Elucidating Links between Cardiopulmonary Bypass and Neurocognitive Function in the Rat. Mackensen et al. (page 1485)

After using identical surgical preparations and anesthetics in a group of 20 rats, Mackensen et al.  then randomized the animals to receive either cardiopulmonary bypass (CPB) or a sham operation without CPB. All animals were allowed to recover and, within 24 h after CPB or sham operation, underwent testing that included assays of prehensile traction, strength, and balance beam performances. The animals were graded on a 0–9 scale (9 = best) and then tested again on the 3rd and 12th postoperative days. Beginning on the 3rd postoperative day, an investigator blinded to group assignment began behavioral testing of the rats in the Morris water maze to evaluate neurocognitive outcomes after CPB and sham operations. The time to locate a submerged platform was measured to test for impairment of visuospatial learning and memory. Rats underwent daily testing with four trials per testing period until the 12th postoperative day, when all were killed.

The rats that had undergone CPB had worse neurologic outcomes compared with sham-operated control group rats on the 1st, 3rd, and 12th postoperative days. Rats in the CPB group also had longer water maze latencies compared with controls, although the rats’ average swimming speeds, evaluated with a video tracking system, did not differ between groups. Histologic analysis of brain sections with light microscopy revealed no difference between the two groups of rats regarding the amount of necrosis observed in hippocampal neurons. Use of this rodent model of CPB may allow advances in the understanding of clinical neurocognitive injury often associated with CPB.