Study participants
After receiving approval by the Ramathibodi hospital research ethics board, this trial was registered in Thai clinical trial registry: TCTR20200228002. The reporting of this study was performed by adhering to the Consolidated Standards of Reporting Trials (CONSORT) statement for the reporting of randomized trial. Written informed consent was obtained from all participants. We enrolled 30 adult patients aged 40–80 years who had American Society of Anesthesiologists physical status IIV and were scheduled to undergo total knee arthroplasty (TKA). We excluded patients who refused to participate in the study, as well as patients with contraindications for performing femoral nerve blocks and spinal anesthesia (e.g., localized infection at puncture site, history of the femoral nerve neuropathy, and history of local anesthetic drug/adhesive glue allergy).
Randomization
Our research coordinator, who was not involved in the study, performed a computer-generated simple 1:1 ratio to assign patients into to 2-octyl cyanoacrylate glue (Dermabond®) (Dermabond group) or normal practice fixation groups (control group). The data on the allocation of patients to each group were concealed in a sealed envelope. The anesthesiologist who performed the femoral nerve block opened the envelope just prior to block performance.
Femoral nerve block
For patients undergoing unilateral TKA, femoral nerve catheters were inserted pre-operatively using a nerve stimulator. A Stimulong® 18-gauge needle was inserted at 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 was slowly threaded until a depth of 3–5 cm from the needle tip was reached, while maintaining quadriceps contraction at a current ≤ 0.5 mA. The needle was withdrawn, and the patients were divided into two groups: the Dermabond group and the control group. In the Dermabond group, the catheter was sealed with 2-octyl cyanoacrylate liquid adhesive (Dermabond®), and the area was covered with a transparent dressing (TegadermTM). In the control group, the catheter was secured with a sterile strip, and the area was covered with transparent dressing (TegadermTM) (Figure 1).
Intra-operatively, spinal anesthesia was performed with a 27-gauge quincke needle using isobaric bupivacaine at 10–15 mg from 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 received a bolus containing 15 ml of bupivacaine 0.125%, and then, continuous infusion with bupivacaine 0.08% at 5 mL/h began. Every patient received acetaminophen at 1,000 mg orally every 6 hours and naproxen at 250 mg orally for every 8 hours for 3 days. If the postoperative pain score was greater than 4 out of 10, IV morphine at 3 mg was administered as rescue analgesia.
Postoperative follow-up
The incidence of pericatheter leakage, catheter displacement, difficult catheter removal, pain score, and patient satisfaction were assessed via the acute pain service nurse.
Pericatheter leakage was classified as 1) no leakage or 2) leakage: fluid was seen under the transparent dressing (TegadermTM).
The catheter displacement was defined as catheter migration from the 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) and, then, at 24 hours and 48 hours using a 10-point numerical rating scale. Patient satisfaction with analgesia was recorded using a 0–10 scale, with 0 = very dissatisfied and 10 = completely satisfied (excellent).
Statistical Methodology
The 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’s exact test, as appropriate. Continuous variables were tested for normality with the Shapiro-Wilk test. A student’s t-test or Mann-Whitney test was used for group comparisons as appropriate. A 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 by assuming that the catheter leakage rate was 50% for the fixation technique used in our institution (Sterile Strip). Based on institutional pilot data, there is at least 80% power to reveal a clinically relevant reduction to zero percent, with a two-sided type-I error rate of 0.05. A sample size of eleven subjects in each arm of each group was considered adequate. An additional four subjects per group were recruited to prevent the loss of power because of early withdrawal or protocol violations. Thus, 15 subjects per group was the derived sample size.