Does a Different Local Anesthetic Improve Pain After Carpal Tunnel Release?

Does Addition of Longer-acting Local Anesthetic Improve the Post-operative Pain After Carpal Tunnel Release? A Randomized Controlled Study

This study is being conducted to determine whether addition of a longer-acting local anesthetic to our current anesthetic protocol improves the post-operative pain after carpal tunnel release. Participants undergoing carpal tunnel release (CTR) will be randomly assigned to one of two groups: the standard anesthetic or the longer-acting anesthetic. Participants will not be aware of their assignment. Carpal tunnel release will be performed in the standard fashion at our hospital. Participants will record their post-operative pain on a visual scale at 2, 4, 6, 8, and 10 hours after surgery. They will also record the location of their post-operative numbness at the same time intervals. The day after surgery, a research nurse will call each participant to inquire about their post-operative pain scores and numbness. Participants will also be asked about their consumption of oral painkillers (e.g. Tylenol, ibuprofen) during the first 24 hours. Participants will be re-assessed 3 months after surgery to evaluate improvement in carpal tunnel symptoms. Participants who wish to have carpal tunnel release on both wrists will be randomized to receive one type of anesthetic for the first side and will receive the other anesthetic for the second side. They will not be made aware of which medication is used for each side. This will allow us to directly compare the difference in pain experience between the two anesthetics. We hypothesize that use of a longer-acting local anesthetic will lead to decreased post-operative pain, especially in the first 4-8 hours after surgery.

A research nurse will meet with each patient presenting for outpatient CTR surgery at the Saskatoon City Hospital procedure room. He or she will obtain informed consent for interested participants. The patient will be assigned a subject number and be randomized to standard vs. bupivacaine treatment based on a computer algorithm. Participants will complete the Boston Carpal Tunnel Questionnaire as a baseline for comparison as well as a brief questionnaire on demographics. For those patients that are having both sides released during the study period, the first side will be randomized based on the study protocol and the second side will be anesthetized with the other treatment. They will be blinded to both procedures such that we can directly compare their operative experience. The surgeon will draw up and mix the pre-determined local anesthetic (LA) for each patient based on the randomization protocol. The research nurse (who will be performing all assessments) and the patient will remain blinded to the type of anesthetic. The two types of anesthetic will be: 10 mL 1% lidocaine with 1:100,000 epinephrine and 1 mL 8.4% sodium bicarbonate (standard treatment) 5 mL 1% lidocaine with 1:100,000 epinephrine + 5 mL 0.5% bupivacaine with 1:100,000 epinephrine and 1 mL 8.4% sodium bicarbonate (bupivacaine treatment) The participants will be anesthetized in the standard fashion, with all 11 mL of LA infiltrated subcutaneously into the area of the incision. After a delay of 20-40 minutes, the CTR will be carried out using the standard mini-open approach. Patients will be provided with the standard post-operative instructions regarding activity and wound care. After the procedure, participants will complete a short questionnaire (VAS) about any pain experienced during the administration of the local anesthetic and during the procedure. Patients will be sent home with instructions to complete a pain and numbness assessment at 2, 4, 6, 8, and 10 hours after surgery. They will be provided with a form containing the VAS and the times at which they are to self-administer this pain scoring system. Additionally, they will be provided with 20 Tylenol tablets (325mg each) and 20 ibuprofen tablets (200mg each), with instructions to take 1-2 tablets of one or both analgesics every 6 hours as needed during the first 24 hours. They will be asked to document the times at which they took the medications, as well as the dosages taken. They will be asked to refrain from using other types of pain medications, if possible. They will also be asked to document use of any other analgesics including Cannabis. Any questions will be answered by the research nurse before leaving clinic. The day after surgery, at the 24 hour mark, the research nurse will call each patient and inquire about their pain scores and numbness at 2, 4, 6, 8, and 10 hours, as well as the present time (24 hours). He or she will also ask about the number of Tylenol and/or ibuprofen pills taken during the first 24 hours, as well as the timing of consumption. This information recorded on a password-protected datasheet which contains only the subject number (no identifiers). The patient will return for their standard follow-ups. At 3 months, the research nurse will repeat the Boston Carpal Tunnel Questionnaire to assess outcome. At this time, if the patient wishes, they may be unblinded. For patients wishing for bilateral CTR, the first will be performed according to the randomization protocol as described above. The contralateral CTR will be performed 2-8 weeks later (as standard in our practice), with the alternate anesthetic (e.g. first CTR with standard treatment, second CTR with bupivacaine treatment). The same post-operative assessment will be performed for the second CTR. Patients will remain blinded to their type of anesthetic in each wrist until 3 months after the second surgery is performed. At that time, they will be asked by the research nurse whether the first or second surgery provided a better pain experience. Only after this will they be unblinded, if desired.

The study model for the primary outcome will be single group (patients randomized to one of two anesthetic types). However, select patients who wish to have bilateral carpal tunnel release will be entered into a crossover model, such that they will be randomized for their first surgery and receive the other type of anesthetic for their second surgery.

The surgeon administering the local anesthetic will not be blinded, however the participant and the research nurse (measuring outcomes) will be.

Administration of subcutaneous lidocaine as local anesthetic prior to carpal tunnel release (lidocaine intervention)

Administration of subcutaneous bupivacaine + lidocaine as local anesthetic prior to carpal tunnel release (bupivacaine intervention)

5 mL 1% lidocaine with 1:100,000 epinephrine + 5 mL 0.5% bupivacaine with 1:100,000 epinephrine and 1 mL 8.4% sodium bicarbonate

Location of total and partial post-operative numbness in hand (thumb, index, middle, ring, little finger)

Location of total and partial post-operative numbness in hand (thumb, index, middle, ring, little finger)

Location of total and partial post-operative numbness in hand (thumb, index, middle, ring, little finger)

Location of total and partial post-operative numbness in hand (thumb, index, middle, ring, little finger)

Location of total and partial post-operative numbness in hand (thumb, index, middle, ring, little finger)

Location of total and partial post-operative numbness in hand (thumb, index, middle, ring, little finger)

For patients with bilateral surgery only (they will have received a different anesthetic for each surgery). Patients will indicate their preference of lidocaine vs bupivacaine on a simple questionnaire asking which anesthetic provided a preferable post-operative pain experience.

Inclusion Criteria: Patients aged >18 years undergoing carpal tunnel release Exclusion Criteria: Patients aged <18 years Patients undergoing repeat carpal tunnel release Patients undergoing simultaneous procedures for other hand/wrist pathology at the time of carpal tunnel release (i.e. trigger finger release, Dupuytren's, etc.) Patients with a history of Rheumatoid Arthritis or a history or previous trauma or surgery to the local area (i.e. distal radius fracture) Patients who lack the capacity to provide informed consent or understand the nature of the project