Effects Of Acute Normovolemic Hemodilution And Controlled Hypotension On Gastrointestinal Perfusion And Oxygenation In Anesthetized Dogs

BackgroundHomologous blood transfusion has carried many potential risks, such as disease transmission, immune depression. Acute normovolemic hemodilution and controlled hypotension have been shown to be cost-effective methods of reducing allogenic RBC transfusion. Many studies have focused on the effects of acute normovolemic hemodilution and controlled hypotension on vital organs, such as the heart, brain and kidneys, little information is available about splanchnic organs.Gastrointestinal blood pressure-flow autoregulation is much less than that of the brain. During acute hypovolemia, hypoxia, blood flow redistribution away from splanchnic region towards vital organs in defending the perfusion of the heart and central nervous system may occur.Gastrointestinal tonometry , the only clinically available noninvasive method for the accurate diagnosis of compromised gastrointestinal blood flow. The current introduction of the Tonocap^TM , as a means of performing automated air tonometry has simplified the clinical application of gastrointestinal tonemetry. Many clinical and experimental validation of gastrointestinal tonometry to assess the adequacy of splanchnic perfusion have been reported. Gastric PCO₂ and its derivatives, pHi and Pco₂gap (gastric luminal PCO₂arterial PCO₂) have been shown to be reliable and sensitive indicators of splanchnic ischemia. Because blood flow redistributes away from peripheral and splanchnic tissue towards vital organs in acute hypovolemia, small increases in tonometrically derived parameters (gastric PCO₂,pH_i ,P_gapCO₂) are detectable before other, more tranditionally hemodynamic parameters became obvious. Foremore, the redistribution of blood flow has also observed during acute normovolemic hemodilution and controlled hypotension .Acute normovolemic hemodilution decrease arterial oxygen contents, while controlled hypotension reduced tissue perfusion. When the degree of hemodilution and controlled hypotension is increasingly deepen, oxygen delivery is also decreasingly reduced . The goal of this study is to investigate the effects of acute normovolemic hemodution and controlled hypotension on systemic hemodynamics, oxygen delivery and uptake, splanchnic perfusion and oxygenation. During acute normovolemic hemodilution and controlled hypotension, blood flow to the splanchnic region may be disproportionally reduced by distribution of the cardiac output to vital organs. Therefore it would be ideal to identify the most sensitive organs and use those as early indicators of ischemia to prevent irreversible cell damage.