Quantification of intestinal blood flow by ultrasonic transit time flowmetry in fed and endotoxaemic rats

Objective: To compare the dye dilution method with ultrasonic transit time flowmetry (UTTF) for quantifying intestinal blood flow in the same experimental animals. Design: Open experimental study. Setting: University hospital, Osaka, Japan. Material: 11 (experiment 1) and 25 (experiment 2) adult male Sprague-Dawley rats. Interventions: In experiment 1, the rats were fasted overnight. Tn experiment 2, endotoxin, Escherichia coli lipopolysaccharide (endotoxin) or saline (sham) was injected intraperitoneally. Main outcome measures: Superior mesenteric venous and abdominal aortic blood flow. Results: Experiment 1: intestinal blood flow measured by UTTF was significantly decreased by 17% (p < 0.05) and 56% (p < 0.05) after 30 minutes infusion through the tertiary branch of the mesenteric vein and during simultaneous drawing of blood samples from both the carotid artery and the superior mesenteric vein over a 1.5 minute period, respectively. The intestinal blood flow measurements obtained by UTTF at different intervals before simultaneous drawing of blood from the carotid artery and the superior mesenteric vein differed significantly (p < 0.05) from those obtained by the dye dilution method. Experiment 2: intestinal blood flow was also decreased by 21%-34% (p < 0.05) during similar simultaneous drawing of blood. Aortic blood flow in the endotoxin group was reduced by 66% (p < 0.05) compared with fed animals and 63% (p < 0.05) compared with sham animals. Simultaneously, intestinal blood flow in the endotoxin group was also reduced by 57% (p < 0.05) compared with fed or 48% (p < 0.05) compared with sham treated animals. Conclusion: Real intestinal blood flow might not be measured by the procedure of simultaneously drawing blood from the carotid artery and the superior mesenteric vein in rats as is usually done in the dye dilution method. Intraperitoneal endotoxin reduced aortic as well as intestinal blood flow. We propose that UTTF is an alternative method for quantifying intestinal blood flow in fed and endotoxaemic animals.