De Q.H. Tran

Minimum effective volume of lidocaine for ultrasound-guided infraclavicular block.

Background: The aim of this study was to determine the minimum effective volume of lidocaine 1.5% with epinephrine 5 &mgr;g/mL in 90% of patients (MEV90) for single-injection ultrasound-guided infraclavicular block (ICB). Methods: Using an in-plane technique, a single-injection ultrasound-guided ICB was performed: a 17-gauge, 8-cm Tuohy needle was advanced until the tip was located dorsal to the axillary artery. Volume assignment was carried out using a biased coin design up-and-down sequential method, where the volume of local anesthetic administered to each patient depended on the response of the previous one. In case of failure, the next subject received a higher volume (defined as the previous volume with an increment of 2.5 mL). If the previous patient had a successful block, the next subject was randomized to a lower volume (defined as the previous volume with a decrement of 2.5 mL), with a probability of b = 0.11, or the same volume, with a probability of 1 − b = 0.89. Lidocaine 1.5% with epinephrine 5 &mgr;g/mL was used in all subjects. Success was defined, at 30 mins, as a minimal score of 14 of 16 points using a composite scale encompassing sensory and motor block. Patients undergoing surgery of the elbow, forearm, wrist, or hand were prospectively enrolled until 45 successful blocks were obtained. Results: Fifty-five patients were included in the study. Using isotonic regression and bootstrap confidence interval (CI), the MEV90 for single-injection ultrasound-guided ICB was estimated to be 35 mL (95% CI, 30-37.5 mL). The probability of a successful response at 35 mL was estimated to be 0.91 (95% CI, 0.8-1.0). All patients with a minimal composite score of 14 points at 30 mins achieved surgical anesthesia intraoperatively. Conclusions: For single-injection ultrasound-guided ICB, the MEV90 of lidocaine 1.5% with epinephrine 5 &mgr;g/mL is 35 mL. Further dose-finding studies are required for other concentrations of lidocaine, other local anesthetic agents as well as techniques involving multiple injections, a more medial approach to ICB, or precise location of all 3 cords of the brachial plexus.

A prospective, randomized comparison between single- and double-injection ultrasound-guided infraclavicular brachial plexus block.

Background and Objectives: This prospective, randomized, observer-blinded study compared single- and double-injection, ultrasound-guided supraclavicular brachial plexus block for upper extremity surgery. Methods: Ninety-two patients were randomly allocated to receive a single-injection (n = 46) or double-injection (n = 46), ultrasound-guided supraclavicular block. Performance time (defined as the sum of imaging and needling times) and the number of needle passes were recorded during the performance of the block. Subsequently, a blinded observer recorded the onset time, block-related pain scores, success rate (surgical anesthesia), and the incidence of complications. The total anesthesia-related time was defined as the sum of the performance and onset times. The main outcome variable was the onset time. Results: The onset time was shorter with the 2-injection technique (17.5 mins [SD, 8.4 mins] vs 21.7 mins [SD, 7.2 mins]; P = 0.021); however, performance time was also longer (7.2 mins [SD, 2.7 mins] vs 6.0 mins [SD, 2.4 mins]; P = 0.037). Thus, no differences were observed in terms of total anesthesia-related time (23.4-24.3 mins). Success rates (95.7%), block-related pain scores, and complication rates were also similar between the 2 groups. As expected, the 2-injection technique required a greater number of needle passes (3.5 [SD, 1.2] vs 1.9 [SD, 1.1]; P < 0.001). In return, it provided a faster onset for sensory and motor block of the musculocutaneous nerve and a faster sensory block of the radial nerve. However, at 30 mins, no differences were observed. Conclusion: The double-injection, ultrasound-guided supraclavicular block provides no significant advantages compared with its single-injection counterpart.

A randomized comparison between subepineural and conventional ultrasound-guided popliteal sciatic nerve block.

Background: This prospective, randomized, observer-blinded trial compared a subepineural sciatic injection at the neural bifurcation (SUB group) and separate postbifurcation injections around the tibial and peroneal nerves. Methods: Ultrasound-guided posterior popliteal sciatic nerve block was carried out in 50 patients. In the group that had separate postbifurcation injections around the tibial and peroneal nerves, the volume of local anesthetic (LA) (30 mL of lidocaine 1%-bupivacaine 0.25%-epinephrine 5 &mgr;g/mL) was divided equally between the tibial and peroneal nerves. In the SUB group, the 2 divisions were identified exactly at the neural bifurcation. In this location, both nerves can still be found inside a common epineural sheath. The entire volume of LA was injected between the 2 branches, inside the common sheath. A blinded observer recorded the success rate (complete sensory block at 30 mins) and onset time. The performance time, number of needle passes, and adverse events were also recorded. Total anesthesia-related time was defined as the sum of performance and onset times. Results: Compared with targeted injections around the tibial and peroneal divisions, a subepineural injection resulted in a higher success rate (84% vs 56%; P = 0.032) as well as improved efficiency (decreased performance/onset/total anesthesia-related times and fewer needle passes; all P ≤ 0.028). In the SUB group, we observed no instance of neural swelling. In 3 subjects randomized to separate injections, sonographic swelling of the tibial nerve occurred after the injection of 2 mL of LA. The needle was carefully withdrawn, and the injection completed uneventfully. In 45 patients, follow-up 1 week after the surgery revealed no sensory or motor deficit. Five subjects were lost to follow-up. Conclusions: Compared with separate injections around the tibial and peroneal divisions, a single subepineural injection at the neural bifurcation provides a higher success rate and requires shorter performance, onset, and total anesthesia-related times. Further studies are required to validate the safety of the subepineural technique.

A prospective, randomized comparison between perivascular and perineural ultrasound-guided axillary brachial plexus block.

Background This prospective, randomized, observer-blinded study compared perivascular (PV) and perineural (PN) ultrasound-guided axillary brachial plexus block (AXB) for upper extremity surgery. Methods Fifty patients were randomly allocated to receive a PV (n = 25) or PN (n = 25) ultrasound-guided AXB. The local anesthetic agent (lidocaine 1.5% with epinephrine 5 &mgr;g/mL) and total volume (32 mL) were identical in all subjects. For both groups, the musculocutaneous nerve was first located and then anesthetized using 8 mL. Subsequently, in the PV group, 24 mL was deposited dorsal to the axillary artery (6-o’clock position). In contrast, for the PN group, the median, ulnar, and radial nerves were individually anesthetized with volumes of 8 mL. During the performance of the block, the performance time, number of needle passes, and complications (vascular puncture, paresthesia) were recorded. Subsequently, a blinded observer assessed the onset time, block-related pain scores, and success rate (surgical anesthesia). The main outcome variable was the total anesthesia-related time (sum of performance and onset times). Results No differences were observed between the 2 groups in terms of success rate (92%–96%), total anesthesia-related time (27.1–29.0 min), and block-related pain scores. However, the PV technique required fewer needle passes (3.5 [SD, 1.0] vs 8.2 [SD, 2.2]; P = 0.000) as well as a shorter performance time (8.2 [SD, 2.3] vs 15.7 [SD, 3.2] min; P = 0.000) and was associated with a lower incidence of paresthesia (8 vs 52%; P = 0.001). In contrast, the PN technique resulted in a quicker onset time (13.8 [SD, 7.0] vs 18.9 [SD, 7.0] min; P = 0.021) and a decreased incidence of vascular puncture (0 vs 24%; P = 0.01). Conclusions Perivascular and PN ultrasound-guided AXBs result in comparable success rates and total anesthesia-related times. Because of fewer needle passes and a shorter performance time, the PV technique provides a simple alternative for ultrasound-guided AXB.

Ultrasonography and stimulating perineural catheters for nerve blocks: a review of the evidence

Purpose: This narrative review summarizes the evidence derived from randomized controlled trials (RCTs) offering blinded assessment and sample size justification, in order to determine the benefits associated with adjunctive ultrasonography (US) and stimulating perineural catheters for nerve blocks.Source: The literature search for this review was conducted during the second week of December 2007 using the MEDLINE (January 1950 to November 2007) and EMBASE (January 1980 to November 2007) databases. For US-guided peripheral and neuraxial blocks, the following medical subject heading (MeSH) terms were searched: “nerve block”, “epidural anesthesia”, “epidural analgesia”, “epidural injection”, “epidural space”, “spinal anesthesia”, and “spinal injection”, the results were combined with “ultrasonography” (MeSH term) and “ultrasound” (key word). For stimulating perineural catheters, the following MeSH terms were cross referenced with the MeSH term, “nerve block”: “peripheral catheterization”, “indwelling catheterization”, “catheterization”, and keywords, “nerve catheter” and “continuous”. Subsequently, the result of this search was combined to “stimulating” (key word). Fifteen RCTs, offering blinded assessment and sample size justification, were retained for analysis.Principal findings: For axillary blocks, US guidance yields a higher success rate than a double-injection, transarterial and a triple-injection, neurostimulation-guided technique. Compared to a quadruple-stimulation technique, no major differences can be found. The addition of nerve stimulation to US guidance offers no clear benefits for axillary blocks. For femoral blocks, compared to neurostimulation, echoguidance is associated with a local anesthetic (LA) sparing effect (up to 42%). In children, US guidance yields a LA sparing effect and a longer duration of action for lower extremity nerve blocks. Compared to their blind counterparts, stimulating catheters seem to offer limited clinical benefits. Despite providing a sparing effect on LA and opioid consumption, stimulating catheters are not associated with a decrease in side effects or analgesia-related expenditures.Conclusions: Published reports of RCTs provide evidence to formulate limited recommendations regarding the use of adjunctive US and stimulating perineural catheters. Further well-designed and meticulously executed RCTs are warranted.RésuméObjectif: Cette synthèse narrative résume les données probantes tirées d’études randomisées contrôlées (ERC) disposant d’une évaluation en aveugle et de justification de la taille de l’échantillon afin d’identifier les bienfaits associés à une utilisation conjointe de l’échographie et de cathéters périneuraux stimulants lors de blocs nerveux.Sources: La recherche de littérature pour cet article de synthèse a été menée la deuxième semaine de décembre 2007 dans les bases de données MEDLINE (janvier 1950 à novembre 2007) et EMBASE (janvier 1980 à novembre 2007). Pour les blocs périphériques et neuraxiaux échoguidés, les termes MeSH suivants ont été recherchés : « nerve block », « epidural anesthesia », « epidural analgesia », « epidural injection », « epidural space », « spinal anesthesia » et « spinal injection », et ont été associés à « ultrasonography » (terme MeSH) et « ultrasound » (mot clé). Pour les cathéters périneuraux stimulants, les termes MeSH suivants ont été croisés avec le terme MeSH « nerve block » : « peripheral catheterization », « indwelling catheterization », « catheterization », et les mots clés « nerve catheter » et « continuous ». Ensuite, les résultats de cette recherche ont été combinés avec le mot clé « stimulating ». Quinze ERC disposant d’une évaluation en aveugle et de justification de la taille de l’échantillon ont été retenues pour être analysées.Constatations principales: Dans le cas de blocs axillaires, l’échoguidage offre un meilleur taux de réussite qu’une technique de double injection transartérielle et qu’une technique de triple injection guidée par neurostimulation. Si on compare l’échoguidage à une technique de quadruple stimulation, aucune différence majeure n’apparaît. L’ajout de stimulation nerveuse à l’échoguidage ne procure pas de bienfaits clairs dans le cas des blocs axillaires. Lorsqu’un bloc fémoral est réalisé, l’échoguidage est associé à un besoin moindre en anesthésique local (AL) (jusqu’à 42 %) par rapport à la neurostimulation. Chez les enfants, l’échoguidage résulte en un besoin moindre en anesthésique local et une durée prolongée d’action pour les blocs nerveux des membres inférieurs. Par rapport à leurs pendants aveugles, les cathéters stimulants semblent n’offrir que des bienfaits cliniques limités. Malgré le fait qu’ils génèrent un besoin moins important en anesthésiques locaux et réduisent la consommation d’opioïdes, les cathéters stimulants ne sont pas associés à une réduction des effets secondaires ou des coûts liés à l’analgésie.Conclusion: Les comptes-rendus publiés d’ERC fournissent des données probantes qui peuvent encourager la formulation de recommandations limitées quant à l’utilisation conjointe d’échoguidage et de cathéters périneuraux stimulants. D’autres ERC bien conçues et menées avec soin sont justifiées.

A prospective, randomized comparison between double-, triple-, and quadruple-injection ultrasound-guided axillary brachial plexus block.

Background This prospective, randomized, observer-blinded study compared double-, triple-, and quadruple-injection ultrasound (US)–guided axillary brachial plexus block (AXB) for upper-extremity surgery. Methods One hundred twenty patients were randomly allocated to receive a double- (n = 40), triple- (n = 40), or quadruple-injection (n = 40) US-guided AXB. The local anesthetic agent (lidocaine 1.5% with epinephrine 5 &mgr;g/mL) and total volume (35 mL) were identical in all subjects. For all 3 groups, the musculocutaneous nerve was identified and anesthetized first. Subsequently, a perivascular technique was performed. Lidocaine was deposited at the 6-o’clock position of the axillary artery for the 2-injection group. For the 3- and 4-injection groups, injections were carried out at the 12-/6-o’clock and 2-/10-/6-o’clock positions, respectively. During the performance of the block, the performance time, number of needle passes, and complications (vascular puncture, paresthesia) were recorded. Subsequently, a blinded observer assessed the onset time, block-related pain scores, and success rate (surgical anesthesia). The main outcome variable was the total anesthesia-related time (sum of performance and onset times). Results No differences were observed among the 3 groups in terms of total anesthesia-related time (29.2–31.4 mins), success rate (90.0%–97.5%), block-related pain scores, vascular puncture, and paresthesia. Compared with its 3- and 4-injection counterparts, the double-injection technique required fewer needle passes (4.0 ± 1.6 vs 5.2–6.0 ± 1.7–2.8; both P ⩽ 0.001). Conclusions Double-, triple-, and quadruple-injection US-guided perivascular AXB result in comparable success rates and total anesthesia-related times. Because it requires fewer needle passes, the double-injection technique provides a simple alternative for US-guided AXB.

A comparison between ultrasound-guided infraclavicular block using the "double bubble" sign and neurostimulation-guided axillary block.

BACKGROUND:Ultrasound-guided infraclavicular block can be performed using the double bubble sign. Previously described, the double bubble sign consists superiorly of the axillary artery (in short axis) superimposed on an inferior bubble created by local anesthetic injection. In this study, we compared this new method of brachial plexus anesthesia to the traditional triple-nerve stimulation axillary block. METHODS:Seventy patients were randomized to receive a single-injection, ultrasound-guided infraclavicular block using the double bubble sign or a triple-stimulation axillary block. RESULTS:Both methods produced similar success rates (89%–91%). However, infraclavicular blocks were associated with a shorter performance time (3.90 ± 2.27 vs 8.03 ± 3.92 min; P < 0.001) and lower block-related pain scores (2.70 ± 2.02 vs 4.17 ± 2.57 on a 0–10 scale; P = 0.01). CONCLUSION:Compared to triple-stimulation axillary block, ultrasound-guided infraclavicular block using the double bubble sign provided a similar efficacy, a shorter performance time and lower procedural pain scores.

A randomized comparison between ultrasound-guided and landmark-based superficial cervical plexus block.

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 anesthesia-related time was defined as the sum of performance and onset times. Results: Success rate (80%-85%) was similar between the 2 groups. Performance time was slightly longer with ultrasonography (119 versus 61 sec, P < 0.001); however, no differences in onset and total anesthesia-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.

Minimum effective volume of lidocaine for double-injection ultrasound-guided axillary block.

Background The aim of this study was to determine the minimum effective volume of lidocaine 1.5% with epinephrine 5 &mgr;g/mL in 90% of patients (MEV90) for double-injection ultrasound-guided axillary block (AXB). Methods All subjects received a double-injection ultrasound-guided AXB with lidocaine 1.5% and epinephrine 5 &mgr;g/mL. A 17-gauge, 8-cm Tuohy needle was initially advanced until its tip was positioned next to the musculocutaneous nerve. Volume assignment was carried out using a biased coin design up-and-down sequential method, where the volume of local anesthetic administered to each patient depended on the response of the previous one. In case of failure, the next subject received a higher volume (defined as the previous volume with an increment of 1.0 mL). If the previous patient had a successful block, the next subject was randomized to a lower volume (defined as the previous volume with a decrement of 1.0 mL), with a probability of b = 0.11, or the same volume, with a probability of 1 − b = 0.89. After injection of the musculocutaneous nerve, the needle was redirected toward the dorsal aspect of the axillary artery. For this second injection, volume assignment was carried out in a similar fashion; however, volume increments/decrements were 3.0 instead of 1.0 mL. Using a composite scale encompassing sensory and motor block, success was defined, at 30 minutes, as a composite score of 4 points (out of 4 points), and 10 points (out of 12 points) for the musculocutaneous and perivascular injection, respectively. Patients undergoing surgery of the forearm, wrist, or hand were prospectively enrolled until 45 successful musculocutaneous blocks or 45 successful perivascular injections were obtained. Results Fifty patients were included in the study. Using isotonic regression and bootstrap confidence interval (CI), the MEV90 was estimated to be 5.5 mL (95% CI, 3.0–6.7 mL) and 23.5 mL (95% CI, 23.1–23.9 mL) for the musculocutaneous and perivascular injection, respectively. Conclusions For double-injection ultrasound-guided AXB, the MEV90 of lidocaine 1.5% with epinephrine 5 &mgr;g/mL is 5.5 and 23.5 mL for the musculocutaneous nerve and perivascular injection, respectively. Further dose-finding studies are required for other concentrations of lidocaine, other local anesthetic agents, and other techniques for ultrasound-guided AXB.

Cervical medial branch block: a novel technique using ultrasound guidance.

Background Cervical medial branch blocks are commonly performed for the diagnosis and treatment of head, neck, and shoulder pain. Intermittent fluoroscopy is widely used for needle positioning and visualization of contrast distribution before medication injection. The purpose of this study was to examine the use of ultrasound as an alternative imaging technique to block the third occipital nerve and the C3 to C6 medial branches. Methods The study involved 2 phases with a total of 53 patients. The purpose of phase 1 was to assess the reliability of needle positioning using an ultrasound target corresponding to the middle of the bony contour of the articular pillar. Twenty patients undergoing 46 cervical medial branch blocks between C3 and C6 were recruited, and the needle tip position was graded on a 3-point scale based on its proximity to the centroid on lateral radiograph. In phase 2, 50 patients undergoing 163 levels were recruited. Using ultrasound guidance, each of the targeted levels was injected with 0.3 mL of a 1:1 mixture of local anesthetic and contrast agent. A blinded assessor reviewed contrast distribution in the anteroposterior and lateral radiograph views. Results In phase 1, all needle tips were positioned on the articular pillars; furthermore, 80.1% were located in the middle 2 quarters of the latter. In phase 2, the contrast was found to cover the appropriate level in 94.5% of cases, and no complications were noted. The incidence of aberrant spread to adjacent levels (13.5%) was similar to that reported with fluoroscopy. Conclusions Ultrasound guidance offers a reliable alternative to fluoroscopy for third occipital nerve and C3–C6 cervical medial branch blocks. Further studies are required to validate the clinical efficacy of our technique.