title: Cardiac output measured by lithium dilution, thermodilution, and transesophageal Doppler echocardiography in anesthetized horses.
abstract: OBJECTIVE
  To assess the suitability of lithium dilution as a method for measuring cardiac output in anesthetized horses, compared with thermodilution and transesophageal Doppler echocardiography.
  
  
  METHODS
  6 horses (3 Thoroughbreds, 3 crossbreeds).
  
  
  METHODS
  Cardiac output was measured in 6 anesthetized horses as lithium dilution cardiac output (LiDCO), thermodilution cardiac output (TDCO), and transesophageal Doppler echocardiographic cardiac output (DopplerCO). For the LiDCO measurements, lithium chloride was administered i.v., and cardiac output was derived from the arterial lithium dilution curve. Sodium nitroprusside, phenylephrine hydrochloride, and dobutamine hydrochloride were used to alter cardiac output. Experiments were divided into 4 periods. During each period, 3 LiDCO measurements, 3 DopplerCO measurements, and 3 sets of 3 TDCO measurements were obtained.
  
  
  RESULTS
  70 comparisons were made between LiDCO, DopplerCO, and triplicate TDCO measurements over a range of 10 to 43 L/min. The mean (+/- SD) of the differences of LiDCO - TDCO was -0.86 +/- 2.80 L/min; LiDCO = -1.90 + 1.05 TDCO (r = 0.94). The mean of the differences of DopplerCO - TDCO was 1.82 +/- 2.67 L/min; DopplerCO = 2.36 + 0.98 TDCO (r = 0.94). The mean of the differences of LiDCO - DopplerCO was -2.68 +/- 3.01 L/min; LiDCO = -2.53 + 0.99 DopplerCO (r = 0.93).
  
  
  CONCLUSIONS
  These results indicate that lithium dilution is a suitable method for measuring cardiac output in horses. As well as being accurate, it avoids the need for pulmonary artery catheterization and is quick and safe to use. Monitoring cardiac output during anesthesia in horses may help reduce the high anesthetic mortality in this species.
authors.affiliation: The Rayne Institute, St Thomas' Hospital, London, UK.
authors.forename: R A
authors.initials: RA
authors.lastname: Linton
authors.forename: L E
authors.initials: LE
authors.lastname: Young
authors.forename: D J
authors.initials: DJ
authors.lastname: Marlin
authors.forename: K J
authors.initials: KJ
authors.lastname: Blissitt
authors.forename: J C
authors.initials: JC
authors.lastname: Brearley
authors.forename: M M
authors.initials: MM
authors.lastname: Jonas
authors.forename: T K
authors.initials: TK
authors.lastname: O'Brien
authors.forename: N W
authors.initials: NW
authors.lastname: Linton
authors.forename: D M
authors.initials: DM
authors.lastname: Band
authors.forename: C
authors.initials: C
authors.lastname: Hollingworth
authors.forename: R S
authors.initials: RS
authors.lastname: Jones
mesh_terms: D000818:Animals; D002302:Cardiac Output / Q000502:physiology*; D002316:Cardiotonic Agents / Q000008:administration & dosage; D004280:Dobutamine / Q000008:administration & dosage; D015150:Echocardiography, Doppler / Q000662:veterinary; D017548:Echocardiography, Transesophageal / Q000662:veterinary; D006736:Horses / Q000502:physiology*; D007201:Indicator Dilution Techniques / Q000662:veterinary; D017736:Ion-Selective Electrodes / Q000662:veterinary; D016014:Linear Models; D018021:Lithium Chloride / Q000008:administration & dosage* / Q000097:blood; D009599:Nitroprusside / Q000008:administration & dosage; D010656:Phenylephrine / Q000008:administration & dosage; D012044:Regression Analysis; D014662:Vasoconstrictor Agents / Q000008:administration & dosage; D014665:Vasodilator Agents / Q000008:administration & dosage
chemical_list: D002316:Cardiotonic Agents; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine; D004280:Dobutamine; D018021:Lithium Chloride