Fluid TherapyIsotonic SolutionsColloidsRehydration SolutionsHyponatremiaPlasma SubstitutesHypovolemiaIntraoperative CarePerioperative CareColorectal SurgeryWater-Electrolyte BalanceBlood Volume DeterminationGoalsTreatment OutcomeHydroxyethyl Starch DerivativesPostoperative CarePostoperative ComplicationsProspective StudiesSodium ChlorideOutcome Assessment (Health Care)HemodynamicsPregnancy OutcomeRetrospective Studies