Sherif Abbas

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.

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.

Early but No Long-term Benefit of Regional Compared with General Anesthesia for Ambulatory Hand Surgery

Background:The purpose of this study was to determine whether either regional anesthesia (RA) or general anesthesia (GA) provided the best analgesia with the fewest adverse effects up to 2 weeks after ambulatory hand surgery. Methods:Patients undergoing ambulatory hand surgery were randomly assigned to RA (axillary brachial plexus block; n = 50) or GA (n = 50). Before surgery, all patients rated their hand pain (visual analog scale) and pain-related disability (Pain-Disability Index). After surgery, eligibility for bypassing the postanesthesia care unit (“fast track”) was determined, and pain, adverse effects, and home-readiness scores were measured. On postoperative days 1, 7, and 14, patients documented their pain, opioid consumption, adverse effects, Pain-Disability Index, and satisfaction. Results:More RA patients were fast-track eligible (P < 0.001), whereas duration of stay in the postanesthesia care unit was shorter in the RA group (P < 0.001). Time to first analgesic request was longer in the RA group (P < 0.001), and opioid consumption was reduced before discharge (P < 0.001). In the RA group, the pain ratings measured at 30, 60, 90, and 120 min after surgery were lower (P < 0.001), and patients spent less time in the hospital after surgery (P < 0.001). More GA patients experienced nausea/vomiting during recovery in the hospital (P < 0.05). However, on postoperative days 1, 7, and 14, there were no differences in pain, opioid consumption, adverse effects, Pain-Disability Index, or satisfaction. Conclusions:Despite significant reduction in pain before discharge from the hospital after ambulatory hand surgery, single-shot axillary brachial plexus block does not reduce pain at home on postoperative day 1 or up to 14 days after surgery when compared with GA. However, RA does provide other significant early benefits, including reduction in nausea and faster discharge from the hospital.

An ultrasonographic and histological study of intraneural injection and electrical stimulation in pigs.

BACKGROUND: In this study we evaluated the minimum stimulating current associated with intraneural needle placement and sonographic appearance of intraneural injection. METHODS: We inserted a needle 2 cm inside 28 pig nerves (brachial plexus in vivo), recorded the minimum current to elicit a motor response, and injected dye (5 mL) under ultrasound (US) imaging. RESULTS: The minimum current to elicit a motor response was 0.43 mA (range: 0.12–1.8 mA). Nerve expansion was visualized by US in 24 of 28 nerves. Histology revealed penetration of the epineurium in these same 24 nerves. There was no evidence of dysplasia within the fascicle of any nerve. CONCLUSIONS: US may prove useful to detect intraneural injection, whereas a motor response above 0.5 mA may not exclude intraneural needle placement. The correlation between intraneural injection and neurological dysfunction remains unclear.

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.

Artifacts and pitfall errors associated with ultrasound-guided regional anesthesia. Part II: a pictorial approach to understanding and avoidance.

t o l he use of real-time ultrasound guidance in regional anesthesia is growing in popularity. Parmount to the successful and safe use of ultrasound s the appreciation and accurate interpretation of ommon ultrasound-generated artifacts. An artifact s any perceived distortion, error, or addition caused y the instrument of observation (signal procesor).1 Imaging artifacts can be considered display henomena, and, therefore, can potentially compliate the planned procedure. There are 4 generic ategories of imaging artifacts:2 (1) Acoustic: error n presentation of ultrasound information; (2) Antomic: error in interpretation (often called “pitfall” rror); (3) Optical illusion: error in perception; and 4) Other: electrical noise. This article builds on the fundamental principles f ultrasound physics that are discussed in Part I of his article.3 The objective of this article is to decribe and illustrate many of the acoustic and anaomic artifacts commonly encountered by the reional anesthesiologist. In the process, we will offer nderlying physical explanations and describe pracical tips on how to negotiate these often misleading henomena.

Development and Validation of a New Technique for Ultrasound-guided Stellate Ganglion Block

Background and Objectives: Although the stellate ganglion is located anteriorly to the first rib, anesthetic block is routinely performed at the C6 level. Ultrasonography allegedly improves accuracy of needle placement and spread of injectate. The technique is relatively new, and the optimal approach has not been determined. Moreover, the location of the cervical sympathetic trunk relative to the prevertebral fascia is debatable. Methods: Three-dimensional sonography was performed on 10 healthy volunteers, and image reconstruction was completed. On the basis of analysis of pertinent anatomy, a lateral trajectory for needle placement was simulated. Accuracy was tested by injection of methylene blue in cadavers. A clinical validation study was then conducted. A block needle was inserted according to the predetermined lateral path, and 5 mL of a mixture of bupivacaine and iohexol was injected. Spread of the contrast agent was verified fluoroscopically. Results: Image reconstruction revealed that the cervical sympathetic trunk is located posterolaterally to the prevertebral fascia on the surface of the longus colli muscle. The mean anteroposterior width of the muscle at the C6 level was 11 mm. The lateral approach does not interfere with any visceral or nerve structures. Anatomic dissection in cadavers confirmed entirely subfascial spread of the dye and staining of the sympathetic trunk. The contrast agent spread was seen in all patients between the C4 and T1 levels in a typical prevertebral pattern. Conclusions: This study revealed that, at the C6 level, the cervical sympathetic trunk lies entirely subfascially. Subfascial injection via the lateral approach ensures reliable spread of a solution to the stellate ganglion.

Ultrasound Examination of Peripheral Nerves in the Forearm

Background and Objectives: We examined in a volunteer population whether nerves in the forearm could be seen consistently using ultrasound imaging and whether this new information could have implications for the way we perform regional anesthesia of the median, radial, and ulnar nerves. Methods: Eleven volunteers underwent ultrasound examination of both forearms. The median, ulnar, and radial nerves were followed and images were obtained at the elbow, proximal forearm, mid forearm, distal forearm and wrist levels. In addition the radial nerve was followed proximally to a point 5 cm above the elbow. Images were compared for consistency of location of the nerves and depth from skin and width was calculated for each nerve at each level. Results: Anatomy of each nerve was consistent except for one forearm where the median nerve was lateral to the brachial artery at the elbow and one forearm where a superficial ulnar artery only joined the ulnar nerve at the wrist. A convenient location for blockade of both median and ulnar nerves is the midforearm combining ease of visualization, ability to block all terminal branches and minimal potential for vascular injury. The radial nerve is seen most easily at the elbow although blockade of the superficial radial nerve may spare radial motor function. Conclusions: Nerves in the forearm are consistently located using ultrasound. Further confirmation in clinical practice is required.

Can Ultrasound of the Tibial Nerve Detect Diabetic Peripheral Neuropathy?: A cross-sectional study

OBJECTIVE Peripheral nerve imaging by portable ultrasound (US) may serve as a noninvasive and lower-cost alternative to nerve conduction studies (NCS) for diagnosis and staging of diabetic sensorimotor polyneuropathy (DSP). We aimed to examine the association between the size of the posterior tibial nerve (PTN) and the presence and severity of DSP. RESEARCH DESIGN AND METHODS We performed a cross-sectional study of 98 consecutive diabetic patients classified by NCS as subjects with DSP or control subjects. Severity was determined using the Toronto Clinical Neuropathy Score. A masked expert sonographer measured the cross-sectional area (CSA) of the PTN at 1, 3, and 5 cm proximal to the medial malleolus. RESULTS Fifty-five patients had DSP. The mean CSA of the PTN in DSP compared with control subjects at distances of 1 (23.03 vs. 17.72 mm2; P = 0.004), 3 (22.59 vs. 17.69 mm2; P < 0.0001), and 5 cm (22.05 vs. 17.25 mm2; P = 0.0005) proximal to the medial malleolus was significantly larger. Although the area under the curve (AUC) for CSA measurements at all three anatomical levels was similar, the CSA measured at 3 cm above the medial malleolus had an optimal threshold value for identification of DSP (19.01 mm2) with a sensitivity of 0.69 and a specificity of 0.77 by AUC analysis. CONCLUSIONS This large study of diabetic patients confirms that the CSA of the PTN is larger in patients with DSP than in control subjects, and US is a promising point-of-care screening tool for DSP.