Perfusion Index and Pain in Ankle Surgery

Study Overview
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Brief Summary
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Perfusion index (PI) measured via a pulse oximeter has been shown to correlate with activation of the sympathetic nervous system, such as by pain stimulation, as a result of involuntary contraction of the arterioles. Thus PI holds potential for use as a tool for objective pain measurement, although its practical usefulness and dependability as such have not previously been investigated. The investigators aim to explore associations between changes in PI and onset of pain following cessation of regional anaesthesia in alert patients following ankle fracture surgery. Methods: The investigators report an exploratory, observational analysis of prospectively gathered PI data from patients undergoing regional anaesthesia with spinal or peripheral nerve block for ankle fracture surgery as participants of the randomised AnAnkle Trial (EudraCT: 2015-001108-76). PI is measured on an unaffected extremity in approximately 20 consecutive patients already included in the AnAnkle Trial at Herlev University Hospital, evenly distributed between spinal anaesthesia (SA) and peripheral nerve block (PNB). Both anaesthesia forms and pain medication regimes are standardised as part of AnAnkle Trial and participants register pain scores on a 0-10 numeric rating scale every three hours and register the time of cessation of anaesthesia identified by return of sensation to the ankle. Morphine consumption is also registered. The investigators will explore correlations of changes in PI to increases in pain upon cessation of the regional anaesthesia and, secondly, differences in cessation related PI changes with SA versus PNB. Ethics: All participants have already given informed, written consent for use of this data for the AnAnkle Trial. All necessary ethical and legislative approvals have been obtained for initiation of AnAnkle Trial in July 2015.

Official Title
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Perfusion Index and Pain in Ankle Surgery - an Exploratory Study

Conditions
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Pain, Postoperative, Ankle Fractures

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Scheduled for internal fixation of an ankle fracture Age > 18 years Ability to read and understand Danish and give informed written consent Exclusion Criteria: Allergy towards NSAID, paracetamol, morphine or local anaesthetics Bodyweight < 52 kg; to avoid toxic doses of local anaesthetics Contraindications for SA Current gastro-intestinal bleeding Proximal fibular fracture or multitrauma / other simultaneous fractures Cognitive or psychiatric dysfunction or alcohol/narcotic substance abuse causing expected inability to comply with study protocol No available anaesthesiologist with PNB capability at scheduled time of operation Neuropathy / neurological dysfunction in the lower extremities Habitual daily use of opioids Pregnancy or breastfeeding Infection at anaesthesia injection site Nephropathy requiring dialysis Acute porphyria

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 100 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 |
| --- | --- | --- |
| PI changes with rebound pain | Correlation of changes in PI to pain upon cessation of the regional anaesthesia | 1 hour prior to 6 hours post cessation of regional anaesthesia effect | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| PI changes in relation to anaesthesia modality | Differences in cessation related PI changes between spinal anaesthesia and PNBs | 1 hour prior to 6 hours post cessation of regional anaesthesia effect | 
| Timing of PI changes | Exploration of timing of the PI changes related to patient reported cessation of regional anaesthesia. | 1 hour prior to 6 hours post cessation of regional anaesthesia effect |