Preconditioning with lidocaine and xylazine in experimental equine jejunal ischaemia.

Background: Pharmacological preconditioning of dexmedetomidine on small intestinal ischaemia/reperfusion injury has been reported in different animal models including horses.

Objectives: The objective was to assess if xylazine and lidocaine have a preconditioning effect in an experimental model of equine jejunal ischaemia.

Study Design: Terminal in vivo experiment.

Methods: Ten horses under general anaesthesia were either preconditioned with xylazine (group X; n = 5) or lidocaine (group L; n = 5). A historical untreated control group (group C; n = 5) was used for comparison. An established experimental model of equine jejunal ischaemia was applied, and intestinal samples were taken pre-ischaemia, after ischaemia and following reperfusion. Histomorphological examination was performed based on a modified Chiu score. Immunohistochemical staining for cleaved caspase-3, TUNEL and calprotectin was performed, and positive cell counts were expressed in cells/mm .

Results: There was no progression of histomorphological mucosal injury from ischaemia to reperfusion, and there were no differences in histomorphology between the groups. After ischaemia, group X had significantly less caspase-positive cells compared to the control group with a median difference of 227% (P = .01). After reperfusion, group X exhibited significantly lower calprotectin-positive cell counts compared to the control group, with a median difference of 6.8 cells/mm in the mucosa and 44 cells in the serosa (P = .02 and .05 respectively). All groups showed an increase in caspase- and calprotectin-positive cells during reperfusion (P < .05). TUNEL-positive cells increased during ischaemia, followed by a decrease after reperfusion (P < .05).

Main Limitations: The small sample size and the use of a historical control group. Preconditioning effects of the tested drugs may be masked by the protective effects of isoflurane in the anaesthetic protocol.

Conclusions: Preconditioning with lidocaine did not have any effect on the tested variables. The lower cell counts of caspase- and calprotectin-positive cells in group X may indicate a beneficial effect of xylazine on ischaemia/reperfusion injury. Due to the absence of a concurrent reduction of histomorphological injury, the clinical significance remains uncertain.