A Device to Determine Return of Sensation From Spinal Block

Study Overview
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Brief Summary
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Participation in this study will involve having a pad wrapped onto the subject's non-surgical leg to detect when sensation returns after spinal anesthetic and while in recovery room. The pad is part of an approved medical device, but which has been modified and will be used in an experimental way. The device will run cold water through the pad wrapped to the subject's leg. The subject will be asked to press a stop button when they feel the pad gets cold. Nurses in the recovery area will also be testing return of sensation using a standard technique and this will be compared to when the subject begins to feel the cold.

Detailed Description
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Regional anesthesia investigators have always shown interest in measuring the specific duration of neuraxial or peripheral nerve blocks, and how variations in block technique or medications affect that duration. Although ostensibly a simple concept, there are many sensory modalities available for block testing (light touch, cold or hot temperature, pain, pressure, etc.) and there is no consensus in the anesthesia literature on how best to measure the duration of nerve block (. Sensory testing is repetitive, and must be practical and consistent. Pinprick and cold sensation are commonly employed, and these modalities share the same afferent fibers (C-delta) so there is close overlap in the sensory loss mapping after regional block. With respect to pinprick sensation there can be variability in the sharpness, pressure, and reproducibility of a pinprick test. Testing for cold sensation may be more consistent, using a controlled stimulus temperature and duration, and there are different methods of testing such as a cooled glass vial (5℃) or Rolltemp (25℃). Testing for long-acting blocks overnight adds an additional challenge since it requires repetitive subject awakening for assessment, and the interval for testing is a compromise between test specificity and sleep disruption. Again, there is no consensus on the proper interval for testing recovery from regional block. Cold therapy is a commonly applied modality following strenuous exercise or during recovery from extremity surgery, and is expected to reduce tissue damage and relieve pain. There is some evidence of benefit but little consensus on the optimum interval and duration of therapy, and there are many approved medical devices available for use. This investigation proposes an adaptation of an approved cold therapy device to administer automated, periodic cold stimulus at a location made insensate by regional block. When the subject perceives cold at that site, they will press a stop switch to discontinue cooling which will also stop a timer and give an accurate duration of the time to recovery of sensation at that site. The concept will be tested by comparing the duration measured to the standard measurement of recovery from nerve block (spinal) employed by post-anesthesia care unit (PACU) nurses who will use pinprick (toothpick) testing of lumbar dermatomes every thirty minutes. If the device shows acceptable agreement with standard block recovery testing, a follow-up study would be its evaluation for long-duration block testing as an alternative to research assistant repeated testing overnight.

Official Title
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Proof-of-Concept: A Device to Determine Return of Sensation After a Regional Anesthetic Block

Conditions
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Sensation Diminished, Pinprick

Intervention / Treatment
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* Device: cooling device


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients 18-75 y/o and scheduled to undergo unilateral primary knee or hip arthroplasty under spinal anesthesia with bupivacaine, ropivacaine or tetracaine will be eligible. Exclusion Criteria: Patients will be excluded if pre-block sensation is abnormal in the L3 dermatome of the non-operative leg (neuropathy), or if spinal anesthesia is not performed or is unsuccessful. They will also be excluded if sensation has already returned in the L3 dermatome on arrival to the PACU.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 Years

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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Design Details

Primary Purpose: Treatment
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: All participants will have the device placed in the recovery room to determine resolution of regional anesthetics.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: cooling device placed<br>A basic medical grade cooling pad will be secured to the non operative leg. Intermittent coolness will be assessed and subject will inform recovery room staff when sensation returns. | Device: cooling device<br>* device placed on patient in recovery on non surgical side to determine resolution of spinal anesthetics.<br>|
| No Intervention: standard of care no intervention<br>Subjects in intervention arm will serve as their own control; standard nursing pinprick testing on the same (non-operative) thigh | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Block Recovery Time (Device) | Time to resolution of subarachnoid block (minutes from injection) will be measured for the device on the (non-operative) thigh. | Baseline, from injection and up to 4 hours after injection | 
| Block Recovery Time (Pinprick Test) | Time to resolution of subarachnoid block (minutes from injection) will be measured for the standard nursing pinprick testing on the same (non-operative) thigh. | Baseline, from injection and up to 4 hours after injection | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Device Temperature Consistency | Percentage of time the temperature sensor displays the pad temperature between 40 and 50 degrees F for the duration of the application | 2 hours after baseline | 
| Cooling Pad Temperature (°F) at Stop Switch Activation |  | 2 hours after baseline | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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nerve block, spinal block, local anesthetic, regional anesthesia