Addition of Clonidine to Ropivacaine in Adductor Canal Block
Addition of Clonidine to Ropivacaine in Adductor Canal Block
Total knee arthroplasty (knee replacement) is a common orthopedic procedure for
 osteoarthritis. This procedure is performed either under general anesthesia or spinal
 anesthesia; after the procedure in the recovery room, these patients undergo adductor canal
 block, which is a nerve block to provide 8-14 hours of postoperative pain control. For this
 nerve block, 15-20 ml of local anesthetic is combined with adjuvant medications to improve
 the quality of pain control as well as the duration of pain relief. The primary local
 anesthetic used for adductor canal block is ropivacaine, and the commonly used adjuvants are
 epinephrine and dexamethasone.

 There is conflicting data available in the literature regarding efficacy of addition of
 clonidine to the local anesthetic injection in peripheral nerve blocks, and there is no data
 assessing the efficacy of this medication in adductor canal blocks.

 Once the consent process is completed, patients are enrolled in two arms. Upon conclusion of
 surgery, a sealed and coded envelope with either clonidine or the placebo syringe will be
 given to the acute pain service staff performing the nerve block. This will be mixed with
 local anesthetic solution and injected in the adductor canal under ultrasound guidance.

 The primary outcome measure will be the duration of analgesia, which will be assessed as the
 time interval between placement of adductor canal block to the first request of opioid
 analgesic by patients (which will be obtained from hospital electronic medical records).
 Secondary outcomes will include:

 1. Duration of sensory block, which will be assessed as the time interval between injection
 of local anesthetic and report of postoperative pain of 3 or more on an 11 point scale
 (0=no pain; 10= worst pain imaginable) by the patient (this will be assessed every 4
 hours).

 2. Duration of motor block, which will be assessed as the time interval between the onset
 of motor block to complete recovery of motor block by assessing straight leg raise
 strength (this will be assessed every 4 hours).

 3. Cumulative 24 and 48 hour opioid analgesic use.

 4. Post-block pain scores, evaluated by an 11 point pain score (0-10), which will be done
 every 15 minutes for the first hour after surgery and every 4 hours thereafter for 24
 hours.
Inclusion Criteria:

 -  Men and women ages 18 and older

 -  ASA physical status classification system I, II and III (healthy patient or patient
 with mild to moderate systemic disease)

 -  Patient coming in for elective total knee arthroplasty under general or neuraxial
 anesthesia and postoperative adductor canal block

 -  Patients staying for at least 24 hrs post operatively

 -  Patients who provide informed consent

 -  Patients presenting for surgery >1 hour in length and <6 hours.

 Exclusion Criteria:

 -  History of recent common colds, upper respiratory infections or immune deficiencies

 -  Patients allergic to clonidine

 -  Pregnant women (all women of childbearing age undergo pregnancy testing prior to
 anesthesia as per UVMMC peri-operative protocol)

 -  Patients who are already on chronic clonidine therapy for management of blood pressure

 -  Patients on chronic opioid therapy defined as more than 10 mg of oxycodone per day (or
 equivalent doses of other opioid analgesics)