Use of a maze to detect cognitive dysfunction in a porcine model of hypothermic circulatory arrest

Hypothermic circulatory arrest (HCA) can result in cognitive impairment not reflected by histopathology or gross neurologic observation. We tested the sensitivity of two multi-room maze tasks in detecting cerebral dysfunction after HCA in pigs.

Twenty-seven pigs were studied, divided between two tasks. 13 underwent 90 minutes HCA at 20 degrees C and were trained from postoperative day (POD) 7; 14 were unoperated controls. The maze includes a holding area, 8 rooms, and a center hallway. One piece of apple is placed in each baited room on each of 10 days of learning evaluation. After a pig enters a room, doors to all other rooms close, and the pig must return to the holding area. In task 1, 6 of 8 rooms were baited, and each day's session ended when each baited room had been entered, or after 20 trials. In task 2, initially only the right- or left-sided rooms were baited. Pigs were evaluated each day until they entered 4 baited rooms, or for 15 trials; the process was then repeated, baiting the other side.

Intraoperative physiology and postoperative recovery showed no differences between task 1 or 2 pigs. Task 1 did not distinguish between control and HCA groups (p = 0.5), but task 2 revealed significantly (p = 0.04) better learning in controls.

The significantly poorer performance of pigs after HCA suggests that the reversal of baited rooms in task 2 provides the sensitivity to detect cognitive dysfunction. The maze is a promising tool to investigate in pigs the mild cerebral damage often seen after HCA.