Predicting Hypotension Related to Spinal Anesthesia

This study aims to identify women at risk of low blood pressure (hypotension) after the usual cesarean anesthetic - a spinal anesthetic. Hypotension may be caused by dehydration. We believe we can predict who will get hypotension by using two anesthesia monitors together with a passive leg raise (PLR) (legs elevated after a period spent reclining). The PLR will cause a shift of blood from the legs to the heart, and the monitors will detect the heart's response to tell if a subject is dehydrated. We want to see if these dehydration tests can also predict hypotension after a spinal anesthetic.