Study participants
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. Reporting of this study was done by adhering to the Consolidated Standards of Reporting Trials (CONSORT) statement for reporting of randomized trial. 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, patients with contraindications for to performing femoral nerve blocks and spinal anesthesia (e.g. localized infection at puncture site, history of the femoral nerve neuropathy, history of local anesthetic drug/ adhesive glue allergy)
Randomization
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 opened the envelope just before the time of block performance.
Femoral nerve block performance
For patients undergoing unilateral TKA, femoral sheath catheters were inserted pre-operatively using a nerve stimulator., A Stimulong® 18-gauge needle was insertedat 1.5 cm lateral to the femoral artery. The nerve stimulator was initially set at 2 Hz and 1.5 mA. When quadriceps contraction was detected, the current was decreased, and the needle position was optimized for contraction at a current output of 0.2–0.5 mA. The Stimulong® 20-gauge catheter was attached to the nerve stimulator and the catheter slowly threaded until a depth of 3–5 cm from the needle tip while maintaining quadriceps contraction at a current ≤ 0.5 mA. The needle was withdrawn, and the patients were divided into two groups: Dermabond group and Control group. In the Demabond group, catheter is sealed with 2-octyl cyanoacrylate liquid adhesive (Dermabond®), and the area is covered with transparent dressing (TegadermTM). In the control group, the catheter is secured with sterile strip, and the area is covered with transparent dressing (TegadermTM) (figure 1).
Intra-operative, a spinal anesthesia was performed with a 27-gauge quincke needle using isobaric bupivacaine 10-15 mg at the second to the fourth lumbar levels. No local anesthetics were given through the femoral catheter during surgery. In the recovery room, the femoral catheter was bolus with 15 ml of bupivacaine 0.125% and then began a continuous infusion with bupivacaine 0.08% at 5 mL/h. Every patient received acetaminophen 1000 mg (every 6 hours) and naproxen 250 mg (every 8 hours) for 3 days. If postoperative pain score was greater than four out of 10, IV morphine 3 mg were administered as rescue analgesia.
Postoperative follow-up
The incidence of pericatheter leakage, catheter displacement, difficult catheter removal, pain score and patient satisfaction were assessed by the acute pain service nurse.Pericatheter leakage was classified into 4 grades: 1) no leakage, 2) mild: fluid around puncture site but no fluid collection under transparent dressing (TegadermTM), 3) moderate: fluid collection seen under transparent dressing (TegadermTM) but did not leak outside , 4) Severe; fluid leak outside of the transparent dressing (TegadermTM).
The catheter displacement was defined as catheter migration from initial recorded depth of insertion. Catheter dislodgement was defined as complete catheter removal from the skin. Catheter removal was reported as “easy” or “difficult”. Post-operative pain was assessed in the postanesthetic care unit (PACU), then 24 hours and 48 hours; using a 10-point numerical rating scale. Patient satisfaction with analgesia using 0-10 scale with 0 = vary dissatisfied and 10 = completely satisfied (excellent).
Statistical Methodology
Demographic characteristics of the subjects in each randomized controlled study was 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. Student T-test or Mann-Whitney test was 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 group was recruited to prevent loss of power because of early withdrawal or protocol violations. Thus, 15 subjects per group was the derived sample size.