Inflammation but not Glycemic Control is Associated with Neurocognitive Decline After Cardiac Surgery

Abstract

Background: Whether perioperative glycemic control or markers of inflammation is associated with neurocognitive decline (NCD) after cardiac surgery was examined. Methods: Thirty patients undergoing cardiac surgery utilizing cardiopulmonary bypass (CPB) were screened for NCD preoperatively and on post-operative day four (POD4). Serum cytokine levels were measured and human transcriptome analysis was performed on blood samples. Neurocognitive data are presented as a change from baseline to POD4 in a score standardized with respect to age and gender. Results: A decline in neurocognitive function was identified in 73% (22/30) of patients on POD4. Patients with postoperative leukocytosis (WBC ≥ 10.5) had more NCD when compared to their baseline function (p=0.03). Patients with elevated IL-8 levels at 6 hours postoperatively had a significant decline in NCD at POD4 (p=0.04). Surprisingly, TNF-α, IL-1β, IL-2, or IL-6 levels were not associated with NCD (p>0.3 for all). There was no difference in neurocognitive function between patients with elevated HbA1c levels preoperatively (p=0.973) or elevated fasting blood glucose levels the morning of surgery (>126mg/dL, p=0.910), or a higher maximum blood glucose levels during CPB (>180mg/dL, p=0.252), or higher average glucose levels during CPB (>160mg/dL, p=0.639). Human transcriptome analysis demonstrated unique and differential patterns of gene expression in patients depending on the presence of DM and NCD. Conclusions: Perioperative glycemic control does not have an effect on NCD soon after cardiac surgery. Postoperative leukocytosis and elevated IL-8 levels are associated with neurocognitive decline. The profile of gene expression was altered in patients with NCD with or without diabetes.

Neurocognitive decline in cardiac surgery—Distraction rather than destruction?

“…The current literature suggests that neurocognitive outcomes may be due to a hyperinflammatory state, 10 which may be the common denominator for all these observations. Scrimgeour et al 3 It may be accidental that the amount of functional decline due to this distraction was similar to the neurocognitive decline measured in the above study 4 days after cardiac surgery using CPB, where a destructive mechanism is entertained. 3 Although the many different tests and characteristics used and assessed may not be directly comparable, such a consideration may be able to explain why postoperatively noted neurocognitive decline is temporary, reversible, not affected by diabetes mellitus, and not different between surgical and other interventional procedures.…”

“…Scrimgeour et al 3 It may be accidental that the amount of functional decline due to this distraction was similar to the neurocognitive decline measured in the above study 4 days after cardiac surgery using CPB, where a destructive mechanism is entertained. 3 Although the many different tests and characteristics used and assessed may not be directly comparable, such a consideration may be able to explain why postoperatively noted neurocognitive decline is temporary, reversible, not affected by diabetes mellitus, and not different between surgical and other interventional procedures. We, therefore, would like to ask, whether neurocognitive decline after cardiac surgery may be more due to mental distraction than cellular destruction.…”

“…The current literature suggests that neurocognitive outcomes may be due to a hyperinflammatory state, 10 which may be the common denominator for all these observations. Scrimgeour et al 3 also based their hypothesis on such an inflammatory scenario and therefore investigated diabetic patients and glycemic control, where a proinflammatory condition is supplemented by the use of CPB. Their findings as well as the other observations of neurocognitive dysfunction in the absence of CPB question CPB as a key contributor to the incidence of neurocognitive dysfunction and argue against a strictly embolic nature of this complication.…”

“…In this issue of the Journal, Scrimgeour et al 3 assessed neurocognitive decline in patients undergoing cardiac surgery using CPB. They performed Repeatable Battery Assessment of Neuropsychological Status tests pre‐ and 4 days postoperatively.…”