I. Overview
When patients are under deep sedation or general anesthesia, their protective choking and swallowing reflexes are weakened or absent. The relaxation of the esophageal dilator muscle makes it easy for gastric contents to reflux into the oropharynx, which can cause respiratory obstruction and aspiration pneumonia once inhaled accidentally, resulting in ventilation and air exchange dysfunction, difficult treatment, and high mortality. Patients undergoing local anesthesia are also at high risk of regurgitant aspiration if they become unconscious during the perianesthesia period or require intravenous sedative and analgesic drugs.
The incidence of anesthesia-related reflux aspiration has been reported to be about 5/10,000 in adults, twice as high in children, and 10 times higher in neonates and infants [1]. Therefore, the issue of fasting before anesthesia should be of great importance to anesthesiologists, related specialists, and patients and families.
However, for infants, children and individual adults, an excessively long fasting period can aggravate discomfort such as thirst and hunger, cause unnecessary crying or irritability in patients, and in severe cases, hypoglycemia and dehydration can occur. In order to ensure the safety of patients during the perianesthesia period and improve the comfort and satisfaction of patients during the perianesthesia period, we combined the relevant fasting guidelines of domestic and foreign anesthesiologists’ societies and formulated the “Guidelines for Fasting Before Surgical Anesthesia for Adults and Pediatricians”.
II. Purpose of fasting before surgical anesthesia
1.To reduce the volume of gastric contents, to prevent the pH of gastric acid from being too low, and to avoid the aspiration caused by gastric contents reflux during the perioperative period.
2. To prevent dehydration and maintain hemodynamic stability.
3.Stop hypoglycemia.
4.Prevent hunger, nausea, vomiting and irritability caused by excessive fasting and drinking.
Fasting time before surgery anesthesia
The main components of daily meals are carbohydrates, fats and proteins, which are emptied in the stomach at different times due to their different digestion and absorption sites and chemical structures. Therefore, different fasting times need to be developed according to the type of food intake.
(A) clear beverages
There are many kinds of clear beverages, including water, sugar water, carbonated beverages, tea, black coffee (without milk) and various kinds of dregs-free juice, but none of them can contain alcohol. In addition to the restrictions on the types of beverages, there are also requirements on the amount of beverage intake. The amount of clear beverages that can be consumed 2 hours before anesthesia should be ≤5ml/kg (or ≤300ml in total).
(II) Breast milk
The content of lactose and unsaturated fat in breast milk is significantly higher than that of cow’s milk and formula, while the content of protein, casein and saturated fat is significantly lower than that of cow’s milk and formula, forming fine granular milk lumps in the stomach, while breast milk contains lipase, amylase and other components that help infants and children digest and absorb. Therefore, the emptying time of breast milk in the stomach is significantly shorter than that of cow’s milk and formula milk, and its average time of emptying is 2.43h.
(C) Milk and formula
The main components of cow’s milk and formula are milk from cows or other animals, which have a high content of casein and saturated fat and tend to form larger lumps in the stomach, which are not conducive to digestion, and their emptying time in the stomach is significantly longer than that of breast milk, so cow’s milk and formula are often considered as solids and require a longer fasting time.
(D) starchy solid foods
Mainly refers to flour and cereals, such as buns, bread, noodles, rice, etc., whose main components are carbohydrates, containing some protein and little fat. Because the gastric juice contains amylase and protease, its emptying time in the stomach is significantly shorter than that of fatty foods, where the emptying time of starchy foods is shorter than that of protein foods.
(E) Fatty solid foods
Mainly refers to meat and fried food, due to its high fat and protein content, and the lack of corresponding digestive enzymes in the stomach, so its emptying time in the stomach is also longer.
Fourth, fasting and drinking precautions
1. Infants and new organisms with low glycogen reserves can be given intravenous infusion of sugar-containing liquid in the ward after 2 hours of fasting to prevent hypoglycemia and dehydration. Emergency surgery in fasting should also be supplemented with fluids. Diabetic patients should be scheduled for the first surgery as much as possible, if not, intravenous infusion of polarizing fluid can be given in the ward.
2.Patients taking oral carbohydrate solution 2 hours before surgery can prevent dehydration, improve circulatory stability, reduce the occurrence of postoperative nausea and vomiting, and also reduce the occurrence of postoperative insulin resistance.
3.Patients who need oral medication before surgery are allowed to crush the tablets and drink 0.25ml/kg~0.5ml/kg of water 1h~2h before surgery, but it should be noted that crushing is strictly prohibited for slow and controlled release preparations.
4, emergency surgery patients, according to the full stomach patient anesthesia treatment.
5.It is necessary to extend the fasting time for those who have the following conditions: patients with severe trauma, eating time to less than 6 hours of injury; patients with gastrointestinal obstruction; obese patients; patients with difficult airway; patients with central nervous system diseases such as craniocerebral injury, intracranial hypertension and coma.
6, Patients with high risk of aspiration (such as patients with reflux esophagitis), H2 receptor blockers (such as ramitidine 1.5mg/kg to 2mg/kg or cimetidine 7.5mg/kg) can be given appropriately before anesthesia.
7, gastrointestinal surgery or other surgeries have special or higher requirements for preoperative fasting and drinking, should be implemented according to the requirements of the specialist.