Arthroscopic knee surgery can cause significant postoperative pain to the degree that can potentially delay timely discharge from the ambulatory surgical setting. Analgesia after knee surgery can be provided by multiple, non-systemic, non-opioid-based methods, including local anesthetic infiltration, peripheral nerve blockade, neuraxial procedures, and intra-articular injections. The femoral nerve block has been shown to be superior to traditional intra-articular injection of local anesthetics in some knee surgeries, but motor blockade of the quadriceps muscle, with the potential risk for falls, limits the value of femoral blocks for less invasive ambulatory surgery. Orthopedic surgery is increasingly being performed on an ambulatory basis, where perioperative analgesia can improve timely discharge in the outpatient setting. A trans-arterial landmark-based distal approach to the saphenous nerve block has been shown to reduce pain significantly by providing sensory block to the tissues around the medial meniscus. The saphenous nerve, a terminal branch of the femoral nerve, provides cutaneous sensation to the peripatellar region, and the medial aspect of the lower extremity below the knee, as well as to the articular branches to the medial aspect of the knee joint. The saphenous nerve separates from the femoral nerve in the proximal third of the thigh, courses through the adductor canal with the nerve to the vastus medialis, and emerges from the adductor hiatus to divide into the infrapatellar branch and the sartorial branch. Traditionally, saphenous nerve blocks have been performed as an anatomical landmark-based technique with marginal rates of success, as low as 33%. With ultrasound guidance, the feasibility of effective saphenous nerve block at the adductor canal has been shown tp increase. The adductor canal block may provide superior analgesia over traditional distal saphenous nerve blocks for surgical procedures of the knee because this block includes the saphenous nerve, the nerve to the vastus medialis, and potentially the articular contribution of the obturator nerve to the knee joint. Our primary hypothesis was that performing an adductor canal block as part of a multimodal analgesic regimen would result in improved analgesia immediately following arthroscopic medial meniscectomy. Dexamethasone improves the quality and duration of peripheral nerve block when used as an adjuvant to local anesthetic. Possible mechanisms include: Dexamethasone (as a corticosteroid) was reported to attenuate C-fiber responses. More recent publications indicate that 8 mg dexamethasone added to perineural local anesthetic injections augment the duration of peripheral nerve block analgesia. Dexmedetomidine is a useful sedative agent with analgesic properties, hemodynamic stability and ability to recover respiratory function in mechanically ventilated patients facilitating early weaning. Besides being a new modality of sedation and analgesia in ICU patient management, it has been studied in several other perioperative settings.~researchers suggested that dexmedetomidine likely affects the Aδ and unmyelinated C fibers differently from motor neurons. This phenomenon has been observed before in the setting of neuraxial blockade; however, the exact mechanism of action remains speculative and has been addressed elsewhere. Rationale for using Adjuvants in Regional anesthesia:- Regional anesthesia researchers have been exploring the strategies to prolong the duration of PNB Peripheral Nerve Blockade analgesia in patients undergoing ambulatory procedures. Although ambulatory catheters are an effective option, their practical utility is governed by a stringent patient selection criteria. Liposomal bupivacaine is another effective alternative, but its use is limited by price, availability, lack of FDA approval, and the similar prolongation of both sensory and motor blockade duration it produces. Adjuvants constitute another option, and numerous local anesthesia additives, have been explored in search of the ideal adjunct that satisfies the criteria of effectively prolonging the duration of analgesia and not being associated with a significant risk of neurotoxicity. Among these adjuncts, dexamethasone has seemed most promising, because researchers have demonstrated its efficacy when administered intravenously. However, dexmedetomidine as a local anesthetic adjunct may ultimately prove superior to dexamethasone in terms of its differential prolongation of sensory-motor blockade.
a comparison shall be conducted between dexamethasone accompanied by bupivacaine, on one hand, and dexmedetomedine accompanied by bupivacaine, on the other hand for pain-free knee arthroscopic surgeries.