Administration of intravascular fluids is one of the methods to prevent SA-induced hypotension, but empirical intraoperative volume repletion carries the risk of fluid overload during elective surgery. Over fluid resuscitation is associated with organ dysfunction and higher mortality rate , thus, to avoid ineffective or even harmful intravascular volume expansion, it is important to have tools to predict hypotension and fluid responsiveness.

Inclusion Criteria:

• ASA grade I, II, III
• Age 18 -65 yrs
• Spinal Anesthesia

Exclusion Criteria:

• Patient refusal
• Patient having contraindication of Spinal Anesthesia (infection at the site of injection, spine deformity, coagulation disorders ) .
• Known cardiac, renal, neurological, metabolic, endocrine, psychiatric, respiratory disease.

Total Knee Replacement Surgeries under Spinal Anesthesia