Does Perineural Clonidine Prolong Duration of a Nerve Block?

Study Overview
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Brief Summary
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The aim of this trial is to investigate if clonidine prolongs the duration of an adductor canal block. By using healthy volunteers the investigators can perform a bilateral adductor canal block and thereby control for a systemic effect to clarify if the effect is actually peripheral or systemic. The investigators hypothesis is that clonidine/dexmedetomidine as an adjunct to a local anaesthetic prolongs the duration of a peripheral nerve block by a peripheral mechanism.

Detailed Description
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Background: Efficient pain management promoting mobilization and convalescence is essential in an ideal perioperative course. Regional nerve blocks are a central element in postoperative regimes for many patients and it is therefore important that these nerve blocks are both long lasting and efficient. This trial will investigate whether it is possible to optimize the postoperative pain management when adding clonidine to the local anaesthetic ropivacaine in peripheral nerve blocks. The prolonging effect of using clonidine as adjuncts in peripheral nerve blocks have been investigated in several studies. However, it remains uncertain whether the effect is mediated by a systemic-, a peripheral- or a combined systemic/peripheral mechanism. In this trial the adjuvating effect of clonidine will be investigated using the adductor canal block. This is a nerve block that besides being efficient as pain treatment after knee surgery, is primarily sensory, and therefore augments mobilization after total knee arthroplasty. Method: On the trial day the volunteers will receive bilateral adductor canal blocks. In one thigh they will receive the local anaesthetic ropivacaine 20ml 5mg/ml and placebo (saline) and in the other thigh ropivacaine 20ml 5mg/ml and Clonidine 150μg. The allocation is blinded to volunteer and investigator. The duration of the nerve block will be measured by five different tests: Temperature test, Pinprick, Pain during tonic heat stimulation, Warmth detection threshold and pain detection threshold. All tests are validated within pain research.

Official Title
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Does Perineural Clonidine Prolong the Duration of an Adductor Canal Block When Controlling for a Systemic Effect? - A Randomised Paired Trial in Healthy Volunteers.

Conditions
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Healthy

Intervention / Treatment
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* Drug: Ropivacaine 20ml 5mg/ml+ Clonidine 150ug
* Drug: Ropivacaine 20ml 5mg/ml+ Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: American Society of Anesthesiologists class 1 Body Mass Index 18-30 Exclusion Criteria: Allergy to study medication Earlier trauma or surgery to lower limb Diabetes Mellitus Alcohol or drug abuse Daily intake of opioids or steroids last 4 weeks Daily intake of any analgesics last 48 hours Heart block Sick sinus node.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Ropivacaine+Clonidine<br>Adductor Canal Block Ropivacaine 20ml 5mg/ml+ Clonidine 150ug | Drug: Ropivacaine 20ml 5mg/ml+ Clonidine 150ug<br> <br> |
| Placebo Comparator: Ropivacaine+Placebo<br>Adductor Canal Block Ropivacaine 20ml 5mg/ml+ saline | Drug: Ropivacaine 20ml 5mg/ml+ Placebo<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Difference in duration of sensory block between clonidine and placebo assessed as cold sensation with an alcohol swab | Duration is defined as time from block performance until recovery of cold sensation to an alcohol swab, assessed every hour post-block (and every half hour when pain scores during the tonic heat stimulation test is above 0) Time for sleep will be provided. | 0-36 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Difference between Clonidine and placebo in the duration of a sensory block assessed by pin-prick | Duration is defined as time from block performance until recovery of normal sensation, assessed on the hour post block Time for sleep will be provided. | 0-36 hours | 
| Difference between clonidine and placebo in the duration of a sensory block assessed as maximum pain during a tonic heat stimulation test | Duration is defined as time from block performance until recovery of normal sensation, assessed on the hour post block Time for sleep will be provided. Recovery of normal sensation is defined as VAS pain scores ± 10 mm of the pre-block value. | 0-36 hours | 
| Difference between clonidine and placebo in the duration of a sensory block assessed as warmth detection threshold | Duration is defined as time from block performance until recovery of normal sensation, assessed on the hour post block Time for sleep will be provided. Recovery of normal sensation is defined as detection thresholds of ± 2 degrees C of the pre-block value. | 0-36 hours | 
| Difference between clonidine and placebo in the duration of a sensory block assessed as heat pain detection threshold | Duration is defined as time from block performance until recovery of normal sensation, assessed on the hour post block. Time for sleep will be provided. Recovery of normal sensation is defined as detection thresholds of ± 2 degrees C of the pre-block value. | 0-36 hour | 
| Difference in maximum pain scores between clonidine and placebo during block and after recovery of normal sensation. | Pain scores during a tonic heat stimulation will be compared every hour post block and 1 h after pain scores have returned to the pre-block values. Time for sleep will be provided. | 0-36 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Volunteers