Will “fatal surgery” really happen?

This is the 4985th article of Da Yi Xiao Hu

Xiao Li will have a laparoscopic cholecystectomy tomorrow. The doctor told him that the operation would require general anesthesia, and he couldn't help but get nervous. Because he had just watched a movie called "The Surgeon". In the movie, the male protagonist had intraoperative knowledge during a heart transplant. He knew everything during the operation, but he couldn't move, and couldn't tell the doctor about his experience... The male protagonist's experience of "being cut open, and the heart-wrenching pain and torture" made Xiao Li deeply suspicious of general anesthesia. However, a patient who had undergone surgery in the same ward told him: "I entered the operating room, the doctor gave me an injection, and I fell asleep soon. When I woke up, the operation was over. I had a dream. In the dream, I kept winning mahjong, and I was so happy." This made Xiao Li very confused. Which one is true?

The male protagonist in "The Surgeon" experienced intraoperative awareness, a serious adverse event during general anesthesia. Intraoperative awareness is shown to the general public in the form of a movie, which does cause people to panic. But will you experience intraoperative awareness during surgery? Can doctors detect it in time and prevent it from happening? Today, let us unveil the mystery of intraoperative awareness.

What is intraoperative awareness?

Intraoperative awareness is also called anesthesia awakening. It refers to the situation in which the patient feels pain due to incomplete analgesia during general anesthesia, but cannot move due to the effect of muscle relaxants and cannot express it to the outside world. In addition to pain, the patient will also have consciousness, touch, vision, hearing, temperature perception, etc. Postoperatively, the patient must meet the two conditions of being conscious during the operation and being able to recall the intraoperative events after the operation to be considered intraoperatively aware. The incidence rate is between 0.2% and 0.4%. Among all surgeries, the incidence of intraoperative awareness in cardiac surgery, obstetric surgery, emergency surgery, and brain trauma surgery is higher than that in other surgeries.

How to prevent intraoperative awareness?

However, there is no need to be overly anxious. Regarding intraoperative awareness, the anesthesia field has issued the "Guidelines on Intraoperative Awareness and Brain Function Monitoring" to guide clinical operations.

Screening high-risk patients

Before the operation, we will make routine visits to the patients, inquire about their basic conditions, and determine whether they are high-risk patients known during the operation based on their medical history, medication history, etc.

Use of drugs to prevent intraoperative awareness

For high-risk patients, we usually use benzodiazepines such as midazolam for prevention during preoperative induction.

Make adequate inspections and preparations: Before anesthesia, we will routinely check the anesthesia machine and monitor to ensure normal operation and accurate monitoring; because some surgeries require fixed body positioning, it increases the difficulty of our operations during surgery. Before the operation begins, we will check whether the venous access is unobstructed, whether the three-way connection is correct, and whether the intravenous push pump can work normally to ensure that the anesthetic will not fail to work due to the detachment of the pipeline during the operation, thereby reducing the depth of anesthesia.

Monitoring the depth of anesthesia

During the operation, we will use instruments to monitor the depth of anesthesia to ensure sufficient depth of anesthesia to avoid the occurrence of intraoperative awareness; we use intravenous inhalation combined anesthesia and maintain the end-expiratory anesthetic concentration at 0.9-1MAC concentration. When encountering highly irritating operations such as difficult airway intubation, we will add sedatives and analgesics to deepen the depth of anesthesia. We can also monitor the depth of anesthesia through various detection methods to reduce the incidence of intraoperative awareness. When muscle relaxation is not enough, the patient will experience muscle tension and body movement; when sedation and analgesia are not enough, the patient will experience increased blood pressure, faster heart rate, tears, etc. In addition to vital sign monitoring, we can currently monitor the depth of anesthesia by monitoring the bispectral index (BIS), auditory evoked potential index (AEP), entropy index, etc. The BIS system converts the depth of anesthesia of the human body into an index of 1 to 100 by analyzing the electroencephalogram. The awake state is 85-100. During the operation, we usually maintain the value between 45 and 60 to ensure the appropriate depth of anesthesia. A value below 40 means that the anesthesia is too deep, hemodynamic instability may occur during the operation, and awakening problems are likely to occur after the operation. By interpreting the changes in BIS data, we can understand the changes in the patient more quickly and make corresponding changes. Through bispectral index monitoring, the incidence of intraoperative awareness can be reduced by 80%.

How to determine whether intraoperative awareness has occurred?

Sometimes, after the operation, when the patient wakes up in the post-anesthesia care unit, he or she will suddenly say, "I could hear you talking during the operation." At this time, your anesthesiologist will be shocked and think frantically about whether the sedation and analgesia were sufficient? Was the depth of anesthesia sufficient during the operation? Was there anything special during the operation? At the same time, we will ask you the following 5 questions to determine whether you really had intraoperative awareness.

It is worth noting that the anesthesia method will also change in different surgeries. For example, spinal anesthesia, regional nerve block, etc., which we commonly call semi-anesthesia. In these surgeries, you will generally be awake throughout the whole process, but for some anxious and timid patients, we will use some sedatives appropriately, but the amount of these drugs is not much, and the patient may wake up when subjected to strong stimulation. Don't misunderstand that this is intraoperative awareness!!!

With our protection, you don’t have to worry about “fatal surgery” becoming a reality. Just take a nap, wake up, and the surgery will be over!

Author: Department of Anesthesiology, Shanghai Geriatric Center

Li Mingyu, Wang Shuxin

Review: Fang Hao