Medical Student Instruction in Peripheral Nerve Blockade Utilizing Fresh Cadaver Limbs in a Simulation Center.

Background: Ultrasound imaging is increasingly used in medical practice, but many institutions have room for growth regarding its incorporation into medical education. An elective hands-on course was developed for preclinical medical students using ultrasound to review and enhance their understanding of anatomy as well as to teach ultrasound-guided nerve blocks on cadaver extremities. The hypothesis was that after 3 instructional sessions students would be able to identify 6 anatomic structures, representing 3 types of tissue, in cadaver upper extremities. Methods: Students received didactic instruction on ultrasound and regional anatomy at the beginning of each class, followed by hands-on practice, including ultrasound use with phantom task trainers, live models, and fresh cadaver limbs. The primary outcome was the students' ability to correctly identify anatomic structures using ultrasound. Secondary outcomes included their ability to perform a simulated nerve block in the cadaver extremities in comparison with a standardized checklist, as well as their response to a post-course survey. Results: Overall, the students had a 91% success rate in identifying anatomic structures and showed capability of performing simulated nerve block with occasional instructor prompting. The post-course survey revealed that the students felt strongly that both the ultrasound and cadaveric components of the course were beneficial to their education. Conclusion: Ultrasound instruction with live models and fresh cadaver extremities in a medical student elective course resulted in a high degree of recognition of anatomic structures, as well as permitted a valued clinical correlation in the form of simulated peripheral nerve blockade.

Non-Fellowship regional anesthesia training and assessment: an international Delphi study on a consensus curriculum.

BACKGROUND AND OBJECTIVES: While there are several published recommendations and guidelines for trainees undertaking subspecialty Fellowships in regional anesthesia, a similar document describing a core regional anesthesia curriculum for non-fellowship trainees is less well defined. We aimed to produce an international consensus for the training and teaching of regional anesthesia that is applicable for the majority of worldwide anesthesiologists. METHODS: This anonymous, electronic Delphi study was conducted over two rounds and distributed to current and immediate past (within 5 years) directors of regional anesthesia training worldwide. The steering committee formulated an initial list of items covering nerve block techniques, learning objectives and skills assessment and volume of practice, relevant to a non-fellowship regional anesthesia curriculum. Participants scored these items in order of importance using a 10-point Likert scale, with free-text feedback. Strong consensus items were defined as highest importance (score ≥8) by ≥70% of all participants. RESULTS: 469 participants/586 invitations (80.0% response) scored in round 1, and 402/469 participants (85.7% response) scored in round 2. Participants represented 66 countries. Strong consensus was reached for 8 core peripheral and neuraxial blocks and 17 items describing learning objectives and skills assessment. Volume of practice for peripheral blocks was uniformly 16-20 blocks per anatomical region, while ≥50 neuraxial blocks were considered minimum. CONCLUSIONS: This international consensus study provides specific information for designing a non-fellowship regional anesthesia curriculum. Implementation of a standardized curriculum has benefits for patient care through improving quality of training and quality of nerve blocks.

Osteonecrosis of Bilateral Mandibular Tori After Direct Laryngoscopy.

A 36-year-old man underwent direct laryngoscopy with routine general anesthesia for a knee procedure. Several days later, he experienced pain involving an ulceration along the medial aspect of the right mandible in the floor of the mouth. This evolved to a painful bony mass, and subsequently, a bony sequestrum was spontaneously shed. The initially misdiagnosed pathologic process occurred several more times on both sides of the mouth. A computed tomography scan eventually revealed large bilateral mandibular tori, a feature that likely predisposed the patient to this course of events. Pain in the floor of the mouth after airway manipulation should be carefully evaluated and the possibility of osteonecrosis considered.

Liposomal bupivacaine infiltration in the surgical site for analgesia after rotator cuff repair: a randomized, double-blinded, placebo-controlled trial.

INTRODUCTION: Arthroscopic rotator cuff repair is among the most painful of orthopedic surgeries. Liposomal bupivacaine is Food and Drug Administration approved for administration into surgical sites to provide postsurgical analgesia and has been used to address postoperative pain after many types of surgery, including total shoulder arthroplasty. However, its efficacy for pain control after rotator cuff repair is unclear. METHODS: In this randomized, double-blind, placebo-controlled trial, we compared liposomal bupivacaine with an equivalent volume of saline injected into the subacromial space and arthroscopy portal sites in patients undergoing rotator cuff repair under the interscalene block with sedation. The primary outcome measure was numeric rating pain score at the time of block resolution, as reported during the follow-up phone call on postoperative day 1. Secondary outcomes included mean pain scores at rest as well as oral morphine equivalent requirements on postoperative days 1, 2, and 3. This study provides Level 1 evidence. RESULTS: There were no statistically significant differences in the primary outcome of numeric rating pain scores on resolution of the interscalene nerve block, nor in those reported on postoperative day 1 or 2. There was a minor but statistically significant difference in mean resting pain scores on day 3, though opioid consumption and patient satisfaction score did not differ between groups. In those instructed to perform passive range-of-motion exercises, there was no difference in reported mean pain scores among the groups. DISCUSSION: In this study of patients undergoing arthroscopic rotator cuff repair, we found no statistically significant difference in mean pain scores on interscalene block resolution, a result consistent with a number of studies investigating liposomal bupivacaine for total shoulder arthroplasty. A modest reduction in pain was evident only on day 3, and there was no impact on perioperative opioid requirements, opioid-related side effects, or pain with motion. Liposomal bupivacaine, when injected into the subacromial space and the tissues around the arthroscopy port sites, provided minimal improvement in pain control in this patient population.

Has the future arrived? Liposomal bupivacaine versus perineural catheters and additives for interscalene brachial plexus block.

PURPOSE OF REVIEW: Single injection interscalene block (ISB) provides effective analgesia for shoulder surgery. However, the duration of these is limited. This review summarizes the effectiveness of three potential means of extending the duration of analgesia: perineural infusion of local anesthetic agents, addition of adjuvant drugs to local anesthetics in single-injection nerve block, and utilization of liposomal bupivacaine in the surgical field or in the block itself. RECENT FINDINGS: Perineural infusion of local anesthetics with interscalene catheters provides superior pain relief with reduction of postoperative opioids. Both dexmedetomidine and dexamethasone effectively extend the duration of single injection ISB. Liposomal bupivacaine holds promise when injected perineurally in ISB, either as a sole agent or when mixed with standard bupivacaine. SUMMARY: Interscalene catheters, adjunctive drugs added to local anesthetics in single-injection interscalene brachial plexus blocks, or liposomal bupivacaine may be used to effectively prolong the duration of analgesia for shoulder surgery patients.

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.

A Porcine Model for Learning Ultrasound Anatomy of the Larynx and Ultrasound-Guided Cricothyrotomy.

BACKGROUND: Difficulty with tracheal intubation is the most common cause of serious adverse respiratory events during anesthesia. Cricothyrotomy is a life-saving procedure that is seldom performed by anesthesiologists. Anesthesiology residents are traditionally trained to perform cricothyrotomy with artificial mannequins and exposed larynx models from animals. These models lack the tissue feel of performing a cricothyrotomy on a patient with difficult neck anatomy. To improve the training experience, we developed a novel training model for cricothyrotomy using a porcine larynx, which incorporates ultrasonographic examination to identify the cricothyroid membrane, and permits varying degrees of difficulty. METHODS: Twenty-five residents were enrolled in a training curriculum consisting of (1) preprocedure training modules, (2) preprocedure hands-on demonstrations, and (3) three separate cricothyrotomy procedures using a porcine trachea. The first two procedures consisted of residents performing an open and a percutaneous cricothyrotomy on a model, which consisted of porcine trachea with chicken skin pinned over the larynx. The third procedure involved performing an open cricothyrotomy on a more challenging model, constructed by placing several layers of bacon fat between the larynx and chicken skin, making digital palpation of the laryngeal landmarks impossible. Before performing the procedure, residents located the cricothyroid interval with ultrasound. A postcurriculum survey was administered. RESULTS: Twenty-three of 25 residents were able to perform the open cricothyrotomy by digital palpation on the airway model on the first attempt. With the more challenging model, all 25 residents were able to locate the cricothyroid membrane by ultrasound and successfully perform open and percutaneous cricothyrotomy. Participants felt that they learned new information regarding ultrasound identification of laryngeal anatomy and gained valuable procedural experience in this training exercise. CONCLUSIONS: Use of the porcine trachea with overlying animal skin and fat provides an effective partial-task trainer for open and percutaneous surgical airway education and lends itself to integration of ultrasound imaging for real-time identification of laryngeal and tracheal anatomy.

Mechanics of anesthetic needle penetration into human sciatic nerve.

Nerve blocks are frequently performed by anesthesiologists to control pain. For sciatic nerve blocks, the optimal placement of the needle tip between its paraneural sheath and epineurial covering is challenging, even under ultrasound guidance, and frequently results in nerve puncture. We performed needle penetration tests on cadaveric isolated paraneural sheath (IPS), isolated nerve (IN), and the nerve with overlying paraneural sheath (NPS), and quantified puncture force requirement and fracture toughness of these specimens to assess their role in determining the clinical risk of nerve puncture. We found that puncture force (123 ±â€¯17 mN) and fracture toughness (45.48 ±â€¯9.72 J m-2) of IPS was significantly lower than those for NPS (1440 ±â€¯161 mN and 1317.46 ±â€¯212.45 Jm-2, respectively), suggesting that it is not possible to push the tip of the block needle through the paraneural sheath only, without pushing it into the nerve directly, when the sheath is lying directly over the nerve. Results of this study provide a physical basis for tangential placement of the needle as the ideal situation for local anesthetic deposition, as it allows for the penetration of the sheath along the edge of the nerve without entering the epineurium.

Updated Retrospective Single-Center Comparative Analysis of Peripheral Nerve Block Complications Using Landmark Peripheral Nerve Stimulation Versus Ultrasound Guidance as a Primary Means of Nerve Localization.

OBJECTIVES: The purpose of this study was to perform an updated analysis of complications associated with upper and lower extremity peripheral nerve blocks (PNBs) performed with ultrasound (US) guidance versus the landmark approach. METHODS: We conducted a single-center retrospective cohort analysis to compare the incidence of PNB complications between the techniques. The primary outcome was local anesthetic systemic toxicity (LAST), whereas the secondary outcomes included short- and long-term nerve injuries. The current query included cases performed between 2012 and 2015. A combined analysis included data extending to 2006. The Statistical examination relied on the χ2 test. RESULTS: During this 4-year period, we performed 7789 US-guided and 498 landmark-guided blocks with no statistically significant difference in the incidence of nerve injury or LAST between the groups. Our 10-year analysis, however, revealed a significant increase (P < .01) in the rate of LAST with the landmark technique: 7 of 5932 versus 0 of 16,858 cases. The combined data also revealed a significant increase (P < .01) in short-term injuries associated with the landmark approach (30 of 5932 versus 33 of 16,858) but no significant difference in the incidence of long-term injuries. CONCLUSIONS: Our analysis supports a conclusion that the use of US guidance during PNBs leads to a significant reduction in the incidence of LAST, adding to growing evidence from similar investigations. The impact of US on the incidence of nerve injuries remains unclear, considering that the nature of transient deficits is thought to be multifactorial, and the frequency of lasting injuries did not differ significantly in this study.

Optimization of Ultrasound Transducer Positioning for Endotracheal Tube Placement Confirmation in Cadaveric Model.

OBJECTIVES: Sonography has been suggested as a possible means of endotracheal tube (ETT) placement confirmation. However, optimum ultrasound transducer placement has not been established. Using a cadaveric model, ETT placement by the sonographic appearance at the thyroid cartilage, cricoid cartilage, and suprasternal notch in the upper airway was assessed to determine which ultrasound transducer placement offered the most optimal images for ETT confirmation in the airway. METHODS: One provider intubated 5 cadavers, with the ultrasound transducer at each of the 3 levels, for a total of 30 intubations per specimen, while 2 providers assigned a visual score of 1 (subtle), 2 (clear), or 3 (pronounced) to each sonogram of the ETT in the airway. RESULTS: At the level of the thyroid cartilage, tracheal intubation was detected at a rate of 40%, with a median visualization scale of 1 (subtle movement). At the level of the cricoid cartilage, the visualization scale improved to a median of 2 (clear movement), with a 70% intubation detection rate. At the level of the suprasternal notch, 100% of the tracheal intubations were visualized on sonography, with a median score of 3 (pronounced movement). CONCLUSIONS: In comparing sonographic detection of ETT placement at 3 levels of the upper airway in a cadaveric model, our results clearly indicate that visualization was superior at the level of the suprasternal notch, with 100% of intubations detected with the best visualization scores.

Ultrasound imaging in medical student education: Impact on learning anatomy and physical diagnosis.

Ultrasound use has expanded dramatically among the medical specialties for diagnostic and interventional purposes, due to its affordability, portability, and practicality. This imaging modality, which permits real-time visualization of anatomic structures and relationships in vivo, holds potential for pre-clinical instruction of students in anatomy and physical diagnosis, as well as providing a bridge to the eventual use of bedside ultrasound by clinicians to assess patients and guide invasive procedures. In many studies, but not all, improved understanding of anatomy has been demonstrated, and in others, improved accuracy in selected aspects of physical diagnosis is evident. Most students have expressed a highly favorable impression of this technology for anatomy education when surveyed. Logistic issues or obstacles to the integration of ultrasound imaging into anatomy teaching appear to be readily overcome. The enthusiasm of students and anatomists for teaching with ultrasound has led to widespread implementation of ultrasound-based teaching initiatives in medical schools the world over, including some with integration throughout the entire curriculum; a trend that likely will continue to grow. Anat Sci Educ 10: 176-189. © 2016 American Association of Anatomists.

Neurologic Outcomes After Low-Volume, Ultrasound-Guided Interscalene Block and Ambulatory Shoulder Surgery.

BACKGROUND AND OBJECTIVES: Postoperative neurologic symptoms after interscalene block and shoulder surgery have been reported to be relatively frequent. Reports of such symptoms after ultrasound-guided block have been variable. We evaluated 300 patients for neurologic symptoms after low-volume, ultrasound-guided interscalene block and arthroscopic shoulder surgery. METHODS: Patients underwent ultrasound-guided interscalene block with 16 to 20 mL of 0.5% bupivacaine or a mix of 0.2% bupivacaine/1.2% mepivacaine solution, followed by propofol/ketamine sedation for ambulatory arthroscopic shoulder surgery. Patients were called at 10 days for evaluation of neurologic symptoms, and those with persistent symptoms were called again at 30 days, at which point neurologic evaluation was initiated. Details of patient demographics and block characteristics were collected to assess any association with persistent neurologic symptoms. RESULTS: Six of 300 patients reported symptoms at 10 days (2%), with one of these patients having persistent symptoms at 30 days (0.3%). This was significantly lower than rates of neurologic symptoms reported in preultrasound investigations with focused neurologic follow-up and similar to other studies performed in the ultrasound era. There was a modest correlation between the number of needle redirections during the block procedure and the presence of postoperative neurologic symptoms. CONCLUSIONS: Ultrasound guidance of interscalene block with 16- to 20-mL volumes of local anesthetic solution results in a lower frequency of postoperative neurologic symptoms at 10 and 30 days as compared with investigations in the preultrasound period.

Correlation of ultrasound appearance, gross anatomy, and histology of the femoral nerve at the femoral triangle.

PURPOSE: Correlation between ultrasound appearance, gross anatomic characteristics, and histologic structure of the femoral nerve (FN) is lacking. Utilizing cadavers, we sought to characterize the anatomy of the FN, and provide a quantitative measure of its branching. We hypothesize that at the femoral crease, the FN exists as a group of nerve branches, rather than a single nerve structure, and secondarily, that this transition into many branches is apparent on ultrasonography. MATERIALS AND METHODS: Nineteen preserved cadavers were investigated. Ultrasonography was sufficient to evaluate the femoral nerve in nine specimens; gross dissection was utilized in all 19. Anatomic characteristics were recorded, including distances from the inguinal ligament to femoral crease, first nerve branch, and complete arborization of the nerve. The nerves from nine specimens were excised for histologic analysis. RESULTS: On ultrasound, the nerve became more flattened, widened, and less discrete as it coursed distally. Branching of the nerve was apparent in 12 of 18 images, with mean distance from inguinal ligament of 3.9 (1.0) cm. However, upon dissection, major branching of the femoral nerve occurred at 3.1 (1.0) cm distal to the inguinal ligament, well proximal to the femoral crease. Histologic analysis was consistent with findings at dissection. CONCLUSION: The femoral nerve arborizes into multiple branches between the inguinal ligament and the femoral crease. Initial branching is often high in the femoral triangle. As hypothesized, the FN exists as a closely associated group of nerve branches at the level of the femoral crease; however, the termination of the nerve into multiple branches is not consistently apparent on ultrasonography.