BupivacaineAnesthesia, SpinalAnesthetics, LocalAnesthesia, ObstetricalAdjuvants, AnesthesiaCesarean SectionSpecific GravitySubarachnoid SpaceInjections, SpinalAnalgesia, ObstetricalSufentanilFentanylSpinal CordPain, PostoperativeAnalgesics, OpioidDouble-Blind MethodSpinal Cord InjuriesPregnancyAnalgesia, EpiduralProspective StudiesAnesthesia, EpiduralAmidesNerve BlockLidocaineAnesthesia, CaudalEtidocaineSpinal NervesAnesthesia, LocalSpinal Nerve RootsAnesthetics, CombinedSpinal Cord DiseasesSpinal CanalPain MeasurementSpinal Cord NeoplasmsMepivacaineSpinal DiseasesSpinal Cord CompressionSpinal NeoplasmsCarticaineAnalgesiaSpinal StenosisSpinal FusionMorphineSensationStereoisomerismRats, Sprague-DawleyTime FactorsSpinal InjuriesMuscular Atrophy, Spinal