Adjuncts for Adductor Block: Dexamethasone,Dexmedetomidine, or Combination to Reduce Pain

Anterior cruciate ligament repair (ACLR) is a surgical procedure of the knee associated with moderate to severe postoperative pain lasting beyond 24 hours following surgery. Provision of adequate postoperative analgesia is a prerequisite for performing this procedure on outpatient basis. By virtue of their analgesic effects, peripheral nerve blocks (PNBs), such as adductor canal block (ACB), have thus become part of the care standard for this surgical procedure.

Though ACB provides effective pain relief, the duration of analgesia associated with this block is limited to eight hours postoperatively. As a result, patients having outpatient ACLR may experience severe pain following discharge, require additional opioid analgesics to control their pain, and even visit the emergency department for acute pain management. Consequently, perioperative care for the young outpatient population undergoing this procedure is an area where improvement is needed.

Mixing adjuncts with local anesthetics can prolong the duration of analgesia of PNBs; both dexmedetomidine and dexamethasone have been shown to effectively extend the duration of PNB analgesia by 60% and 80% hours, respectively. The use of dexamethasone is wide spread, and dexmedetomidine is progressively gaining popularity.

At Toronto Western Hospital, the use of adjuncts is left to the discretion of the anesthesiologists administering PNB; and dexamethasone is occasionally used to prolong block duration. The alternative approach to prolonging block duration is using ambulatory ACB catheters, but this is an expensive option that is applicable to select patients, and it is not available at the TWH.

Importantly, these adjuncts seem to exert their effect through independent mechanisms; thus there may be an advantage to combining adjuncts together. Further prolongation of the duration of analgesia is desirable, as the prolongation of block duration associated with each of these two adjuncts, alone, falls short of the duration of worst postoperative pain following ACLR. Consequently, the investigators aimed to explore whether the combination of these two adjuncts offers an incremental benefit over either of them alone, by examining their potential additive or synergistic effect.

This randomized controlled trial compares the effect of using perineural dexamethasone, dexmedetomidine, and their combination to Control on the duration of postoperative analgesia in patients having ambulatory ACLR with ACB.

• Dexamethasone 4mg (Drug), also known as Preservative free Dexamethasone: To guarantee rapid onset as well as effective postoperative analgesia, a 20 mL volume of local anesthetic has been selected for performing the ACB. The block solution will be a 20 ml volume for all groups, prepared by mixing 18 ml of ropivacaine 0.5% mixed with an additional 2 ml prepared according to the randomization.
• Dexmedetomidine (Drug), also known as Dexmedetomidine Hydrochloride 0.5 MG/ML: To guarantee rapid onset as well as effective postoperative analgesia, a 20 mL volume of local anesthetic has been selected for performing the ACB. The block solution will be a 20 ml volume for all groups, prepared by mixing 18 ml of ropivacaine 0.5% mixed with an additional 2 ml prepared according to the randomization.
• Saline (Other): Control/Placebo intervention

Primary outcomes

• Oral opioid consumption [time of the block to 24 hours after]: Cumulative 24 hour oral morphine equivalent consumption

Secondary outcomes

• Intra-operative opioid consumption [Duration of surgery: From start of surgery (defined as anesthesia start) to end of surgery (defined as anesthesia end)]: Cumulative intra-operative opioid consumption in morphine equivalent
• PACU opioid consumption [From time of arrival (hh:mm) in PACU to time of PACU discharge (hh:mm) assessed up to 24 hours]: Cumulative oral morphine equivalent consumption during time stayed in PACU
• Time to first analgesic request in PACU [From time of arrival in PACU (hh:mm) up to time of PACU discharge (hh:mm) assessed in minutes up to 24 hours ((e.g. patient arrives in PACU 12:00 then patient is given first pain medication in PACU at 12:30; Time to first analgesic request = 30 min)]: The time (hh:mm) first pain medication given in PACU
• Time to PACU discharge [From time of arrival (hh:mm) in PACU to time discharged (hh:mm) from PACU assessed in minutes (e.g. patient arrives in PACU 12:00 then patient discharged from PACU 12:30; Time to PACU discharge = 30 min)]: how fast patient recovered and discharged from PACU (measured in minutes)
• Visual Analogue Scale-Pain scores - minimum score = 0 and maximum score = 10 [discharge from hospital to 2 days after surgery]: pain scores at 0, 2, 4, 6, 12, 24, 36, and 48 hours postoperatively
• Opioid consumption [discharge from hospital to 2 days after surgery]: analgesic consumption at 6, 12, 24, 36, and 48 hours postoperatively
• Risk of block-related complications [one week post operatively]: adverse symptoms related to the block
• Risk of opioid-related side effects [two week post operatively]: adverse symptoms related to oral pain medication consumption
• Quality of recovery-15 (QoR15) (0-10, where 0 = none of the time [poor] and 10 = all of the time [excellent] [discharge from hospital to 24 hours after surgery]: measured using the Quality of recovery-15 at 12 and 24 hours postoperatively
• Time to hospital discharge [From time of end of surgery [(hh:mm) defined as anesthesia end] up to time of hospital discharge (hh:mm) assessed in minutes up to 24 hours (e.g. surgery ends 12:00, then patient discharged from the hospital at 13:00; Time to hospital discharge = 60min]: Measures of recovery (how many minutes from end of surgery to discharge from hospital)
• Time to first analgesic request at home (after discharge) [discharge from hospital to 24 hours after surgery]: first time(hh:mm) patient took an oral pain medication
• Visual Analogue Scale-Satisfaction scores - where 0 = not satisfied and 10 = very satisfied [evaluated at 12 and 24 hours post-surgery]: A visual analogue scale used to measure how satisfied the study participant is with the pain relief received for shoulder surgery
• Presence/absence of nerve block complications [time from block onset to 2 days,2 weeks after surgery]: adverse symptoms related to the block

Sex: All, ages: 18 Years to 50 Years

Inclusion Criteria:

* English Speaking
* ASA 1-3 patients
* BMI <40

Exclusion Criteria:

* Refusal or inability to provide informed consent
* Any contraindication to regional anesthesia including coagulopathy or bleeding diathesis, allergy to local anesthetics, infection, nerve injury or malignancy at the site of the block
* History of alcohol/drug dependence
* History of long term opioid intake or chronic pain disorder
* History of preexisting neuropathy in the operative leg
* History of significant psychiatric conditions that may affect patient assessment
* Inability to understand the informed consent and demands of the study
* Allergy to any of the components of the multimodal analgesic regimen
* Revision of ACL repair
* Diabetes
* Significant bradycardia (baseline heart rate ≤ 40 beats per minute)

• Richard Brull, MD, Principal investigator, Women's College Hospital