The purpose of this study is to compare accuracy of a new three-dimensional ultrasound (3D US) technique with the traditional palpation method for identification of the needle insertion site on patients' skin before epidural needle placement in pregnant women. The investigators hypothesize that the needle puncture site identified by 3D US is located within a 5 mm radius from the puncture site identified by palpation.
Traditionally, the manual palpation of lower back is used to identify the skin insertion point for the epidural needle placement in obstetric patients. Recently, two-dimensional ultrasound (2D US) scanning before the epidural needle insertion proved to improve an accurate determination of inter-vertebral levels and spine midline. 2D US is also useful in determining the depth to the epidural space and needle insertion angle. A three-dimensional ultrasound (3D US) technique is a new advancement in the ultrasound technology. 3D US allows for a real-time, visual guidance of the epidural needle insertion. This study will assess weather 3D US, compared to palpation, can accurately identify the skin needle insertion site for the epidural needle placement.
Study Type
OBSERVATIONAL
Enrollment
20
Paramedian ultrasound scanning of L2-3 and L3-4 lumbar interspaces to visualize ligamentum flavum. Palpation of the same intervertebral spaces to identify spine midline and needle insertion point.
BC Women's Hospital
Vancouver, British Columbia, Canada
Distance between two needle insertion points
To measure the distance between the needle puncture site identified by the 3D US transducer to the needle puncture site identified by palpation, measured on a transparency film.
Time frame: 20 minutes of testing prior to delivery
Distance between needle insertion point and spine midline
To measure the perpendicular distance between the needle puncture site identified by the 3D US transducer to the midline identified by manual palpation (to the P-line), measured on a transparency film.
Time frame: 20 minutes of testing prior to delivery
assess quality of 3D US images
To obtain US images of the epidural anatomy with various settings of the image-processing system to determine the optimal 3D US parameters that give the clearest images. An experienced sonographer will analyze the US images in the UBC laboratory using a qualitative measure of clarity (scale of 1 to 5) of the depiction of the ligamentum flavum and laminae. This quality measure will be correlated to the image acquisition parameters to determine the optimal set of parameters.
Time frame: one year
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