title: Cardiovascular effects of hypoxia/hypercarbia and tension pneumothorax in newborn piglets.
abstract: OBJECTIVE
  To test the hypothesis that, in newborn piglets, the presence of a tension pneumothorax modifies the cardiovascular responses to hypoxia/hypercarbia.
  
  
  METHODS
  Prospective laboratory study.
  
  
  METHODS
  Perinatal cardiovascular research laboratory at a university school of medicine.
  
  
  METHODS
  Seven newborn piglets.
  
  
  METHODS
  We sequentially exposed the piglets to a baseline (control I) measure, hypoxia/hypercarbia, tension pneumothorax with normoxia/normocarbia, and tension pneumothorax with hypoxia/hypercarbia added.
  
  
  RESULTS
  Brain and systemic blood pressures and blood flow (radionuclide-microspheres) were measured. Hypoxia/hypercarbia resulted in increased brain perfusion (207 +/- 61% of control, mean +/- SEM, p < .05) and heart perfusion (176 +/- 58% of control, p < .05) and decreased gastrointestinal perfusion (-37 +/- 9% of control, p < .05). Tension pneumothorax with normoxia/normocarbia reduced the cardiac output (-70 +/- 8% of control, p < .05), which was redistributed toward the brain (p < .05) at the expense of the gastrointestinal tract (p < .05). Although this redistribution in cardiac output persisted during tension pneumothorax with hypoxia/hypercarbia added, sustained reductions in cardiac output (-57 +/- 11%, of control, p < .01) were associated with smaller increases in perfusion to brain (55 +/- 54 vs. 207 +/- 61% of control, tension pneumothorax with hypoxia/hypercarbia added, and hypoxia/hypercarbia time periods, respectively, p < .05) and heart (65 +/- 49 vs. 176 +/- 58% of control, tension pneumothorax with hypoxia/hypercarbia added, and hypoxia/hypercarbia time periods, respectively, p < .05) and larger decreases in blood flow to gastrointestinal tract, pancreas, and kidneys (p < .05) than with hypoxia/hypercarbia alone.
  
  
  CONCLUSIONS
  Tension pneumothorax-induced reductions in cardiac output limit the hypoxia/hypercarbia-mediated increases in perfusion to brain and heart and accentuate the hypoxia/hypercarbia-related decreases in perfusion to kidneys and splanchnic organs.
authors.affiliation: Department of Pediatrics, Brown University School of Medicine, Women and Infant's Hospital of Rhode Island, Providence 02905.
authors.forename: B S
authors.initials: BS
authors.lastname: Brann
authors.forename: S R
authors.initials: SR
authors.lastname: Mayfield
authors.forename: M
authors.initials: M
authors.lastname: Goldstein
authors.forename: W
authors.initials: W
authors.lastname: Oh
authors.forename: B S
authors.initials: BS
authors.lastname: Stonestreet
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D002319:Cardiovascular System / Q000503:physiopathology*; D006439:Hemodynamics / Q000502:physiology; D006935:Hypercapnia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D011030:Pneumothorax / Q000503:physiopathology*; D013552:Swine