Pablo Escovedo Helayel

Learning Curves and Mathematical Models for Interventional Ultrasound Basic Skills

BACKGROUND:We aimed to construct learning curves and mathematical learning models for ultrasound basic skills: optimizing needle-ultrasound beam alignment and reaching a target inside a phantom. METHODS:Thirty subjects participated in the study. Each subject performed 25 trials. Linear ultrasound probes and a bovine muscular phantom were used. In Experiment 1, subjects tried to insert a needle parallel to the ultrasound beam with full imaging of the needle. For Experiment 2, a segment of tendon was inserted longitudinally into the phantom at a depth of 1 to 1.5 cm. Subjects tried to insert the needle until contacting the tendon. Learning curves were constructed using the cumulative sum (cusum) method. Bush and Mosteller’s mathematical learning models were constructed for each skill. RESULTS:Only 30% and 11% of subjects attained proficiency in Experiments 1 and 2, respectively. The predicted average numbers of trials to achieve 95% success rates as estimated from Bush and Mosteller’s models were 37 and 109, respectively. CONCLUSIONS:Learning interventional ultrasound basic skills may require a considerable number of trials. Cusum charts revealed that individuals acquire such abilities at variable rates. As skills were assessed in phantoms, our results do not apply to blocks given to real patients.

Bloqueios nervosos guiados por ultra-som

BACKGROUND AND OBJECTIVES Ultrasound-guided nerve blocks are based on the direct visualization of nerve structures, needle, and adjacent anatomic structures. Thus, it is possible to place the local anesthetic precisely around the nerves and follow its dispersion in real time, obtaining, therefore, more effective blockades, reduced dependency on anatomic references, decreased anesthetic volume, and increased safety. CONTENTS The aim of this paper was to review the physical mechanisms of image formation, ultrasound anatomy of the neuro axis and of the brachial and lumbosacral plexuses, equipment and materials used in the blockades, settings of the ultrasound equipment to improve the image, planes of visualization of the needles, the techniques, and training in ultrasound-guided nerve blocks. CONCLUSIONS The steps for a successful regional block include the identification of the exact position of the nerves, the precise localization of the needle, without causing injuries to adjacent structures, and, finally, the careful administration of the local anesthetic close to the nerves. Although neurostimulation is very useful in identifying nerves, it does not fulfill all those requirements. Therefore, it is believed that ultrasound-guided nerve blocks will be the technique of choice in regional anesthesia in a not too distant future.JUSTIFICATIVA E OBJETIVOS: As tecnicas de bloqueios nervosos guiados por ultra-som sao baseadas na visualizacao direta das estruturas nervosas, da agulha de bloqueio e das estruturas anatomicas adjacentes. Desta maneira, e possivel depositar a solucao de anestesico local precisamente em torno dos nervos e acompanhar a sua dispersao em tempo real, obtendo-se, assim, um bloqueio mais eficaz, de menor latencia, menor dependencia de referencias anatomicas, menor volume de solucao anestesica e maior seguranca. CONTEUDO: O artigo revisa os aspectos relativos aos mecanismos fisicos para formacao de imagens, a anatomia ultra-sonografica do neuroeixo e dos plexos braquial e lombossacral, os equipamentos e materiais empregados nos bloqueios, os ajustes do aparelho de ultra-som para melhorar as imagens, os planos de visualizacao das agulhas de bloqueio e as tecnicas e o treinamento em bloqueios guiados por ultra-som. CONCLUSOES: Os passos para se obter sucesso em anestesia regional incluem a identificacao exata da posicao dos nervos, a localizacao precisa da agulha, sem lesoes nas estruturas adjacentes e, finalmente, a injecao cuidadosa de anestesico local junto aos nervos. Embora a neuroestimulacao forneca grande auxilio na identificacao dos nervos, esta nao consegue, isoladamente, preencher todas essas exigencias. Por isso, acredita-se que os bloqueios guiados por ultra-som serao a tecnica de eleicao para anestesia regional num futuro nao muito distante.

A comparative study between ultrasound and neurostimulation guided axillary brachial plexus block

UNLABELLED Conceição DB, Helayel PE, Oliveira Filho GR - A Comparative Study between Ultrasound- and Neurostimulation-Guided Axillary Brachial Plexus Block. BACKGROUND AND OBJECTIVES The use of ultrasound in Regional Blocks is increasingly more frequent. However, very few studies comparing ultrasound and neurostimulation have been conducted. The objective of this study was to compare neurostimulation-guided axillary brachial plexus block with double injection and ultrasound-guided axillary plexus block for hand surgeries. The time to perform the technique, success rate, and complications were compared. METHODS After approval by the Ethics on Research Committee of the Hospital Governador Celso Ramos, 40 patients scheduled for elective hand surgeries under axillary plexus block were selected. Patients were randomly divided into two groups with 20 patients each: Neurostimulation (NE) and Ultrasound (US) groups. The time to perform the technique, success rate, and complication rate were compared. RESULTS Complete blockade, partial failure, and total failure rates did not show statistically significant differences between the US and NE groups. The mean time to perform the technique in the US group (354 seconds) was not statistically different than that of the NE group (381 seconds). Patients in the NE group had a higher incidence of vascular punctures (40%) when compared with those in the US group (10%, p < 0.05). The rate of paresthesia during the blockade was similar in both groups (15%). CONCLUSIONS The success rate and time to perform the blockade were similar in ultrasound- and neurostimulation-guided axillary plexus block for hand surgeries. The rate of vascular puncture was higher in neurostimulation-guided axillary plexus block.

Prevalence and predictive factors of urinary retention assessed by ultrasound in the immediate post-anesthetic period

BACKGROUND AND OBJECTIVES Urinary retention is a common condition in the post-anesthetic care unit (PACU). Vesical overdistension and consequent damage of the detrusor muscle of the urinary bladder represent situations that can be prevented. The ultrasound allows the reliable measurement of the urinary volume, determining the prevalence of postoperative vesical distension. The objective of the present study was to determine the prevalence of postoperative urinary retention and identify independent predictive factors. METHODS Two-hundred and fifty-seven patients admitted to the PACU were included prospectively in this study. Parameters collected included: age, gender, physical status, site of surgery, type of anesthesia, time of the surgery and anesthesia, use of opioids, volume of fluids administered, and history of urinary symptoms. Vesical volumes were measured by ultrasound after admission and upon discharge from the PACU. The criteria to characterize urinary retention were: vesical volume equal or higher than 600 mL associated with incapacity of spontaneous micturition for 30 minutes after the diagnosis. Univariate and multivariate analyses were used to indentify independent predictive factors. RESULTS Urinary retention was observed in 19 patients (7.39%), independent predictive factors identified included urinary volume equal to or greater than 360 mL upon admission to the PACU (Mantel-Haenszel Chi-square test (1 dF) = 18.76; p < 0.01), with an odds ratio of 9.82 (95% confidence interval = 3.26-29.55) and surgeries of the lower limbs (Mantel-Haenszel Chi-square test (1 dF) = 5.33; p = 0.02), with odds ratio of 4.33 (95% confidence interval = 1.34-14.02). CONCLUSIONS Due to the prevalence of urinary retention, we suggest that a systematic evaluation of the urinary volume at the PACU should be done, especially in those patients with predictive factors.

Estudo comparativo entre ultrassom e neuroestimulação no bloqueio do plexo braquial pela via axilar

JUSTIFICATIVA Y OBJETIVOS: El uso del ultrasonido en Anestesia Regional ha venido creciendo. Existen pocos estudios comparando el uso del ultrasonido con la neuroestimulacion. El objetivo de este estudio, fue comparar la ejecucion del bloqueo del plexo braquial por la via axilar, guiado por neuroestimulacion con doble inyeccion y guiado por ultrasonido en procedimientos quirurgicos en la mano. Para eso, se compararon el tiempo de realizacion, la tasa de exito y las complicaciones. METODO: Despues de la aprobacion por parte del Comite de Etica en Investigacion del Hospital Governador Celso Ramos, se seleccionaron 40 pacientes para operaciones por eleccion en la mano, con bloqueo de plexo braquial via axilar. Los pacientes se distribuyeron aleatoriamente y electronicamente en dos grupos de 20 pacientes: Grupo Neuroestimulacion (NE) y Grupo Ultrasonido (US). Se compararon el tiempo de realizacion, la tasa de exito y las complicaciones. RESULTADOS: Las tasas de bloqueo completo, falla parcial y falla total, no presentaron diferencias estadisticas significativa entre los grupos US y NE. El tiempo promedio para la realizacion del procedimiento en el grupo US (354 segundos) no presento diferencia estadistica significativa cuando se le comparo al grupo NE (381 segundos). Los pacientes del grupo NE presentaron una tasa mas elevada de puncion vascular (40%), cuando se les comparo con el grupo US (10%, p < 0,05). La tasa de presencia de parestesia durante la realizacion del bloqueo fue igual entre los dos grupos (15%). CONCLUSIONES: La tasa de exito y el tiempo para la realizacion, fueron similares entre el bloqueo de plexo braquial via axilar guiado por ultrasonido, cuando se le comparo con el guiado por neuroestimulacion con los de los estimulos en operaciones sobre la mano. Un tasa mas elevada de puncion vascular se dio en el bloqueo guiado por neuroestimulacion.

Curva de aprendizado da sonoanatomia do plexo braquial na região axilar

JUSTIFICATIVA E OBJETIVOS: A proficiencia em bloqueios guiados por ultrassom exige quatro habilidades: reconhecimento da sonoanatomia, capacidade de geracao de imagens, alinhamento da agulha ao feixe ultrassonografico e reconhecimento da dispersao do anestesico local. O objetivo deste estudo foi construir e avaliar curvas de aprendizado da geracao de imagens e identificacao ultrassonografica das estruturas neurovasculares axilares. METODO: Sete medicos em especializacao em Anestesiologia receberam nocoes teoricas e praticas sobre principios basicos da ultrassonografia e sonoanatomia axilar visando identificar ramos terminais do plexo braquial e vasos axilares. Cada um dos ME realizou seis exames. Foram avaliados a acuracia e o tempo transcorrido para identificacao das estruturas. Em cada exame foram calculadas taxas de sucesso. Regressao linear simples avaliou o tempo para identificacao de cada estrutura em relacao ao numero do exame. RESULTADOS: Os vasos axilares foram identificados em 100% dos exames. O nervo mediano foi identificado em 83% dos exames entre o primeiro e quinto. O nervo radial foi identificado em 100% dos exames. O nervo ulnar foi encontrado em 67% dos casos no primeiro exame e em 83% dos casos do segundo ao quinto procedimento. O nervo musculo-cutâneo foi localizado em 50% dos casos no primeiro exame, em 83% no quarto e no quinto exames. Todas as estruturas foram corretamente detectadas no sexto exame. O tempo medio para identificacao das estruturas diminuiu significativamente entre o primeiro e sexto exames (r = - 0,37). CONCLUSOES: A memorizacao sonoanatomica axilar e a aquisicao de habilidade manual de exame ultrassonografico foram obrigatorias para progressao do aprendizado e taxas de sucesso crescentes se associaram com reducao significativa do tempo para identificacao das estruturas.BACKGROUND AND OBJECTIVES Proficiency in ultrasound-guided blocks demands four skills: recognition of the ultrasound anatomy, capacity to generate images, aligning the needle with the ultrasound beam, and recognizing the dispersion of the local anesthetic. The objective of this study was to construct and evaluate learning curves for image generation and ultrasound identification of the neurovascular structures in the axilla. METHODS Seven Anesthesiology residents received theoretical and practical notions on the basic principles of ultrasound and the ultrasound anatomy of the axillary region with the objective to identify the terminal branches of the brachial plexus and axillary vessels. Each resident performed six exams. The accuracy and the time to identify the structures were evaluated. The success rate of each exam was calculated. Simple linear regression evaluated the time necessary to identify each structure in relation to the number of the exam. RESULTS The axillary vessels were identified in 100% of the exams. The median nerve was identified in 83% of the cases from the first to the fifth exams. The radial nerve was identified in 100% of the exams. The ulnar nerve was identified in 67% of the cases in the first exam, and in 83% of the cases from the second to the fifth exams. The musculocutaneous nerve was identified in 50% of the cases in the first exam and in 83% of the cases in the fourth and fifth exams. All structures were identified correctly on the sixth exam. The mean time for the correct identification of the structures decreased considerably from the first to the sixth exam (r = - 0.37). CONCLUSIONS Learning progression required the memorization of the ultrasound anatomy of the axillary region and acquisition of manual ability, and increasing success rates were associated with a significant reduction in the time to identify the structures.

Learning curve for the ultrasound anatomy of the brachial plexus in the axillary region

JUSTIFICATIVA E OBJETIVOS: A proficiencia em bloqueios guiados por ultrassom exige quatro habilidades: reconhecimento da sonoanatomia, capacidade de geracao de imagens, alinhamento da agulha ao feixe ultrassonografico e reconhecimento da dispersao do anestesico local. O objetivo deste estudo foi construir e avaliar curvas de aprendizado da geracao de imagens e identificacao ultrassonografica das estruturas neurovasculares axilares. METODO: Sete medicos em especializacao em Anestesiologia receberam nocoes teoricas e praticas sobre principios basicos da ultrassonografia e sonoanatomia axilar visando identificar ramos terminais do plexo braquial e vasos axilares. Cada um dos ME realizou seis exames. Foram avaliados a acuracia e o tempo transcorrido para identificacao das estruturas. Em cada exame foram calculadas taxas de sucesso. Regressao linear simples avaliou o tempo para identificacao de cada estrutura em relacao ao numero do exame. RESULTADOS: Os vasos axilares foram identificados em 100% dos exames. O nervo mediano foi identificado em 83% dos exames entre o primeiro e quinto. O nervo radial foi identificado em 100% dos exames. O nervo ulnar foi encontrado em 67% dos casos no primeiro exame e em 83% dos casos do segundo ao quinto procedimento. O nervo musculo-cutâneo foi localizado em 50% dos casos no primeiro exame, em 83% no quarto e no quinto exames. Todas as estruturas foram corretamente detectadas no sexto exame. O tempo medio para identificacao das estruturas diminuiu significativamente entre o primeiro e sexto exames (r = - 0,37). CONCLUSOES: A memorizacao sonoanatomica axilar e a aquisicao de habilidade manual de exame ultrassonografico foram obrigatorias para progressao do aprendizado e taxas de sucesso crescentes se associaram com reducao significativa do tempo para identificacao das estruturas.BACKGROUND AND OBJECTIVES Proficiency in ultrasound-guided blocks demands four skills: recognition of the ultrasound anatomy, capacity to generate images, aligning the needle with the ultrasound beam, and recognizing the dispersion of the local anesthetic. The objective of this study was to construct and evaluate learning curves for image generation and ultrasound identification of the neurovascular structures in the axilla. METHODS Seven Anesthesiology residents received theoretical and practical notions on the basic principles of ultrasound and the ultrasound anatomy of the axillary region with the objective to identify the terminal branches of the brachial plexus and axillary vessels. Each resident performed six exams. The accuracy and the time to identify the structures were evaluated. The success rate of each exam was calculated. Simple linear regression evaluated the time necessary to identify each structure in relation to the number of the exam. RESULTS The axillary vessels were identified in 100% of the exams. The median nerve was identified in 83% of the cases from the first to the fifth exams. The radial nerve was identified in 100% of the exams. The ulnar nerve was identified in 67% of the cases in the first exam, and in 83% of the cases from the second to the fifth exams. The musculocutaneous nerve was identified in 50% of the cases in the first exam and in 83% of the cases in the fourth and fifth exams. All structures were identified correctly on the sixth exam. The mean time for the correct identification of the structures decreased considerably from the first to the sixth exam (r = - 0.37). CONCLUSIONS Learning progression required the memorization of the ultrasound anatomy of the axillary region and acquisition of manual ability, and increasing success rates were associated with a significant reduction in the time to identify the structures.

Imagens ultra-sonográficas do plexo braquial na região axilar

BACKGROUND AND OBJECTIVES The axillary artery is the anatomical reference, in the surface, for axillary brachial plexus block. Anatomic studies suggest variability in the location of the structures in the brachial plexus in relation to the axillary artery. These variations can hinder blocks by neurostimulation. The ultrasound allows the identification of the structures within the brachial plexus(1). The objective of this report was to describe the position of the nerves in the brachial plexus in relation to the axillary artery. METHODS Thirty volunteers of both genders were studied. They were in the supine position with 90 degrees abduction and external rotation of the shoulder and 90 masculine flexion of the elbow. Using a 5 cm and 5-10 MHz digital transducer, median, ulnar and radial nerves were identified and their position in relation to the artery were recorded in an 8-sector sectional graphic chart, numbered in crescent order starting at the 12-hour position (medial), whose center represented the axillary artery. RESULTS The median nerve was located mainly in sectors 8 (55%) and 1 (28%) (medial); the radial nerve was predominantly in sectors 4 (59%) and 5 (34%) (lateral); and the ulnar nerve in sectors 2 and 3 (inferior) in 69% and 24% of the cases, respectively. There was a considerable variation in the location of the nerves in relation to the superior and inferior aspects of the artery. CONCLUSIONS Real-time ultrasound inspection of the neurovascular structures of the brachial plexus in the axilla demonstrated that the median, ulnar and radial nerves have different relations with the axillary artery.JUSTIFICATIVA Y OBJETIVOS: La arteria axilar es una referencia anatomica de superficie para el bloqueo del plexo braquial por via axilar. Estudios anatomicos sugieren variabilidad de las posiciones de las estructuras nerviosas del plexo braquial con relacion a la arteria. Esas variaciones pueden dificultar bloqueos por neuro estimulacion. El ultrasonido permite la identificacion de las estructuras del plexo braquial 1. Ese estudio busco describir el posicionamiento de los nervios del plexo braquial con relacion a la arteria axilar. METODO: Fueron estudiados 30 voluntarios de los dos sexos, en posicion supina con abduccion a 90° y rotacion externa del hombro y flexion del codo a 90°. Utilizando transductor digital de 5 cm y 5-10 MHz, fueron identificados los nervios mediano, ulnar y radial, y las respectivas posiciones en relacion a la arteria fueron marcadas en una carta grafica seccional de 8 sectores, enumerados en orden creciente a partir de la hora 12 (medial), cuyo centro representaba la arteria axilar. RESULTADOS: El nervio mediano se ubico predominante en el sector 8 (55%) y en el sector 1 (28%) (mediales); el nervio radial se ubico predominantemente en los sectores 4 (59%) y 5 (34%) (laterales) y el nervio ulnar en los sectores 2 y 3 (inferiores) en un 69% y un 24% de los casos, respectivamente. Hubo una considerable variacion de la localizacion de los nervios con relacion a los aspectos superior e inferior de la arteria. CONCLUSION: La inspeccion en tiempo real, por ultrasonido, de las estructuras neuro vasculares del plexo braquial en la axila mostro que los nervios mediano, ulnar y radial pueden presentar diferentes relaciones con la arteria axilar.

Volumes efetivos de anestésicos locais para o bloqueio do compartimento da fáscia ilíaca: estudo comparativo duplamente encoberto entre ropivacaína a 0,5% e bupivacaína a 0,5%

JUSTIFICATIVA Y OBJETIVOS: El bloqueo del compartimento de la fascia iliaca es ampliamente empleado como parte de las tecnicas anestesicas para intervenciones quirurgicas de la cadera, muslo y rodilla. La mayoria de los estudios han utilizado volumenes fijos de ropivacaina o de bupivacaina. Este estudio tuvo como objetivo calcular los volumenes de ropivacaina a 0,5% y de bupivacaina a 0,5% efectivos en 50% (VE50), 95% (VE95) y 99% (VE99) de los casos para la realizacion de bloqueos del compartimento de la fascia iliaca. METODO: Cincuenta y un adultos con cirugias marcadas electivas de la cadera, diafisis femoral y rodilla se sometieron al bloqueo del compartimento de la fascia iliaca. Los pacientes fueron aleatoriamente distribuidos y recibieron ropivacaina a 0,5% (n = 25) o bupivacaina a 0,5% (n = 26). El exito del bloqueo fue definido como bloqueo sensitivo completo de las regiones anterior, media y lateral del muslo. El volumen anestesico fue determinado por el metodo up-and-down de Massey y Dixon y los volumenes efectivos fueron calculados por las formulas de Massey y Dixon (VE50) y por regresion de probits (VE50, VE95 y VE99). RESULTADOS: Los volumenes anestesicos capaces de producir bloqueo nervioso efectivo en 50% de los casos, calculados por la formula de Massey y Dixon, fueron 28,79 mL (IC 95% : 26,31 -31,5 mL) para ropivacaina y 29,56 mL (IC 95% : 25,22 - 34,64 mL) para bupivacaina (p = 0,62). Los volumenes efectivos de ropivacaina capaces de bloquear 50%, 95% y 99% de los casos se estimaron por la regresion de probits como 28,8 mL (27,2 - 30,4), 34,3 mL (32,5 - 37,3) y 36,6 mL (34,3 - 40,5), respectivamente. Los volumenes correspondientes de bupivacaina fueron 29,5 mL (28,1 - 31,1), 36,1 mL (33,5 - 38,1), y 37,3 mL (35,1 - 41,3) (p > 0,05). CONCLUSIONES: Los volumenes necesarios de ropivacaina a 0,5% y bupivacaina a 0,5% con adrenalina 1:200.000 para el bloqueo del compartimento de la fascia iliaca son semejantes.BACKGROUND AND OBJECTIVES Fascia iliac compartment block is widely used as one of the anesthetic techniques used for surgical interventions of the hip, thigh, and knee. The majority of the studies have used fixed volumes of ropivacaine or bupivacaine. The objective of this study was to calculate the effective volume of 0.5% ropivacaine and 0.5% bupivacaine in 50% (EV50%), 95% (EV95), and 99% (EV99) of the cases to achieve fascia iliac compartment block. METHODS Fifty-one adults scheduled for elective surgical interventions of the hip, femoral diaphysis, and knee underwent fascia iliac compartment block. Patients were randomly assigned to receive either 0.5% ropivacaine (n = 25) or 0.5% bupivacaine (n = 26). The success of the block was defined as a complete sensitive block of the anterior, medial, and lateral regions of the thigh. The volume of the anesthetic was determined by Massey and Dixons up-and-down method, while the effective volume was calculated by Massey and Dixons formula (EV50) and by probits regression (EV50, EV95, and EV99). RESULTS The volume of anesthetic capable of producing an effective nervous anesthesia in 50% of the cases, calculated by Massey and Dixon formula, were 28.79 mL (CI 95%: 26.31 - 31.5 mL) for ropivacaine, and 29.56 mL (CI 95%: 25.22 - 34.64 mL) for bupivacaine (p = 0.62). The effective volumes of ropivacaine capable of producing a blocking in 50%, 95%, and 99% of the cases were estimated by probits regression as 28.8 mL (27.2 - 30.4), 34.3 mL (32.5 - 37.3), and 36.6 mL (34.3 - 40.5), respectively. The corresponding volumes of bupivacaine were 29.5 mL (28.1 - 31.1), 36.1 mL (33.5 - 38.1), and 37.3 mL (35.1 - 41.3) (p > 0.05). CONCLUSIONS The volumes of 0.5% ropivacaine and 0.5% bupivacaine with adrenaline 1:200,000 for the fascia iliac block are similar.

Urinary incontinence after bilateral parasacral sciatic-nerve block: report of two cases.

Objective: The authors describe the occurrence of urinary incontinence after bilateral parasacral sciatic-nerve blocks. Case Report: Two female patients scheduled for bilateral hallux valgus corrective surgery under bilateral parasacral sciatic-nerve block developed urinary incontinence manifested by 3 episodes of enuresis in the first 5 hours after surgery. Physical examination revealed bilateral perineal and gluteal anesthesia and no bladder distention in both patients. Ten hours after block placement, both patients had recovered perineal sensibility and were able to control micturition. Conclusion: Given the anatomic relations between the sacral plexus and the autonomic and somatic afferent and efferent innervation of the bladder and urethra, the urinary incontinence observed in our 2 patients could be explained by loss of afferent activity by spread of the local-anesthetic solution to pelvic nerves, loss of the efferent innervation of the posterior urethral sphincter by spread of the local-anesthetic solution to the urethral branches of the hypogastric plexus, and loss of external urethral sphincter tonus by block of the pudendal nerves. Anesthesiologists should consider the possibility of occurrence of urinary incontinence when performing bilateral parasacral sciatic-nerve blocks.