Aplicação da técnica de eletrodiagnóstico em pacientes críticos: uma revisão sistemática / Application of electrodiagnostic technique in critically ill patients: a systematic review

O ambiente de terapia intensiva está evoluindo em tecnologias para avaliação e tratamento sendo uma das técnicas mais atuais aplicadas neste ambiente o eletrodiagnóstico. Esta é uma revisão sistemática desenvolvida com base nos resultados de pesquisa das principais bases de dados, seguindo o PRISMA. Neste foram incluídos somente artigos observacionais que utilizaram a técnica de eletrodiagnóstico em pacientes críticos, para os mais diferentes objetivos e desfechos. As bases de dados consultadas foram: MEDLINE (acessado via PubMed), Fisioterapia Evidence banco de dados (Pedro), Registro de Ensaios Controlados (CENTRAL Cochrane) e EMBASE além de uma busca manual de referências adicionais. Um total de 10 artigos foram encontrados, sendo que dois apresentaram-se repetidos e outros seis foram excluídos por não contemplarem os critérios de inclusão obtendo-se ao final um total de dois artigos totalizando 33 pacientes. Um dos artigos apresentou resultados seguros, sem lesão muscular e o protocolo foi viável para ser aplicado em terapia intensiva. O outro artigo que após lesão cerebral traumática os pacientes podem apresentar distúrbios eletrofisiológicos, além de atrofia muscular generalizada sendo evidenciados pela técnica de eletrodiagnóstico. (AU)

The intensive care environment is evolving in technologies for evaluation and treatment, and these include a recent technique named electrodiagnosis. This systematic review was based on search results from major databases, following PRISMA guidelines. Only observational studies using the electrodiagnostic technique in critically patients for different objectives and outcomes were included. The following databases were searched: MEDLINE (accessed via PubMed), Physiotherapy Evidence database (Pedro), Controlled Trials Registry (CENTRAL Cochrane) and EMBASE, in addition to a manual search for additional references. Ten articles were found, two of which were repeated and six were excluded because they did not meet the inclusion criteria; thus, two articles were selected, with a total of 33 patients. One of the articles showed safe results, without any muscle injury, and the protocol was applicable in intensive care. The other article demonstrated that, after traumatic brain injury, patients may present with electrophysiological disorders and generalized muscle atrophy, which can be revealed by the electrodiagnostic technique. (AU)

Limb immobilization alters functional electrophysiological parameters of sciatic nerve

Immobilization, used in clinical practice to treat traumatologic problems, causes changes in muscle, but it is not known whether changes also occur in nerves. We investigated the effects of immobilization on excitability and compound action potential (CAP) and the ultrastructure of the rat sciatic nerve. Fourteen days after immobilization of the right leg of adult male Wistar rats (n=34), animals were killed and the right sciatic nerve was dissected and mounted in a moist chamber. Nerves were stimulated at a baseline frequency of 0.2 Hz and tested for 2 min at 20, 50, and 100 Hz. Immobilization altered nerve excitability. Rheobase and chronaxy changed from 3.13±0.05 V and 52.31±1.95 µs (control group, n=13) to 2.84±0.06 V and 59.71±2.79 µs (immobilized group, n=15), respectively. Immobilization altered the amplitude of CAP waves and decreased the conduction velocity of the first CAP wave (from 93.63±7.49 to 79.14±5.59 m/s) but not of the second wave. Transmission electron microscopy showed fragmentation of the myelin sheath of the sciatic nerve of immobilized limbs and degeneration of the axon. In conclusion, we demonstrated that long-lasting leg immobilization can induce alterations in nerve function.

Potencial de ação: do estímulo à adaptação neural / Action potential: from excitation to neural adaptation

INTRODUÇÃO: O potencial de ação (PA) origina-se graças a uma perturbação do estado de repouso da membrana celular, com consequente fluxo de íons, por meio da membrana e alteração da concentração iônica nos meios intra e extracelular. OBJETIVOS: Sintetizar o conhecimento científico acumulado até o presente sobre o potencial de ação neural e o seu processo de adaptação sob aplicação de um estímulo constante. MATERIAIS E MÉTODOS: Busca realizada nas bases Springer, ScienceDirect, PubMed, IEEE Xplore, Google Acadêmico, Portal de Periódicos da Capes, além de livros referentes ao assunto. O idioma de preferência selecionado foi o inglês, com as keywords: action potential; adaptation; accommodation; rheobase; chronaxy; nerve impulse. Efetuou-se a procura de artigos com uma janela de tempo de 1931 a 2010 e livros de 1791 a 2007. RESULTADOS: Dos trabalhos selecionados, foram extraídas informações a respeito dos seguintes tópicos: potencial de ação e suas fases; condução nervosa; reobase; cronaxia; acomodação; e adaptação neuronal. CONCLUSÃO: Um estímulo que crie PA, se aplicado de maneira constante, pode reduzir a frequência de despolarizações em função do tempo e, consequentemente, adaptar a célula. O tempo que a célula demora, na ausência de estímulos, para recuperar sua frequência original é definido como desadaptação.

INTRODUCTION: The action potential (AP) arises due to a disturbance of the resting state of the cell membrane with consequent flow of ions across the membrane and ion concentration changes in intra and extra cellular space. OBJECTIVES: This article aims to summarize the scientific knowledge accumulated to date on the action potential and neural adaptation in the process of applying a constant stimulus. MATERIALS AND METHODS: This is a literature review on the bases Springer, ScienceDirect, PubMed, IEEE Xplore, Google Scholar, Capes Periodicals Portal as well as books on the topic. The selected preferred language was English with the keywords: action potential; adaptation, accommodation; rheobase; chronaxy; nerve impulse. We conducted a search of articles with a wide time window from 1931 to 2010 and books from 1791 to 2007. RESULTS: In the selected studies was extracted information about the following topics: action potential and its stages; nerve conduction; rheobase; chronaxie, accommodation, and adaptation. CONCLUSION: A stimulus that creates AP, if applied consistently, can reduce the frequency of depolarization as a function of time and, consequently, to adapt the cell. The time it takes the cell in the absence of stimuli, to recover its original frequency, is defined as a disadaptation.

Alteracoes da cronaxia, da reobase e da acomodacao no musculo esqueletico desnervado submetido a eletroestimulacao / Alterations of the chronaxie, reobase and accomodation in denervated skeletal muscle submitted to electrical stimulation

O uso da eletroestimulacao (EE) no tratamento das lesoes nervosas perifericas e controverso. Este estudo avaliou a alteracao da cronaxia, da reobase e da acomodacao no musculo tibial anterior (TA) desnervado de ratos submetidos a EE. Quatro grupos de ratos forma divididos: TA desnervado com eletrodiagnostico (ED) semanal (DSN+ED); TA desnervado com EE em dias alternados (DSN+EE+ED); TA direito desnervado (DSN); e TA inervado (INV). O eletrodiagnostico do grupo DSN+EE+ED forneceu os parametros EE (20 contracoes intensas com corrente monopolar, exponencial; periodo de pulso igual a 2x o valor da cronaxia; frequencia de 20Hz; amplitude em nivel motor; e tempo ON 3,0 s e OFF 6,0 s). Apos 4 semanas, nota-se, em todos os musculos desnervados, diminuicao na reobase, caracterizando hiperexcitabilidade muscular. A reobase foi mairo no musculo so desnervado (1+0 mA), se comparada ao DSN+ED (0,5+0mA, p=0,00006) e ao DSN+EE+ED (0,58+0,19mA, P=0,0001). A cronaxia do grupo DSN+EE+ED foi melhor (4,06+2,1ms) se comparada aos grupos DNS+ED (8,4+0,93MS,P=0006) e DSN (5,31+0,53ms, p=0,45). A acomodacao diminuiu nos grupos DSN+ED (0,75+0,42mA) e DSN+EE+ED (0,75+0,6mA), mantendo-se com valores proximos a pre-desnervacao no grupo somente desnervado (DSN 1,8+0,45mA). Concluiu-se que, embora a EE e o ED tenha atrasado a recuperacao da reobase e da acomodacao, sua utilizacao conjunta favoreceu a rcuperacao da cronaxia. Esse resultado indica o efeito benefico no tratamento do musculo desnervado

Estudo sobre a reprodutividade das provas eletrodiagnósticas da reobase, cronaxia e curvas I/T em indivíduos sadios / Study about the reproductive of electrodiagnosis test of rheobase, cronaxie and curves I/T in individual healthy

Neste estudo foi realizada uma comparaçäo entre os dados obtidos por 2 examinadores para as provas da reobase, cronaxia e curva I-D aplicadas em 5 indivíduos, a fim de estudar as prováveis variaçöes que podem influenciar no critério de contraçäo mínima e suas possíveis causas. Apesar da ocorrência de variaçäo inter e intra-examinadores, existe uma margem de erro que deve ser levada em consideraçäo no exame eletrodiagnóstico clínico, uma vez que pequenas variaçöes podem näo refletir alteraçäo do estado patológico de um indivíduo, mas sim, uma faixa de erro possível no processo de investigaçäo

Experimental Injection Injury of the Sciatic Nerve: Part 11 Physiological Study

In clinical practice a serious sciatic nerve injury may result from an errornous injection of commonly used antibiotics and other therapeutic or prophylactic agents into the gluteal region which can occur at any age, especially common in infants, children and small debilitated patients. Although many isolated cases and several large series of injuries have been reported, the pathogenesis, pathology and its physiology of injection injury of the peripheral nerves in man have been poorly studied. This experimental study was conducted in order to observe the changes and degree of the functional disability of the sciatic nerve following injection of various drugs such as Rheumapyrine, Chloromycetin, Penicillin and physiological normal saline solution. Fourty-three normal adult rabbits were divided into four groups depending on injected materials and also divided into two groups of acute and chronic stages. The drugs were injected into the right sciatic nerve intraneurally and around the left sciatic nerve perineurally. For the functional study in the nerve, contractability of the calf muscle was recorded on a physiograph at intervals of 1, 3, 5, 15 and 30 minutes after the injection of the drugs. Rheobase, chronaxie and strength-duration curve of both extensor and flexor muscles of fet were recorded and measured on a chronaxie meter at intervals of 1, 2, 3 and 4 weeks after the injection. The physiogram showed the greatest reduction in contractability of the muscles in Rheumapyrine, moderate reduction in Penicillin and the least reduction in Chloromycetin group. In the measurements of rheobase and chronaxie there were marked increase of values in group of Rheumapyrine injection. There was no significant differences in values among the group of Penicillin, Chloromycetin and saline injections in comparison with those in the control group. In the analysis of strength-duration curve, it showed a pattern of complete denervation in 3 cases and a pattern of partial denervation in 3 out of 8 cases with Rheumapyrine injection, and a pattern of partial denervation in 3 out of 6 cases with Penicillin and 2 out of 8 cases with Chloromycetin injection. There was no significant differences in values of rheobase, chronaxie and strength-duration curve as time elapsed following the injury. It was postulated the functional and physiological disabilities were developed after the injection when there was a severe degree of nerve damages on the basis of histopathological study.