ObjectiveWe have reported that initial distribution volume of glucose indicates the central extracellular fluid volume in the presence of fluid gain or loss. The purpose of this study was to describe changes in initial distribution volume of glucose, plasma volume determined by the indocyanine green dilution method (PV-ICG), and thoracic fluid content by thoracic electrical bioimpedance in patients with or without apparent thoracic fluid accumulation in the absence of pleural effusion. We also sought to test whether initial distribution volume of glucose rather than PV-ICG mirrors thoracic fluid content.DesignProspective, clinical study.SettingGeneral intensive care unit.PatientsEleven consecutive patients with apparent thoracic fluid accumulation as judged by thoracic fluid content >0.05/ohm and underlying pathology and 20 consecutive acute myocardial infarction patients within 24 hrs after its onset were selected for study. None of the acute myocardial infarction patients had thoracic fluid content >0.05/ohm.InterventionsFive grams of glucose and 25 mg of indocyanine green were administered simultaneously to calculate initial distribution volume of glucose and PV-ICG daily for the fluid-accumulated patients, and the same dosages were administered to the acute myocardial infarction patients immediately after their admission to the intensive care unit after percutaneous coronary angioplasty. Only the data on the day of the maximal and minimal thoracic fluid content in the fluid-accumulated patients were used for the study. The relationship between these two fluid volumes and thoracic fluid content was evaluated in the two patient groups.Measurements and Main ResultsInitial distribution volume of glucose and thoracic fluid content rather than PV-ICG and thoracic fluid content moved together in the same direction in each fluid-accumulated patient. Neither pulmonary artery occlusion pressure, central venous pressure, nor PV-ICG produced a better correlation with cardiac index when compared with initial distribution volume of glucose in patients with or without thoracic fluid accumulation.ConclusionsWe suggest that initial distribution volume of glucose rather than PV-ICG is a better indicator of the intrathoracic blood volume status, even although intravenously administered glucose cannot stay in the intravascular compartment.