Brazilian Journal of Anesthesiology
https://bjan-sba.org/article/doi/10.1590/S0034-70942011000600008
Brazilian Journal of Anesthesiology
Clinical Information

Angulação cefálica da inserção da agulha peridural pode ser um fator importante para a abordagem segura do espaço peridural: um modelo matemático

Cephalad angulation of epidural needle insertion may be an important factor for safe epidural space approach: a mathematical model

Satoki Inoue; Masahiko Kawaguchi; Hitoshi Furuya

http://dx.doi.org/10.1590/S0034-70942011000600008 Braz J Anesthesiol, vol.61, n6, p.767-769, 2011
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Resumo

JUSTIFICATIVA E OBJETIVOS: O ângulo de abordagem peridural é um dos fatores determinantes da profundidade de inserção da agulha para se atingir o espaço peridural. A margem de segurança contra punção acidental da dura-máter deve ser afetada pelo ângulo de abordagem porque o espaço disponível para o movimento da ponta da agulha no espaço peridural depende do ângulo de inserção. O objetivo deste estudo é investigar os efeitos do ângulo formado entre a pele e uma agulha peridural na margem de segurança contra a punção acidental da dura-máter, usando-se um modelo matemático. RELATO DO CASO: Suponha que a profundidade do espaço peridural seja A mm, que a força do cateter que avança seja C kgf e o diâmetro do cateter, D mm. Nessa situação, presumindo-se que o ângulo cefálico formado na linha média entre a pele e a agulha seja θ, os seguintes parâmetros podem ser determinados: a distância disponível para a ponta da agulha no espaço peridural = A/senθ mm; a força cefálica do cateter que avança = C*cosθ kgf; e a pressão no local da dura-máter onde o cateter peridural está empurrando = 400*C*senθ.πD-2 kgf.cm-2. Quanto maior a distância disponível para a ponta da agulha, maior será a margem de segurança para lesão da dura-máter pela agulha peridural. Supõe-se que θ deva ser o menor possível para que a margem de segurança seja maior. Da mesma maneira, θ pode reduzir a pressão de empuxo e criar uma força cefálica de avanço mais eficaz. CONCLUSÕES: Deve-se considerar o ângulo cefálico agudo para aumentar a margem de segurança na cateterização do espaço peridural.

Palavras-chave

ANESTESIOLOGIA, TÉCNICAS ANESTÉSICAS, TÉCNICAS ANESTÉSICAS

Abstract

BACKGROUND AND OBJECTIVES: Epidural approach angle is one of the determining factors for needle traveling length to reach the epidural space. Likewise, the margin of safety against accidental dural puncture should be affected by epidural approach angle because the space available for epidural needle tip movement in the epidural space is depending on the inserting angle to the epidural space. The purpose of this study is to conjecture the effect of the angle formed with the skin and an epidural needle on the margin of safety against accidental dural puncture using a mathematical model. CASE REPORT: Suppose that the width of the epidural space is A mm and that the force advancing the epidural catheter is C kgf and the diameter of the catheter is D mm. In this situation, assuming that the cephalad angle with the midline approach formed with the skin and an epidural needle is θ, the following parameters can be determined: the available distance for the needle tip in the epidural space = A/sinθmm; cephalad advancing force of catheter = C*cosθ kgf; and the pressure at the site of dura matter where the epidural catheter is pushing = 400*C*sinθ.πD-2 kgf.cm-2. The longer the distance available for the needle tip, the larger the margin of safety for dura injury by the epidural needle. It is supposed that θ should be set smaller to make the margin of safety larger. Likewise, smaller θ could decrease the pushing pressure and more effectively create a distinct cephalad advancing force. CONCLUSIONS: Acute cephalad angulation should be considered to increase the margin of safety for epidural approach and catheterization.

Keywords

Epidural Space, Anesthesia, Models, Safety Management

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