Deflation of the pneumatic tourniquet used in lower limb surgery is usually associated with hemodynamic instability, metabolic and respiratory changes. These changes are usually tolerated by young, healthy patients; However, these complications are risky for elderly and cardiac patients. The aim of this study is to assess the effect of gradual deflation of thigh tourniquet on the hemodynamics and arterial blood gases compared to the usual practice

Pneumatic tourniquet will be applied on the mid- thigh with cuff pressure of 350 mm Hg. After the end of surgery, the lower limb will be elevated at 45-degree and the patients will randomized into one of the three groups:

G 50 (n=30) : The tourniquet cuff pressure will be deflated gradually by 50 mm Hg every 2 minutes till complete deflation.

G 100 (n=30): The tourniquet cuff pressure will be deflated gradually by 100 mm Hg every 2 minutes till complete deflation.

G 0 (n=30): The tourniquet cuff will be released till complete deflation. If hypotension is observed during the procedure, it will be managed by 10 mg ephedrine.

Inclusion Criteria:

• scheduled for elective orthopedic lower limb surgery under pneumatic tourniquet

Exclusion Criteria:

• BMI ≥35Kg/ m2
• patients with unstable angina, left ventricular dysfunction , cerebrovascular disease ,bleeding disorders
• contraindication to tourniquet insertion
• patients requiring massive intraoperative blood transfusion (Blood loss more than 50% of the patients' blood volume (70 ml/Kg) ).

patients above 50 years scheduled for orthopedic lower limb surgery under pneumatic tourniquet