Brazilian Journal of Anesthesiology
Brazilian Journal of Anesthesiology
Clinical Research

Correlation of the epidural space measured intraoperatively and estimated by MRI or US: an observational study

Correlação entre a profundidade do espaço peridural medida no intraoperatório e a estimada por RM ou US: estudo observacional

Mehmet Canturk, Nazan Kocaoglu, Meltem Hakki

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Background and objectives
To assess the agreement between the epidural depth measured from the surgical site with the epidural depths estimated with magnetic resonance imaging (MRI) and ultrasound scanning.

Fifty patients of either sex, scheduled for L4‒5 lumbar disc surgery under general anesthesia were enrolled in this prospective observational study, and the results of 49 patients were analyzed. The actual epidural depth was measured from the surgical site with a sterile surgical scale. The MRI-derived epidural depth was measured from the MRI scan. The ultrasound estimated epidural depth was measured from the ultrasound image obtained just before surgery.

The mean epidural depth measured from the surgical site was 53.80 ± 7.67 mm, the mean MRI-derived epidural depth was 54.06 ± 7.36 mm, and the ultrasound-estimated epidural depth was 53.77 ± 7.94 mm. The correlation between the epidural depth measured from the surgical site and MRI-derived epidural depth was 0.989 (r2 = 0.979, p < 0.001), and the corresponding correlation with the ultrasound-estimated epidural depth was 0.990 (r2 = 0.980, p < 0.001).

Both ultrasound-estimated epidural depth and MRI-derived epidural depth have a strong correlation with the epidural depth measured from the surgical site. Preprocedural MRI-derived estimates of epidural depth are slightly deeper than the epidural depth measured from the surgical site, and the ultrasound estimated epidural depths are somewhat shallower. Although both radiologic imaging techniques provided reliable preprocedural estimates of the actual epidural depth, the loss of resistance technique cannot be discarded while inserting epidural needles.


Epidural,  Anesthesia,  Ultrasound,  Magnetic resonance imaging,  Intraoperative


Justificativa e objetivos
Avaliar a concordância entre a profundidade peridural medida no campo cirúrgico com a profundidade peridural estimada pela Ressonância Magnética (RM) e ultrassonografia.

Cinquenta pacientes de ambos os sexos, agendados para cirurgia de disco lombar L4‒5 sob anestesia geral, foram incluídos neste estudo observacional prospectivo, e os resultados de 49 pacientes foram analisados. A profundidade peridural real foi medida no campo cirúrgico com uma régua cirúrgica estéril. A profundidade peridural obtida pela Ressonância Magnética (RM) foi medida a partir das imagens do exame de RM. A profundidade peridural estimada pelo ultrassom foi medida a partir da imagem do ultrassom obtida imediatamente antes da cirurgia.

A profundidade peridural média medida no campo cirúrgico foi de 53,80 ± 7,67 mm; a profundidade peridural média da RM foi de 54,06 ± 7,36 mm; e a profundidade peridural estimada por ultrassom foi de 53,77 ± 7,94 mm. A correlação entre a profundidade peridural medida no campo cirúrgico e a profundidade peridural derivada da RM foi de 0,989 (r2 = 0,979; p < 0,001); e a correlação correspondente com a profundidade peridural estimada por ultrassom foi de 0,990 (r2 = 0,980; p < 0,001).

Tanto a profundidade peridural estimada por ultrassom quanto à profundidade peridural derivada da RM mostram forte correlação com a profundidade peridural medida no campo cirúrgico. As estimativas pré-operatórias da profundidade peridural derivadas da RM são um pouco mais profundas do que a profundidade peridural medida no campo cirúrgico, e as profundidades peridurais estimadas por ultrassom são um pouco mais rasas. Embora ambas as técnicas de imagem radiológica tenham fornecido estimativas pré-operatórias confiáveis ​​da profundidade peridural real, a técnica de perda de resistência não pode ser descartada durante a inserção da agulha peridural.


Peridural,  Anestesia,  Ultrassonografia,  Ressonância magnética Intraoperatória


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