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Print version ISSN 0034-7094
On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.58 no.2 Campinas Mar./Apr. 2008
Simulation of ultrasound-guided peripheral nerve block: learning curve of CET-SMA/HSL anesthesiology residents
Simulacro de bloqueos periféricos guiados por ultrasonido: curva de aprendizaje de los residentes de anestesiología del CET-SMA/HSL
Marilia Bonifácio BaranauskasI; Clarita Bandeira Margarido, TSAII; Cláudia PanossianI; Enis Donizetti Silva, TSAIII; Murilo Awada CampanellaIV; Pedro Paulo KimachiV
do São Paulo Serviços Médicos de Anestesia (SMA) do Hospital
IIDoutora em Medicina pela FMUSP, Responsável pela Pesquisa do São Paulo SMA
IIIPresidente do São Paulo SMA; Responsável pelo CET do São Paulo SMA
IVME2 do São Paulo SMA do Hospital Sírio Libanês
VAnestesiologista do São Paulo SMA
OBJECTIVES: The use of ultrasound imaging in peripheral nerve block has
been increasing. However, there are few reports in the literature on the learning
curve of the ultrasound technique. The objective of this report was to evaluate
the learning curve of CET-SMA/HSL Anesthesiology residents of ultrasound-guided
peripheral block using an experimental agar model.
METHODS: An experimental model was developed by filling a bowl with agar and olives. Nine residents were randomly divided in three groups (G1, G2, and G3), each one with a R1, a R2, and a R3. All three groups received theoretical explanation. G1 also had two hours of practical training, G2 had one hour, and G3 had no training. Residents were then asked to place a needle at the middle of the olive wall, near the transducer, and then reposition the needle between the olive and the bottom of the bowl, simulating the epidural injection of anesthetic. The speed and efficacy of the tasks, as well as technical flaws, were evaluated.
RESULTS: The mean length of time to perform the tasks was 37.63 seconds for G1, without technical flaws; 64.40 seconds for G2, with two technical flaws; and 93.83 seconds for G3, with 12 technical flaws.
CONCLUSIONS: This study allows us to conclude that the longer training of ultrasound-guided peripheral nerve block in an experimental model improved the learning curve of the technique.
Key Words: ANESTHESIA, Regional; ANESTHETIC TECHNIQUES, Regional; EQUIPMENT, Ultrasound; TEACHING, Simulators.
Y OBJETIVOS: La técnica de ultrasonido ha sido cada vez más
utilizada para la realización de bloqueos de nervios periféricos.
Existen pocos relatos en la literatura que analizan la curva de aprendizaje
de la técnica de ultrasonido. El objetivo del estudio fue evaluar la
curva de aprendizaje de los residentes de Anestesiología del CET-SMA/HSL
en bloqueos periféricos guiados por ultrasonido a través de modelo
experimental de gelatina.
MÉTODO: Fue desarrollado un modelo experimental con un recipiente lleno de gelatina y aceituna sumergida. Nueve residentes se distribuyeron aleatoriamente en tres grupos (G1, G2, G3) compuestos cada uno, por un R1, un R2 y un R3. Los tres grupos recibieron una explicación teórica. El G1 recibió dos horas de entrenamiento práctico, el G2 una hora y el G3 no fue entrenado. Acto seguido, se les solicitó a los participantes que pusiesen la aguja en el punto medio de la pared de la aceituna, cerca del transductor y reposicionar la aguja entre la aceituna y el fondo del recipiente, simulando la inyección perineural del anestésico. Se evaluaron la velocidad y la eficacia de las tareas, además de las fallas técnicas.
RESULTADOS: El G1 presentó un promedio de tiempo para la realización de las tareas de 37,63 segundos, sin fallas técnicas; en el G2 se observó un promedio de 64,40 segundos, ocurriendo dos fallas técnicas y el G3 presentó un promedio de 93,83 segundos, con doce fallas técnicas.
CONCLUSIONES: El estudio permite concluir que el mayor tiempo de entrenamiento en un modelo experimental de bloqueos periféricos guiados por ultrasonido mejoró la curva de aprendizaje en el simulacro de la técnica.
Ultrasound imaging is an increasingly popular technique in peripheral nerve block 1. Ultrasound-guided techniques are based on direct visualization of nerves, needle, and adjacent anatomical structures. This visualization with high-frequency transducers ensures the safety of proper needle placement and real-time monitoring of the distribution of the local anesthetic, therefore improving the quality of the blockade. It also avoids traumatic and non- traumatic (p. ex.: paresthesia, hematoma) neurological complications, and reduction of the volume of anesthetic administered, when compared with conventional techniques, such as nerve stimulation, loss of resistance, or the development of paresthesia 2.
Clinical and technological understanding of ultrasound images has greatly improved in the last decade. The daily use of ultrasound-guided techniques requires a high-resolution device and a high degree of training. Anesthesiologists should fully develop their knowledge of the anatomical structures involved and acquire a solid background on ultrasound technology, besides the practical ability to visualize nerve structures, since proper performance depends on the ability of the operator.
There are few reports in the literature analyzing the learning curve of the ultrasound technique 3. The objective of this study was to evaluate the learning curve of Anesthesiology residents of CET of São Paulo Serviços Médicos de Anestesia of the Hospital Sírio e Libanês (SMA/HSL) of ultrasound-guided peripheral blocks using an experimental agar model 4.
This study involved all CET SMA/HSL residents. Nine residents were randomly divided in three groups, and each group was composed of one R1, one R2, and one R3 (first, second, and third year residents, respectively). The first group (G1) received theoretical orientation on the ultrasound equipment (USG) and blockade techniques. This was done by the more experienced anesthesiologist on USG-guided nerve block. After the theoretical explanation, this group underwent two hours of free training with the experimental model under supervision of the same anesthesiologist. The second group (G2) received theoretical orientation, but only one hour of free training. The third group (G3) received only theoretical orientation.
All residents had to perform the same tasks. Each one was allowed three attempts. Tasks were divided in: 1) proper visualization of the structure; 2) touching the olive with the tip of the needle; 3) reposition the needle between the olive and the bottom of the bowl; 4) avoid touching the bottom of the bowl with the needle. The following were considered technical flaws: failure to visualize the structure, incorrect positioning of the needle, and touching the bottom of the bowel with the needle. Failure to perform each task and technical flaws were evaluated by the observer. All residents were evaluated by the same observer, who did not know which group the residents belonged to.
The mean length of time to perform the tasks and the number of technical flaws in each group were evaluated.
The mean length of time to perform the tasks was 37.63 seconds for G1, which did not presented any technical flaws; 64.4 seconds for G2, with two technical flaws; and 93.83 seconds for G3, with twelve technical flaws (Table I and Chart I).
The use of simulators is common in aeronautical and nuclear industries, in which the operators should be attentive and be trained to deal with situations that might have catastrophic consequences. Proper training allows for fast responses, development of abilities, and improvement of the technique. Anesthesiology is similar to those activities, since it deals with critical situations that demand immediate, effective, and non-iatrogenic responses.
The possible development of a complication during anesthetic blocks justifies the use of the ultrasound, and the proper technique should be developed through simulations and training in experimental models, in teaching and training institutions, under direct supervision of experienced, licensed instructors, before performing nerve blocks in patients.
In the present study, the main finding was the relationship between longer training and better performance of the tasks with reduced incidence of technical flaws, confirming the data reported in the literature, demonstrating that individuals with specific training perform better that those without5.
Experimental models currently used to train ultrasound-guided techniques consist of: pig shoulders, breast of turkey, bovine muscle and agar pieces4.
The experimental model used has several advantages since it is easily reproducible, available to any anesthesiologist or CET and has a low cost. After the training, residents had more confidence to perform ultrasound-guided blocks in humans. It is important that the anesthesiologist handle and be familiarize with the ultrasound equipment before performing the technique in humans.
The limitation of this study was the small number of participants, and for this reason the results were not subjected to statistical analysis. Besides, it would be ideal to evaluate the performance of the residents before and after the training. More studies are needed to validate the method of simulation used.
This study allowed us to conclude that longer training in an experimental model of ultrasound-guided peripheral nerve block improved the learning curve of the technique simulation.
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Dra. Marilia Bonifácio Baranauskas
Rua Itamarati, 88 Santa Teresinha
02460-010 São Paulo, SP
Submitted em 27
de abril de 2007
Accepted para publicação em 30 de dezembro de 2007
* Received from Instituto de Ensino e Pesquisa (IEP), localizado no Hospital Sírio Libanês (HSL), São Paulo, SP