Into the depths: studies on intraoperative consciousness, postoperative neurocognitive disorders, and anaesthetic depth

Understanding and improving anaesthetic practice relies on investigating critical outcomes such as the appropriate depth of anaesthesia, preventing patient awareness during surgery, and managing cognitive decline afterwards. By extension, the work presented in this thesis is an effort at studying these topics.

Accidental awareness during anaesthesia is highlighted as a significant concern, representing a failure of anaesthesia's fundamental objectives. Existing studies on this topic underscore the challenges in accurately detecting intraoperative consciousness, using methods like the Isolated Forearm Technique (IFT) and electroencephalogram (EEG)-based Depth of Anaesthesia (DOA) monitors. Therefore, a large-scale study was conducted across multiple medical centres to determine the incidence of IFT responsiveness during routine anaesthetic practice. The study identified factors associated with responsiveness and found a lower incidence rate than previously reported.

The next part of this thesis explored depth of anaesthesia by assessing its possible neuroprotective effects. The impact of deep versus light anaesthesia on rat brains during hypoxia was investigated. This suggested potential neuroprotective benefits of deep anaesthesia. The use of dexmedetomidine was also explored, considering its role as an adjuvant to other anaesthetics and its possible neuroprotective mechanisms.

Additionally, the cognitive consequences of anaesthesia and surgery were discussed, including short and long-term disturbances. The relationship between physical inactivity and postoperative cognitive dysfunction was also explored in patients undergoing heart surgery.

Overall, this thesis aims to improve anaesthetic safety and efficacy by addressing critical clinical outcomes and proposing strategies for optimization. Ongoing research is vital for advancing patient care in this field.