Analgesic Efficacy of Ropivacaine Alone or in Combination With Adjuvants on Post-operative Analgesia Following Video-Assisted Thoracoscopic Surgery.

Patients will receive subcutaneous wound infiltration with total volume of 24 mL of 0.25% ropivacaine + 1mg/kg ketamine (8 mL per incision) (ketamine group).

Patients will receive subcutaneous wound infiltration with total volume of 24 mL of 0.25% ropivacaine + 2mg/kg tramadol (8 mL per incision) (Tramadol group).

Patients will receive subcutaneous wound infiltration with total volume of 24 mL of 0.25% ropivacaine + 50 μg/kg midazolam (8 mL per incision) (Midazolam group).

Patients will receive subcutaneous wound infiltration with total volume of 24 mL of 0.25% Ropivacaine + 0.5μg/kg dexmedetomidine (8mL per incision) (Dexmedetomidine group).

Patients will receive subcutaneous wound infiltration with total volume of 24 mL of 0.25% ropivacaine+ 8mg dexamethasone (8 mL per incision) (Dexamethasone group).

Patients will receive subcutaneous wound infiltration with 24ml of 0.25% Ropivacaine in three divided doses (i.e. 8 mL per incision) (control group). Total dose of Ropivacaine will be 60 mg.