Spinal Anesthesia in Patients With Poorly-palpable Surface Landmarks

Study Overview
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Brief Summary
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Anesthesia trainees can perform spinal anesthesia in patients who have poorly-palpable surface landmarks with fewer needle passes using an ultrasound-guided technique compared to the conventional surface landmark-guided technique.

Detailed Description
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Neuraxial blockade has traditionally been accomplished using a surface landmark-guided technique, in which the approximate location of the neuraxial midline, lumbar interspinous and interlaminar spaces are determined based on palpation of the intercristal line and the tips of the spinous processes. It is not surprising, therefore, that the technical difficulty of neuraxial blockade (usually measured in terms of the number of needle passes required for success) correlates with the quality of palpable surface landmarks. Reducing the technical difficulty of neuraxial blockade is desirable as multiple needle insertion attempts may increase the risk of complications such as post-dural puncture headache, paresthesiae, and epidural hematoma. Ultrasound (US) imaging of the spine can help in this regard by more precisely identifying landmarks, determining the intervertebral level, and measuring the depth to the epidural space. It has been shown to facilitate the performance of neuraxial block in the obstetric population, and our group has also demonstrated similar benefits in the older non-obstetric population. In a feasibility study of US-guided spinal anesthesia for total joint replacement surgery, achieved successful spinal anesthesia with a single needle insertion attempt in 84% of these patients, despite the fact that nearly half of them had poorly palpable surface landmarks.This compares well with large prospective cohort studies which report successful neuraxial blockade on the first needle insertion attempt in 61-64% of all patients. Investigators recently completed a randomized controlled trial in which 120 patients with difficult anatomical landmarks (defined as poorly palpable surface landmarks and a BMI>35 kgm-2, significant spinal deformity, or spinal surgery resulting in distortion or absence of surface landmarks) received spinal anesthesia performed by experienced anesthesiologists using either a conventional surface landmark-guided technique or an US-guided technique. There was a two-fold difference between the US-guided group and the control group in the first-attempt success rate (62% vs 32%, P<0.001), and the median number of needle passes required for success (6 vs 13, P=0.003). The main limitation of all clinical studies conducted to date on US-guided neuraxial block is that ultrasound imaging was performed solely by experienced operators; although in two studies the neuraxial block itself (but not the ultrasound scan) was performed by trainees. Investigators believe that the benefits of the US-guided technique can be realized when it is performed in its entirety by novices, e.g. anesthesia trainees. Investigators therefore designed this study to establish if novices are able to use the US-guided technique to facilitate the performance of spinal anesthesia in obese patients with poorly-palpable landmarks.

Official Title
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Can Anesthesia Trainees Effectively Use Ultrasound Imaging to Facilitate the Performance of Spinal Anesthesia in Patients With Poorly-palpable Surface Landmarks?

Conditions
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Regional Anesthesia

Intervention / Treatment
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* Procedure: Landmark Technique Control group
* Procedure: Neuroaxial block using Ultrasound Guidance


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients presenting for elective total hip or knee replacement under spinal anesthesia who have poorly palpable or impalpable spinous processes BMI ≥ 35 kgm-2 Exclusion Criteria: Inability or refusal to provide informed consent, Bleeding diathesis, Allergy to local anesthetics Contra-indication to spinal anesthesia
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Landmark Technique<br>Control group | Procedure: Landmark Technique Control group<br>* Spinal Anesthetic<br>|
| Ultrasound guided technique<br>Neuroaxial block using Ultrasound guidance | Procedure: Neuroaxial block using Ultrasound Guidance<br>* Ultrasound guided Spinal Anesthetic<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The rate of successful dural puncture on the first needle insertion attempt. | Insertion attempts are defined as complete withdrawal of the needle or introducer from the skin followed by re-insertion, and are distinguished from redirection attempts, which are defined as changes in needle trajectory that do not involve complete withdrawal of the needle from the skin. 1,2.14,15 This will be assessed by two blinded observers from an anonymized video recording of the operator's hands as they perform the spinal anesthetic. | 2012-2013 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The total number of needle passes required for dural puncture. | Needle passes are defined as any forward advancement of the needle, including the first insertion and any subsequent insertion and redirection attempts. This will be assessed by two blinded observers from an anonymized video recording of the operator's hands as they perform the spinal anesthetic. | 2012-2013 | 
| Block performance time | Block performance time, defined as the sum of the following: a. Time taken to establish landmarks. In the US-guided technique, this is defined as the time between first placement of the ultrasound probe on the patient and completion of the last skin marking. In the surface landmark-guided technique, this is defined as the time between first placement of the operator's hands on the patient and completion of the last skin marking. | 2012-2013 | 
| Time taken to perform spinal anesthetic | Time taken to perform spinal anesthetic. This is defined as the period between insertion of the needle used for skin infiltration, and withdrawal of the spinal needle following injection of the | 2012-2013 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Spinal Anesthetic,, Ultrasound guided Neuroaxial block,, Anesthesia Trainees