Protracted Effect of the Ultrasound-guided Saphenous Block

Study Overview
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Brief Summary
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This study focuses on optimizing the postoperative pain treatment after major foot and ankle surgery by prolonging the duration of the ultrasound-guided saphenous block. The currently used single shot saphenous block only covers half of the pain intensive period from the saphenous territory, which results in a sharp, break-through pain requiring opioids. The hypothesis is that this protracted mixture will keep the patients free of pain without the use of opioids for the entire pain intensive period and thus increase rehabilitation and patients' satisfaction.

Detailed Description
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Half of the patients will receive a single shot saphenous block with 10 mL bupivacaine-adrenalin and 1 mL of sodium chloride solution, while the other half will receive 10 mL of bupivacaine-adrenalin and 1 mL of dexamethasone. The block is strictly a sensory block because it is a selective, sub-sartorial saphenous block at mid-thigh level without any anesthetic effect on the femoral nerve. The adjuvant dexamethasone has increasingly become a subject of interest regarding a protracted effect, which has been shown in several studies. However, the precise mechanism of action remains speculative, and the results are contradictory regarding the discussion whether the effect is systemic or local. The effect may stem from decreased nociceptive C-fibre activity via a direct action on glucocorticoid receptors and inhibitory potassium channels. Another suggestion is a vasoconstrictive effect, which reduces the systemic uptake of local anaesthetics or a systemic anti-inflammatory effect. Prolonging the effect of the single shot saphenous block by adding dexamethasone will reduce the need for opioids, which will reduce the risk of adverse effects like nausea, vomiting and respiratory depression. Furthermore, newer studies show that inadequate pain alleviation in the early postoperative period is a risk factor in developing chronic persistent pain.

Official Title
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Comparison of the Effect of a Single Shot Saphenous Block With Plain Bupivacaine vs. Protracted Bupivacaine Mixture as a Supplement to Continuous Sciatic Catheter After Major Ankle and Foot Surgery

Conditions
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Arthrosis, Unspecified, Ankle and Foot

Intervention / Treatment
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* Drug: Bupivacaine-adrenaline
* Drug: Dexamethasone
* Other: Sodium chloride


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Elective ankle or hind foot surgery either: (1) total ankle arthroplasty, (2) ankle arthrodesis or (3) subtalar arthrodesis Age ≥ 18 American Society of Anaesthesiology Classification I-III Informed consent both orally and in writing after the patient has fully understood the protocol and its limitations. Exclusion Criteria: Communication problems or dementia Allergies to any medical product used in the study Neuropathy of the sciatic or femoral nerve prior to the operation Morbus Charcot-Marie-Tooth disease, diabetic neuropathy, peripheral vascular disease BMI > 35 Pregnancy Daily use of opioids Coagulation disorders Infection at the site of injection or systemic infection

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 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: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Bupivacaine-adrenalin + sodium chloride<br>Single shot saphenous block: 10 mL of 5 mg/mL bupivacaine with 5 μg/mL adrenalin = 50 mg bupivacain and 50 μg adrenalin 1 mL sodium chloride solution | Drug: Bupivacaine-adrenaline<br>* 50 mg bupivacaine and 50 μg adrenalin<br>* Other names: Marcain-adrenalin;Other: Sodium chloride<br>* 1 mL of sodium chloride solution as placebo<br>* Other names: NaCL;|
| Experimental: Bupivacaine-adrenaline + Dexamethasone<br>Single shot saphenous block: 10 mL of 5 mg/mL bupivacaine with 5 μg/mL adrenalin = 50 mg bupivacain and 50 μg adrenalin 1 mL of 4 mg/mL dexamethasone = 4 mg dexamethasone | Drug: Bupivacaine-adrenaline<br>* 50 mg bupivacaine and 50 μg adrenalin<br>* Other names: Marcain-adrenalin;Drug: Dexamethasone<br>* 4 mg<br>* Other names: Dexagalen;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Duration of the saphenous nerve block | The duration is registered as the time until the first dose of morphine is taken, and when the pain score is above 3 and located to the frontal or medial side of the ankle. Morphine is administered intravenously by a patient controlled pump (PCA - Patient Controlled Analgesia) | 48 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cumulated opioid consumption | Registered by the PCA pump | 48 hours | 
| Pain score | NRS (numeric rating scale) | Arrival at the Perioperative Section which will be within 30 minutes after surgery. Departure from the Perioperative Section which is expected to be on average 2 hours after surgery. 6, 12, 24, 30, 36, 42 and 48 hours after surgery | 
| Pain localization | Lateral or medial side of the ankle | Arrival at the Perioperative Section which will be within 30 minutes after surgery. Departure from the Perioperative Section which is expected to be on average 2 hours after surgery. 6, 12, 24, 30, 36, 42 and 48 hours after surgery | 
| Test of sensory block | The sensory block of the peroneal nerve is tested on the dorsal side of the toes and the tibial nerve on the plantar side of the toes. The ankle and lower leg is covered in cast, and therefore the saphenous nerve is tested around the tibial tuberosity because this area is innervated by the infra-patellar nerve, which is a branch of the saphenous nerve | Arrival at the Perioperative Section which will be within 30 minutes after surgery. Departure from the Perioperative Section which is expected to be on average 2 hours after surgery. 6, 12, 24, 30, 36, 42 and 48 hours after surgery |