Comparison of post operative analgesic efficacy of dexamethasone with dexmedetomidine as an adjuvant to ropivacaine in ultrasound guided femoral nerve block in unilateral total knee arthroplasty under spinal anaesthesia: a prospective randomized control study

This study is a double blind prospective randomized control trial to evaluate the analgesic efficacy of dexamethasone and dexmedetomidine, as an adjuvant to 0.375% ropivacaine in ultrasound guided femoral nerve block. This study will be done on 120 ASA I -II patients undergoing unilateral total knee arthroplasty at of Fortis hospital, Mohali. All eligible and consenting patients will be explained VAS score beforehand and given intrathecal 0.5% heavy bupivacaine (dose in range of 2.8-3.4 ml) along with femoral nerve block. Under no circumstances the dose of bupivacaine will exceed 2mg/kg body weight. Patients will be divided between two groups via computer generated randomisation. For femoral nerve block, Group A will receive 8mg dexamethasone with 30ml of 0.375% ropivacaine and group B will receive 1mcg /kg dexmedetomidine with 30ml of 0.375% ropivacaine. The investigator as well as the patient will be blinded about the drug being used. Post operative VAS score and need for rescue analgesia, will be assessed for 24 hours and compared between the two groups. Any adverse effects will also be reported. Based on existing studies using said adjuvants in femoral nerve block, both dexamethasone and dexmedetomidine have been shown to prolong the duration of block and reduce the requirement of opioids. There is a dearth of studies comparing both adjuvants in femoral nerve block, hence our study aims to fill that gap in knowledge. based on similar studies in other blocks, running hypothesis is that both adjuvants provide adequate analgesia but dexamethasone might prove to have a lower over-all VAS score and requirement for rescue analgesia.