RESUMO
BACKGROUND: The reduction in hematocrit (Hct) by hemodilution tends to cause an increase in cardiac output and a proportional decrease in arterial oxygen content. Additionally the reduction of systemic oxygen delivery (DO2) leads to significant differences in regional blood flow. It is therefore important to characterize the effects of hemodilution on regional oxygen metabolism in individual organs. This study was undertaken to evaluate and compare the effects of acute normovolemic anemia induced by hemodilution. METHODS: Six dogs were anesthetized and mechanically ventilated. Catheters were inserted in the right femoral and pulmonary arteries for blood sampling, and a gastric tonometer catheter was inserted into the gastric lumen. Baseline measurements of systemic hemodynamics, arterial ketone body ratio (AKBR), gastric intramucosal pH (pHi) and arterial lactate were recorded. Hemodilution was then begun by 6% pentastarch and was made in four levels of hematocrit values of 20%, 15%, 10% and 6%. RESULTS: Mean arterial pressures of Hct 10% and 6% was decresaed (P < 0.05) and Hct 15% and 10% increases in cardiac output and pulmonary capillary wedge pressure (PCWP) were observed. Central venous pressure and mean pulmonary arterial pressure were incresed (P < 0.05) at Hct 15%, 10% and 6%. DO2 progressively decreased (P < 0.05). AKBR and pHi began to decreased at Hct 15%. Arterial lactate decrease at Hct 15% and was above 7.4 mmol/L at Hct 6%. CONCLUSIONS: By the measurements of AKBR and pHi, the disturbance of splanchnic oxygenation can be detected early compared to those of O2 in terms of oxygen metabolism and the critical point of DO2 during acute normovolemic anemia induced by hemodilution.
