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Unable to Assess Due to Body Habitus: High Frequency of Inappropriately High Neuraxial Block Placement in Super-Obese (BMI ≥ 50) Parturients
Abstract Number: O2-01
Abstract Type: Original Research
Background: Morbid obesity increases the difficulty of palpating anatomic landmarks and may increase the risk for inappropriately high dural puncture during neuraxial procedures. Dural puncture above the tip of the conus medullaris, which lies at or above the L2 vertebral body in >98% of adults (1), carries the risk of damage to the spinal cord. The accuracy of anesthesiologists’ estimates of interspinous level has been examined and is imperfect (2,3), but there are no data on accuracy in super-morbidly obese (body mass index (BMI) ≥ 50) parturients. Our goal was to evaluate the frequency of inadvertently high epidural/intrathecal catheters (at or above the L1/L2 interspace) in parturients with a BMI ≥ 50.
Methods: The anesthetic records and x-rays taken to rule out retained foreign objects of 150 women with a BMI ≥ 50 who underwent cesarean delivery with an epidural or intrathecal catheter were retrospectively reviewed. The pre-specified primary outcome was the percentage of catheters placed at or above the L1/L2 interspace. Secondary outcomes were agreement between the estimated and actual catheter location, as well as subgroup analysis of those catheters placed with ultrasound guidance.
Results: 125 cases were included after excluding 15 cases where it was not possible to determine catheter location and 10 cases where the estimated level was not recorded. 26/125 (21%) catheters were unintentionally placed at or above L1/L2. There was poor agreement between the estimated and actual catheter level (Figure, kappa statistic 0.02). 88/125 (70%) of catheters were placed more cranially than estimated. High catheter placement occurred despite the use of ultrasound: 11/39 (28%) catheters placed with ultrasound were at or above L1/L2. No patients experienced neurologic complications.
Conclusions: Super-morbidly obese parturients are at high risk for inappropriately high neuraxial block placement. Prior studies in non-obese parturients demonstrate a 1-6% incidence of catheter placement at or above L1/L2 (2,3) compared to the 21% incidence in our super-obese population. The use of ultrasound did not prevent high catheter placement. Retrospectively, we are unable to determine whether ultrasound was used to explicitly identify intervertebral level. We suggest close attention to intervertebral level in this high risk population and rigorous use of ultrasound.
1:Saifuddin et al Spine 1998
2:Schlotterbeck et al BJA 2008
3:Tanaka et al Braz J Anes 2013