title: Low hematocrit impairs gastric mucosal CO2 removal during experimental severe normovolemic hemodilution.
abstract: OBJECTIVE
  The net effects of acute normovolemic hemodilution with different hemoglobin levels on splanchnic perfusion have not been elucidated. The hypothesis that during moderate and severe normovolemic hemodilution, systemic and splanchnic hemodynamic parameters, oxygen-derived variables, and biochemical markers of anaerobic metabolism do not reflect the adequacy of gastric mucosa, was tested in this study.
  
  
  METHODS
  Twenty one anesthetized mongrel dogs (16 +/- 1 kg) were randomized to controls (CT, n = 7, no hemodilution), moderate hemodilution (hematocrit 2 5% +/- 3%, n = 7) or severe hemodilution (severe hemodilution, hematocrit 15% +/- 3%, n = 7), through an isovolemic exchange of whole blood and 6% hydroxyethyl starch, at a 20 mL/min rate, to the target hematocrit. The animals were followed for 120 min after hemodilution. Cardiac output (CO, L/min), portal vein blood flow (PVF, mL/min), portal vein-arterial and gastric mucosa-arterial CO2 gradients (PV-artCO2 and PCO2 gap, mm Hg, respectively) were measured throughout the experiment.
  
  
  RESULTS
  Exchange blood volumes were 33.9 +/- 3.3 and 61.5 +/- 5.8 mL/kg for moderate hemodilution and severe hemodilution, respectively. Arterial pressure and systemic and regional lactate levels remained stable in all groups. There were initial increases in cardiac output and portal vein blood flow in both moderate hemodilution and severe hemodilution; systemic and regional oxygen consumption remained stable largely due to increases in oxygen extraction rate. There was a significant increase in the PCO2-gap value only in severe hemodilution animals.
  
  
  CONCLUSIONS
  Global and regional hemodynamic stability were maintained after moderate and severe hemodilution. However, a very low hematocrit induced gastric mucosal acidosis, suggesting that gastric mucosal CO2 monitoring may be useful during major surgery or following trauma.
authors.affiliation: Research Division, Heart Institute, São Paulo University Medical School, São Paulo, SP, Brazil.
authors.forename: Daniel
authors.initials: D
authors.lastname: Perin
authors.forename: Ruy J
authors.initials: RJ
authors.lastname: Cruz
authors.forename: Eliezer
authors.initials: E
authors.lastname: Silva
authors.forename: Luiz Francisco
authors.initials: LF
authors.lastname: Poli-de-Figueiredo
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001803:Blood Transfusion; D001810:Blood Volume / Q000502:physiology*; D001811:Blood Volume Determination; D002245:Carbon Dioxide / Q000097:blood*; D002303:Cardiac Output, Low / Q000503:physiopathology; D004195:Disease Models, Animal; D004285:Dogs; D005440:Fluid Therapy / Q000592:standards; D005753:Gastric Mucosa / Q000098:blood supply*; D006400:Hematocrit; D006438:Hemodilution; D008297:Male; D008365:Manometry; D010101:Oxygen Consumption / Q000502:physiology; D011169:Portal Vein / Q000502:physiology; D011897:Random Allocation; D012039:Regional Blood Flow / Q000502:physiology; D012720:Severity of Illness Index; D013152:Splanchnic Circulation / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide