title: Investigating the relationship between intrathoracic blood volume index and cardiac index.
abstract: OBJECTIVE
  To determine whether cardiac index and intrathoracic blood volume index are "mathematically coupled" under euvolaemic conditions with increasing levels of inotropic support.
  
  
  METHODS
  Prospective case series.
  
  
  METHODS
  A 14-bed general intensive care unit in a university-affiliated hospital.
  
  
  METHODS
  Twelve mechanically ventilated patients, monitored with the COLD system and receiving dobutamine as inotropic support.
  
  
  METHODS
  After measuring cardiac index and intrathoracic blood volume index the rate of dobutamine infusion was increased until cardiac index rose by at least 20%. A further measurement of intrathoracic blood volume index was made at the new cardiac index.
  
  
  RESULTS
  The mean increase in cardiac index was 31.7%, compared with a mean increase in intrathoracic blood volume index of only 2.84%.
  
  
  CONCLUSIONS
  Under euvolaemic conditions, raising cardiac index by increasing inotropic support does not alter intrathoracic blood volume index significantly, thus demonstrating that the two measurements are not 'mathematically coupled' under these conditions.
authors.affiliation: Department of Intensive Care, Guy's and St Thomas' NHS Trust, St Thomas' Hospital, London, UK. Angela.McLuckie@gstt.sthames.nhs.uk
authors.forename: A
authors.initials: A
authors.lastname: McLuckie
authors.forename: D
authors.initials: D
authors.lastname: Bihari
mesh_terms: D000328:Adult; D000368:Aged; D001810:Blood Volume / Q000187:drug effects*; D001811:Blood Volume Determination / Q000379:methods*; D002302:Cardiac Output / Q000187:drug effects*; D002316:Cardiotonic Agents / Q000008:administration & dosage*; D004396:Coloring Agents; D004280:Dobutamine / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007208:Indocyanine Green; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D011446:Prospective Studies; D012121:Respiration, Artificial; D013909:Thorax
chemical_list: D002316:Cardiotonic Agents; D004396:Coloring Agents; D004280:Dobutamine; D007208:Indocyanine Green