HypovolemiaBlood VolumeLower Body Negative PressureShockPlasma VolumeDehydrationBlood Volume DeterminationFluid TherapyHypotension, OrthostaticFluid ShiftsVascular CapacitanceDiureticsIsotonic SolutionsPlasma SubstitutesFurosemideShock, HemorrhagicThirstHypernatremiaBed RestHead-Down TiltHemodilutionInappropriate ADH SyndromeHemodynamicsIntracranial HypotensionHemorrhageBlood PressureCardiac OutputHeart RateSupine PositionHypotensionHyponatremiaDrinkingStroke VolumeWater-Electrolyte BalanceHydroxyethyl Starch DerivativesSpectroscopy, Near-InfraredHematocritResuscitationCardiovascular System