Venous PressureCentral Venous PressurePressureBlood PressureCranial SinusesMaxillary SinusParanasal SinusesSinus of ValsalvaPortal PressureCavernous SinusCarotid SinusHydrostatic PressureFrontal SinusParanasal Sinus DiseasesSphenoid SinusHemodynamicsBlood Pressure DeterminationTransducers, PressureCoronary SinusHypertension, PortalCapillary ResistanceHeart RateSinus Thrombosis, IntracranialIntracranial PressureSick Sinus SyndromeJugular VeinsEthmoid SinusVascular ResistanceDogsIntraocular PressureRegional Blood FlowVeinsCardiac OutputHypertensionPulmonary Wedge PressureBlood VolumeParanasal Sinus NeoplasmsHepatic VeinsTachycardia, SinusArterial PressureVenous InsufficiencyLiver CirculationPressoreceptorsBlood Pressure Monitoring, AmbulatoryPlasma SubstitutesVascular CapacitancePlethysmographyLower Body Negative PressureMaxillary Sinus NeoplasmsFluid TherapyAir PressureAtmospheric PressurePostureMonitoring, IntraoperativePortal VeinCerebral VeinsTime FactorsSympathetic Nervous SystemHypovolemiaCerebrospinal Fluid PressurePilonidal SinusSplanchnic CirculationTourniquetsLiver CirrhosisBlood CirculationTransverse SinusesEsophageal and Gastric VaricesVentricular PressureBlood Flow VelocityReflexHypotensionSupine PositionAnesthesiaVena Cava, SuperiorMonitoring, PhysiologicSuperior Sagittal SinusAntihypertensive AgentsPortal SystemLegHeartProspective StudiesFemoral VeinHydroxyethyl Starch DerivativesHead-Down TiltOsmotic PressureElectrocardiographyBaroreflexTreatment OutcomeCompliancePositive-Pressure RespirationRespirationDiastoleIsotonic SolutionsSinoatrial NodeVaricose VeinsAnesthesia, GeneralOxygenAtrial Function, RightHeart AtriaSclera