Intraoperative Awakening: Risk Factors

Often, anaesthesiologists, in the pre-anaesthesia consultation, we meet patients who are afraid of waking up during surgery. This “fear of waking up” This early awakening, called intraoperative awakening, does exist, but it is very, very rare. Patients who have to undergo surgery often refer to this fear in the consultation room with phrases such as “am I going to find out anything”, “I won’t wake up too early, will I” or “I don’t want to hear anything”.

Concept of intraoperative awakening and current strategies to prevent it

By intraoperative awakening we mean all those conscious memories of intraoperative events. These memories range from vivid experiences to vague dreams. The incidence of intraoperative awakening is estimated to be 0.1-0.2%. This is a very low incidence indeed, but it causes a lot of fear in patients who are going to undergo surgery under general anaesthesia.

Nowadays, anaesthesiologists have many strategies at their disposal to prevent this dreaded intraoperative awakening. In addition to the clinical assessment of autonomic signs such as heart rate or blood pressure, we have anaesthetic depth monitoring systems. The most widely used technology at present is called Bispectral Index (BIS) and consists of a type of electroencephalographic analysis that manages to show, with a high level of reliability, the level of hypnosis (anaesthetic depth) experienced by the patient.

BIS consists of electrodes placed in the frontotemporal area of the patient, which provide us with data that, after being processed, give us a numerical representation of the patient’s level of sedation. Moreover, this type of monitoring allows the anaesthesiologist to better dose the anaesthetic drugs. This allows us to better adapt our anaesthesia to the needs of each patient. In this way, we are able to individualise anaesthesia and thus reduce the complications associated with anaesthesia.

Are there different ways of intraoperative awakening?

Absolutely, yes. As mentioned above, intraoperative awakening can vary from vague memories where patients report hearing the operating theatre staff, to more specific memories, which are more specific to the patient and in which they report experiencing pain, a feeling of weakness or paralysis, and anxiety.

Risk factors for intraoperative awakening

💉 Anaesthetic superficiality

👶🏻 ♥️Some types of surgery such as obstetric and cardiac surgery

⏰ Prolonged surgeries

🚨 Urgent surgery

💊 Patients with increased pharmacological requirements. For example, in the case of patients with a previous history of intraoperative awakening, chronic alcohol or other drug intake, or genetic resistance to anaesthetics

what are the consequences?

We will usually find patients who will tell us in the postoperative period that they have heard conversations in the operating theatre and little else. These are patients who have been able to regain consciousness for a few moments but have a vague memory and have not experienced pain. In extreme cases, which are very rare, we will find bewildered patients in whom the intraoperative awakening has been experienced by them as a series of more vivid memories and who may present with anything from sleep disorders or anxiety to post-traumatic stress disorder. Clearly, in these cases, anaesthesiologists are prepared to offer psychological support and follow up of patients even after discharge from hospital.

In summary

Intraoperative awakening, although it exists, is very rare. We now have very advanced systems for monitoring the patient’s level of hypnosis. So, trust your anaesthesiologist and dismiss this fear and remember that the aim of our speciality is to ensure not only the safety of patients during surgery but also their comfort. Studies are currently continuing on methods of neurological monitoring of brain activity that may help us to completely eliminate this complication in the future.

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