Consciousness in deep hypothermic circulatory arrest: a feasibility study.

Area of Science:

• Neuroscience
• Cardiovascular Surgery
• Critical Care Medicine

Background:

• Consciousness during deep hypothermic circulatory arrest (DHCA) remains unexplored.
• Previous studies in cardiac arrest suggest a spectrum of consciousness.
• This study investigates the feasibility of assessing consciousness during DHCA.

Purpose of the Study:

• To determine the feasibility of studying consciousness during DHCA.
• To assess implicit learning and explicit recall in DHCA patients.
• To measure electrocortical markers of consciousness and cerebral oxygenation.

Main Methods:

• Prospective study in 36 DHCA patients undergoing thoracic aortic aneurysm repair or pulmonary endarterectomy across 10 hospitals.
• Audiovisual stimuli delivered via tablet and headphones to test implicit learning and explicit recall.
• Electroencephalography (EEG) and near-infrared spectroscopy (NIRS) used to monitor brain activity and oxygenation.

Main Results:

• Feasibility established: 81% had tablet setup, 100% had EEG/NIRS setup.
• EEG data showed delta waves in 33% and theta waves in 11% during arrest; others showed isoelectric patterns.
• No explicit recall of stimuli, but 9% showed implicit learning (guessing fruits) and 9% recalled other memories.

Conclusions:

• A spectrum of consciousness, including implicit learning and electrocortical biomarkers, may exist during DHCA.
• These findings suggest awareness despite the absence of visible signs of consciousness.
• Potential to explain psychological outcomes in cardiac arrest survivors.