Inferior Venacava Ultrasound to Guide Fluid Management for Prevention of Hypotension After Spinal Anesthesia.

The IVC will be visualized using a paramedian long-axis view via a subcostal approach. A two-dimensional image of the IVC as it enters the right atrium will be first obtained. Variations in IVC diameter with respiration will be assessed using M-mode imaging performed 2 to 3 cm distal to the junction of right atrium and IVC. Maximum and minimum diameter will be measured from inner wall to inner wall and collapsibility index(CI) will be calculated using formula: CI = \[(dIVCmax - dIVCmin)/dIVCmax\] x 100% CI of ˃36% will be accepted as predicted fluid responder and ≤36% will be regarded as predicted fluid non responders. Predicted fluid responders will receive a bolus of 500 ml of Ringer's lactate over a time period of 15 min, after which the IVC diameter variation will be reassessed. Additional 250ml of Ringer's lactate bolus will be applied until a non fluid responder pattern is observed during IVC USG. Thereafter,spinal anaesthesia will be performed.