Perfusion index is one such attempt to address the problem of hypotension by predicting which group of parturient may develop hypotension. This is a type of non-invasive method of assessing the relative vascular tone with the use of pulse oximeter which calculates the ration of pulsatile versus the non-pulsatile component of the blood flow. During normal physiological changes in pregnancy, there is relative loss of vascular tone which predisposes this group of patient to sudden development of hypotension after the sympathetic block due to spinal anesthesia.