title: Clinical applications of wall-stress analysis in the pediatric intensive care unit.
abstract: OBJECTIVE
  To determine whether serial, noninvasive assessment of afterload, contractility, and Doppler-derived cardiac output reliably detects variations in cardiac function in unstable pediatric patients.
  
  
  METHODS
  Prospective, blinded clinical trial.
  
  
  METHODS
  The pediatric intensive care unit at Massachusetts General Hospital.
  
  
  METHODS
  Fourteen critically ill pediatric patients.
  
  
  METHODS
  Pediatric patients meeting criteria for hemodynamic instability underwent serial echocardiograms every 6 hrs until they met exit criteria, generating 75 studies.
  
  
  RESULTS
  Shortening fraction, cardiac index (CI), end-systolic wall stress (ESWS), and corrected velocity of circumferential shortening (Vcfc) were measured in each patient. Data points were plotted as a stress-velocity relationship, compared with published normal values, then correlated with changes in vital signs and pharmacologic interventions. Fourteen of 16 patients who were enrolled completed the study. A strong negative correlation between ESWS and Vcfc was confirmed (p < .001). As an internal measure of validity, Vcfc had a strong positive correlation with CI measurements (p = .012). An increase in dopamine infusion was associated with a fall in ESWS (p = .02), an increase in Vcfc (p = .03), and an increase in the CI as measured by Doppler (p = .035). The infusion of dopamine above renal perfusion levels moved patients from zones of normal or compensated contractility for afterload on a modified stress-velocity relationship to a zone of high contractility for afterload. Urine output was the only clinical index of cardiac function that had a significant correlation with the echocardiographic indices. Hemodynamically unstable patients followed similar patterns of deterioration and recovery on the modified stress-velocity graph. All surviving patients returned to a normal or compensated zone.
  
  
  CONCLUSIONS
  Wall-stress analysis of cardiac function is easily and safely performed on mechanically ventilated pediatric patients with the production of consistently high-quality data. For internal validity, Vcfc and CI measurements were correlated and were strongly positive. Wall-stress indices reliably detected patient deterioration, recovery, and response to changes in dopamine infusion. Patients who failed to return to areas of normal or compensated levels of contractility and afterload did poorly in this study. Noninvasive measures of afterload and contractility appear useful for monitoring cardiac function of critically ill children in an intensive care setting.
authors.affiliation: Department of Pediatric Critical Care Medicine, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Courand
authors.forename: J
authors.initials: J
authors.lastname: Marshall
authors.forename: Y
authors.initials: Y
authors.lastname: Chang
authors.forename: M E
authors.initials: ME
authors.lastname: King
mesh_terms: D000293:Adolescent; D001783:Blood Flow Velocity / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D002316:Cardiotonic Agents; D002648:Child; D002675:Child, Preschool; D003422:Critical Care / Q000379:methods; D016638:Critical Illness; D004298:Dopamine; D015150:Echocardiography, Doppler / Q000379:methods* / Q000592:standards; D005080:Exercise Test / Q000379:methods* / Q000592:standards; D005260:Female; D006331:Heart Diseases / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy; D006801:Humans; D007223:Infant; D007262:Infusions, Intravenous; D015278:Intensive Care Units, Pediatric; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods / Q000592:standards; D009200:Myocardial Contraction / Q000187:drug effects; D011446:Prospective Studies; D012121:Respiration, Artificial; D016037:Single-Blind Method; D013318:Stroke Volume / Q000187:drug effects
chemical_list: D002316:Cardiotonic Agents; D004298:Dopamine