title: Reliability of lithium dilution cardiac output in anaesthetized sheep.
abstract: BACKGROUND
  Cardiac output (CO) measurement with lithium dilution (COLD) has not been fully validated in sheep using precise ultrasonic flow probe technology (COUFP). Sheep generate important cardiovascular research models and the use of COLD has become more popular in experimental settings.
  
  
  METHODS
  Ultrasonic transit-time perivascular flow probes were surgically implanted on the pulmonary artery of 13 sheep. Paired COLD readings were taken at six time points, before and after implantation of a left ventricular assist device (LVAD) and compared with COUFP recorded just after lithium injection.
  
  
  RESULTS
  The mean COLD was 5.7 litre min(-1) (range 3.8-9.6 litre min(-1)) and mean COUFP 5.9 litre min(-1) (range 4.0-9.2 litre min(-1)). The bias (standard deviation) was 0.3 (1.0) litre min(-1) [5.1 (16.9)%] and limits of agreement (LOA) were -1.7 to 2.3 litre min(-1) (-28.8 to 39.0%) with a percentage error (PE) of 34.4%. Data to assess trending [rate (95% confidence intervals)] included a 78 (62-93)% concordance rate in the four-quadrant plot (n=27). In the half moon polar plot (n=19), the mean polar angle was +5°, the radial LOA were -49 to +35° and 68 (47-89)% of data points fell within 22.5° of the mean polar angle. Both tests indicated moderate to poor trending ability.
  
  
  CONCLUSIONS
  COLD is not precise when evaluated against COUFP in sheep based on the statistical criteria set, but the results are comparable with previously published animal studies.
authors.affiliation: Section of Anaesthesia, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
authors.forename: S M
authors.initials: SM
authors.lastname: Axiak Flammer
authors.forename: L A
authors.initials: LA
authors.lastname: Critchley
authors.forename: A
authors.initials: A
authors.lastname: Weber
authors.forename: T
authors.initials: T
authors.lastname: Pirbodaghi
authors.forename: H
authors.initials: H
authors.lastname: Brinks
authors.forename: S
authors.initials: S
authors.lastname: Vandenberghe
mesh_terms: D000818:Animals; D002302:Cardiac Output / Q000502:physiology*; D003625:Data Collection; D003627:Data Interpretation, Statistical; D005260:Female; D006352:Heart Ventricles; D006353:Heart-Assist Devices; D007201:Indicator Dilution Techniques; D018021:Lithium Chloride; D008991:Monitoring, Physiologic; D015203:Reproducibility of Results; D018401:Sample Size; D012756:Sheep
chemical_list: D018021:Lithium Chloride
keywords: anaesthesia, veterinary; data interpretation, statistical; measurement techniques, cardiac output; measurement techniques, lithium dilution; sheep