Peripheral Nerve Block in Patients With Painful Diabetic Polyneuropathy

Study Overview
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Brief Summary
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The purpose of the present study is to evaluate the role of peripheral afferent input for spontaneous pain in painful diabetic polyneuropathy

Detailed Description
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Both peripheral and central changes in the nervous system contribute to the development of painful diabetic neuropathy, but how these changes contribute to the pain generation remains yet to be fully understood. The purpose of this study is to evaluate if a peripheral regional nerve block relieves spontaneous pain in painful diabetic polyneuropathy.

Official Title
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Peripheral Nerve Block in Patients With Painful Diabetic Polyneuropathy: How Important is the Peripheral Signaling?

Conditions
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Painful Diabetic Neuropathy, Neuropathic Pain, Neuropathy;Peripheral

Intervention / Treatment
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* Diagnostic Test: Xylocaine 1%
* Diagnostic Test: NaCl 9mg/ml


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Aged 18 years or older. Probably diabetic neuropathy confirmed using the Toronto criteria in a conservative manner, i.e. three out of three symptoms/signs of neuropathy must be present (sensory neuropathy symptoms, distal reduced sensibility, reduced ankle reflexes) 7. Definite or probable neuropathic pain for minimum the last 6 months Mean pain intensity at > 4 NRS the last week17. Since we expect a large effect of the block it is not necessary to discontinue pain medication. Exclusion Criteria: Other causes of pain in the same area or other pain that cannot be distinguished from the neuropathic pain. Unable to understand and speak Danish. Non-cooperative. Warfarin or other medication that contraindicate regional anesthesia. Infection in the injection area. Allergy to lidocaine. Pregnancy or lactating (fertile women must to show negative pregnancy test or use anticonception). Severe psychiatric disease e.g. severe depression during the last 6 months. Alcohol or drug abuse.

Ages Eligible for Study
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Minimum Age: 18 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: Diagnostic
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Xylocaine<br>Nerve block | Diagnostic Test: Xylocaine 1%<br>* Nerve block<br>|
| Placebo Comparator: Isotonic saline<br>Nerve block | Diagnostic Test: NaCl 9mg/ml<br>* Nerve block<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Indication of pain relieved extremity | Number of participants who indicated the leg with lidocaine as most pain relieved 30 minutes after block And number of participants who indicated the leg with saline as most pain relieved 30 minutes after block | 30 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pain intensity | Intensity of spontaneous pain (Numeric Rating Scale (NRS) 0-10, 0=no pain 10=worst pain imaginable) 30, 45, 60 and 90 minutes after block | 90 minutes | 
| Hyperalgesia and allodynia | Intensity of hyperalgesia and allodynia from -5 to 5 (-5 = no sensation, 0=normal sensation, 5=extremely intense sensation) to brush, pinprick, cold and warm at baseline and if there is registered any signs of hyperexcitability at baseline then 35, 60 and 90 minutes after nerve block. | 90 minutes | 
| Pain relief | Pain relief at 45 minutes after block assessed using a 6-point scale compared to pain intensity at baseline. (-1 = worse pain 0=no relief 1= little 2= moderate 3=good 4=complete) | 45 minutes | 
| Pain symptomps | Intensity of neuropathic pain symptoms 50 minutes after nerve block Burning: NRS (0-10), 0=no burning 10=worst burning imaginable Squeezing: NRS (0-10), 0=no squeezing 10=worst squeezing imaginable Pressure: NRS (0-10), 0=no pressure 10=worst pressure imaginable Tingling: NRS (0-10), 0=no tingling 10=worst tingling imaginable | 50 minutes | 
| Distribution of evoked pain | The distribution of any evoked pain to brush, pinprick, cold and warm before and 60 minutes after nerve block will be mapped using a filt pen and afterwards photographed. | 60 minutes |