Daquan Xu

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.

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 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.

Disclosure of Risks Associated With Regional Anesthesia: A Survey of Academic Regional Anesthesiologists

Background and Objectives: In view of the relatively few large studies available to estimate the rates of complications following regional anesthesia, we aimed to identify and quantify the risks that academic regional anesthesiologists and regional anesthesia fellows disclose to their patients before performing central and peripheral nerve blockade. Methods: We asked 23 North American regional anesthesia fellowship program directors to distribute a questionnaire to the regional anesthesiologists and regional anesthesia fellows at their institutions. The questionnaire was designed to capture the risks and corresponding incidences that are routinely disclosed to patients before performing the most common central and peripheral nerve block techniques. Results: The total number of respondents was 79 from 12 different institutions. Fifty-eight (74%) respondents disclose risks of regional anesthesia in order to allow their patients to make an informed choice, whereas 20 (26%) disclose risks for medicolegal reasons. For central neural blockade, the most commonly disclosed risks are headache, local pain/discomfort, and infection. For peripheral nerve blockade, the most commonly disclosed risks are transient neuropathy, local pain/discomfort, and infection. For both central and peripheral nerve blockade, the risks most commonly disclosed are also those with the highest-reported incidences. Conclusions: The risks of regional anesthesia most commonly disclosed to patients by academic regional anesthesiologists and regional anesthesia fellows are benign in nature and occur frequently. Severe complications of regional anesthesia are far less commonly disclosed. The incidences of severe complications disclosed by academic regional anesthesiologists and their fellows can be inconsistent with those cited in the contemporary literature.