Lithium microdialysis and its use for monitoring of stomach and colon submucosal blood perfusion--a pilot study using ischemic preconditioning in rats

During shock, exposure of gut to ischemia determines patient's survival. Ischemic preconditioning (ISP) elevates nitric oxide and blood perfusion, whereby it protects organs against subsequent severe ischemia/reperfusion. Using appropriate flow marker, microdialysis may serve to monitor interstitial microcirculation. Hence, our aim was to test the reliability of lithium as a flow marker (lithium microdialysis, LM) on an ISP model. Rats were divided into three groups. Two (ischemic and preconditioned) groups underwent 30 min celiac artery occlusion (CAO) with 2.5 h reperfusion. 25 min before CAO, the latter experienced 5 min ischemia. Sham-operated animals served as controls. LM in stomach and colon submucosa, serum nitric oxide, hepatic and pancreatic enzymes were measured. In stomach, LM indicated a decrease in blood perfusion evoked by CAO (p < 0.01) in both experimental groups. During reperfusion, the ischemic animals showed a restoration of microcirculation, unlike the preconditioned ones, whose blood perfusion failed to regenerate (p < 0.001). For any group, LM showed no microcirculation modification in colon. Serum analytes remained unchanged. We conclude that LM appears to be a potentially suitable indicator of gastrointestinal interstitial microcirculation. However, we failed to demonstrate any beneficial effect of ISP on pancreas, systemic nitric oxide and local/remote microcirculation within studied organs.