Comparison of Intra-articular Dexmedetomidine and Magnesium in Postoperative Pain

Arthroscopic meniscus surgeries are the most frequent orthopedic procedures. The objective of the study is to compare the effects of intraarticular local anesthetic and adjuvant (dexmedetomidine vs magnesium) combinations in postoperative pain and analgesic requirement. The investigators' hypothesis is adjuvants added to the local anesthetics decreases the total local anesthetic dose, provides more effective pain relief according to local anesthetic only, and decreases the postoperative systemic non-steroidal analgesic and opioid doses.

Arthroscopic meniscus surgeries are the most frequent orthopedic procedures. However, irritation of free nerve endings in the synovial tissue and anterior fat pads and stretching and resection in the joint capsule lead to pain at various levels. Proper pain management enhances recovery, provides early mobilization and shortens length of hospital stay.

"Opioid-free" analgesia methods are frequently emphasized in published postoperative pain management guidelines and multimodal treatment approaches such as local anesthetic infiltration is recommended. In the treatment of knee pain, intra-articular drug injections are the most commonly used method because of minimal systemic side effects.

The drugs most commonly administered intraarticularly included local anesthetics (bupivacaine, levobupivacaine, lidocaine), opioids (morphine, fentanyl), magnesium sulfate, steroids, and α2 agonists (clonidine, dexmedetomidine).

Dexmedetomidine is a selective, specific, lipophilic and potent α2 adrenergic receptor agonist with sedative, anxiolytic, analgesic, antihypertensive and sympatholytic effects. It provides analgesic activity through both the central and peripheral nervous system. The analgesic effects of intra-articular administration of dexmedetomidine in arthroscopic surgeries have been demonstrated. Most side effects of this drug included hypotension and bradycardia. However, these side effects have never been encountered with intra-articular injection of the drug.

Magnesium is also an adjuvant drug which has a key role in nociceptive transmission, and acts as a NMDA (N-Methyl-D-Aspartate) antagonist in spinal neurons.

While opioid free anesthesia and analgesia methods gain importance nowadays, there has been increased interest in non-opioid analgesic drugs and multimodal analgesia applications. In order to increase the effects of local anesthetics and prolong their analgesic times, the addition of various adjuvants to local anesthetics is frequently used.

In the randomized controlled trials, intraarticular local anesthetic drugs combined with adjuvant drugs for postoperative analgesia were found to be superior to local anesthetic drugs alone. It is also known that local anesthetics have negative effects on chondrocytes. One of the goals of the investigators' in this study is to reduce the amount of local anesthetic used by adding adjuvant to local anesthetics.

In this study, the investigators plan to compare the efficacy of 2 adjuvants (magnesium sulfate and dexmedetomidine) combined with local anesthetics to be given intraarticularly for postoperative pain management after elective arthroscopic surgery.

Intraarticular high-volume drug injections may cause pain due to tension in the joint capsule. Additionally, the investigators aim to decrease the total drug volume with adjuvant drugs used in combination with local anesthetic, and thus to prevent joint capsule tension pain.

Eligibility Criteria:
Inclusion Criteria:

* age \>18, \<65
* scheduled for elective knee arthroscopy under spinal anesthesia
* ASA I and ASA II

Exclusion Criteria:

* age \<18 and \>65
* patients who received general anesthesia
* diabetes
* refusal of the patient
* known allergy to the specified drugs