Why are you not allowed to eat before anesthesia?

The operation is coming soon, so I need to take a few bites to replenish my energy.

I will have an operation later, so I need to drink some water to calm my nerves.

Don't!

Before the operation, many patients had this question: didn't you say that you should sleep during the operation? Why can't I eat and drink before going to bed?

In fact, the experience of letting patients "sleep" during the operation is what we are pursuing. It is actually an advanced job to make you "sleep well and wake up safely". Advanced to the point of not breathing, we will manage breathing; You don't feel pain, neither deep nor shallow; The occurrence of arrhythmia and the fluctuation of blood pressure during your operation are regulated.

Seeing this, everyone knows that this "deep sleep" is dangerous, and some risks can be greatly reduced through perfect preoperative preparation.

The purpose of fasting water before operation is to completely empty the stomach, reduce the contents of the stomach, reduce the acidity of gastric juice, and prevent aspiration pneumonia caused by reflux of stomach contents with high acidity such as lung.

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Then, why is the stomach contents likely to return to the lungs during general anesthesia?

Because the physiological function of preventing reflux aspiration during general anesthesia is inhibited, the factors leading to reflux increase.

First, under general anesthesia, the sphincter at the lower end of the esophagus relaxes. In normal people, the pressure of the part of the esophagus connected with the stomach (lower esophageal sphincter) is higher than that of the stomach to prevent the stomach contents from entering the esophagus reversely. However, under general anesthesia, due to the inhibition of nerves, the lower esophageal sphincter relaxes and the pressure zone disappears, which leads to reflux.

Second, under general anesthesia, swallowing reflex and cough reflex are inhibited. The former reflex promotes the swallowing of food in the pharynx into the stomach, while the latter reflex prevents foreign bodies in the throat from entering the trachea. Under normal circumstances, even if we have reflux of stomach contents (vomiting), we can avoid them from entering the lungs (vomiting, swallowing and coughing). However, both reflexes are inhibited under general anesthesia, and the risk can only be reduced by reducing hidden dangers (stomach contents).

Thirdly, during anesthesia and surgery, there are many factors that cause the increase of gastric pressure. For example, some anesthetics themselves can increase the intragastric pressure, and other conditions, such as wearing a mask, surgery, and coughing when patients wake up, will lead to higher pressure than the lower esophageal sphincter, and then reflux will occur.

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Therefore, during general anesthesia, patients undergoing non-emergency surgery need to be deprived of water before operation. But everyone's requirements for fasting water are different, which is related to age and physical condition. Let's talk about this in detail when the next question comes up.

Anyone who has had an operation should know that the doctor will explain the precautions of the operation to the patient the day before the operation. For example, I often say which xxx bed is going to have surgery tomorrow, 12 pm can't eat or drink after that.

Some patients may have misunderstandings. It doesn't matter if you don't eat or drink. I'll eat something else without affecting the operation. I met a patient. When I met him in the ward, the doctor asked: No food, no water. The patient replied very neatly: no, the doctor asked again, didn't you eat anything else? The patient replied: I just ate a small apple half an hour ago. The doctor was helpless and told the patient to postpone the operation.

After anesthesia, patients feel no pain, muscles are in a relaxed state, and normal physiological reflex will disappear. There are many kinds of anesthesia, which will be risky, and the smooth operation can not be separated from the cooperation of patients.

After anesthesia, the patient's muscles are in a relaxed state, and the normal physiological reflex will disappear. If the patient is in a "full" state, the contents of the stomach may reflux and aspiration, leading to pneumonia. When vomiting, stomach contents may block the respiratory tract, leading to suffocation and death. Therefore, surgical patients must pay attention to everything the doctor tells them.

Different patients have different fasting and drinking times.

Therefore, in order to ensure the safety of anesthesia, surgical patients should have a regular fasting and strictly follow the requirements of fasting and drinking. 1. Adult anesthesia: Fasting for at least 6 hours and drinking for 4 hours before anesthesia to ensure gastric emptying. 2. Anesthesia in children: Children can be fasted for drinking water for less than adults, fasting for 4 8 hours before operation and water deprivation for 2 3 hours. 4. Patients with acute abdomen and severe trauma should retain gastric tube before anesthesia, reduce gastric contents appropriately, use antiemetic drugs before operation, and prepare aspirator and transparent mask.

We must do a good job in the preoperative visit of patients undergoing surgery, and explain the importance of fasting and drinking to patients and their families (especially the families of children) to ensure the smooth operation.

Answer: Zhang Xiaoyu, Master of Medicine.

"So-and-so, I have an operation tomorrow. I can't eat anything after ten o'clock tonight, not even water! " This is what clinicians often tell patients the night before surgery. Most patients are confused and even think that they need surgery. They should eat or drink something to replenish their energy. Actually, it's not.

Why can't I eat before the operation?

Clinically, patients have a perioperative period before operation, mainly for patients to make preoperative preparation and promote postoperative repair. One of the perioperative management is gastrointestinal preparation, which generally means fasting 8 ~ 12 hours before operation and drinking water 4 hours before operation. The main reason is that muscle relaxants are used in anesthesia. If the stomach is not emptied, it may lead to reflux of stomach contents, and the patient will be in an unconscious state after anesthesia, which is very likely to cause asphyxia or aspiration pneumonia during anesthesia and surgery. This is very critical. Some operations, even preoperative gastrointestinal decompression, to meet the needs of surgery.

Patients involved in gastrointestinal surgery usually start liquid diet 1 ~ 2 days before operation. Patients with pyloric obstruction need gastric lavage before operation. For general surgery, soap and water enema should be performed on the day before surgery as appropriate. For colon or rectal surgery, clean enema or colon enema should be performed as appropriate on the day before operation and in the early morning of the day of operation, and intestinal antibacterial drugs should be taken orally 2 ~ 3 days before operation to reduce the chance of postoperative infection.

Therefore, fasting and drinking before surgery is for the safety of patients, rather than doctors deliberately refusing to eat. For general anesthesia, it is necessary to strictly abstain from diet, because once asphyxia and aspiration pneumonia occur, it will endanger the life of patients. As a doctor, we should not only let the patients fall asleep quietly and perform the operation smoothly, but also let the patients wake up safely.

This question is a good question, and it is also the confusion of many patients.

Why are you not allowed to eat before anesthesia? A similar question is, why do you want to fast before doing bronchoscopy, gastroscopy and colonoscopy?

Physiologically, the lower esophageal sphincter at the junction of esophagus and stomach can act as a "gate" to prevent food and gastric acid from flowing back to esophagus and oral cavity.

Under anesthesia, the lower esophageal sphincter is anesthetized and in a relaxed state, and the function of this "door" disappears. If there is food in the stomach, it may flow back to the esophagus and mouth. However, under anesthesia, some normal physiological functions of the human body (swallowing reflex and coughing reflex) are suppressed and the reflex disappears. These gastric contents (including food) that flow back to the mouth may regurgitate and vomit, and be sucked into the trachea by mistake, leading to aspiration pneumonia, which may be serious. At the same time, some anesthetics can increase the pressure in the stomach. During the induction of anesthesia, the pressure in the stomach may be increased by pressurized oxygen supply from the mask and the patient coughing, which may lead to reflux of gastric contents.

Inhalation is a serious complication in clinical anesthesia, and it is also a key concern of anesthesiologists. Therefore, in addition to simple local infiltration anesthesia, other anesthesia methods should be fasting and drinking water before operation, which is also the key issue for anesthesiologists to follow up patients before operation. In my years of anesthesia work, I have to follow up the patients the day before the operation. It must be noted that fasting and drinking are forbidden, and adults usually start fasting at least 8 hours before anesthesia. Children are also forbidden to fast and drink water at least 8 hours before operation, but infants can be fed glucose water every 4 hours before operation. ASA children in the United States are forbidden to drink water for 2 hours, drink water for 4 hours and eat food, including milk, for 6 hours within 36 months.

It is necessary to explain the importance of fasting and drinking to patients and their families in order to win cooperation. I have also met patients who secretly drink water, milk and even biscuits because of thirst and hunger. No way, the operation was postponed until the fasting time was enough to allow them to enter the operating room again for anesthesia.

There is a situation that anesthesia is needed even after eating (full stomach), that is, emergency anesthesia for emergency surgery, which is also a difficult problem that anesthesiologists sometimes encounter, because people who are full have a high probability of aspiration and high risk, and the harm caused by aspiration is often fatal. The principle of anesthesia management, as far as possible to reduce and deal with the risk of perioperative reflux aspiration, all considerations are based on the safety of patients with full stomachs.

thank you

Friends who have had surgery, especially general anesthesia surgery, should know that before the operation, the doctor will tell you when to start fasting water, and hold back! Don't eat when you are hungry, and you can't drink water!

Why is this? It's the doctor who deliberately makes things difficult for people! No! This is a doctor to protect you! Let you go to the operating table as safely as possible, and then come down safely!

When there is a lot of food in the stomach, there may be a risk of aspiration during general anesthesia. You can't control your body when you fall asleep under anesthesia. At this time, due to drugs, the lower esophageal sphincter will relax. If there is no emptying in the stomach, there will be reflux, which will cause aspiration pneumonia and even vomiting. Vomiting will block the airway and may be fatal!

Therefore, in order to avoid this risk as much as possible, the stomach will be emptied as much as possible before the operation, and nothing will be eaten or drunk beforehand. Everyone must follow the doctor's advice, follow the doctor's advice!

There used to be a classic joke. The doctor told the patient not to eat or drink before the operation. As a result, the patient is very obedient. During the operation, I told the doctor that I didn't eat or drink, so I ate two cakes and drank a cup of milk tea!

"Hello, I am your anesthesiologist. You will have an operation tomorrow. I need to know something about you ... I can't eat or drink after ten o'clock tonight. " I believe that many people will hear such advice from anesthesiologists before surgery!

So what is the scientific basis for not eating before surgery?

Whether it is general anesthesia or local anesthesia, we will require fasting before operation, in order to avoid local anesthesia becoming general anesthesia during operation.

We know that after general anesthesia, many physiological protection mechanisms have lost their functions. The main reasons related to anesthesia here are sphincter relaxation, throat reflex and epiglottis out of control. If you don't fast, food residues that cause vomiting will enter the respiratory tract, causing aspiration, pneumonia and suffocation, which can directly lead to death.

So what principles should be followed before fasting:

Fasting mainly depends on how long food stays in the stomach. According to the latest anesthesia guidelines, preoperative fasting follows the 2468 principle:

A small amount of drinking water is prohibited within 2.2 hours.

4: refers to breast-fed babies. It is forbidden to drink breast milk within 4 hours. If it is milk, it will take 6 hours.

6: refers to digestible carbohydrates without fat and meat, such as steamed bread and porridge, and fasted for at least 6 hours.

8: Fasting ordinary food for at least 8 hours.

For people with traumatic emergency, intestinal obstruction or gastrointestinal peristalsis, we usually treat them with satiety, just for fear that there will be food residue in the stomach that will cause aspiration!

Your praise and concern are our greatest support.

Xiong Chaogang, Xi 'an Chest Hospital

I believe many people know that anesthesiologists will deliberately emphasize that they can't eat when talking to patients before surgery, but not all operations can't eat. Different anesthesia methods have different requirements for fasting.

Anesthesia surgery is divided into local anesthesia and general anesthesia. Local anesthesia refers to the conscious application of local anesthetics to the body to temporarily block the sensory nerve conduction function in a certain part of the body, while the motor nerve conduction remains intact or blocked to varying degrees. Some minor body surface operations use local anesthesia, such as thoracic puncture and lumbar puncture. General anesthesia refers to the temporary inhibition of general anesthesia on the central nervous system, and its clinical manifestations are loss of consciousness, general pain, forgetfulness, reflex inhibition and skeletal muscle relaxation. General anesthesia is generally used for major operations, such as thoracoscopic surgery and laparoscopic surgery.

Under local anesthesia, because the consciousness is not affected, there is no risk of reflux aspiration, and people can't help eating, such as thoracic puncture or abdominal puncture. But you can't eat before local anesthesia through the digestive tract and respiratory tract.

For general anesthesia, it is necessary to strictly prohibit eating and drinking, because emptying the stomach contents can avoid reflux and vomiting of the stomach contents and inhalation into the trachea. Reducing stomach contents can reduce the risk of reflux and aspiration during anesthesia. Once reflux and aspiration occur, it may burn the airway and even cause aspiration pneumonia.

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Before anesthesia, doctors often ask patients to fast. Why? Why not let the patient eat before anesthesia?

In fact, in clinical anesthesia, aspiration is a very serious complication, and it is also the focus of clinical anesthesiologists. Generally speaking, in addition to simple local infiltration anesthesia, other anesthesia methods require patients to abstain from food and alcohol. For adults, fasting usually begins at least 8 hours before anesthesia, while children also fast and ban alcohol at least 8 hours before surgery.

Clinicians must pay attention to the importance of fasting and drinking before operation, and explain it clearly to patients and their families in order to win their active cooperation. For some special cases, even if the patient has eaten, that is, when he has a full stomach, anesthesia surgery must be performed at this time, which generally refers to emergency surgery anesthesia for first aid and rescue.

However, the probability of aspiration in patients with satiety is often high, and the risk of clinical onset is also high. Therefore, in practice, doctors should try their best to reduce and deal with the risk of reflux aspiration during perioperative period, and try their best to reduce some unnecessary hazards on the premise of the safety of patients with full stomachs.

Instructor: Wang Jiashuang, national second-class professor, chief physician, top ten famous doctors in Guangzhou. Former vice chairman of Pain Society of Chinese Medical Association, chief expert of Pain Department of Jinshazhou Hospital of Guangzhou University of Chinese Medicine, and lifelong honorary professor of Pain Department of Guangzhou Red Cross Hospital of Jinan University Medical College.

Specialty: Specializing in the treatment of neuropathic pain, especially the diagnosis and treatment of post-herpetic neuralgia and cervical and lumbar disc herniation.

The purpose of fasting before anesthesia is to reduce gastric acid secretion and increase the PH value of the stomach, thus reducing the risk of chemical system damage caused by accidental inhalation of lung caused by vomiting and reflux. Anesthesia, drugs used in surgery and surgeon's operation, especially gastrointestinal surgery, will all lead to reflux of gastric contents in patients' surgery. If inhaled into the lungs, it will cause chemical damage. The higher the acidity, the more serious the injury, and even the possibility of death. Therefore, water must be fasted before the operation. Emergency surgery can't require an empty stomach because of the critical condition, but you must tell the anesthesiologist whether you have eaten or drunk, so that the anesthesiologist can be prepared to prevent aspiration.

Muscle relaxants are mainly used during anesthesia. If the stomach is not emptied, it may lead to reflux of contents. If choking into the lungs, it will lead to aspiration pneumonia, which may be life-threatening in severe cases.