title: Esophageal capnometry during hemorrhagic shock and after resuscitation in rats.
abstract: BACKGROUND
  Splanchnic perfusion following hypovolemic shock is an important marker of adequate resuscitation. We tested whether the gap between esophageal partial carbon dioxide tension (PeCO2) and arterial partial carbon dioxide tension (PaCO2) is increased during graded hemorrhagic hypotension and reversed after blood reinfusion, using a fiberoptic carbon dioxide sensor.
  
  
  METHODS
  Ten Sprague-Dawley rats were anesthetized, tracheotomized, and cannulated in one femoral artery and vein. A calibrated fiberoptic PCO2 probe was inserted into the distal third of the esophagus for determination of luminal PeCO2 during maintained anesthesia (pentobarbital 15 mg/kg per hour), normothermia (38 +/- 0.5 degrees C), and fluid balance (saline 5 ml/kg per hour). Three out of 10 rats were used to determine the limits of hemodynamic stability during gradual hemorrhage. Seven of the 10 rats were then subjected to mild and severe hemorrhage (15 and 20-25 ml/kg, respectively). Thirty minutes after severe hemorrhage, these rats were resuscitated by reinfusion of the shed blood. Arterial gas exchange, hemodynamic variables, and PeCO2 were recorded at each steady-state level of hemorrhage (at 30 and 60 min) and after resuscitation.
  
  
  RESULTS
  The PeCO2-PaCO2 gap was significantly increased after mild and severe hemorrhage and returned to baseline (prehemorrhagic) values following blood reinfusion. Base deficit increased significantly following severe hemorrhage and remained significantly elevated after blood reinfusion. Significant correlations were found between base deficit and PeCO2-PaCO2 (P < 0.002) and PeCO2 (P < 0.022). Blood bicarbonate concentration decreased significantly following mild and severe hemorrhage, but its recovery was not complete at 60 min after blood reinfusion.
  
  
  CONCLUSIONS
  Esophageal-arterial PCO2 gap increases during graded hemorrhagic hypotension and returns to baseline value after resuscitation without complete reversal of the base deficit. These data suggest that esophageal capnometry could be used as an alternative for gastric tonometry during management of hypovolemic shock.
authors.affiliation: Associate Professor and Research Director, Division of Critical Care Medicine, Miami Children's Hospital, Miami, Florida, USA. Dan.Torbati@MCH.Com
authors.forename: Balagangadhar R
authors.initials: BR
authors.lastname: Totapally
authors.forename: Harun
authors.initials: H
authors.lastname: Fakioglu
authors.forename: Dan
authors.initials: D
authors.lastname: Torbati
authors.forename: Jack
authors.initials: J
authors.lastname: Wolfsdorf
mesh_terms: D000136:Acid-Base Equilibrium; D000818:Animals; D001158:Arteries / Q000737:chemistry; D001784:Blood Gas Analysis / Q000379:methods*; D002245:Carbon Dioxide / Q000032:analysis*; D004947:Esophagus / Q000503:physiopathology*; D007022:Hypotension / Q000097:blood / Q000150:complications; D010313:Partial Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D012151:Resuscitation; D012771:Shock, Hemorrhagic / Q000150:complications / Q000503:physiopathology* / Q000628:therapy*
chemical_list: D002245:Carbon Dioxide