Trinity study helps to identify those who require higher doses of anaesthetic

Some common experiences recalled by those who have had subjective experiences throughout their procedure included hearing voices or the sound of equipment, and the sensation of paralysis or pain.

Although anaesthesia has been used in clinical medicine for more than 150 years, aiding medical staff in completing many important procedures and surgeries with ease, it does not come without its complications.

The effect it has on individuals is extremely varied, with scientists still at a loss as to why this is the case.

Recent studies conducted by Trinity College Dublin have shown that one in four patients presumed to be unconscious during general anaesthesia may have been having subjective experiences, such as dreaming.

In very rare cases, (0.05% - 0.2%), individuals have become "accidentally aware" during a medical procedure.

Some common experiences recalled by those who have had subjective experiences throughout their procedure, also known as intraoperative awareness, included hearing voices or the sound of equipment, and the sensation of paralysis or pain.

Many of the experiences reported have negative connotations such as the awareness of tracheal intubation, which resulted in patients feeling unable to breathe.

These sensations are often accompanied by feelings of anxiety, panic, and fears of being permanently paralysed or dying.

Scientists in Trinity have identified brain structures which hold invaluable information in the prediction of an individual’s chance of having accidental awareness under an anaesthetic.

The findings of the study, published in the journal Human Brain Mapping, could help identify individuals who may require higher than average doses of anaesthetic.

One key takeaway from the research was the identification of differences in brain structure of participants who were resistant to anaesthesia versus those who remained fully unconscious. These brain differences could be noted before they were given anaesthesia.

Associate professor of psychology Lorina Naci said this breakthrough could have “important implications for patient safety and wellbeing”, allowing medical professionals to have improved “monitoring of awareness during clinical anaesthesia”.

“Although rare, accidental awareness during an operation can be very traumatic and lead to negative long-term health outcomes, such as post-traumatic stress disorder, as well as clinical depression or phobias.”

Lead author on the paper, Professor Naci said although there were several types of technology used to monitor whether the patient was adequately sedated, several factors were not fully understood yet, and could limit the accuracy of these monitors, including patient age, genetic background, intensity of the surgical stimulus, the use of other drugs in the anaesthetic cocktail, and the presence of multiple medical conditions.