Consciousness in deep hypothermic circulatory arrest: a feasibility study

Abstract Background Studies have not explored consciousness during deep hypothermic circulatory arrest (DHCA). However, as studies in cardiac arrest have identified a spectrum of consciousness, we sought to establish the feasibility of studying consciousness during DHCA. Methods This was a prospecti...

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Main Authors: Joshua Ross, Thomas Jan, Deane Smith, Anelly Gonzales, Aubrey Galloway, Natalia Leontovich, Tara Keshavarz, Analise Dickinson, David Friedman, Emmeline Koopman, Elise Huppert, Ian Jaffe, Christopher Burke, John Kern, Paul Stelzer, Ashraf Sabe, Rebecca Spiegel, Andrew Klein, Arvind Rajagopal, Gage Parr, Charles Deakin, Sam Parnia
Format: Article
Language:English
Published: BMC 2025-05-01
Series:Journal of Cardiothoracic Surgery
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Online Access:https://doi.org/10.1186/s13019-025-03484-w
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author Joshua Ross
Thomas Jan
Deane Smith
Anelly Gonzales
Aubrey Galloway
Natalia Leontovich
Tara Keshavarz
Analise Dickinson
David Friedman
Emmeline Koopman
Elise Huppert
Ian Jaffe
Christopher Burke
John Kern
Paul Stelzer
Ashraf Sabe
Rebecca Spiegel
Andrew Klein
Arvind Rajagopal
Gage Parr
Charles Deakin
Sam Parnia
author_facet Joshua Ross
Thomas Jan
Deane Smith
Anelly Gonzales
Aubrey Galloway
Natalia Leontovich
Tara Keshavarz
Analise Dickinson
David Friedman
Emmeline Koopman
Elise Huppert
Ian Jaffe
Christopher Burke
John Kern
Paul Stelzer
Ashraf Sabe
Rebecca Spiegel
Andrew Klein
Arvind Rajagopal
Gage Parr
Charles Deakin
Sam Parnia
author_sort Joshua Ross
collection DOAJ
description Abstract Background Studies have not explored consciousness during deep hypothermic circulatory arrest (DHCA). However, as studies in cardiac arrest have identified a spectrum of consciousness, we sought to establish the feasibility of studying consciousness during DHCA. Methods This was a prospective study across 10 hospitals with 36 DHCA patients undergoing thoracic aortic aneurysm repair or pulmonary endarterectomy. A tablet computer delivered audiovisual stimuli (images and names of three fruits) using headphones during each procedure as a potential test of implicit learning and explicit recall. We also established electroencephalography (EEG) and near-infrared spectroscopy (NIRS) to measure electrocortical markers of consciousness and cerebral oxygenation. Post-procedure interviews were carried out to test patients’ ability to recall the audiovisual stimuli as well other explicit memories. Primary outcomes: 1) Feasibility of establishing tests of explicit recall and implicit learning, 2) Electroencephalography testing during DHCA. Secondary outcomes: 1) Signs of explicit recall of memories or implicit learning, and 2) identification of electrocortical biomarkers of consciousness during DHCA. Results Overall, 29/36 (81%) had the tablet set up. All 36 had NIRS and EEG set up, but 9 (25%) had useable EEG data, and 23 (66%) NIRS data. Delta EEG waves were observed during circulatory arrest in 3/9 (33%) patients, while 1/9 (11%) had theta waves just prior to circulatory arrest. All others showed isoelectric pattern. 35/36 (97%) agreed to follow up interviews. None had explicit recall of the names of the three fruits, but 3/36 (9%) correctly guessed them as a potential sign of implicit learning and 3 (9%) recalled other memories including events around the procedure and themes consistent with a recalled experience of death. Conclusions A spectrum of consciousness and awareness, including signs of implicit learning and electrocortical biomarkers of consciousness may be present during DHCA, despite absence of visible signs of consciousness. This can be further used to help explain the negative psychological outcomes that cardiac arrest survivors face.
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spelling doaj-art-93de890981384556b60f18cc3fa650762025-08-20T03:22:11ZengBMCJournal of Cardiothoracic Surgery1749-80902025-05-012011810.1186/s13019-025-03484-wConsciousness in deep hypothermic circulatory arrest: a feasibility studyJoshua Ross0Thomas Jan1Deane Smith2Anelly Gonzales3Aubrey Galloway4Natalia Leontovich5Tara Keshavarz6Analise Dickinson7David Friedman8Emmeline Koopman9Elise Huppert10Ian Jaffe11Christopher Burke12John Kern13Paul Stelzer14Ashraf Sabe15Rebecca Spiegel16Andrew Klein17Arvind Rajagopal18Gage Parr19Charles Deakin20Sam Parnia21NYU Langone HealthNYU Langone HealthNYU Langone HealthNYU Langone HealthNYU Langone HealthNYU Langone HealthNYU Langone HealthNYU Langone HealthNYU Langone HealthNYU Langone HealthNYU Langone HealthNYU Langone HealthUniversity of WashingtonUniveristy of Virginia HealthMount Sinai HospitalBrigham and Women’s HospitalStony Brook University HospitalRoyal Papsworth HospitalRush University Medical CenterGeorge Washington University HospitalSouthampton General HospitalNYU Langone HealthAbstract Background Studies have not explored consciousness during deep hypothermic circulatory arrest (DHCA). However, as studies in cardiac arrest have identified a spectrum of consciousness, we sought to establish the feasibility of studying consciousness during DHCA. Methods This was a prospective study across 10 hospitals with 36 DHCA patients undergoing thoracic aortic aneurysm repair or pulmonary endarterectomy. A tablet computer delivered audiovisual stimuli (images and names of three fruits) using headphones during each procedure as a potential test of implicit learning and explicit recall. We also established electroencephalography (EEG) and near-infrared spectroscopy (NIRS) to measure electrocortical markers of consciousness and cerebral oxygenation. Post-procedure interviews were carried out to test patients’ ability to recall the audiovisual stimuli as well other explicit memories. Primary outcomes: 1) Feasibility of establishing tests of explicit recall and implicit learning, 2) Electroencephalography testing during DHCA. Secondary outcomes: 1) Signs of explicit recall of memories or implicit learning, and 2) identification of electrocortical biomarkers of consciousness during DHCA. Results Overall, 29/36 (81%) had the tablet set up. All 36 had NIRS and EEG set up, but 9 (25%) had useable EEG data, and 23 (66%) NIRS data. Delta EEG waves were observed during circulatory arrest in 3/9 (33%) patients, while 1/9 (11%) had theta waves just prior to circulatory arrest. All others showed isoelectric pattern. 35/36 (97%) agreed to follow up interviews. None had explicit recall of the names of the three fruits, but 3/36 (9%) correctly guessed them as a potential sign of implicit learning and 3 (9%) recalled other memories including events around the procedure and themes consistent with a recalled experience of death. Conclusions A spectrum of consciousness and awareness, including signs of implicit learning and electrocortical biomarkers of consciousness may be present during DHCA, despite absence of visible signs of consciousness. This can be further used to help explain the negative psychological outcomes that cardiac arrest survivors face.https://doi.org/10.1186/s13019-025-03484-wDHCACardiac ArrestCirculatory arrestConsciousnessLearningEEG
spellingShingle Joshua Ross
Thomas Jan
Deane Smith
Anelly Gonzales
Aubrey Galloway
Natalia Leontovich
Tara Keshavarz
Analise Dickinson
David Friedman
Emmeline Koopman
Elise Huppert
Ian Jaffe
Christopher Burke
John Kern
Paul Stelzer
Ashraf Sabe
Rebecca Spiegel
Andrew Klein
Arvind Rajagopal
Gage Parr
Charles Deakin
Sam Parnia
Consciousness in deep hypothermic circulatory arrest: a feasibility study
Journal of Cardiothoracic Surgery
DHCA
Cardiac Arrest
Circulatory arrest
Consciousness
Learning
EEG
title Consciousness in deep hypothermic circulatory arrest: a feasibility study
title_full Consciousness in deep hypothermic circulatory arrest: a feasibility study
title_fullStr Consciousness in deep hypothermic circulatory arrest: a feasibility study
title_full_unstemmed Consciousness in deep hypothermic circulatory arrest: a feasibility study
title_short Consciousness in deep hypothermic circulatory arrest: a feasibility study
title_sort consciousness in deep hypothermic circulatory arrest a feasibility study
topic DHCA
Cardiac Arrest
Circulatory arrest
Consciousness
Learning
EEG
url https://doi.org/10.1186/s13019-025-03484-w
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