HypotensionHypotension, ControlledHypotension, OrthostaticIntracranial HypotensionBlood PressurePost-Exercise HypotensionTrimethaphanBradycardiaHeart RateEphedrineAnesthesia, SpinalAnesthesia, ObstetricalHemodynamicsAutonomic Nervous System DiseasesShockAnesthesiaShock, SepticMidodrineCerebrovascular CirculationVascular ResistanceNitroprussideOcular HypotensionCardiac OutputHypovolemiaFerricyanidesSyncopeShy-Drager SyndromePure Autonomic FailureBlood Patch, EpiduralPostureIntraoperative ComplicationsSubdural EffusionTilt-Table TestIntracranial PressureVasoconstrictor AgentsShock, HemorrhagicCardiovascular SystemFluid TherapyHemorrhageSympathetic Nervous SystemDogsBlood VolumeCesarean SectionMethyldopaAnesthesia, EpiduralAutonomic Nervous SystemBionicsIsotonic SolutionsPressoreceptorsPhenylephrineNorepinephrineRegional Blood FlowTime FactorsBaroreflexAntihypertensive AgentsSplanchnic CirculationClonidineVasodilationLypressinDose-Response Relationship, DrugPlasma SubstitutesSyncope, VasovagalInfusions, IntravenousRats, Sprague-DawleyFludrocortisoneValsalva ManeuverRenal DialysisHydralazineIsofluraneInjections, IntravenousBupivacaineReflexSupine PositionProspective StudiesAnesthesia, GeneralHypertensionVasodilator AgentsHeat StrokeAnaphylaxisTachycardiaMonitoring, IntraoperativeResuscitationBlood Volume DeterminationArterial PressureBlood Gas AnalysisTreatment OutcomeMyelographyPlasma VolumeHalothaneHemodiafiltrationHomeostasisBrainHeadacheCentral Venous PressureGanglionic BlockersNitric OxideDysautonomia, FamilialVasopressinsEpinephrineFentanyl