Opioid-induced Hyperalgesia After Remifentanil Infusion

Study Overview
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Brief Summary
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Remifentanil is a rapid-acting opioid which has been widely used in pain treatment during surgery for the last 15 years 1. Remifentanil is rapidly eliminated (minutes) from the body after end of infusion, and this makes it easily manageable compared to other opioids. However, there are both experimental and clinical studies indicating that remifentanil, after end of infusion, triggers increased pain sensation and increased opioid consumption post-operatively. Increased post-operative opioid consumption should be avoided due to the adverse effects of these drugs (nausea/vomiting, pruritus, dizziness, fatigue and reduced respiratory rate). Thus, it's important to investigate relevant strategies to avoid the increased pain sensation (opioid-induced hyperalgesia = hypersensitivity to pain stimuli) after end of infusion of remifentanil after surgery. Several experimental and clinical trials have been conducted in this field. Ketamine has been shown to block this effect, but its adverse effect profile (i.a. hallucinations) makes it not suitable in normal clinical use. In a study of healthy volunteers, it has been demonstrated that parecoxib (a COX-2 selective NSAID) can prevent remifentanil-induced hyperalgesia. Our group has previously shown that a relatively COX-1 selective NSAID (ketorolac) can prevent hyperalgesia in an experimental pain model. This is of interest since NSAIDs are frequently administered as premedication before surgery. There are several disadvantages associated with the use of COX-2 inhibitors, e.g. the risk of myocardial infarction after long-term use (> 1 year), and potentially reduced bone healing after orthopedic surgery. However, this has not been shown with short-term use (days/week). The disadvantages associated with the use of e.g. ketorolac (a COX-1 inhibitor) are i.a. increased bleeding tendency, which is unfavourable for the surgeon, and increased risk of gastric ulcer. Therefore, it is of interest to investigate other ways of preventing opioid-induced hyperalgesia. In a recent animal study it has been shown that gradual dose reduction of remifentanil (vs. abrupt withdrawal of a relatively high remifentanil dose) can prevent the development of hyperalgesia after end of infusion. In this study we will i.a. investigate whether this is also the case in humans. In this new model, the study participants will get remifentanil infusion with two different dose reduction regimes: gradual reduction or abrupt withdrawal.

Official Title
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Can Opioid-induced Hyperalgesia be Prevented by Gradual Dose Reduction vs. Abrupt Withdrawal of Remifentanil?

Conditions
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Hyperalgesia

Intervention / Treatment
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* Drug: Remifentanil


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Male Age 18-60 Body mass index 17-30 Healthy volunteers Exclusion Criteria: Use of medication; alternative medicine Substance abuse Allergies towards medication used in the study Participation in other clinical studies the previous 6 months

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 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: Prevention
Intervention Model: Single Group Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Remifentanil<br>The study has only one arm. Same group of volunteers will receive remifentanil infusion with abrupt withdrawal, remifentanil infusion with gradual dose reduction and saline infusion at three separate trials. | Drug: Remifentanil<br> <br> * Other names: Ultiva;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Hyperalgesia measured by numeric rating scale for pain | Two pain models will be used - a heat-pain and a cold-pain model. Testing will be done before, during and after remifentanil infusion. NRS (Numeric rating Scale) will be used for pain scoring. Heat model: A computer-controlled Medoc ATS Thermal stimulator (3 x 3 cm) is applied to the left volar forearm at pre-defined areas. Cold model: In the cold test the study participant should keep his right hand in circulating cold water (3 ̊C) in up to 90 seconds. The pain models will be applied during three separate trials using remifentanil infusion with abrupt withdrawal, remifentanil infusion with gradual withdrawal and saline infusion(placebo). | 3 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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opioid induced hyperalgesia, Pain, Postoperative pain, Hyperalgesia