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

Discriminative Ability of Dye Injected Into a Meat Model to Determine Accuracy of Ultrasound-Guided Injection

INTRODUCTION

The utility of using meat models for ultrasound-guided regional anesthesia simulation training has been well established. Feedback is considered the most important element of successful simulation-based education, and simulation offers an opportunity for evaluation. The objective of this study was to establish the discriminative ability of dye injected into a meat model to determine whether injectate is properly placed in the perineural (PN) space, thus providing an additional tool for learner feedback and evaluation.

METHODS

Meat models containing a beef tendon (simulating a nerve) were injected with dye in one of 3 locations: PN, intraneural, and intramuscular. Blinded assessors then independently interpreted the dye staining on the models, marked the interpreted injection location, ease of interpretation, and whether staining was present on the beef tendon.

RESULTS

Thirty meat models were injected with dye and independently assessed. Determining the location of injection was deemed to be easy or very easy in 72% of the models. Assessors correctly identified PN, intraneural, and intramuscular injections 100%, 95%, and 85% of the time, respectively. Assessor agreement was 87%.

CONCLUSIONS

The location of dye injected into a meat model, simulating a peripheral nerve blockade, can be accurately and reliably scored to provide feedback to learners. This technique offers a novel means of providing feedback to trainees and assessing block success in ultrasound-guided regional anesthesia simulation.

Efficacy and safety of extrafascial injection versus intrafascial injection for interscalene brachial plexus block: a systematic review and meta-analysis

INTRODUCTION

This systematic review and meta-analysis aimed to assess the efficacy and safety of interscalene brachial plexus block (ISB) techniques in upper limb and shoulder surgeries.

EVIDENCE ACQUISITION

We conducted a comprehensive search of PubMed, Web of Science, Cochrane Central Register of Controlled Trials, Embase, Medline, and Scopus databases up to May 14th, 2023. We employed a search strategy involving keywords such as "brachial plexus block," "interscalene brachial plexus block," "ISB," "extrafascial," and "intrafascial," without applying search restrictions or filters. Eligible studies consisted of randomised controlled trials (RCTs) that compared extrafascial and intrafascial ISB techniques in adult patients undergoing upper limb and shoulder surgeries.

EVIDENCE SYNTHESIS

Our analysis included six RCTs encompassing 485 participants. Extrafascial injection demonstrated superiority over intrafascial injection in reducing the incidence of hemidiaphragmatic paresis (RR 0.33, 95% CI 0.124 to 0.47, P<0.00001) and preserving respiratory function (MS 0.31, 95% CI 0.1 to 0. 52, P=0.003 FEV1 in liters). Additionally, extrafascial ISB exhibited a lower risk of block-related complications (RR 0.35, 95% CI 0.25 to 0.50, P<0.00001). However, the intrafascial technique offered a faster sensory and motor block onset. The duration of sensory block did not significantly differ. The incidence of Horner syndrome showed no statistically significant difference.

CONCLUSIONS

Our findings favor extrafascial ISB techniques because they reduce hemidiaphragmatic paresis, preserve respiratory function, and lower block-related complications. However, further research is necessary to establish their safety and efficacy in specific patient populations.

Accuracy of ultrasonography predicting spread location following intraneural and subparaneural injections: a scoping review

INTRODUCTION

Ultrasonography is useful for detecting intraneural injections. However, the reliability of the sonographic findings of intraneural and subparaneural injections in terms of true spread location and their association with intrafascicular deposits has not been systematically evaluated.

EVIDENCE ACQUISITION

Our objectives were: i) to explore the reliability of sonographic findings of intraneural and subparaneural injections when validated with tests of true spread such as histology, dissection or imaging, and ii) to evaluate their association with intrafascicular deposits. A Scoping Review was conducted according to Joanna Briggs guidelines. Cinahl, PubMed, ProQuest, ScienceDirect, Scopus and Cochrane databases were searched for studies on adults, cadavers and animal models. Paediatric studies were excluded.

EVIDENCE SYNTHESIS

The search strategy found 598 citations. Following screening, 19 studies were selected. Intraneural injections occurred in the brachial plexus, sciatic, femoral and median nerves. Subparaneural injections in popliteal, supraclavicular and interscalene blocks. Sixteen different ultrasound findings were used to label injection location. Subepineural deposits within individual nerves occurred occasionally following subparaneural injections, regardless of nerve expansion. Overall five studies reported intrafascicular deposits, two of which frequently, following intraneural and subparaneural injections. None of the currently used ultrasound findings was predictive of intrafascicular deposits.

CONCLUSIONS

Our results suggest that sonographic parameters of intraneural and subparaneural injections are reliable in terms of detecting spread location. Intrafascicular injectate deposition may occur, albeit infrequently, particularly in the proximal brachial plexus. Our findings support the judicious interrogation of sonographic parameters suggestive of incipient intraneural injection.

Evaluating parameters affecting drug fate at the intramuscular injection site

Intramuscular (IM) injections are a well-established method of delivering a variety of therapeutics formulated for parenteral administration. While the wide range of commercial IM pharmaceuticals provide a wealth of pharmacokinetic (PK) information following injection, there remains an inadequate understanding of drug fate at the IM injection site that could dictate these PK outcomes. An improved understanding of injection site events could improve approaches taken by formulation scientists to identify therapeutically effective and consistent drug PK outcomes. Interplay between the typically non-physiological aspects of drug formulations and the homeostatic IM environment may provide insights into the fate of drugs at the IM injection site, leading to predictions of how a drug will behave post-injection in vivo. Immune responses occur by design after e.g. vaccine administration, however immune responses post-injection are not in the scope of this article. Taking cues from existing in vitro modelling technologies, the purpose of this article is to propose "critical parameters" of the IM environment that could be examined in hypothesis-driven studies. Outcomes of such studies might ultimately be useful in predicting and improving in vivo PK performance of IM injected drugs.

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.

Extraplexus versus intraplexus ultrasound-guided interscalene brachial plexus block for ambulatory arthroscopic shoulder surgery: A randomized controlled trial

Background

This randomized study compared the efficacy and safety of extraplexus and intraplexus injection of local anesthetic for interscalene brachial plexus block.

Methods

208 ASA I-II patients scheduled for elective shoulder arthroscopy under general anesthesia and ultrasound-guided interscalene brachial plexus block were randomly allocated to receive an injection of 25mL ropivacaine 0.5% either between C5-C6 nerve roots (intraplexus), or anterior and posterior to the brachial plexus into the plane between the perineural sheath and scalene muscles (extraplexus). The primary outcome was time to loss of shoulder abduction. Secondary outcomes included block duration, perioperative opioid consumption, pain scores, block performance time, number of needle passes, onset of sensory blockade, paresthesia, recovery room length of stay, patient satisfaction, incidence of Horner’s syndrome, dyspnea, hoarseness, and post-operative nausea and vomiting.

Results

Time to loss of shoulder abduction was faster in the intraplexus group (log-rank p-value<0.0005; median [interquartile range]: 4 min [2–6] vs. 6 min [4–10]; p-value <0.0005). Although the intraplexus group required fewer needle passes (2 vs. 3, p<0.0005), it resulted in more transient paresthesia (35.9% vs. 14.5%, p = 0.0004) with no difference in any other secondary outcome.

Conclusion

The intraplexus approach to the interscalene brachial plexus block results in a faster onset of motor block, as well as sensory block. Both intraplexus and extraplexus approaches to interscalene brachial plexus block provide effective analgesia. Given the increased incidence of paresthesia with an intraplexus approach, an extraplexus approach to interscalene brachial plexus block is likely a more appropriate choice.

Vulnerability of different nerves to intrafascicular injection by different needle types and at different approach angles: a mathematical model

BACKGROUND AND OBJECTIVES

We assume that intrafascicular spread of a solution can only occur if a large enough portion of the distal needle orifice is placed inside the fascicle. Our aim is to present and evaluate a mathematical model that can calculate the theoretical vulnerability of fascicles, analyzing the degree of occupancy of the needle orifice in fascicular tissue by performing simulations of multiple positions that a needle orifice can take inside a cross-sectional nerve area.

METHODS

We superimposed microscopic images of two routinely used nerve block needles (22-gauge, 15° needle and 22-gauge, 30° needle) over the microscopic images of cross-sections of four nerve types photographed at the same magnification. Fascicular tissue that was overlapped between 80% and 100% by a needle orifice was considered at risk to possible intrafascicular injection. The effect of three angular approaches was evaluated.

RESULTS

There were statistical differences between the vulnerability of fascicular tissue depending on nerve type, the bevel angle of the needle and the angle approach. Fascicular vulnerability was greater in nerve roots of the brachial plexus after using a 22-gauge 30° needle, as was choosing a 45° angle approach to the longitudinal axis of the nerve.

CONCLUSIONS

Our results suggest that clinicians may want to consider needle insertion angle and bevel type as they perform peripheral nerve blocks. Furthermore, researchers may want to consider this mathematical model when estimating vulnerabilities of various nerves, needle types and angles of approach of needles to nerves.

The Ultrasound Anatomy of Nerves in the Interscalene Groove: Can We Reliably Distinguish the Nerve Structures for Needle Placement During Nerve Blocks?

In the interscalene groove, nerve structures are in close proximity and may not be visible as separate structures, increasing the risk of insertion of the needle tip within the epineurium. We evaluated whether experienced regional anesthesiologists can distinguish between nerve elements lying in close proximity on ultrasound images.Brachial plexus elements from 4 nonpreserved cadavers were arranged in a water bath. Ultrasound images of the nerve roots and trunks were taken. Regional anesthesiologists and residents were asked whether they could distinguish the nerves as 2 separate structures and if they could identify a pair of nerve roots versus a single trunk.Attending anesthesiologists reported the ability to discriminate 2 nerve structures when a 2-mm space was arranged between them in 54% of images; however, when in direct contact, this recognition was significantly lower. The residents reported a higher ability to discriminate the 2 nerves in all scenarios. In addition, the attending anesthesiologists successfully identified paired nerve roots versus nerve trunks in 70% of the images, significantly higher than chance (P = 0.01), whereas the fraction of correct resident responses was not significantly different from guessing.When nerves were placed in close proximity, experienced regional anesthesiologists had difficulty identifying them as separate structures and were incorrect nearly one-third of the time in discriminating 2 closely positioned roots versus a nerve trunk. This underscores the importance of cautious needle insertion into the interscalene groove, where nerve elements are often juxtaposed one to another.

Effects of Stellate Ganglion Block on Analgesia Produced by Cervical Paravertebral Block as Established by Quantitative Sensory Testing: A Randomized Controlled Trial

Objective

To use quantitative sensory testing (QST) to assess whether a stellate ganglion block (SGB) modulates the analgesia induced by cervical paravertebral block (CPVB).

Design

A prospective double-blind randomized controlled trial.

Setting

Department of Anesthesia, Antwerp University Hospital, October 2011 to December 2015.

Subjects

Twenty-eight adults scheduled for arthroscopy of a nonfractured shoulder were enrolled.

Methods

Participants were randomly assigned to receive either single CPVB (5 mL of levobupivacaine 0.5%) or combined CPVB + SGB (5 mL and 3 mL of levobubivacaine 0.5%, respectively). The detection thresholds for cold/warm sensations and cold/heat pain were established using thermal QST on the C4-C7 dermatomes before local anesthetic infiltration and at 0.5, 6, 10, and 24 hours thereafter. Our primary outcome was the time course of QST thresholds for the different neurosensitive/nociceptive modalities. As secondary and tertiary outcomes, we evaluated the degree of motor block and the time to first administration of rescue analgesics.

Results

We randomized 20 patients. There were no significant differences in the detection thresholds for the neurosensitive/nociceptive modalities, motor block, or timing for rescue analgesics between the groups (P = 0.15-0.94). All patients with CPVB + SGB exhibited Horner's signs, whereas patients in the CPVB group did not exhibit these signs; however, this does not exclude sympathetic block.

Conclusions

We were unable to demonstrate any analgesic benefit of CPVB + SGB in arthroscopic shoulder surgery. It is therefore not unreasonable to suppose that pain from soft tissue injuries without bony lesions is transmitted mainly by somatic nerves with no or only minimal involvement of the sympathetic nervous system.