title: A proposed relationship between increased intra-abdominal, intrathoracic, and intracranial pressure.
abstract: OBJECTIVE
  To determine the effect of acutely increased intra-abdominal pressure on pleural pressure, intracranial pressure, and cerebral perfusion pressure, and to clarify the relationship between these parameters.
  
  
  METHODS
  Nonrandomized, controlled study.
  
  
  METHODS
  Laboratory at a university medical center.
  
  
  METHODS
  Yorkshire swine, weighing 15 to 20 kg.
  
  
  METHODS
  Anesthetized, ventilated swine had a balloon inserted into the peritoneal cavity and catheters placed for measurement of intracranial pressure, pleural pressure, central venous pressure, pulmonary artery occlusion pressure, and mean arterial pressure. Following baseline measurements, intra-abdominal pressure was increased by incrementally inflating the intraperitoneal balloon. All parameters were remeasured 30 mins after each increase in intra-abdominal pressure. Two groups were studied: a) group 1 (n = 9) animals had intra-abdominal pressure increased to 25 mm Hg above baseline, then released; b) group 2 (n = 3) animals underwent sternotomy and pleuropericardotomy to prevent an increase in pleural pressure with increasing intra-abdominal pressure.
  
  
  RESULTS
  Increase of intra-abdominal pressure to 25 mm Hg above baseline caused significant (p < .05) increases in intracranial pressure (7.3 +/- 0.6 [SEM] to 16.4 +/- 1.9 mm Hg), pleural pressure (4.3 +/- 1.3 to 11.8 +/- 1.9 mm Hg), pulmonary artery occlusion pressure (9.0 +/- 0.6 to 14.3 +/- 0.8 mm Hg), and central venous pressure (6.6 +/- 0.7 to 10.7 +/- 0.9 mm Hg). The cardiac index (3.4 +/- 0.3 to 1.6 +/- 0.1 L/min/m2) and cerebral perfusion pressure (75.6 +/- 3.6 to 62.0 +/- 6.8 mm Hg) deceased significantly (p < .05), whereas mean arterial pressure (82.8 +/- 3.2 to 78.4 +/- 6.6 mm Hg) remained essentially constant. Sternotomy and pleuro-pericardotomy negated all effects of increased intra-abdominal pressure except the decreased cardiac index (1.6 +/- 0.1 to 2.5 +/- 0.2 L/min/m2).
  
  
  CONCLUSIONS
  Acutely increased intra-abdominal pressure causes a significant increase in intracranial pressure and a decrease in cerebral perfusion pressure. Increased intra-abdominal pressure appears to produce this effect by augmenting pleural and other intrathoracic pressures and causing a functional obstruction to cerebral venous outflow via the jugular venous system. It is possible that the same phenomenon may be why persons with chronically increased intra-abdominal pressure, such as the morbidly obese, suffer from a high frequency rate of idiopathic intracranial hypertension.
authors.affiliation: Division of General/Trauma Surgery, Medical College of Virginia, Richmond 23298-0519, USA.
authors.forename: G L
authors.initials: GL
authors.lastname: Bloomfield
authors.forename: P C
authors.initials: PC
authors.lastname: Ridings
authors.forename: C R
authors.initials: CR
authors.lastname: Blocher
authors.forename: A
authors.initials: A
authors.lastname: Marmarou
authors.forename: H J
authors.initials: HJ
authors.lastname: Sugerman
mesh_terms: D000006:Abdomen, Acute / Q000150:complications / Q000503:physiopathology*; D000818:Animals; D001794:Blood Pressure; D002560:Cerebrovascular Circulation; D003161:Compartment Syndromes / Q000150:complications / Q000503:physiopathology*; D004195:Disease Models, Animal; D006439:Hemodynamics; D008991:Monitoring, Physiologic; D010492:Pericardiectomy; D010994:Pleura / Q000503:physiopathology*; D011312:Pressure; D011559:Pseudotumor Cerebri / Q000209:etiology*; D013552:Swine