title: Hemodynamics and cerebral oxygenation following repair of tetralogy of Fallot: the effects of converting from positive pressure ventilation to spontaneous breathing.
abstract: OBJECTIVE
  Following corrective surgery for tetralogy of Fallot (TOF), approximately one-third of these patients develop low cardiac output (CO) due to right ventricular (RV) diastolic heart failure. Extubation is beneficial in these patients because the fall in intrathoracic pressure that occurs with conversion from positive pressure breathing to spontaneous breathing improves venous return, RV filling and CO. We hypothesized that if CO were to increase but remain limited following extubation, the obligatory increase in perfusion to the respiratory pump that occurs with loading of the respiratory musculature may occur at the expense of other vital organs, including the brain.
  
  
  METHODS
  We conducted a retrospective analysis of all patients undergoing repair of TOF and monitoring of cerebral oxygenation using near infrared spectroscopy. We evaluated the following parameters two hours prior to and following extubation: mean and systolic arterial blood pressure (MBP, SBP), right atrial pressure (RAP), heart rate (HR) and cerebral oxygenation.
  
  
  RESULTS
  The study included 22 patients. With extubation, MBP and SBP increased significantly from 67.3 ± 6.5 to 71.1 ± 8.4 mm Hg (P= 0.004) and from 87.2 ± 8.6 to 95.9 ± 10.9 mm Hg (P= 0.001), respectively, while the HR remained unchanged (145 vs. 146 bpm). The RAP remained unchanged following extubation (11.9 vs. 12.0 mm Hg). Following extubation, cerebral oxygen saturations increased significantly from 68.5 ± 8.4 to 74.2 ± 7.9% (P < 0.0001). Cerebral oxygen saturations increased by ≥5% in 11 of 22 patients and by ≥10% in 5 of 22 patients.
  
  
  CONCLUSIONS
  We conclude that converting from positive pressure ventilation to spontaneous negative pressure breathing following repair of TOF significantly improves arterial blood pressure and cerebral oxygenation.
authors.affiliation: Division of Pediatric Critical Care Medicine, Children's Hospital of Orange County, Orange, California 92868, USA. rbronicki@choc.org
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Bronicki
authors.forename: Marilyn
authors.initials: M
authors.lastname: Herrera
authors.forename: Richard
authors.initials: R
authors.lastname: Mink
authors.forename: Michele
authors.initials: M
authors.lastname: Domico
authors.forename: Dawn
authors.initials: D
authors.lastname: Tucker
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Chang
authors.forename: Nick G
authors.initials: NG
authors.lastname: Anas
mesh_terms: D001794:Blood Pressure; D001921:Brain / Q000098:blood supply / Q000378:metabolism*; D002140:California; D002302:Cardiac Output; D002303:Cardiac Output, Low / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D006348:Cardiac Surgical Procedures / Q000009:adverse effects; D002317:Cardiovascular Agents / Q000627:therapeutic use; D002560:Cerebrovascular Circulation; D002675:Child, Preschool; D005440:Fluid Therapy; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D007223:Infant; D008991:Monitoring, Physiologic / Q000379:methods; D010101:Oxygen Consumption; D011175:Positive-Pressure Respiration; D015656:Respiratory Mechanics; D012189:Retrospective Studies; D019265:Spectroscopy, Near-Infrared; D013771:Tetralogy of Fallot / Q000378:metabolism / Q000503:physiopathology / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome; D015300:Ventilator Weaning
chemical_list: D002317:Cardiovascular Agents