HypotensionHypotension, ControlledHypotension, OrthostaticIntracranial HypotensionBlood PressureHeart RatePost-Exercise HypotensionTrimethaphanHemodynamicsBradycardiaEphedrineAnesthesia, SpinalAnesthesia, ObstetricalAutonomic Nervous System DiseasesVascular ResistanceAnesthesiaShockHypertensionCerebrovascular CirculationShock, SepticAntihypertensive AgentsNitroprussideBaroreflexOcular HypotensionMidodrineHypovolemiaShock, HemorrhagicIntracranial PressureSyncopePostureRegional Blood FlowDogsFerricyanidesVasoconstrictor AgentsTime FactorsCardiac OutputTilt-Table TestCardiovascular SystemShy-Drager SyndromeOxygenBlood VolumePressoreceptorsPure Autonomic FailureBlood Gas AnalysisCarbon DioxideBlood Patch, EpiduralIntraoperative ComplicationsRats, Sprague-DawleyFluid TherapyPhenylephrineNorepinephrineVasodilationAutonomic Nervous SystemSubdural EffusionProspective StudiesPressureBlood Pressure DeterminationArterial PressureReflexIsotonic SolutionsSplanchnic CirculationAnesthesia, EpiduralDose-Response Relationship, DrugMethyldopaVasodilator AgentsIsofluraneValsalva ManeuverHemorrhageTreatment OutcomeCentral Venous PressureSupine PositionLower Body Negative PressureCesarean SectionPartial PressureInfusions, IntravenousSympathetic Nervous SystemBionicsPlasma SubstitutesResuscitationLypressinRats, WistarClonidineSyncope, VasovagalInjections, IntravenousRenal DialysisAnesthesia, GeneralNitric OxideGanglionic BlockersCarotid SinusVasoconstrictionBlood Flow VelocityOxygen ConsumptionAnoxiaHalothaneTachycardiaMonitoring, IntraoperativeAnesthesia, InhalationConsciousnessBupivacaineKidney