Date of Award

January 2014

Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

John A. Elefteriades

Subject Area(s)

Medicine

Abstract

Few (conflicting) studies have quantitatively assessed neurocognitive effects of deep hypothermic circulatory arrest (DHCA), and even fewer have looked at the long-term effects of DHCA. In this study, we aim to determine if DHCA negatively affects neurocognitive function and if so, are the effects long-term. We assess neurocognitive function quantitatively before and after DHCA and also in comparison with non-DHCA patients. 62 aortic surgical patients underwent a battery of neuropsychometric tests, both pre and post-operatively, evaluating multiple aspects of memory, processing speed, executive function, and global cognition. 33 patients did not require DHCA, and 29 underwent DHCA as the sole means of cerebral protection. Of these, 19 patients who tested positive for cognitive deficits, 8 of whom underwent DHCA and 11 who did not, were followed long-term with an additional testing months to years post-operatively. "Neurocognitive deficit" was defined as greater than 20% decline in two or more cognitive areas. Pre and post-operative test scores, as well as incidence of "neurocognitive deficit", were compared within each group (post versus pre-operatively), and between the non-DHCA and DHCA groups. There were no significant differences in the post versus pre-operative scores in any cognitive area tested between DHCA and non-DHCA groups. There was also no difference between the two groups in incidence of "neurocognitive deficit": 13 non-DHCA, 11 DHCA (p = 1.00). In addition, there was no correlation between time under DHCA and incidence of "neurocognitive deficit". Within both groups, there was a mild decline in memory in the areas of acquisition, retention, and delayed recall. Within the DHCA group, recognition was also affected. Time under DHCA up to 40 minutes was also found to be safe neurocognitively. Of the 24 patients that who incurred a "neurocognitive deficit," 19 participated in further follow-up, and of these, 4 DHCA and 2 non-DHCA patients had persistent memory deficits (p = 0.32). There was also no statistically significant difference in duration under DHCA between those who did or did not recover from their deficits (p = 0.56). DHCA patients who did have persistent memory deficits tended to have additional aspects of memory become affected when tested at further follow-up. There was a statistically significant difference in age, above or below 70 years old, between patients whose memory deficits persisted or recovered (p < 0.001). While cardiac surgery had some effects on memory, overall neurocognitive function was well preserved and did not differ between DHCA and non-DHCA patients. DHCA does not affect whether or not memory deficits incurred post-operatively persist, but in those patients who underwent DHCA whose memory deficits did persist, those deficits tended to affect additional memory aspects that on previous testing had not been affected. What does affect the temporal nature of memory deficits is age, with patients over the age of 70 having a higher incidence of persistent long-term memory deficits. This study provides strong evidence that straight DHCA effectively preserves neurocognitive function.

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This is an Open Access Thesis.

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