 5 cm (ISB group) and 10 cm (CCB group). Two investigators (JA or DB) supervised all the blocks. Independently of their status, operators were considered experts for a given approach if, prior to the start of the study, they possessed an experience level equal or superior to 60 blocks. Otherwise, they were considered trainees.13 Using a computer-generated sequence of random numbers and a sealed envelope technique, patients were randomly allocated to receive ISB (n=22) or CCB (n=22).
Prior to the performance of ISB or CCB, all patients received an US-guided intermediate cervical plexus block. This step was undertaken to ensure that postoperative pain from arthroscopic port insertion and skin closure would not constitute a confounding variable.9 10 Using a previously described technique, 5 mL of LA were injected in the intermuscular plane between the sternocleidomastoid and scalene muscles at the level of the thyroid cartilage.14
In the ISB group, the US transducer was applied in a sterile fashion on the lateral side of the neck at the level of the cricoid cartilage in order to obtain a view of the three hypoechoic structures, which represent the roots/trunks of the brachial plexus.10 A skin weal was raised with 3 mL of lidocaine 1%. Using an in-plane technique and a lateral-to-medial direction, the block needle was advanced until its tip was positioned under the prevertebral fascia between the two most superficial hypoechoic structures.15 16 Twenty milliliters of LA were deposited in this location (figure 1).
In the CCB group, patients were placed in a supine position with the surgical limb in 90-degree abduction.11 17 The US transducer was initially placed directly on top of the middle third of the clavicle. Subsequently, the probe was translocated off the inferior border of the clavicle and positioned in the medial infraclavicular fossa. In the costoclavicular space, the axillary artery was identified underneath the subclavius muscle. The three cords of the brachial plexus were visualized lateral to the artery. A skin weal was raised with 3 mL of lidocaine 1.0%. Using an in-plane technique and a lateral-to-medial direction, the block needle was advanced until its tip was located in the middle of the three cords.11 17 Twenty milliters of the LA mix were incrementally injected (figure 2).
Subsequently, whether the sensorimotor blocks were complete or incomplete at 30 min (vide infra), all patients underwent general anesthesia with endotracheal intubation using intravenous propofol (1.5–2 mg/kg), fentanyl (1 µg/kg), rocuronium (0.6 mg/kg), and sevoflurane (end tidal minimal alveolar concentration 0.8–1.0). All subjects were placed in the beach chair position. Although treating anesthesiologists were not blinded to block allocation, they were only allowed to administer intraoperative fentanyl (25 µg boluses) if heart rate or blood pressure exceeded 20% of preoperative values. At the end of the case, prior to extubation, all patients received nausea prophylaxis (ondansetron 4 mg) as well as intravenous acetaminophen (1 g) and ketoprofen (100 mg). The surgical duration (defined as the temporal interval between skin incision and closure) was recorded.
Postoperatively, in the post anesthesia care unit (PACU), all patients received intravenous morphine patient-controlled analgesia (PCA) (bolus=1 mg; lockout interval=8 min). On the surgical ward, all subjects continued to receive acetaminophen 1 g per os every 8 hours and ketoprofen 100 mg per os every 12 hours as well as morphine PCA. All nursing personnel (PACU and surgical ward) were blinded to group allocation. All patients were discharged in the afternoon of the first postoperative day.
Primary outcome measurement
In the PACU, a blinded investigator recorded pain scores at 30 min using a 0–10 numerical rating scale (0=no pain; 10=worst imaginable pain). Only pain at rest was assessed, as our surgical colleagues requested that the surgical limb not be mobilized during the postoperative period. All blocks, whether complete or incomplete (vide infra), were included in the primary outcome analysis (ie, intent-to-treat analysis).
Secondary outcomes measurement
During the performance of ISBs and CCBs, the coauthor supervising the blocks (JA or DB) recorded the performance time. The latter was defined as the temporal interval between the start of skin disinfection and the end of LA injection through the block needle.9 10 The number of needle passes was also recorded. The initial needle insertion counted as the first pass. Any subsequent needle advancement that was preceded by a retraction of at least 10 mm counted as an additional pass.18 The supervising coauthor also recorded potential adverse events (eg, vascular puncture, toxic effects of LA, paresthesia) occurring during the performance of the blocks.
After the performance of the blocks, a blinded investigator assessed the latter every 5 min until 30 min using a sensorimotor composite scale. Sensory function was tested on the cutaneous area overlying the clavicle (supraclavicular nerves) and the lateral surface of the deltoid (axillary nerve). Each territory was graded according to a three-point scale using a cold test: 0=no block, 1=analgesia (patient can feel touch, not cold), 2=anesthesia (patient cannot feel touch).9 10 Motor function was tested using shoulder abduction (axillary nerve) and external shoulder rotation (suprascapular nerve) using a three-point scale: 0=no block, 1=paresis, 2=paralysis.9 10 We considered the blocks complete if, at 30 min, a global composite score equal or superior to 6 points (out of a maximum of 8 points) was achieved.9 10 Thus, onset time was defined as the time required to reach a minimal composite score of 6 points.
The blinded investigator also assessed the presence of hemidiaphragmatic block at 30 min after the performance of the blocks and 30 min after the patient’s arrival in the PACU. A 2–5 MHz curvilinear US transducer (General Electric LOGIC E, General Electric Healthcare, Wauwatosa, Wisconsin, USA) and the M-mode were employed in all subjects; the liver and spleen served as acoustic windows on the right and left side, respectively. Patients were scanned along the anterior axillary line and the US probe was angled cranially.19 HDP was defined as the absence of diaphragmatic motion during normal respiration coupled with absent or (paradoxical) cranial diaphragmatic movement when the patient forcefully sniffs.19
Postoperatively, on the surgical ward, the blinded assessor evaluated pain scores at rest at 1, 2, 3, 6, 12, and 24 hours using a 0–10 numerical rating scale (0=no pain; 10=worst imaginable pain).
The blinded investigator also tabulated demographic data (sex, age, weight, height), the type and duration of surgery, the operator’s level of experience, the incidence of hoarseness and Horner syndrome (30 min after the performance of the blocks), total intraoperative and postoperative opioid consumption, opioid-related side effects (eg, postoperative nausea/vomiting and pruritus), and patient satisfaction at 24 hours using a 0–10 scale (0=not satisfied; 10=very satisfied). One week after the surgery, all patients were contacted by the blinded investigator to inquire about complications such as persistent numbness/paresthesia or motor deficit. All blocks, whether complete or incomplete, were included in the analysis of secondary outcomes.
A pilot study (n=15) previously conducted at the Hospital Clínico Universidad de Chile revealed that, after ISB, patients undergoing arthroscopic shoulder surgery reported a mean pain score of 1.0 (1.7) on a 0–10 scale at 30 min in the PACU (unpublished data). Our research hypothesis was that CCB would provide equivalent postoperative analgesia to ISB at 30 min. We elected to set the equivalence margin at two points in terms of pain scores because Tashijian et al 20 have previously reported that a difference <1.4 point carries minimal clinical significance for patients afflicted with rotator cuff disease. Thus, a calculated sample size of 40 patients was required for a statistical power of 0.90 and a type I error of 0.025. We anticipated a possible 10% dropout rate and therefore elected to recruit 44 subjects.
Statistical analysis was performed using SPSS V.21 statistical software. Postoperative pain scores did not follow a normal distribution (Lilliefors test p<0.05 for all time periods), thus equivalency was assessed by examining the 95% CIs of the differences of the medians using the Hodges-Lehmann method. For other data, normality was first assessed with the Lilliefors test and then analyzed with the Student’s t-test. Data that did not have a normal distribution, as well as ordinal data, were analyzed with the Mann-Whitney U test. For categorical data, the χ2 or Fisher’s exact test were used. All p values presented were two-sided and values inferior to 0.05 were considered significant.
The ISB and CCB groups were found to be equivalent in terms of the primary outcome (ie, PACU pain scores at 30 min) (median (IQR)=0 (0) and 0 (2) for ISB and CCB, respectively; difference of the medians=0.0; 95% CI of the difference of the medians, 0 to 0). Furthermore, postoperative pain scores were also equivalent at 1, 2, 3, 6, 12, and 24 hours (table 2 ). The 95% CIs for the differences of the medians for these time periods are 1 hour (0 to 0); 2 hours (0 to 0); 3 hours (0 to 0); 6 hours (0 to 0); 12 hours (0 to 0); and 24 hours (0 to 1) (table 2).
ISB resulted in a higher incidence of HDP 30 min after the performance of the blocks as well as 30 min after the patient’s arrival in the PACU (100% for both time intervals vs 0% for both time intervals; both p<0.001). Onset time was also shorter with ISB compared with CCB (14.0 (5.0) vs 21.6 (6.4) min; p<0.001). However, no intergroup differences were found in terms of performance time, proportion of patients with minimal composite scores of 6 points at 30 min, procedural pain, number of needle passes, intraoperative/postoperative opioid consumption, adverse events, and patient satisfaction at 24 hours (table 3).
Patient follow-up at 1 week revealed no sensory or motor deficit.
In this randomized trial, we compared US-guided ISB and CCB for arthroscopic shoulder surgery. Our findings suggest that both blocks provide equivalent postoperative analgesia, as postoperative pain scores fall within the two-point equivalence margin. However, CCB results in a significantly lower incidence of HDP (0% vs 100%; p<0.001).
The rationale behind our study merits detailed discussion. HDP after ISB stems from two possible mechanisms: rostral LA spread toward the C3–C5 nerve roots or LA migration from the interscalene groove towards the phrenic nerve.1 At the C6 level (where ISBs are commonly performed), the phrenic nerve is situated on the anterior scalene muscle a mere 0.18 cm from the brachial plexus.1 However, as the phrenic nerve and the brachial plexus move caudally, they start to diverge from each other at a rate of 3 mm/cm.21 This anatomical fact explains why the incidence of HDP decreases from 100% to less than 67% when one transitions from conventional interscalene to supraclavicular brachial plexus blocks.1
Moving further caudally (ie, toward a paracoracoid infraclavicular location) would further lower the risk of HDP.22 However, because the shoulder joint and its adjacent structures derive their sensory innervation from the lateral cord (ie, lateral pectoral nerve), posterior cord (ie, axillary and subscapular nerves), and upper trunk (ie, suprascapular nerve),1 too distal an approach may fail to anesthetize one of these neural structures (especially the suprascapular nerve). Thus, during the inception phase of our trial, we hypothesized that the CCB would constitute the ‘sweet spot’, as it could reliably anesthetize the lateral and posterior cords11 and, through the purported retrograde channel to the supraclavicular brachial plexus,12 the suprascapular nerve as well. Furthermore, we speculated that the CCB’s puncture site (caudal to the clavicle) would occur in a location where the phrenic nerve and the brachial plexus are situated far enough from each other to circumvent HDP.
The LA volume used for CCB for ISB also deserves special mention. In a recent dose-finding study, we reported that the minimum effective volume of adrenalized lidocaine 1.5% in 90% of patients (MEV90) is 34 mL for CCB.23 However, in the current trial, we intentionally selected the smaller volume (20 mL) previously recommended by Karmakar et al.11 Since shoulder surgery requires anesthesia of the lateral and posterior cords (but not of the medial cord), we reasoned that the full 34 mL would not be necessary. Nonetheless, we concede that future dose-finding studies are needed to elucidate the optimal analgesic/ diaphragm-sparing LA volume for CCB. In order to standardize the LA administered to the two study groups, we also used 20 mL for ISB. We recognize that some authors have advocated lower volumes (5–10 mL) in order to decrease the risk of HDP.1 However we opine that a low ISB injectate (eg, 5 mL) would not have impacted our findings, as 5 mL is unlikely to provide better postoperative analgesia than 20 mL. More importantly, in the best-case scenario, 5 mL would have resulted in a 27% incidence of HDP after ISB.24 Compared with the 0% rate of HDP seen with CCB, this would still have resulted in a statistically significant difference (p=0.02).
Although our findings appear promising and suggest that CCB may constitute the optimal diaphragm-sparing equianalgesic alternative to ISB, initial enthusiasm must be tempered with caution. In light of the small number of patients enrolled in our trial, larger studies are required to confirm that CCB reliably sidesteps HDP. More importantly, the ideal diaphragm-sparing block for shoulder surgery should not only provide postoperative analgesia but also circumvent general anesthesia, endotracheal intubation and mechanical ventilation altogether. Thus, CCB needs to be investigated in terms of provision of surgical anesthesia. For such studies, the two-point pain equivalence margin used in our current and previous trials9 10 may prove too lax, as two points (of pain) could be difficult for patients to tolerate throughout the entire duration of the surgical intervention. Therefore, future studies investigating surgical anesthesia with CCB should consider using an even smaller equivalence margin.
Since the protocol employed in the current trial was identical to the ones used in our two previous studies,9 10 it is inherently afflicted with similar shortcomings. First, although we sought to investigate CCB as a diaphragm-sparing alternative to ISB for patients in whom HDP might be problematic, we purposefully excluded such subjects for ethical reasons, as the randomized design would have intentionally exposed the control (ISB) group to HDP. Second, our composite scale encompassed sensory and/or motor function of the axillary and suprascapular nerves, but not that of the subscapular nerve. The latter, which mediates internal rotation of the humeral head, may be difficult to evaluate in patients with rotator cuff tears. Finally, our protocol did not investigate continuous analgesic blocks. This constitutes a methodological limitation because continuous blocks provide significant benefits compared to their single injection counterparts.25 Furthermore, although CCB could initially spare the phrenic nerve, HDP may occur with continuous infusion due to LA accumulation.1
In conclusion, compared with ISB, CCB results in equivalent postoperative analgesia while circumventing the risk of HDP. Since our findings are derived from a single-center study, further confirmatory trials are required. Future studies should also investigate if CCB can provide surgical anesthesia for arthroscopic shoulder surgery.
The authors thank Miss Alejandra Castillo as well as Dr Estela Maulén for their invaluable assistance with patient recruitment.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Comité Ético Científico Hospital Clínico Universidad de Chile.
Provenance and peer review Not commissioned; externally peer reviewed.
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