After obtaining institutional board approval (registration number 29-3), we reviewed the anesthesia and medical records of all adult patients who underwent catheter insertion to receive continuous interscalane block administered by anesthesiologists using the catheter-over-needle method at the Ehime Prefectural Imabari Hospital from July 2015 to July 2017. We excluded patients in whom the catheter was inserted by orthopedists. We collected data on patient characteristics, the incidence of pericatheter leakage of the local anesthetic, insufficient anesthetic effect (postoperative pain numerical rating scale score ≥ 3), 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. Informed consent to perform continuous interscalane block was obtained from all patients. The study was registered with the UMIN Clinical Trials Registry (UMIN000037673).
Catheter insertion procedure
In all patients, the catheter was inserted just before the 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 performed using the Contiplex® C Catheter-Over-Needle Continuous Nerve Block Set (B.Braun Melsungen AG, Melsungen, Germany) under in-plane ultrasound guidance without nerve stimulation via a lateral approach. The catheter tip was passed through and placed between C5 and C6 in the brachial plexus. After injecting 2 to 3 mL of lidocaine to confirm that the catheter tip was correctly placed for the administration of anesthetic, 10 mL of 0.75% ropivacaine was administered in a bolus through the catheter under ultrasound visualization for surgical anesthesia. The catheter insertion site was sealed with topical medical cyanoacrylate glue (Dermabond; Ethicon, San Angelo, Tex.) and draped with a clear film (3M TegadermTM Film, 6cm×7cm; 3M Health Care, St. Paul, Minn.).
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 using 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 included 50 mg of flurbiprofen axetil and 1000 mg of acetaminophen administered intravenously, or delivered via local anesthetic bolus, depending on patients’ and nurses’ preferences. If adverse events occurred, the local anesthetic flow was stopped or decreased until the event subsided, and then the flow was resumed.
From July 2015 to May 2016, all patients received 0.2% ropivacaine at 4 mL/h until postoperative day 1 and then 2 mL/h until catheter removal. From June 2016 to July 2017, all patients received 0.2% ropivacaine at 6 mL/h until postoperative day 1, 4 mL/h until postoperative day 2, and 2 mL/h until catheter removal.
All statistical analyses were performed using R 3.1.2 software. Continuous variables are presented as means and standard deviations. Categorical variables were compared using Fisher’s exact test or c2 test as appropriate; continuous variables were compared using Student’s t-test. All the reported p values were two-sided, and a p value of <0.05 was considered significant.