The Rewarming Rate and Increased Peak Temperature Alter Neurocognitive Outcome After Cardiac Surgery

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Abstract
Neurocognitive dysfunction is a common complication after cardiac surgery. We evaluated in this prospective study the effect of rewarming rate on neurocognitive outcome after hypothermic cardiopulmonary bypass (CPB). After IRB approval and informed consent, 165 coronary artery bypass graft surgery patients were studied. Patients received similar surgical and anesthetic management until rewarming from hypothermic (28 degrees -32 degrees C) CPB. Group 1 (control; n = 100) was warmed in a conventional manner (4 degrees -6 degrees C gradient between nasopharyngeal and CPB perfusate temperature) whereas Group 2 (slow rewarm; n = 65) was warmed at a slower rate, maintaining no more than 2 degrees C difference between nasopharyngeal and CPB perfusate temperature. Neurocognitive function was assessed at baseline and 6 wk after coronary artery bypass graft surgery. Univariable analysis revealed no significant differences between the Control and Slow Rewarming groups in the stroke rate. Multivariable linear regression analysis, examining treatment group, diabetes, baseline cognitive function, and cross-clamp time revealed a significant association between change in cognitive function and rate of rewarming (P = 0.05). Slower rewarming during cardiopulmonary bypass (CPB) was associated with better cognitive performance at 6 wk. These results suggest that a slower rewarming rate with lower peak temperatures during CPB may be an important factor in the prevention of neurocognitive decline after hypothermic CPB.