Benefits and Pitfalls of Cadavers as Learning Tool for Ultrasound-guided Regional Anesthesia

Development and validation of an assessment tool for adult simulated ultrasound-guided fascia iliaca block: a prospective monocentric study

BACKGROUND

Fascia iliaca block (FIB) is an effective technique for analgesia. While FIB using ultrasound is preferred, there is no current standardised training technique or assessment scale. We aimed to create a valid and reliable tool to assess ultrasound-guided FIB.

METHOD

This prospective observational study was conducted in the ABS-Lab simulation centre, University of Poitiers, France between 26-29 October and 14-17 December 2021. Psychometric testing included validity analysis and reliability between two independent observers. Content validity was established using the Delphi method. Three rounds of feedback were required to reach consensus. To validate the scale, 26 residents and 24 emergency physicians performed a simulated FIB on SIMLIFE, a simulator using a pulsated, revascularised and reventilated cadaver. Validity was tested using Cronbach's α coefficient for internal consistency. Comparative and Spearman's correlation analysis was performed to determine whether the scale discriminated by learner experience with FIB and professional status. Reliability was analysed using the intraclass correlation (ICC) coefficient and a correlation score using linear regression (R2).

RESULTS

The final 30-item scale had 8 parts scoring 30 points: patient positioning, preparation of aseptic and tools, anatomical and ultrasound identification, local anaesthesia, needle insertion, injection, final ultrasound control and signs of local anaesthetic systemic toxicity. Psychometric characteristics were as follows: Cronbach's α was 0.83, ICC was 0.96 and R2 was 0.91. The performance score was significantly higher for learners with FIB experience compared with those without experience: 26.5 (22.0; 29.0) vs 22.5 (16.0; 26.0), respectively (p=0.02). There was a significant difference between emergency residents' and emergency physicians' scores: 20.5 (17.0; 25.0) vs 27.0 (26.0; 29.0), respectively (p=0.0001). The performance was correlated with clinical experience (Rho=0.858, p<0.0001).

CONCLUSION

This assessment scale was found to be valid, reliable and able to identify different levels of experience with ultrasound-guided FIB.

Comparison of human cadaver and blue phantom for teaching ultrasound-guided regional anesthesia to novice postgraduate students of anesthesiology: A randomized controlled trial

Background and Aims

Simulation is increasingly used in medical teaching. Various studies have evaluated different simulation models for training of regional anesthesia (RA). We compared the use of human cadaver and blue phantom models for training of regional anesthesia to novice postgraduate students of anesthesiology.

Material and Methods

Fifty students were taught knobology of the ultrasonography (USG) machine. They were divided into two equal groups by computer-generated random number table, and the groups assigned were kept in sealed envelopes. In group BP, students were trained on a blue phantom model, and in group HC, students were trained on human cadaver. After training, a didactic video of sonoanatomy of the supraclavicular block was shown to all participants. The block performance was then judged on patients requiring supraclavicular block. The primary objective of the study was to compare the block performance time, and secondary objectives were the quality of image acquired, orientation of transducer to the target, identification of ultrasound artifacts, errors committed, complications, and success rate.

Results

The mean block performance time was shorter in group HC compared to group BP (451.96 ± 50.25 and 526.48 ± 43.486 s, respectively; P < 0.001). The image quality score, transducer orientation to the target, and identification of USG artifacts were better in group HC compared to group BP, with lesser number of needle passes.

Conclusion

Cadaver-based training produced better results compared to blue phantom simulator model for teaching of ultrasound-guided RA to novice postgraduate trainees of anesthesiology.

Ultrasound-guided injection of the hip: Cadaveric description for the lateral approach

BACKGROUND

Ultrasound (US)-guided intraarticular hip joint injections are commonly performed using an in-plane anterior approach, which has several limitations.

OBJECTIVE

To describe and report a "lateral" (lateral to medial) approach for US-guided intraarticular hip injection.

DESIGN

Cadaveric investigation.

SETTING

Academic institution, department of anatomy.

PARTICIPANTS

One cadaveric specimen.

METHODS

Both hips of a single cadaver were injected using the US-guided lateral approach. In the left hip, the needle was inserted and kept in situ. The right hip was injected with white-colored water-diluted latex dye. Subsequently, a layer-by-layer anatomical dissection was performed.

MAIN OUTCOME MEASURES

Presence and distribution of latex dye and location of needle tip within the joint capsule of the hip.

RESULTS

Anatomical dissection of the left and right hips confirmed the correct intraarticular position of the needle tip and the placement of the latex dye, respectively. During layer-by-layer dissection of the left hip, positions of the lateral cutaneous nerve and the lateral circumflex femoral artery were observed anterior to the needle, 30 mm for the nerve and 8 mm for the artery.

CONCLUSIONS

This preliminary study demonstrated that the US-guided lateral approach is a convenient technique to access the hip joint in a cadaveric specimen. Compared with the "classical" anterior technique, the lateral approach may provide several advantages, including improved needle visibility, theoretically decreased risk of vascular injury, and less risk of needle contamination. Because injury to the lateral epiphyseal arteries is possible when lateral approach is used, caution is required, especially in children. These preliminary conclusions will need to be validated in future/larger clinical studies.

Two Affordable, High-Fidelity Central Venous Models for Ultrasound-Guided Interventional Training

INTRODUCTION

Ultrasound-guided vascular access is an increasingly popular technique due to its reduced complication and higher success rates. Commercially bought training phantoms allow providers to develop tactile skills in a low-risk setting, but are also expensive and poorly accessible. This study analyzes the efficacy of homemade, low-cost, gelatin-based central line vascular models to teach vascular anatomy and intravascular access techniques in training physicians.

METHODS

A gelatin mold was created using a mixture of unflavored gelatin, hot water, psyllium husk powder, and rubbing alcohol. Latex tubing, balloons, precooked hot dog, and tofu were inserted to simulate arteries, veins, nerves, and the sternocleidomastoid muscle, respectively. Medical students from a single institution participated in a 90-minute workshop led by interventional radiology residents. Participants completed presurveys and postsurveys that assessed knowledge acquisition and confidence levels related to acquiring central access. All images were obtained using a USB-C Butterfly iQ probe.

RESULTS

Twenty medical students were analyzed after the workshop. There was a statistically significant increase in self-reported confidence in basic ultrasound use (adjusting gain, depth, probe manipulation), localizing major anatomical structures, using ultrasound for vessel access, and reported ease in identifying muscle, nerves, and major blood vessels under ultrasound. There was also a significant increase in correctly identified anatomical landmarks after the workshop, including the sternocleidomastoid muscle, internal jugular vein, carotid artery, femoral nerve, femoral artery, and femoral vein.

CONCLUSIONS

Our findings suggest that our homemade, low-cost, gelatin-based models were effective in teaching vascular anatomy and ultrasound-guided vascular access techniques to training physicians.

Cross-Sectional Study on the Comparative Assessment of Mandibular Anesthesia (Inferior Alveolar Nerve Blockage) Manual Skills Shaping among Dentists on Plastic and Biomaterial Models

Background: Providing regional anesthesia skills shaping remains relevant nowadays. A number of studies show that dentists have difficulties with these working independently. The study aim is the comparative analysis of the results of mandibular anesthesia (IANB) manual-skills shaping among dentists on plastic models and cadavers. Methods: In total, 999 participants were training in the skills of mandibular anesthesia from 2017 to 2021. The participants were divided in a random way into two groups: 700 participants were trained on plastic models, and 299 were trained on the cadaver material. After a lecture on the clinical and anatomical guidelines for IANB, a demonstration of the technique was provided, with subsequent testing of the injection technique. Satisfaction with the aspects of the training was assessed using the Likert scale. Results: the analysis of average values showed that participants from the group in which the manual skills were practiced on cadavers were more satisfied with the main aspects of the training, according to the sum of the main criteria of the modified scale. Conclusions: The important advantages of cadaver educational technology are that the sensations of tissue resistance are identical to natural ones, the individuality of each object, and the possibility of the visual study of the anesthesia technique, by dissection of the needle course and the location of the anesthetic depot.

Formalin-free soft embalming of human cadavers using N-vinyl-2-pyrrolidone: perspectives for cadaver surgical training and medical device development

The traditional apprenticeship approach to surgical skill education for young surgeons has drastically changed to more systematic surgical training using cadavers. Cadavers fixed with formalin are not suitable for surgical training because of their associated health hazards and overhardening. Recently, we established a formalin-free soft preservation method for human cadavers using N-vinyl-2-pyrrolidone. Since 2012, 61 cadavers have been embalmed with pyrrolidone in our institution. Tissues of pyrrolidone-embalmed cadavers are soft and pliable, and their bodies can be preserved for as long as 37 months without any signs of corruption. In this review, we introduce our recent attempts to apply pyrrolidone-embalmed cadavers in surgical and medical procedure training, including endotracheal intubation, motion physiology of the vocal folds, laparoscopic surgery, endoscopic skull base surgery, and development of novel medical devices. Future research perspectives on pyrrolidone embalming are discussed.

Comparative study of the reliability of ultrasound to confirm the position of endotracheal tube with cuff inflated with saline versus air

Aim: To compare the reliability of transtracheal ultrasound to confirm the endotracheal tube position with saline versus air inflated cuff. Methods: This was a prospective randomized cadaveric study. Four techniques were randomized: endotracheal tube in the trachea with air or saline inflated cuff, and endotracheal tube in the esophagus with air or saline inflated cuff. The investigator used the Mcgrath to randomly place the endotracheal tube in the trachea or in the esophagus with saline or air inflated cuff. During the first series of measurements, nine residents performed transtracheal ultrasound with linear transducer placed transversely at the suprasternal notch. They were recorded with a cut off fixed to 30 seconds, and a questionnaire was completed by the residents after each transtracheal ultrasound in order to report where the endotracheal tube is positioned according to them. The second series followed the same protocol and included three residents who had participated in the first series. The primary outcome was the success rate in determining the position of the endotracheal tube. Results: In the first series, the success rate was 46.5%. In the second series, the success rate was 72.9%. There was no significant difference between cuff inflated with saline and air (p = 1.00). The overall mean time required was 20.6 s (95% CI 13.0–28.2 s). Based on an empirical data set, transtracheal ultrasound had a sensitivity of 62.2%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 26.08%. Conclusion: This investigation shows that regardless of the contents of the endotracheal tube cuff, the use of transtracheal ultrasound to confirm the position of endotracheal tube reports disappointing results.

In vivo Visualization of Pig Vagus Nerve "Vagotopy" Using Ultrasound

Background: Placement of the clinical vagus nerve stimulating cuff is a standard surgical procedure based on anatomical landmarks, with limited patient specificity in terms of fascicular organization or vagal anatomy. As such, the therapeutic effects are generally limited by unwanted side effects of neck muscle contractions, demonstrated by previous studies to result from stimulation of (1) motor fibers near the cuff in the superior laryngeal and (2) motor fibers within the cuff projecting to the recurrent laryngeal. Objective: Conventional non-invasive ultrasound, where the transducer is placed on the surface of the skin, has been previously used to visualize the vagus with respect to other landmarks such as the carotid and internal jugular vein. However, it lacks sufficient resolution to provide details about the vagus fascicular organization, or detail about smaller neural structures such as the recurrent and superior laryngeal branch responsible for therapy limiting side effects. Here, we characterize the use of ultrasound with the transducer placed in the surgical pocket to improve resolution without adding significant additional risk to the surgical procedure in the pig model. Methods: Ultrasound images were obtained from a point of known functional organization at the nodose ganglia to the point of placement of stimulating electrodes within the surgical window. Naïve volunteers with minimal training were then asked to use these ultrasound videos to trace afferent groupings of fascicles from the nodose to their location within the surgical window where a stimulating cuff would normally be placed. Volunteers were asked to select a location for epineural electrode placement away from the fascicles containing efferent motor nerves responsible for therapy limiting side effects. 2-D and 3-D reconstructions of the ultrasound were directly compared to post-mortem histology in the same animals. Results: High-resolution ultrasound from the surgical pocket enabled 2-D and 3-D reconstruction of the cervical vagus and surrounding structures that accurately depicted the functional vagotopy of the pig vagus nerve as confirmed via histology. Although resolution was not sufficient to match specific fascicles between ultrasound and histology 1 to 1, it was sufficient to trace fascicle groupings from a point of known functional organization at the nodose ganglia to their locations within the surgical window at stimulating electrode placement. Naïve volunteers were able place an electrode proximal to the sensory afferent grouping of fascicles and away from the motor nerve efferent grouping of fascicles in each subject (n = 3). Conclusion: The surgical pocket itself provides a unique opportunity to obtain higher resolution ultrasound images of neural targets responsible for intended therapeutic effect and limiting off-target effects. We demonstrate the increase in resolution is sufficient to aid patient-specific electrode placement to optimize outcomes. This simple technique could be easily adopted for multiple neuromodulation targets to better understand how patient specific anatomy impacts functional outcomes.

Comparison of Haptic and Biometric Properties, Bacterial Load, and Student Perception of Fixative Solutions: Formaldehyde Versus Chilean Conservative Fixative Solution with and without Formaldehyde in Pig Kidneys

One of the most widely used solutions to fix and preserve organic tissues is formaldehyde, despite reservations regarding its toxicity and the fact that formaldehyde-embalmed bodies lose their original characteristics. Anatomy laboratories have been replacing formaldehyde with solutions that retain the characteristics of fresh tissue. For this purpose, alternative solutions with a very low concentration of formaldehyde or without any formaldehyde have been analyzed. The objective of this study was to compare biometry, coloration, haptic properties, and bacterial load on animal specimens (pig kidneys) embalmed with formaldehyde, and with Chilean Conservative Fixative Solution with and without formaldehyde (formaldehyde chCFS and formaldehyde-free chCFS). Also, the perception of health and biological science students toward specimens treated with different solutions was assessed. The results indicated that there were no significant differences in specimens' retraction, or bacterial load. Students showed a preference for organs embalmed in formaldehyde chCFS and formaldehyde-free chCFS; indicating that with these treatments they could better visualize structures and that the prosections had greater flexibility and the colors were more similar to those of fresh tissue. Additionally, students recommended the material embalmed in formaldehyde chCFS and formaldehyde-free chCFS for anatomy learning. In contrast, students indicated that formaldehyde-fixation negatively affected their practical experience. In conclusion, embalming with formaldehyde chCFS or formaldehyde-free chCFS provides an advantageous practical experience over the use of formaldehyde and may be an alternative to replace the use of formaldehyde in anatomy laboratories.

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.

Enhanced Experiential Learning in Airway Management: Surgical Modification of Cadavers

INTRODUCTION

Failure of airway management remains a significant source of morbidity and mortality. Advanced airway management has been addressed effectively by simulation-based training. However, simulation of difficult airways in manikins is limited by the pre-set conditions provided by the manufacturer. Life-like conditions in the form of the softness of the tissue and true anatomy as seen in cadaver models are needed to create simulated models with a closer resemblance to real patients. The goal of this study was to determine the feasibility of simulating difficult airway from submandibular abscess in cadaver models by surgical modification of the cadaver heads for use in enhanced experiential learning of the management of difficult airways.

METHODS

The cadaver heads were modified surgically to simulate a submandibular abscess. The models were used in an airway course where participants provided feedback on the realistic nature of the model and its benefits for difficult airway training. The ease of tracheal intubation of the models with the assistance of video laryngoscopy was assessed.

RESULTS

The modified cadavers were acceptable in simulating difficult airway as demonstrated by the feedback from the participants. All participants (100% [95% confidence interval = 89.1%-100%]) found the models to be realistic and beneficial for difficult airway training. A good proportion (56.3%) felt that the intubation technique was made easier with the video laryngoscopy.

CONCLUSIONS

Cadavers can be modified to simulate pathologies associated with difficult airways. These models can be used to enhance experiential learning and the management of difficult airways.

Development of Competency in Needle-Guided Procedures Through the Use of Soft-Embalmed Cadavers

This study evaluated soft-embalmed human cadavers for ultrasound needle-guidance training. Second-year medical students used peripherally inserted central catheter (PICC) line and central line models and a Thiel-embalmed cadaver for training and provided feedback. Most (85%) agreed the cadaver was useful. There were positive correlations between performing the PICC line (r=0.44, P=.11) and central line (r=0.63, P=.03) procedures on a cadaver and in a clinical setting. Thiel-embalmed cadavers may provide important hands-on training.

The Utility of Color Doppler to Confirm Endotracheal Tube Placement: A Pilot Study

Introduction

Grayscale ultrasound (US) imaging has been used as an adjunct for confirming endotracheal tube (ETT) placement in recent years. The addition of color Doppler imaging (CDI) has been proposed to improve identification but has not been well studied. The aim of this study was to assess whether CDI improves correct localization of ETT placement.

Methods

A convenience sample of emergency and critical care physicians at various levels of training and experience participated in an online assessment. Participants viewed US video clips of patients, which included either tracheal or esophageal intubations captured in grayscale or with CDI; there were five videos of each for a total of 20 videos. Participants were asked to watch each clip and then assess the location of the ETT.

Results

Thirty-eight subjects participated in the online assessment. Levels of training included medical students (13%), emergency medicine (EM) residents (50%), EM attendings (32%), and critical care attendings (5%). The odds ratio of properly assessing tracheal placement using color relative to a grayscale imaging technique was 1.5 (p = 0.21). Regarding the correct assessment of esophageal placement, CDI had 1.4 times the odds of being correctly assessed relative to grayscale (p = 0.26). The relationship between training level and correct assessments was not significant for either tracheal or esophageal placements.

Conclusion

In this pilot study we found no significant improvement in correct identification of ETT placement using color Doppler compared to grayscale ultrasound; however, there was a trend toward improvement that might be better elucidated in a larger study.

Novel ultrasound-guided lateral approach for femoral nerve block in cats: a pilot study

OBJECTIVES

The aim of this study was to describe the technique for a novel lateral approach to femoral nerve block in cat cadavers.

METHODS

Five feline cadavers were used in our prospective cadaveric experimental study. Ultrasonography was used to identify the anatomy injection site. Both pelvic limbs were injected with a volume (0.1 ml/kg) of methylene blue in each cat. The cadavers were placed in lateral recumbency, with the limb to be blocked positioned uppermost. The transducer was held perpendicular to the most proximal area of the pelvic limb, ventral to the greater trochanter and slightly cranial to the femur. Methylene blue was injected after the localisation of the femoral nerve. Immediately after the injection, the cat was turned and the technique was repeated on the contralateral side. After performing the 'block' in both limbs, the area was dissected bilaterally and the success was evaluated. A positive femoral nerve staining was considered for a coverage of ⩾1 cm.

RESULTS

A total of 10 ultrasound-guided femoral nerve injections were performed. Ninety percent (n = 9/10) of the nerves were successfully dyed.

CONCLUSIONS AND RELEVANCE

The novel ultrasound-guided lateral approach may be suitable and reproducible for a successful femoral nerve blockade in cats. Further investigations about the clinical usefulness and safety of this femoral nerve block in live cats are required.

Inter-rater reliability of an ultrasound protocol to evaluate the anterolateral ligament of the knee

Objectives: The aim of this study was to validate an ultrasound protocol for evaluating the anterolateral ligament of the knee. Methods: A Thiel technique cadaveric specimen was used to validate an optimal scanning position and develop an ultrasound protocol to evaluate the anterolateral ligament. Three musculoskeletal sonographers acquired short- and long-axis images of the anterolateral ligament in 36 knees from 18 healthy volunteers. Anterolateral ligament length, thickness, width, and distance between anterolateral ligament insertion and lateral tibia plateau were measured. Intraclass Correlation Coefficient (ICC) was calculated. Results: The inter-rater reliability for anterolateral ligament thickness was poor, ICC = 0.35 (95% CI: –0.06–0.63). The inter-rater reliability for anterolateral ligament length and width was good, ICC = 0.80 (95% CI 0.64–0.89), ICC = 0.88 (95% CI 0.79–0.94), respectively; and the inter-rater reliability for the distance between insertion and lateral tibia plateau was excellent, ICC = 0.96 (95% CI 0.93–0.98). Conclusions: Ultrasonography is a reliable method for evaluating the anterolateral ligament. There is an excellent reliability for the distal part of the anterolateral ligament. As injuries usually occur in this part of the ligament, this protocol may be used to evaluate the anterolateral ligament in patients with suspected anterior cruciate ligament tears in clinical practice.

Intra and Inter-rater Reliability between Ultrasound Imaging and Caliper Measures to determine Spring Ligament Dimensions in Cadavers

The purpose was to evaluate intra and inter-rater reliability, repeatability and absolute accuracy between ultrasound imaging (US) and caliper measures to determine Spring ligament (SL) dimensions in cadavers. SLs were identified from 62 human feet from formaldehyde-embalmed cadavers. Intra and inter-observer reliability, repeatability and absolute accuracy of SL width, thickness and length between US and caliper measurements were determined at intra and inter-session by intraclass correlation coefficients, Pearson´s correlation coefficients, Student t tests, standard errors of measurement, minimum detectable changes, values of normality, 95% limits of agreement, and Bland-Altman plots. Excellent inter-session and inter-rater reliability, adequate absolute accuracy, almost perfect agreement and strong correlations were shown for caliper, US and their comparison for all SL dimensions. US measurements presented higher absolute accuracy than caliper measures for SL length and thickness dimensions, while caliper displayed greater absolute accuracy for SL width dimensions. Good repeatability (P > 0.05) was shown for all SL dimensions by US, caliper and their comparison, except for SL width dimension measured with US (P = 0.019). Both US and caliper could be recommended for all SL dimensions evaluation due to their excellent reliability and absolute accuracy in cadavers, although width dimensions should be considered with caution due to US repeatability differences.