Leg Amputation and Continuous Sciatic Nerve Block

Introduction:

Analgesia following leg amputation is based on morphine administration. For elderly patients of ASA physical status 2 or 3, morphine sparing is possible when perinervous block techniques are used. Indeed, per operative placement of a perinervous catheter by the surgeon allows a morphine consumption decrease of about 30%. Nevertheless, the interest of a sciatic block providing analgesia in the tibial and fibular territories has still to be assessed in this indication.

Phantom limb pain complicates leg amputation in 50 to 80% of cases. Risk factors of this complication are numerous, from central or peripheral origin. Phantom limb pain postpones patients' social and professional rehabilitation, and results in an increased medical consumption. Prevention of these pains has been studied in various clinical trials, and results need confirmation. Thus, epidural analgesia alone does not decrease the long term incidence of phantom limb pain.

Objectives:

Primary : To compare intravenous morphine consumption during the 72 first postoperative hours following leg (below knee) amputation of patients randomly assigned in two groups. One group benefit from perioperative locoregional analgesia by ropivacaine via a popliteal sciatic catheter, the other group is given placebo through the catheter.

Secondary :

• To assess tolerance and adverse effects (myalgia, infection, adverse effects of local anaesthetics) of the popliteal sciatic catheter during the 72 first postoperative hours and on the 7th postoperative day, in patients with ASA physical status 2 or 3
• To compare tolerance and adverse effects of morphine during the protocol in the 2 groups of patients
• To assess the long term effects of the preoperative continuous popliteal sciatic nerve block: incidence of stump pain and phantom limb pain, time of outbreak, intensity (VAS), characteristics (French version of the McGill Pain Questionnaire and DN4 questionnaire), and the analgesic consumption over a year.
• To assess the possibility for the patients to use a prosthesis

Population:

Eighty four patients scheduled for leg amputation (below knee), randomly allocated in 2 groups of forty patients, according to the type of analgesia. Patients were enrolled in the general and vascular surgery unit, CHU (University Hospital) Pellegrin Bordeaux.

Methods:

Randomised clinical trial, with two parallel groups, with direct individual benefit, double-blinded, realised on a population of patients undergoing leg amputation, comparing different clinical parameters of postoperative pain evaluation, and outbreak of phantom limb pain according to the group of analgesia.

• One group of patients with locoregional analgesia associated with morphine administration (assessed treatment)
• One group of patients with morphine analgesia only (reference treatment). Patients will be followed for one year. This study will last 3 years in a general and vascular surgery unit, inclusion will be realised during 34 months by anaesthetists and surgeons, an extension of this study for one year will be done with the objective of a cohort follow-up.

Statistical analysis will be done with intention to treat.

Anticipated results:

To prove the efficacy of the continuous popliteal sciatic nerve block in postoperative analgesia after leg amputation.

To prove the efficacy of a perioperative analgesia by continuous popliteal sciatic nerve block to prevent phantom limb pain after leg amputation in patients of ASA physical status 2 or 3.