Critical structures in the needle path of the costoclavicular brachial plexus block: a cadaver study.

PURPOSE: The costoclavicular block is a relatively novel alternative to the infraclavicular block. We aimed to determine the anatomical structures vulnerable to needle injury during a costoclavicular block. METHODS: The needle path consistent with a costoclavicular block approach was performed bilaterally on four lightly embalmed cadavers using ultrasound guidance. Careful dissection was performed with 18-G Tuohy needles in situ and photographs were taken. RESULTS: The needle penetrated the deltoid in six of eight cases and the pectoralis minor in three of eight cases. The subclavius tendon or its fascia were punctured in two of eight cases. The lateral cord was in contact with the needle in six procedures and punctured in three. The posterior cord was contacted in two instances, and the medial cord in one. In a single dissection, the needle was in contact with the medial antebrachial cutaneous nerve. The needle was close to the medial brachial cutaneous nerve in one case and close to the pectoral nerves in two of eight cases. While the cephalic vein and thoracoacromial artery were consistently nearby, there were no cases of vascular puncture. CONCLUSION: We found that the needle path may be close to the medial antebrachial cutaneous nerve, medial brachial cutaneous nerve, and pectoral nerves but did not traverse any critical structures aside from the lateral cord. This suggests relative safety when compared with other approaches to the infraclavicular brachial plexus. Structures dans la trajectoire de l'aiguille du bloc de plexus brachial costoclaviculaire : une étude cadavérique.

RéSUMé: OBJECTIF: Le bloc costoclaviculaire est une alternative relativement nouvelle au bloc infraclaviculaire. Notre objectif était de déterminer quelles structures anatomiques étaient vulnérables aux lésions provoquées par l'aiguille pendant un bloc costoclaviculaire MéTHODE: Nous avons simulé, sous échoguidage, une trajectoire d'aiguille correspondant à l'approche pour un bloc costoclaviculaire en bilatéral sur quatre cadavres légèrement embaumés. Une dissection minutieuse a ensuite été exécutée avec des aiguilles Tuohy 18-G laissées in situ et des photographies ont été prises. RéSULTATS: L'aiguille a pénétré le deltoïde dans six des huit cas et le muscle petit pectoral dans trois des huit cas. Le tendon sous-clavier ou son fascia ont été perforés dans deux des huit cas. Le cordon latéral a été en contact avec l'aiguille dans six interventions et perforé dans trois cas. Le cordon postérieur a été touché dans deux cas, et le cordon médial dans un cas. L'aiguille a touché le nerf cutané antébrachial médial dans une seule dissection. L'aiguille était proche du nerf cutané brachial médial dans un cas et proche des nerfs pectoraux dans deux des huit cas. Alors que la veine céphalique et l'artère thoraco-acromiale étaient toujours à proximité, il n'y a eu aucun cas de ponction vasculaire. CONCLUSION: Nous avons constaté que la trajectoire de l'aiguille peut être à proximité du nerf cutané antébrachial médial, du nerf cutané brachial médial et du nerf pectoral, mais l'aiguille n'a pas traversé de structures critiques hormis le cordon latéral. Ceci suggère l'innocuité relative de ce type de bloc par rapport à d'autres approches du plexus brachial infraclaviculaire.

Incidence of sub-perineural injection using a targeted intracluster supraclavicular ultrasound-guided approach in cadavers.

BACKGROUND: Multi-injection targeted intracluster injection ultrasound-guided supraclavicular brachial plexus block has been advocated to provide a faster onset of anaesthesia compared with a double injection technique. By placing the needle within clusters of hypoechoic structures, corresponding to neural tissue, this technique may increase needle trauma and the incidence of nerve injury. This study assessed the rate of sub-perineural needle placement with a single intracluster brachial plexus injection in the supraclavicular fossa of human cadavers. METHODS: A single ultrasound-guided intracluster brachial plexus injection was performed bilaterally at the supraclavicular fossa on 21 lightly embalmed clinical grade cadavers. Using an in-plane technique, an echogenic needle was positioned to target the middle or lower trunk 'cluster', where 0.2 ml black India ink was injected. An effort was taken to avoid the hypoechoic structures with the needle tip. Tissue samples were assessed histologically by two experienced reviewers. RESULTS: All 42 injections were sonographically assessed to be within the 'main cluster'. Ink was extra-epineural in 13/41 (32%), sub-epineural but outside perineurium in 18/41 (44%), and sub-perineural in 10/41 sections (24%; 95% confidence interval, 13-41%). The histology from one injection was uninterpretable. Of the 10 sub-perineural deposits, the ink was intrafascicular in nine sections. CONCLUSIONS: We observed a high rate of sub-perineural injection with a single intracluster injection. Thus the targeted intracluster injection supraclavicular block cannot be recommended until further evidence is available regarding the safety of this technique.

Histological confirmation of needle tip position during ultrasound-guided interscalene block: a randomized comparison between the intraplexus and the periplexus approach.

PURPOSE: Ultrasound-guided interscalene block can be performed using either periplexus or intraplexus needle placement. In this novel study, we histologically examined the needle tip position in relation to the neural tissues with the two techniques. Our objective was to investigate the variable risk of subepineurial needle tip placement resulting from the two ultrasound-guided techniques. METHODS: In an embalmed cadaveric model, periplexus or intraplexus interscalene injections were performed with the side, order, and technique assigned randomly. Under real-time ultrasound guidance, the block needle was placed next to the hyperechoic layer of the plexus (periplexus) or between the hypoechoic nerve roots (intraplexus). Once positioned, 0.1 mL of black acrylic ink was injected. The brachial plexus tissues were then removed and histology sections were prepared and then coded in order to blind two reviewers to group allocation. The area of ink staining was used to determine needle tip location, and the groups were compared for the presence of subepineurial ink. RESULTS: Twenty-six cadavers had each of the blocks performed on either brachial plexus (i.e., 52 injections). No subepineurial ink deposits were observed in the periplexus group (0%), but subepineurial ink deposition was observed in 3/26 (11.5%) intraplexus injections (odds ratio, 0; 95% confidence interval, 0 to 2.362; P = 0.235). Furthermore, in the intraplexus group, two (of the three) subepineurial ink deposits were observed under the perineurium. CONCLUSION: Although our study was somewhat underpowered due to a lower than previously reported rate of subepineurial needle tip positioning, our results suggest that there may be an increased likelihood of subepineurial needle tip position with the intraplexus approach. The periplexus technique resulted in no subepineurial spread of ink, suggesting that this approach may be less likely to result in mechanical trauma to nerves from direct needle injury.

A Cadaver Study Investigating Structures Encountered by the Needle During a Retroclavicular Approach to Infraclavicular Brachial Plexus Block.

BACKGROUND AND OBJECTIVES: Retroclavicular block is designed to overcome the negative aspects of the commonly utilized ultrasound-guided parasagittal approach to the infraclavicular block. However, this approach necessitates the needle traversing an area posterior to the clavicle inaccessible to ultrasound wave conduction. This study sought to document the structures vulnerable to needle injury during a retroclavicular block. METHODS: A Tuohy needle was inserted using a retroclavicular approach to the infraclavicular block in 3 lightly embalmed cadavers followed by a catheter insertion 4 cm beyond the needle tip. The process was repeated on the contralateral side. With the needle and catheter in position, the cadavers were dissected and photographed. RESULTS: In 4 of the 6 dissections, the needle was directly touching the suprascapular nerve deep to the clavicle. In the remaining 2 dissections, the suprascapular nerve was within 2 cm of the needle. In 1 dissection, the suprascapular vein was indented, behind the clavicle. The trapezius was the only muscle layer traversed by the needle in all dissections. In 3 of the 6 dissections, the catheter penetrated the posterior cord. In the remaining 3, the catheter threaded along the neurovascular bundle. CONCLUSIONS: The suprascapular nerve is consistently in the path of the block needle posterior to the clavicle. This raises the possibility of risk of injury to the suprascapular nerve when using this approach to the brachial plexus. Vascular injury is also possible deep to the clavicle, and because of the noncompressible location, caution is advised in patients with disordered coagulation.

Minimal illumination for direct laryngoscopy and intubation in different ambient light settings.

OBJECTIVES: This study sought to investigate the minimal laryngoscope illumination required for proper laryngoscopy and intubation in different ambient light settings as determined by paramedics. METHODS: Paramedics qualified to intubate patients in the field were recruited to intubate a cadaver embalmed with a minimal fixation technique designed to maintain tissue integrity. All paramedic participants intubated the cadaver under three different ambient light settings representing possible out-of-hospital settings: an outdoor night setting, an indoor setting, and an outdoor day setting. Paramedics were asked to determine the minimal illumination required for intubation of the cadaver under each of these settings. RESULTS: Twenty-three paramedics participated in the study. The mean (+/-SD) minimal illumination required for intubation was 39.1 (+/-35.4) lux at the night setting, 92.5 (+/-57.3) lux at the indoor setting, and 209.7 (+/-117.4) lux at the day setting. There was a statistically significant difference in minimal illumination required between each of the three light settings (p < 0.0001). CONCLUSIONS: Minimal illumination requirements in the out-of-hospital setting may be lower than previously recommended. Ambient light intensity affects this minimal illumination requirement, with brighter ambient light conditions necessitating more laryngoscope light output. Further studies assessing out-of-hospital laryngoscope illumination should consider ambient light conditions.