After obtaining institutional board approval (registration number 29-3), we reviewed the anesthesia records and medical records of all adult patients who inserted the catheter with a continuous interscalane block administered by anesthesiologists via the catheter-over-needle method at Ehime Prefectural Imabari Hospital from July 2015 to July 2017. We excluded the patients in whom the catheter was inserted by orthopedists. We collected data about patient characteristics, the incidence of pericatheter leakage of the local anesthetic, insufficient anesthetic effect (postoperative pain numerical rating scale score 3 or higher), and symptoms suggestive of a neurological complication (e.g. dyspnea, hoarseness, dizziness, cough reflex during drinking and ptosis) from the time of insertion of the catheter to its removal. The study was registered with the UMIN Clinical Trials Registry (UMIN000037673).
Catheter insertion procedure
In all patients, the catheter was inserted just before induction of general anesthesia in the operating room, without preoperative sedation or premedication. Each patient was placed in the supine position, the arm on the side to be operated on was at the patient’s side, and the head was turned slightly to the contralateral side. A Sonosite M-Turbo ultrasound system with a 6- to 13-MHz linear probe (Sonosite Inc., Bothell, Wash.) was used. After preoperative scanning around the interscalene brachial plexus for correct location of catheter placement, the area was sterilized, and continuous interscalene block was induced with the Contiplex® C Catheter-Over-Needle Continuous Nerve Block Set (B.Braun Melsungen AG, Melsungen, Germany) under ultrasound guidance without nerve stimulation. The catheter tip was passed through and placed between C5 and C6 in the brachial plexus. After 2 to 3 mL of lidocaine was injected to confirm that the catheter tip was placed correctly for administration of anesthetic, patients received 10mL of 0.75% ropivacaine in a bolus through the catheter under ultrasound visualization for surgical anesthesia. The catheter insertion site sealed with topical medical cyanoacrylate glue (Dermabond; Ethicon, San Angelo, Tex.) and draped with clear film (3M TegadermTM Film, 6cm×7cm; 3M Health Care, St. Paul, Minn.).
Perioperative management
In all patients, a standard anesthetic technique was used, wherein the non-invasive arterial blood pressure, electrocardiogram, and oxygen saturation were routinely monitored in the operating room. General anesthesia was induced with propofol (1.5–2 mg/kg), remifentanil (0.15–0.3 μg/kg/min), and rocuronium bromide (0.8 mg/kg) and maintained with sevoflurane (1.5%–2%) and remifentanil (0.15–0.3 μg/kg/min). The airway was secured with an LMA ProSealTM laryngeal mask (Teleflex, Westmeath, Ireland). After a patient’s emergence from anesthesia, the catheter was connected to an elastomeric pump (Coopdech® Balloonjector®: Daiken Medical Co., Ltd Osaka, Japan), and the patient received an infusion of 0.2% ropivacaine at 4 or 6 ml/h and was given access to a patient-controlled system to receive a bolus of 5mL with lock out time 30 min. Drugs used for postoperative analgesia were 50mg of flurbiprofen axetil, 1000mg of acetaminophen intravenously, or delivered via local anesthetic bolus, depending on patients’ and nurses’ preference. If adverse events occurred, the local anesthetic flow was stopped or decreased until the event subsided, and then the flow of local anesthetic was restarted.
From July 2015 to May 2016, all patients received 4mL of 0.2% ropivacaine per hour until postoperative day1 and then 2ml/h until catheter removal. From June 2016 to July 2017, all patients received 6mL of 0.2% ropivacaine per hour until postoperative day1, 4ml/h until postoperative day2, and 2ml/h until catheter removal.
Statistics
All Statistical analyses were performed with R 3.1.2 software. Continuous variables are presented as means and standard deviations. Categorical variables were compared in Fisher’s exact test or the c2 test as appropriate; continuous variables were compared in Student’s t-test. All the reported p values were two-sided, and a p value of less than 0.05 was considered significant.