title: Relation of echocardiographic preload indices to stroke volume in critically ill patients with normal and low cardiac index.
abstract: OBJECTIVE
  To examine the usefulness of preload indices obtained by transoesophageal echocardiography (TOE) for estimating stroke volume at various levels of cardiac index.
  
  
  METHODS
  Prospective clinical study.
  
  
  METHODS
  Intensive care unit with surgical patients.
  
  
  METHODS
  16 ventilated patients monitored via Swan-Ganz catheterization and TOE.
  
  
  METHODS
  Echocardiographic images of left ventricular cross-sectional short-axis areas were analysed for the preload indices end-diastolic area (EDA), stroke area and end-diastolic wall stress. The relation between these indices and stroke volume, calculated from thermodilution cardiac output, was analysed in all patients and in nine patient groups discriminated by various ranges in heart rate (< or = 70 to > 110 beats/min), pulmonary artery occlusion pressure (< or = 8 to > 12 mmHg) and cardiac index (< or = 3.0 to > 4.2 l/min per m2).
  
  
  RESULTS
  Overall stroke volume (n = 155) correlated significantly (p < 0.0001) with EDA (r = 0.89) and stroke area (r = 0.80). The correlation with end-diastolic wall stress was non-significant (r = 0.51). Linearity in the relation between stroke volume and EDA or stroke area was independent of variations in heart rate and pulmonary artery occlusion pressure. Stroke volume correlated well with EDA and stroke area, when cardiac index was normal or high, but the relation slightly deteriorated (r = 0.63 to < or = 0.72) when the cardiac index was low. Changes in EDA and stroke area by more than 1, 2 or 3 cm2 were weak predictors for changes in stroke volume greater than 20%.
  
  
  CONCLUSIONS
  Stability of the relation between echocardiographic preload indices and stroke volume emphasize the potential of TOE for continuous preload monitoring in the critically ill.
authors.affiliation: Clinic of Anaesthesiology, University Hospital, Würzburg, Germany.
authors.forename: C A
authors.initials: CA
authors.lastname: Greim
authors.forename: N
authors.initials: N
authors.lastname: Roewer
authors.forename: C
authors.initials: C
authors.lastname: Apfel
authors.forename: G
authors.initials: G
authors.lastname: Laux
authors.forename: J
authors.initials: J
authors.lastname: Schulte am Esch
mesh_terms: D002302:Cardiac Output; D003422:Critical Care / Q000379:methods*; D017548:Echocardiography, Transesophageal / Q000592:standards*; D005069:Evaluation Studies as Topic; D006801:Humans; D016014:Linear Models; D016555:Matched-Pair Analysis; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods* / Q000592:standards; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013318:Stroke Volume