Validation of the soft-embalmed Thiel cadaver as a high-fidelity simulator of pressure during targeted nerve injection

Abstract

IntroductionAlthough administration of regional anesthesia nerve blocks has increased during the COVID-19 pandemic, training opportunities in regional anesthesia have reduced. Simulation training may enhance skills, but simulators must be accurate enough for trainees to engage in a realistic way—for example, detection of excessive injection pressure. The soft-embalmed Thiel cadaver is a life-like, durable simulator that is used for dedicated practice and mastery learning training in regional anesthesia. We hypothesized that injection opening pressure in perineural tissue, at epineurium and in subepineurium were similar to opening pressures measured in experimental animals, fresh frozen cadavers, glycol soft-fix cadavers and patients.MethodsWe systematically reviewed historical data, then conducted three validation studies delivering a 0.5 mL hydrolocation bolus of embalming fluid and recording injection pressure. First, we delivered the bolus at 12 mL/min at epimysium, perineural tissue, epineurium and in subepineurium at 48 peripheral nerve sites on three cadavers. Second, we delivered the bolus at using three infusion rates: 1 mL/min, 6 mL/min and 12 mL/min on epineurium at 70 peripheral nerve sites on five cadavers. Third, we repeated three injections (12 mL/min) at 24 epineural sites over the median and sciatic nerves of three cadavers.ResultsMean (95%) injection pressure was greater at epineurium compared with subepineurium (geometric ratio 1.2 (95% CI: 0.9 to 1.6)), p=0.04, and perineural tissue (geometric ratio 5.1 (95% CI: 3.7 to 7.0)), p<0.0001. Mean (95%) injection pressure was greater at 12 mL/min compared with 1 mL/min (geometric ratio 1.6 (95% CI: 1.2 to 2.1), p=0.005). Pressure measurements were similar in study 3 (p>0.05 for all comparisons).DiscussionWe conclude that the soft-embalmed Thiel cadaver is a realistic simulator of injection opening pressure.

Accuracy of injection pressure measurement at peripheral nerves using high-resolution 40 MHz ultrasound in an anesthetized porcine model

“…The imaging, needle insertion and injection procedures were performed by two operators, one a regional anesthesiologist and the other a PhD engineering student, trained previously to conduct ultrasound guided nerve injection on Thiel cadavers18 19 and pigs 20. We identified the radial, median and axillary nerves according to the schemata provided by Steinfeld et al 25…”

“…First, histology studies characterized the microscopic anatomy of nerves13 14; delineated spread using a novel heparinised blood marker15 within adipocyte-containing neural compartments16 and questioned the value of extrapolating results obtained from different animal models 17. Second, Thiel cadaver studies identified the wide, log-normal distribution of pressure and force data at tissue interfaces18 and dependence of injection pressure on flow rate 19. Third, application of 40 MHz microultrasound of the axillary brachial plexus in anaesthetized pigs showed highly detailed anatomy and precise location of needle tips relative to the target nerve 20…”

“…Therefore, our primary objective was to compare fluid injection pressures during microultrasound-guided injection in muscle, on epineurium and within subepineurium in the anaesthetized pig model using the same 0.5 mL injected volumes and infusion rates as in our soft embalmed cadaver model 19. In addition, we wished to identify, using ultrahigh 40 MHz ultrasound resolution, fluid spread within the muscle, within different fat compartments demarcated by the circumneurium, within the nerve (subepineurium) or between or within fascicles.…”

Patterns of Skills Acquisition in Anesthesiologists During Simulated Interscalene Block Training on a Soft Embalmed Thiel Cadaver: Cohort Study

“…To date, our work has validated the physical and functional alignment of the Thiel embalmed cadaver simulator [10], developed and validated checklist and eye tracking metrics that reflect skills performance [11], introduced mastery learning and dedicated 1:1 training to regional anesthesia [5], measured learning curves using new needle technology [5], and showed translation of skills from cadavers to patients 3 weeks after training. We also used eye tracking to measure the performance of the simulators and patients [4].…”

Recovery of motor function in ambulatory hand trauma using chloroprocaine 2%

“…Abdelhadi, R. Vanstone and M. Oldman University Hospitals Plymouth NHS Trust, Plymouth, UK Chloroprocaine 2% is an ester local anaesthetic offering a shorter onset, duration of action, and offset than other commonly used agents, making it particularly suitable for ambulatory surgery. 1 Although established for short-acting spinal anaesthesia, it has only recently launched on the UK market for peripheral nerve block. 2 We evaluated recovery of motor function in patients undergoing awake surgery using chloroprocaine 2% for ambulatory hand trauma procedures.…”