Peripheral Nerve Block Anaesthesia for Ankle Fracture Surgery - an Exploratory Study: Is Rebound Pain a Problem?

Study Overview
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Brief Summary
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The purpose of this exploratory study is to characterize the postoperative pain profile of patients undergoing operation with internal fixation of an ankle fracture under nerve block anaesthesia. Special attention is payed towards the possible existence and clinical relevance of a rebound pain phenomenon upon cessation of the nerve block. Results are used to guide the set up of a randomized controlled trial on the subject.

Detailed Description
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Peripheral nerve blocks (PNB) are widely used as anaesthesia and postoperative pain control for surgery. Several studies have suggested multiple benefits of PNB's but primarily shown in elective surgery. Acute conditions like ankle fractures have a different pain profile and risks and benefits of PNB's have not been sufficiently researched in these cases. A recent study (Goldstein et al. 2012) suggested that a rebound pain effect occur upon cessation of PNB effect defined as a pain increase to a significantly higher level than observed in patients with no PNB at the same point after surgery. With this prospective, exploratory study we aim to examine the postoperative pain profile after PNB anaesthesia for ankle fracture surgery with focus on plausibility of a rebound pain effect (as defined above) upon PNB cessation. Secondarily to explore a variety of factors related to postoperative pain profile and feasibility of PNB anaesthesia for ankle surgery including efficacy, risk factors, time factors as well as postoperative recovery and overall patient satisfaction. Results will provide focus for a following randomized controlled trial.

Official Title
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Peripheral Nerve Block Anaesthesia for Ankle Fracture Surgery - an Exploratory Study: Is Rebound Pain a Problem?

Conditions
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Postoperative Pain

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients >= 18 years old scheduled for internal fixation of an ankle fracture as defined above. Ability to read and understand Danish and give informed oral and written consent Exclusion Criteria: Multitrauma patients / other simultaneous fractures Cognitive or psychiatric dysfunction causing expected inability to comply with study protocol CAVE nonsteroidal antiinflammatory drugs (NSAID) or Morphine or Local Anaesthetics as evaluated by anesthesiologist for any reason Primary investigator unavailable for PNB administration at scheduled time of operation Infection at PNB injection site Time from fracture to operation > 5 days Existing neuropathy with functional impairment of the fractured extremity Bodyweight < 50 kg Daily use of opioids > 2 weeks preoperatively Pregnancy Nephropathy requiring dialysis

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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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Clinically relevant pain increase based on analysis of Numeric Rating Scale pain score (NRS) area under the curve (AUC) for the time period 12-24 hours compared to 0-12 hours postoperatively. | Pain scores are assessed and marked by the patient on a 0-10 numeric rating pain scale (NRS). | 0, 2, 4, 6, 9, 12, 15, 18, 21 and 24 hours postoperatively | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Opioid use 12-24 hours compared to 0-12 hours postoperatively | Rescue morphine doses are administered intravenously via a patient controlled analgesia (PCA) pump when needed. Times of use are electronically registered. | 0-24 hours continuous measurement | 
| Calculated Composite Score for the time intervals 0-24h, 0-12h and 12-24h postoperatively | We will calculate the Silverman composite score of opioid use and pain score combined. This in order to illustrate any increase in pain and to use for sample size calculations for a future randomised study on the subject. | 0-24 hours postoperatively | 
| Time to first opioid dose postoperatively |  | 0-24 hours postoperatively | 
| Time to patient estimated cessation of block effect |  | 0-24 hours postoperatively | 
| NRS day 1-7 as both average and worst of the day | NRS are filled out by the patient in a diary. | Days 1-7 postoperatively | 
| Daily opioid consumption day 1-7 | Registered in a diary. | Days 1-7 postoperatively | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Ankle fracture, Nerve block, Postoperative pain, Pain profile, Rebound pain