Effect of Dexamethasone on Post-spinal Hypotension

The goal of this clinical trial is to learn if intravenous dexamethasone is effective for prevention of post spinal hypotension in geriatric population undergoing orthopedic surgeries. The main question aim to answer is: Does intravenous dexamethasone in participants undergoing orthopedic procedures of lower limb under spinal anesthesia prevents post spinal hypotension? Researchers are comparing two groups of participants * Participants in (Dexamethasone Group) Group D are receiving intravenous dexamethasone 8mg preoperatively * Participants in (Placebo Group) Group P are receiving placebo preoperatively.