After receiving approval by the Ramathibodi hospital research ethics board. This trial was registered on Thai clinical trial registry: TCTR20200228002, registered 24 February 2020- Retrospectively registered, http://www.clinicaltrials.in.th/index.php?tp=regtrials&menu=trialsearch&smenu=lsresult&task=search&task2=ls. Written informed consent was obtained from all participants. We enrolled 30 adult patients aged 40–80 years, with American Society of Anesthesiologists physical status I-IV who were scheduled to undergo total knee arthroplasty (TKA). We excluded patients who refused to participate in the study, those with localized infection at the inguinal area of the operated leg and patient who contraindicate to femoral nerve block or allergy to local anesthetic drug/ adhesive glue.
Randomization and blinding
Our research coordinator who was not involve in the study performed computer-generated simple 1:1 ratio to 2-octyl cyanoacrylate glue (Demabond®) (Dermabond group) or normal practice fixation (Control group). Allocation of patients to each group was concealed in a sealed envelope. The anesthesiologist who performed femoral nerve block open the envelope just before the time of block performance. All other research outcome assessor and caregiver were blinded to group allocation. Patient blinding was maintained by standardizing the perceptible elements of block between both groups: position, ultrasound probe placement, needle insertion site, use of nerve stimulation, and local anesthetic injection volume. Our study was adhered to CONSORT guideline.
Femoral nerve block performance
For patients undergoing unilateral TKA, femoral sheath catheters were inserted pre-operatively using a nerve stimulator. A Stimulong® continuous nerve block set 18-gauge 50 mm Tuohy needle and 20-gauge catheter). After sterile preparation and draping of the femoral area on the operative side, stimulation at 2 Hz and 1.5 mA was applied after the needle was felt to have gone through two fascial planes, 1.5 cm lateral to the femoral artery. When quadriceps contraction was detected, the current was decreased, and the needle position was optimized for evident contraction at a current output of 0.2–0.5 mA. The Stimulong® catheter was attached to the nerve stimulator and the catheter slowly thread until a depth of 3–5 cm from the needle tip while maintaining quadriceps contraction at a current ≤ 0.5 mA. The catheter was repositioned as necessary to sustain continuous quadriceps contraction at a current ≤ 0.5 mA. The needle was withdrawn, and the patients were divided into the following 2 groups: Dermabond group; catheter is sealed with 2-octyl cyanoacrylate liquid adhesive (Dermabond®), and the area is covered with transparent dressing (Tegaderm™) (Fig. 1). Control group; catheter is secured with sterile strip to secure the catheter, and the area is covered with transparent dressing (Tegaderm™) (Fig. 1).
The patients were then transferred to the operating room for spinal anesthesia. We perform spinal anesthesia using a 27-gauge quicke needle with a solution of isobaric Marcaine 10–15 mg at the second to the fourth lumbar level. No local anesthetics were given through the femoral catheter during surgery. In the recovery room, the patients were given a 15-mL bolus of bupivacaine 0.125% injected through the femoral catheter. The femoral catheter was then infused with bupivacaine 0.08% at 5 mL/h. Every patient received acetaminophen 100 mg (every 6 hours) and naproxen 250 mg (every 8 hours) for 3 days. If patient had postoperative pain score more than 4, morphine 3 mg were administered as rescue analgesia.
The primary outcome was the leakage at the catheter site, classified as Mild; fluid was around the catheter, < 1 cm from the insertion site Moderate; fluid was around the catheter, > 1 cm from the insertion site but still in the transparent dressing (Tegaderm™). Severe; fluid out of the transparent dressing (Tegaderm™)
The secondary outcomes, which included catheter migration, difficulty of catheter removal, and patient satisfaction, were assessed by the acute pain service nurse at postanesthetic care unit (PACU), 24 h and 48 h postoperative period.
Demographic characteristics of the subjects in each randomized controlled study were analyzed. Continuous variables are reported using mean and standard deviation values or median and range values. Categorical variables are presented using counts and percentages and tested using Chi-Square or Fisher exact test, as appropriate. Continuous variables were tested for normality with the Shapiro-Wilk test. T test or Mann-Whitney test were used for group comparisons as appropriate. P-value < 0.05 implied statistical significance. The statistical software SPSS 20.0 for Windows was used for data analyses.
The sample size was calculated assuming a catheter leakage rate of 50% with standard fixation techniques based on previous literature (9) and institutional pilot data to have at least 80% power to see a clinically relevant reduction to zero percentage with a 2-sided type I error rate of 0.05. A sample size of 11 subjects in each arm of each group was considered adequate. Additional 4 subjects per groups were recruited to prevent loss of power because of early withdrawal or protocol violations. Thus, 15 subjects per group was the derived sample size.