Effects of different time courses and depths of acute normovolemic hemodilution on injury to mucous membrane of small intestines in rabbits

Abstract

Objective To evaluate the effects of different time courses and depths of acute normovolemic hemodilution(ANH)with hematocrit(Hct)on injury to the mucous membrane of small intestines in rabbits. Methods Thirty-two adult rabbits, weighing 2.0-2.5 kg, were randomly divided into 4 groups(n=8 each)using a random number table: control group(group C), Hct 18% group(H1 group), Hct 15% group(H2 group)and Hct 12% group(H3 group). The animals were anesthetized with iv 20% urethane 4 ml/kg, tracheostomized and mechanically ventilated.Blood samples were taken from the left femoral artery.Blood withdrawn from the femoral artery = 2×body weight×body fluid per kilogram ×(initial Hct-target Hct)÷(initial Hct+ target Hct), and was simultaneously replaced with the equal volume of 6% hydroxyethyl starch 130/0.4 infused over 30 min via the left femoral vein until the target Hct was achieved in H1, H2 and H3 groups.At 30 min of stabilization after puncture(T0)and 2, 4 and 8 h after ANH(T1-3), blood samples were obtained from the superior mesenteric artery and vein for blood gas analysis and for determination of plasma concentrations of tumor necrosis factor-α(TNF-α)in the superior mesenteric vein.Oxygen extraction rate(ERO2)was calculated.Small intestinal mucosal tissues were obtained at T3 to observe the pathological changes with light microscope. Results Compared with those at T0, the plasma concentrations of TNF-α at T3 and ERO2 at T1-3 were significantly increased in H1 group, and the plasma concentrations of TNF-α at T3 and ERO2 at T1-3 were increased in H2 and H3 groups.The injury to the mucous membrane of small intestine was mild in group H1, and was severe in H2 and H3 groups. Conclusion ANH performed with 6% hydroxyethyl starch causes injury to the mucous membrane of small intestine when Hct is 18% and the time course ≥ 8 h, and when Hct ≤ 15% and the time course ≥ 2 h in the rabbits. Key words: Hemodilution; Intestinal mucosa