Protracted Effect of the Ultrasound-guided Saphenous Block

Phase 4

Completed

Interventions: Drug: Bupivacaine-adrenaline
Other: Sodium chloride
Drug: Dexamethasone

Brief Summary: 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: 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.

Recruitment & Eligibility

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

Arm && Interventions

Group	Intervention	Description
Bupivacaine-adrenalin + sodium chloride	Bupivacaine-adrenaline	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
Bupivacaine-adrenalin + sodium chloride	Sodium chloride	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
Bupivacaine-adrenaline + Dexamethasone	Bupivacaine-adrenaline	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
Bupivacaine-adrenaline + Dexamethasone	Dexamethasone	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

Primary Outcome Measures

Name	Time	Method
Duration of the saphenous nerve block	48 hours	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)

Secondary Outcome Measures

Name	Time	Method
Cumulated opioid consumption	48 hours	Registered by the PCA pump
Pain score	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	NRS (numeric rating scale)
Pain localization	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	Lateral or medial side of the ankle
Test of sensory block	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	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

Locations (1): Department of Anesthesiology, Aarhus University Hospital
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Aarhus, Midtjylland, Denmark