The ultrasound-guided selective blockade of the saphenous nerve in the adductor canal provides effective analgesia and reduces postoperative pain in patients undergoing arthroscopic medial meniscectomy. Selective blockade of the saphenous nerve in the adductor canal provides effective analgesia without quadriceps muscle weakness. It has been shown that usage of tourniquet during performing the adductor canal block (ACB) block increases the spread of local anesthetics in a distal and proximal way. Therefore, the proximal spread of local anesthetics may cause possible quadriceps weakness. The distal spread of local anesthetics may increase analgesic effect via sciatic nerve. The timing of the tourniquet inflation for ACB is a topic of discussion.The aim of this study is to compare the different times of US-guided ACB performing for postoperative analgesia management after arthroscopic knee surgery.

Knee arthroscopy is one of the most common orthopedic procedures. Knee arthroscopy is commonly used for the repairement of meniscus tears, debridement and reshaping of cartilage flaps, and ligament reconstruction. Knee arthroscopy is a minimally invasive procedure, however patients may complain severe pain due to the port-site incisions and the ligaments in the knee joint. Opioid agents are commonly used for analgesia management. However, opioids have adverse effects such as nausea, vomiting, sedation and respiratory depression. Peripheral nerve blocks such as femoral block, adductor canal block (ACB) may be performed to reduce opioid consumption and opioid-related side effects.

Selective blockadge of the saphenous nerve in the adductor canal for knee surgery provides effective analgesia without quadriceps muscle weakness. This is an important advantage of ACB since it there is no motor blockadge in the postoperative period. Blocking of the motor branches leads to delaying of the mobilization and it increases the patient's falling risk. ACB, targets the saphenous nerve and the vastus medialis branch which are the two largest sensorial nerves of the femoral nerve that innervates the knee. ACB blocks the articular branches of the obturator nerve at the same time. Since the ACB is performed at the distal site of thigh it does not target majority of the efferent branches of the quadriceps muscle, therefore the strength of this muscle may not be affected.

ACB is an effective and safely block. It has been shown that usage of the tourniquet during performing the ACB block increases the spread of local anesthetics in a distal and proximal way. There are two questions in this issue. Firstly, the proximal spread of local anesthetics may cause possible quadriceps weakness. Secondly the distal spread of local anesthetics may increase analgesic effect via sciatic nerve blockade. In the routine surgical procedure, at the beginning of the surgery a tourniquet is attached to the thigh and inflated following the induction of anesthesia. Then at the end of the procedure the tourniquet is deinflated and the patient is extubated. ACB may be performed preoperatively or postoperatively. It may be performed before or after the inflation of the tourniquet.

The aim of this study is to compare the different performing times of US-guided ACB for postoperative analgesia management after arthroscopic knee surgery. The primary aim is to compare postoperative opioid consumption and the secondary aim is to evaluate postoperative pain scores (VAS), and adverse effects related with opioids (allergic reaction, nausea, vomiting).

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) classification I-II
• Scheduled for arthroscopic knee surgery under general anesthesia

Exclusion Criteria:

• Bleeding diathesis
• Receiving anticoagulant treatment
• Known local anesthetics and opioid allergy
• Infection of the skin at the site of the needle puncture
• Pregnancy or lactation
• Patients who do not accept the procedure

Individual participant data (IPD) will not be shared

Outcomes Assessor and participant were blinded to the study