Anatomical studies show that the 0.2% methylene blue was injected into the upper and lower surface of the gastrocnemius muscle and then diffused to the periphery.The common peroneal nerve, the medial sural cutaneous nerve, the lateral sural cutaneous nerve and the tibial nerve below the gastrocnemius muscle are all strongly stained (3 / 4 color of the nerve) or fully stained.~Previous clinical studies have shown that a single gastrocnemius muscle plane block can provide good postoperative analgesia after 16 hours for patients with foot and ankle surgery, significantly reduce the dose of opioids, and see no nerve injury.~Therefore, the investigators hypothesized that continuous gastrocnemius plane block could provide more lasting analgesia in patients undergoing foot-ankle surgery.~This clinical study uses a single-center, randomized, single-blind, parallel controlled trial design, divided into screening period, treatment period and follow-up periods.~Patients were randomized into two groups, the ropivacaine group and the control group.The venous access was open after home invasion and was routinely monitored electrocardiogram(ECG), non-invasive blood pressure(NBP) ，oxygen saturation(SpO2)，bispectral index(BIS). General anesthesia was performed.~Induction of anesthesia: propofol 1 milligram / kg, cis atracurium 0.2 milligrams / kilogram, sufentanil 10 micrograms ,remifentanil at 1.5 micrograms/ kilogram. Anesthesia maintenance: Propofol and sevoflurane static aspiration compound bispectral index was maintained at 40~60, remifentanil 0.3~0.4 μg / kg/min intravenous pump, and additional cis atracurium was added according to neuromuscular monitoring. In the postoperative ropivacaine group, the patient took a lateral decubitus position, and underwent a gastrocnemius plane block and catheterization under ultrasound guidance to connect a disposable electron infusion pump. (Formula of 0.125% ropivacaine of 300 milliliters, background dose of 3.0 milliliters / hour, patient controlled analgesia(PCA) dose of 8 milliliters , and locking time of 25 minutes). The control group received intravenous oxycodone titrated according to the numerical rating scale (NRS) score, and received no background dose of oxycodone patient-controlled intravenous analgesia (PCIA) pump for analgesia (single dose 1milligram, locking time 5minutes, 4 hours limit 12milligrams). All patients were given 50 milligrams of fluorophenol ester intravenously. Remedial analgesia: if patient controlled analgesia still can not tolerate the pain and numerical rating scale(NRS) ≥4, can be given intravenously oxycodone was done 2milligrams, separated by over 3 minutes, until numerical rating scale(NRS) ≤3.~Record: block range of 15 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes, 1 hour, 4 hours, 8 hours, 12 hours, 24 hours, 48hours and numerical rating scale(NRS) score during rest and exercise; time of first pressing of the analgesic pump; times of controlled analgesia (PCA); 0-4 hours, 0-8 hours, 0-16 hours, 0-24 hours, 8-16 hours, 16-24 hours, 24-32 hours, 32-40 hours,40-48 hours pain intensity-time curve (AUC); dose and times of remedial analgesic administration; Records: affected limb muscle strength and paresthesia, length of hospitalization, time of first ambulation, nausea and vomiting, neurological complications, patient satisfaction, physician and nurse satisfaction, etc.~The patient had open venous access after home invasion and was routinely monitored for electrocardiogram(ECG), non-invasive blood pressure(NBP) ，oxygen saturation(SpO2) and bispectral index(BIS). Induction and maintenance were performed according to a uniform anesthesia protocol. Postoperatively, the block was performed by the same anesthesiologist familiar with the ultrasound-guided nerve block. Various study indicators and data were collected by the same anesthesiologist who was not aware of the grouping situation.
This study aims to evaluate the efficacy and safety of a continuous gastrocnemius plane block for perioperative analgesia in patients undergoing foot and ankle surgery under elective general anesthesia.