Original ContributionPreprocedural ultrasound assessment does not improve trainee performance of spinal anesthesia for obstetrical patients: a randomized controlled trial☆
Introduction
Spinal anesthesia is one of the most commonly used techniques in obstetric patients undergoing elective cesarean delivery. It can be challenging because of poorly palpable surface landmarks and positioning challenges due to pregnancy-related changes [1]. Spinal ultrasound can provide effective information to perform spinal anesthesia [2], be used as a preoperative assessment tool predicting the feasibility/difficulty of neuraxial blockade [3], [4], and assist with difficult spinal patients [5].
When learning to place spinal anesthesia, junior residents are encouraged to conceptualize the anatomy based on previous didactic teaching, models, and palpation and then direct the needle blindly to the intrathecal space. The sources of anatomical knowledge may include anatomy laboratory sessions, didactic learning, physical and virtual spinal models, anatomy text books, videos presentations, Internet resources, and others. The educational benefits of ultrasound imaging for teaching regional anesthesia have been validated [6]; for anesthesiology trainees placing epidural catheters, preprocedure ultrasound examination has been shown to reduce the number of attempts and the number of failures [7].
Neuraxial ultrasound studies in obstetric patients have shown that ultrasound can assist epidural placement [8] and have been reviewed [9] and led to National Institute for Health and Care Excellence guidelines [10], but for intrathecal anesthetic placement, the benefits are less clear [11]. Spinal ultrasound allows more accurate identification of axial anatomical structures and intervertebral spaces than palpation [9], [11], [12], [13], [14], but the ergonomic challenges with needle angulation and depth have limited real-time utilization to a few practitioners. A meta-analysis [15] of epidural anesthesia, spinal anesthesia, combined spinal-epidural anesthesia, and lumbar puncture found benefit with ultrasound, although only 1 contributory study [5] featured spinal anesthesia. A recent study of residents performing epidurals did not demonstrate a benefit using ultrasound assistance [16], and a recent study of ultrasound assistance for spinal anesthesia for nonobstetric patients also did not demonstrate benefit [17]. Although supportive of this technology, the literature has been limited to small studies by a limited number of centers/experts [11].
This randomized controlled trial was designed to evaluate the impact of additional information provided by preprocedure ultrasound examination among trainee anesthesiologists performing spinal anesthesia for obstetric patients undergoing elective cesarean deliveries. We hypothesized that trainees would require fewer attempts for successful spinal placement with the addition of a preprocedural ultrasound examination to demonstrate the spinal anatomy.
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Materials and methods
This randomized clinical trial took place at the 2 obstetrical teaching hospitals in London, Ontario, Canada. The trial was registered at clinicaltrials.gov (NCT01444638), and institutional research ethics board approval was obtained. Written informed consent was obtained from all patients and residents.
Anesthesia residents in their first or second postgraduate year were invited to participate when they had experience of at least 3 and no more than 25 obstetric spinal anesthetics.
Results
Between February 2011 and October 2012, 17 residents were approached; all 17 of the residents consented and participated between 1 and 8 times. A total of 102 obstetric patients were approached to participate in the study; 16 patients refused and 4 patients were excluded because of the body mass index criterion. Two patients' surgeries were postponed by their obstetricians in favor of more emergent cases. The remaining 80 patients were randomized, contributed data, and were analyzed in the
Discussion
In this randomized controlled trial, there was no observed benefit to demonstrating a preprocedural ultrasound examination in addition to landmark technique for junior anesthesia residents performing spinal anesthesia in obstetric patients. This may be because spinal anesthesia in parturients using landmark techniques is of comparatively limited difficulty, limiting the benefit of an intervention. This could be exacerbated by the exclusion of morbidly obese patients or anticipated potentially
Acknowledgment
The authors gratefully acknowledge the respiratory therapists who assisted as timers and the obstetricians whose patients were involved in this trial. The authors also gratefully acknowledge the Lawson Health Research Institute for funding this trial and Dr Philip Jones for reviewing the manuscript.
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Disclosure statement: This study was funded by a grant from the Lawson Health Research Institute and internal funding from the Western University Department of Anesthesia and Perioperative Medicine. No author has any competing interests. This trial was registered at www.clinicaltrials.gov, NCT01444638.