Intrathecal Administration of Levobupivacaine and Opioids in Elderly

The study will be conducted to assess the impact of a 10 independent variables (dose and combination of Levobupivacaine with Fentanyl or Sufentanil, age, basal systolic blood pressure (SBP), basal mean arterial pressure (MAP), time to lowest spinal SBP, upper limit of sensory block (dermatoma level), time intervals of sensory recovery for two consecutive dermatoma level (two-segment regression), time intervals of sensory recovery to the twelfth thoracic dermatoma (T12 regression), time intervals of sensory recovery to the first sacral dermatoma (S1 regression) and Body Mass Index) on the likelihood of not developing hypotension after intrathecal injection.