Anahi Perlas

Ultrasound guidance improves success rate of axillary brachial plexus block.

PurposeThe purpose of this study is to determine if real time ultrasound guidance improves the success rate of axillary brachial plexus blockade.MethodsPatients undergoing elective hand surgery were randomly assigned to one of three groups. Axillary blocks were performed using three motor response endpoints in the nerve stimulator (NS) Group, real-time ultrasound guidance in the ultrasound (US) Group and combined ultrasound and nerve stimulation in the USNS Group. Following administration of a standardized solution containing 2% lidocaine with 1:200,000 epinephrine and 0.5% bupivacaine (total 42 mL), sensory and motor functions were assessed by a blinded observer every five minutes for 30 min. A successful block was defined as complete sensory loss in the median, radial and ulnar nerve distribution by 30 min. The need for local and general anesthesia supplementation and post-block adverse events were documented.ResultsOne hundred and eighty-eight patients completed the study. Block success rate was higher in Groups US and USNS (82.8% and 80.7%) than Group NS (62.9%) (P = 0.01 and 0.03 respectively). Fewer patients in Groups US and USNS required supplemental nerve blocks and/or general anesthesia. Postoperatively, axillary bruising and pain were reported more frequently in Group NS.ConclusionThis study demonstrates that ultrasound guidance, with or without concomitant nerve stimulation, significantly improves the success rate of axillary brachial plexus block.RésuméObjectifLe but de cette étude est de déterminer si l’échoguidage en temps réel améliore le taux de succès du bloc du plexus brachial par approche axillaire.MéthodeDes patients devant subir une chirurgie élective de la main ont été randomisés en trois groupes. Des blocs axillaires ont été effectués en utilisant: trois points de réponses motrices dans le groupe neurostimulateur (NS), l’échoguidage en temps réel dans le groupe échographie (EG), et l’échographie combinée à la stimulation nerveuse dans le troisième groupe (EGNS). Suite à l’administration d’une solution standardisée contenant de la lidocaïne 2 % avec épinéphrine (1:200 000) et de la bupivacaïne 0,5 % (total 42 mL), les fonctions sensitives et motrices ont été évaluées par un observateur neutre toutes les cinq minutes pendant 30 min. Un bloc réussi a été défini comme la perte complète de sensation dans la distribution des nerfs médian, radial et cubital après 30 min. La nécessité d’une anesthésie locale et générale supplémentaire ainsi que les effets négatifs post-bloc ont été documentés.RésultatChez les 188 patients qui ont terminé l’étude, le taux de succès du bloc a été plus élevé dans les groupes EG et EGNS (82,8 % et 80,7 %) que dans le groupe NS (62,9 %) (P) =0,01 et 0,03 respectivement). Un nombre moins élevé de patients des groupes EG et EGNS a nécessité des blocs nerveux supplémentaires et/ou une anesthésie générale. Après l’opération, les hématomes et douleurs axillaires ont été plus fréquemment observés dans le groupe NS.ConclusionCette étude démontre que l’échoguidage, avec ou sans neurostimulation concomitante, améliore de façon significative le taux de succès du bloc du plexus brachial par approche axillaire.

The Sensitivity of Motor Response to Nerve Stimulation and Paresthesia for Nerve Localization As Evaluated by Ultrasound

Background and Objective: Seeking paresthesia and obtaining a motor response to an electrical stimulus are the two most common methods of nerve localization for the performance of peripheral-nerve blocks. However, these two endpoints do not always correlate, and the actual sensitivity and specificity of either method remains unknown. The objective of this study is to determine the sensitivity of paresthesia and motor response to electrical nerve stimulation as tools for nerve localization when a 22-gauge insulated needle is used for the performance of axillary-nerve block. Methods: After IRB approval and informed consent, 103 patients were enrolled. Real-time ultrasonography was used as the reference test. After needle-to-nerve contact was confirmed by ultrasonography, the patient was requested to report the presence of paresthesia, and a nerve stimulator was used to seek a motor response, with a stimulating current of 0.5 mA or less. Results: One patient was excluded from analysis because of protocol violation. Paresthesia was found to be 38.2% sensitive and motor response was 74.5% sensitive for detection of needle-to-nerve contact. Conclusion: The very different and relatively low sensitivity of either technique may explain, in part, the lack of correlation previously reported between the 2 endpoints.

Brachial plexus examination and localization using ultrasound and electrical stimulation: A volunteer study

Background Current techniques of brachial plexus block are “blind,” and nerve localization can be frustrating and time consuming. Previous studies on ultrasound-assisted brachial plexus blocks are mostly performed with scanning probes of 10 MHz or less. The authors tested the usefulness of a state-of-the-art, high-resolution ultrasound probe (up to 12 MHz) in identifying the brachial plexus in five locations of the upper extremity and in guiding needle advancement to target before nerve stimulation. Methods In this prospective observational study, 15 volunteers underwent brachial plexus examination using an L12–L5 MHz probe and a Philips-ATL 5000 ultrasound unit in the interscalene, supraclavicular, infraclavicular, axillary, and midhumeral regions. Thereafter, an insulated block needle was advanced under direct ultrasound guidance to target nerves before confirmation by electrical nerve stimulation in five volunteers in each of the interscalene, supraclavicular, and axillary regions. The quality of brachial plexus images, anatomic variations, and the technique of needle advancement for nerve localization were recorded. Results The brachial plexus components were successfully identified in the transverse view as round to oval hypoechoic structures with small internal punctuate echos in all regions examined except the infraclavicular area (visualized in 27% of the cases). The authors’ technique of advancing the needle in-line with the ultrasound beam allowed moment-by-moment observation of the needle shaft and tip movement at the time of nerve localization. Hypoechoic structures were stimulated electrically and confirmed to be nerves. Conclusions These preliminary data show that the high-resolution L12–L5 probe provides good quality brachial plexus ultrasound images in the superficial locations i.e., the interscalene, supraclavicular, axillary, and midhumeral regions. The needle technique described here for ultrasound-assisted nerve localization provides real-time guidance and is potentially valuable for brachial plexus blocks.

Ultrasound Guidance Improves the Success of Sciatic Nerve Block at the Popliteal Fossa

Background and Objectives: Real time ultrasound guidance is a recent development in the area of peripheral nerve blockade. There are limited data from prospective randomized trials comparing its efficacy to that of traditional nerve localization techniques. In the present study, we tested the hypothesis that ultrasound guidance improves the success rate of sciatic nerve block at the popliteal fossa when compared with a nerve stimulator‐guided technique. Methods: After Institutional Research Ethics Board approval and informed consent, 74 patients undergoing elective major foot or ankle surgery were randomly assigned to receive a sciatic nerve block at the popliteal fossa guided by either ultrasonography (group US, transverse view, needle in plane approach above the sciatic nerve bifurcation), or nerve stimulation (group NS, single injection, 10 cm proximal to the knee crease). A standardized local anesthetic admixture (15 mL of 2% lidocaine with 1:200,000 epinephrine and 15 mL of 0.5% bupivacaine) was used. Sensory and motor function was assessed by a blinded observer at predetermined intervals for up to 1 hour. Block success was defined as a loss of sensation to pinprick within 30 minutes in the distribution of both tibial and common peroneal nerves. Results: Group US had a significantly higher block success rate than group NS (89.2% vs. 60.6%, P = .005), while the procedure time was similar. Conclusions: Ultrasound guidance enhances the quality of popliteal sciatic nerve block compared with single injection, nerve stimulator‐guided block using either a tibial or peroneal endpoint. Ultrasound guidance resulted in higher success, faster onset, and progression of sensorimotor block, without an increase in block procedure time, or complications.

The ASRA evidence-based medicine assessment of ultrasound-guided regional anesthesia and pain medicine: Executive summary.

Objectives: The American Society of Regional Anesthesia and Pain Medicine charged an expert panel to examine the evidence basis for ultrasound guidance as a nerve localization tool in the clinical practices of regional anesthesia and interventional pain medicine. Methods: The panel searched, examined, and assessed the literature of ultrasound-guided regional anesthesia (UGRA) from the past 20 years. The qualities of studies were graded using the Jadad score. Strength of evidence and recommendations were graded using an accepted rating tool. Results: The panel made specific literature-based assessments concerning the relative advantages and limitations of UGRA relative to traditional nerve localization methods as they pertained to block characteristics and complications. Assessments and recommendations were made for upper and lower extremity, neuraxial, and truncal blocks and include pediatrics and interventional pain medicine. Conclusions: Ultrasound guidance improves block characteristics (particularly performance time and surrogate measures of success) that are often block specific and that may impart an efficiency advantage depending on individual practitioner circumstances. Evidence for UGRA impacting patient safety is currently limited to the demonstration of improvements in the frequency of surrogate events for serious complications.

Ultrasound assessment of gastric content and volume.

Background:Aspiration of gastric contents can be a serious perioperative complication, attributing up to 9% of all anesthesia-related deaths. However, there is currently no practical, noninvasive bedside test to determine gastric content and volume in the perioperative period. Methods:The current study evaluates the feasibility of using bedside ultrasonography for assessing gastric content and volume. In the pilot phase, 18 healthy volunteers were examined to assess the gastric antrum, body, and fundus in cross-section in five prandial states: fasting and after ingestion of 250 mL of water, 500 mL of water, 500 mL of effervescent water, and a solid meal. In the phase II study, the authors concentrated on ultrasound examination of the gastric antrum in 36 volunteers for whom regression analysis was used to determine the correlation between gastric volume and antral cross-sectional area. Results:The gastric antrum provided the most reliable quantitative information for gastric volume. The antral cross-sectional area correlated with volumes of up to 300 mL in a close-to-linear fashion, particularly when subjects were in the right lateral decubitus position. Sonographic assessment of the gastric antrum and body provides qualitative information about gastric content (empty or not empty) and its nature (gas, fluid, or solid). The fundus was the gastric area least amenable to image and measure. Conclusions:Our preliminary results suggest that bedside two-dimensional ultrasonography can be a useful noninvasive tool to determine gastric content and volume.

Ultrasound examination and localization of the sciatic nerve: a volunteer study.

Background:Few studies have examined the use of ultrasound for sciatic nerve localization. The authors evaluated the usefulness of low-frequency ultrasound in identifying the sciatic nerve at three locations in the lower extremity and in guiding needle advancement to target before nerve stimulation.

Gastric sonography in the fasted surgical patient: a prospective descriptive study.

BACKGROUND: Aspiration pneumonia remains a serious anesthetic-related complication. A reliable diagnostic tool to assess gastric volume is currently lacking. We recently demonstrated that gastric sonography can provide reliable qualitative and quantitative information about gastric content and volume in healthy volunteers. In the current study, we performed a prospective qualitative and quantitative analysis of the gastric antrum in 200 fasted patients undergoing elective surgery. METHODS: A standardized gastric scanning protocol was applied before anesthetic induction. Patients were classified following a 3-point grading system based solely on qualitative sonographic assessment of the antrum in the supine and right lateral decubitus positions. RESULTS: Eighty-six patients were classified as grade 0 (empty antrum); 107 patients as grade 1 (minimal fluid volume detected only in the right lateral decubitus position); and 7 patients were classified as grade 2 (antrum clearly distended with fluid visible in both supine and lateral positions). The 3-point grading system correlated with total gastric fluid volume as predicted by a previously reported mathematical model. Essentially grade 0 corresponds to a completely empty stomach, grade 1 corresponds to negligible fluid volumes (16 ± 36 mL) within normal ranges expected for fasted patients, and grade 2 correlates with significantly higher predicted gastric fluid volumes (180 ± 83 mL) beyond previously reported “safe” limits. One patient with a grade 2 antrum had an episode of significant regurgitation of gastric contents on emergence from anesthesia. CONCLUSION: We propose a 3-point grading system based exclusively on qualitative sonographic assessment of the gastric antrum that correlates well with predicted gastric volume. This grading system could be a promising “biomarker” to assess perioperative aspiration risk. Before it can be applied widely to clinical practice, this diagnostic tool needs to be further validated and characterized.

Analgesic effect of interscalene block using low-dose bupivacaine for outpatient arthroscopic shoulder surgery.

Background and Objectives. Although interscalene brachial plexus block (ISBPB) is often used to provide anesthesia for arthroscopic shoulder surgery, its selective analgesic effect, provided by low‐dose local anesthetic, has not been studied. We hypothesized that ISBPB using a low volume and low concentration of bupivacaine can provide effective postoperative analgesia for shoulder surgery without producing significant sensory or motor block elsewhere. Methods. In this double‐blind study, 30 outpatients scheduled to undergo shoulder arthroscopy were randomly assigned to receive either an ISBPB with 10 mL 0.125% bupivacaine with epinephrine 1:400,000 (n = 15) or 10 mL of normal saline (n = 15). The block was performed preoperative, prior to a standardized general anesthetic. Postoperative pain scores, morphine and oral analgesic consumption, recovery profile, and patient satisfaction were recorded. Results. In the ISBPB group, verbal analog pain scores within 120 minutes after surgery were lower, morphine consumption in the postanesthesia care unit was significantly lower (2.7 ± 2.6 mg vs 9.5 ± 5.2 mg), the time to postoperative administration of the first systemic or oral analgesic was significantly longer (141 ± 182 minutes vs 13 ± 10 minutes), the degree of motor and sensory block 120 minutes after surgery was minimal, time to reach hospital discharge criteria was earlier, and patient satisfaction with postoperative analgesia at 24‐hour follow‐up was greater. Thirty‐three percent of the patients receiving ISBPB did not require any analgesic prior to hospital discharge. Conclusions. Interscalene brachial plexus block with low‐dose bupivacaine is a useful and selective analgesic technique for outpatient shoulder arthroscopic surgery.

Ultrasound Imaging Facilitates Spinal Anesthesia in Adults with Difficult Surface Anatomic Landmarks

Background:Poor surface anatomic landmarks are highly predictive of technical difficulty in neuraxial blockade. The authors examined the use of ultrasound imaging to reduce this difficulty. Methods:The authors recruited 120 orthopedic patients with one of the following: body mass index more than 35 kg/m2 and poorly palpable spinous processes; moderate to severe lumbar scoliosis; or previous lumbar spine surgery. Patients were randomized to receive spinal anesthetic by the conventional surface landmark-guided technique (group LM) or by an ultrasound-guided technique (group US). Patients in group US had a preprocedural ultrasound scan to locate and mark a suitable needle insertion point. The primary outcome was the rate of successful dural puncture on the first needle insertion attempt. Normally distributed data were summarized as mean ± SD and nonnormally distributed data were summarized as median [interquartile range]. Results:The first-attempt success rate was twice as high in group US than in group LM (65% vs. 32%; P < 0.001). There was a twofold difference between groups in the number of needle insertion attempts (group US, 1 [1–2] vs. group LM, 2 [1–4]; P < 0.001) and number of needle passes (group US, 6 [1–10] vs. group LM, 13 [5–21]; P = 0.003). More time was required to establish landmarks in group US (6.7 ± 3.1; group LM, 0.6 ± 0.5 min; P < 0.001), but this was partially offset by a shorter spinal anesthesia performance time (group US, 5.0 ± 4.9 vs. group LM, 7.3 ± 7.6 min; P = 0.038). Similar results were seen in subgroup analyses of patients with body mass index more than 35 kg/m2 and patients with poorly palpable landmarks. Conclusion:Preprocedural ultrasound imaging facilitates the performance of spinal anesthesia in the nonobstetric patient population with difficult anatomic landmarks.