A complete revelation about general anesthesia, helping you overcome your fear!

Author: Feng Jiayu Foshan First People's Hospital

Reviewer: Yao Weifeng, deputy chief physician, the Third Affiliated Hospital of Sun Yat-sen University

General anesthesia (abbreviated as "GA") is an important pillar of modern medicine. It allows patients to undergo surgery in a painless and muscle-relaxed state, ensuring the smooth progress of the operation while protecting the patient's life. However, many patients are still curious and confused about GA: "Is the anesthetic taken orally or by injection?" "Does GA feel like being drunk?" "Will I suddenly wake up during GA surgery?" In fact, patients after GA are like entering a magical "hibernation" state. Patients will fall asleep unknowingly and will not wake up until the operation is over. Modern anesthesia technology is very safe, and the anesthesiologist will monitor the patient's condition throughout the process to ensure the patient's safety and comfort.

1. What types of general anesthesia are there?

General anesthesia is subdivided into non-intubation general anesthesia, laryngeal mask general anesthesia and endotracheal intubation general anesthesia according to different airway management methods. Non-intubation general anesthesia is mostly used for short operations and examinations, such as painless artificial abortion, circumcision, painless gastrointestinal endoscopy, etc. The operation time is generally short and the dosage is small. The patient can sleep and wake up to complete the operation/examination. For operations that last for a long time, require high muscle relaxation, and require airway protection, such as cranial surgery, laparoscopic surgery, nasopharyngeal surgery, etc., the patient cannot breathe smoothly on his own, so the anesthesiologist needs to use professional tools and methods during the operation, such as inserting a laryngeal mask or endotracheal tube to help the patient breathe. Except for patients with short necks, small chins, things in the throat, etc., who are difficult to insert laryngeal masks or endotracheal tubes, in most cases, laryngeal masks or endotracheal tubes are inserted after the patient enters the anesthesia state, and the patient will not feel uncomfortable. Patients who have undergone surgery under general anesthesia will find a tube in their mouth or nose when they wake up. There is no need to panic, as the tube can be removed after they resume regular breathing on their own.

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2. Where is the anesthetic drug for general anesthesia administered?

Generally speaking, before performing general anesthesia surgery, an intravenous access will be established for the patient, that is, a tube will be placed in the patient's blood vessels so that the doctor can inject necessary drugs or other fluids into the patient through this tube during the operation. Most of the "tubes" here are intravenous catheters. If the operation does not require the hands to be sterile or the patient has no special needs, they are mostly left in the hands. If the patient's condition is serious, or there is a need for rapid intraoperative fluid replacement and medication, postoperative parenteral nutrition, etc., a central venous catheter will be placed in the patient before the operation, and the internal jugular vein (neck) or femoral vein (thigh root) that is thicker than the peripheral veins will be selected. With these venous accesses, you only need to inject anesthetics into the venous access to let the patient "fall asleep" safely.

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Some friends may say: "No, when I had surgery before, I was put on a mask full of plastic smell, and then I fell asleep after taking a few sips of anesthetics?" This... It is most likely that the anesthetics were oxygen! During anesthesia induction, in addition to infusing anesthetics through the "intravenous access" mentioned above, the anesthesiologist will also let the patient inhale high-concentration oxygen through the mask. This is to provide sufficient oxygen supply to patients who have entered the anesthesia state but have not been inserted into the laryngeal mask or tracheal tube, and to reserve a certain amount of tube operation time for the anesthesiologist. Some friends may ask: "Isn't there an anesthetic that can 'knock people down' after a few sips?" Yes, there are, and the pharmacological properties of inhaled anesthetics also make anesthesiologists tend to use it for anesthesia induction in certain situations. At this time, what is inhaled through the mask is a mixture of oxygen and drugs. However, if inhaled anesthetics are used for induction, air pollution will inevitably occur (anesthetics will leak into the air in the operating room). Therefore, inhaled anesthetics are not used for anesthesia induction of every patient, but are more used for anesthesia induction of children or other patients with special conditions who cannot cooperate with the opening of intravenous access, as well as anesthesia maintenance after the establishment of an artificial airway.

3. How long does the effect of general anesthesia last?

It is said that different professions are like different worlds. Sometimes the questions raised by patients really make anesthesiologists feel that they are so cute. For example, some patients think that the doctor should choose the duration of anesthesia before the operation, such as 30 minutes, 1 hour, or 2 hours, and then the doctor should complete the operation before the set anesthesia time is over, just like in a game. There are also many patients who think that the anesthesiologist will run away after "knock them down" with one shot, and they are worried that they will wake up before the operation is completed, or that they will still be in anesthesia after the operation is completed. In fact, from the beginning of using drugs to put the patient into an anesthesia state, to adjusting the dosage of anesthetics according to the progress of the operation, until the patient wakes up from anesthesia after the operation, the anesthesiologist monitors the patient's condition throughout the process. Generally speaking, current general anesthesia operations are mainly based on the combined use of short-acting anesthetics, and most patients will wake up within half an hour after the operation.

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4. Under general anesthesia, will the patient feel pain during the operation?

The basic requirements of general anesthesia are loss of consciousness, complete analgesia, muscle relaxation, and suppression of stress response. Therefore, for most patients who have undergone general anesthesia, they will not feel pain during the operation. However, there is one exception, that is, "intraoperative awareness", which means that the patient under general anesthesia regains consciousness or feels pain during the operation, but the body cannot move, and can recall the events related to the operation after the operation. Due to different patient groups, assessment methods, and anesthesia practices, the incidence of intraoperative awareness varies greatly. The incidence is lowest in pediatric patients [1], and can be as high as 1/256 to 1/670 in obstetric patients [2-3]. In many different large-scale studies, the incidence of intraoperative awareness in general anesthesia surgery is 1.7/10,000 to 1.5/1,000 [4-5]. There is no need to panic.

To sum up, anesthesiologists usually administer drugs through intravenous access for general anesthesia. After general anesthesia, patients are usually unable to perceive the situation during the operation and usually wake up about half an hour after the operation. In layman's terms, "the operation/examination is done after a nap." Therefore, patients do not need to be too nervous!

【References】

[1] LEE AC, REDDING AT, TJIA I, et al. Self-reported awareness during general anesthesia in pediatric patients: A study from Wake Up Safe[J]. Paediatr Anaesth, 2021, 31(6): 676.

[2]PM ODPR, S BAMPOE, DN LUCAS, et al. Incidence of accidental awareness during general anaesthesia in obstetrics: a multicentre, prospective cohort study[J]. Anaesthesia, 2021, 76(6):759.

[3] PANDIT JJ, ANDRADE J, BOGOD DG, et al. 5th National Audit Project (NAP5) on accidental awareness during general anaesthesia: summary of main findings and risk factors[J]. Br J Anaesth, 2014, 113(4): 549.

[4]BOMBARDIERI AM, MATHUR S, SOARES A, et al. Intraoperative awareness with recall: a descriptive, survey-based, cohort study[J]. Anesth Analg, 2019, 129(5):1291.

[5]CHANG L, LUO Q, CHAI Y, et al. Accidental awareness while under general anaesthesia[J]. Biosci Trends, 2019, 13(4): 364.