EFFECT OF THE EPIDURAL POSITIONING DEVICE ON THE ACOUSTIC TARGET WINDOW FOR LUMBAR NEURAXIAL ACCESS
Abstract Number: F-31
Abstract Type: Original Research
Introduction: Neuraxial anesthesia is frequently used in obstetric patients. During pregnancy, neuraxial anesthesia can be problematic due to anatomical changes. . Positioning manoeuvres have been shown to improve the sonographic target window for needle access to the neuraxial space [2-3]. The effect of the epidural positioning device (EPD) on the lumbar sonographic target window has not been evaluated. The paramedian sonographic window provides superior ultrasound (US) images of structures within the vertebral canal, compared with a transverse midline view [4-6]. The visualization of the posterior longitudinal ligament (PLL) represents an open acoustic window between adjacent vertebral laminae . We hypothesized that the application of the EPD would increase the measured lengths of the PLL (primary outcome), interlaminar distance (ILD) and ligamentum flavum (LF) (secondary outcomes).
Methods: Local REB approval was obtained. A convenience sample of 30 term pregnant, non-labouring women were consented and recruited. Two anesthesiologists independently scanned the L3-4 right paramedian space using a curvilinear ultrasound transducer (SonoSite M-Turbo, Bothell, WA, USA). Two positions were investigated for each patient: Position1 (P1): traditional sitting with lumbar flexion without the EPD; Position2 (P2): sitting with lumbar flexion with support from the EPD (Manual EPD, Meditek, Winnipeg, Manitoba, Canada). The PLL, ILD and LF lengths were measured using the ultrasound calliper software and recorded, with the anesthesiologists blinded to the results. Patients were asked to rate their comfort in both positions using a Likert scale.
Results: There were no significant differences between the measured lengths of the PLL, ILD and LF in the two positions (Table 1). Intraclass correlation coefficients showed good agreement for the primary outcome (0.8 for P1, 0.7 for P2) between anesthesiologists . Patient comfort was significantly higher with the application of the EPD (OR=10, 95% CI 2.4 to 88).
Discussion: The application of an EPD did not improve the paramedian lumbar acoustic window in term parturients. Future research is needed to verify clinical effects of the EPD for the obstetric population.
1. BJA 2001; 86: 798–804.
2. Anaesth 2001; 56: 262–6.
3. Anaesth 2013; 68: 27–30.
4. J Clin Anesth 2001 May; 13: 213–7.
5. Reg Anaesth Pain Med 2009; 34: 581–5.
6. Anesthesiol 2011; 114: 1459–85