In recent years, there has been a great development in nutrition, and the research on the nutrition of surgical patients has also achieved remarkable results. The wide application of complete gastrointestinal nutrition and the continuous improvement of elemental diet formulas have not only expanded the scope of surgical procedures, but also created favorable conditions for the later treatment of some complex patients. Therefore, we should pay attention to the management of nutrition of surgical patients and make it a key element in the surgical period for in-depth study.
A, the body’s normal need for nutrition Wuxi City Hospital of Chinese medicine Wu Chunfu
Normal people must take in enough nutrients from food every day to ensure the growth and development of the body, replenish the metabolic consumption, enhance resistance to disease and prolong life. A normal diet should include six nutrients, including protein, sugar, fat, vitamins, inorganic salts and water. Sugars (carbohydrates) and fats mainly provide calories, and proteins mainly provide nitrogen sources. Normal adults need to consume about 1,500-1,800 calories per day in the base case, and as the intensity of physical activity increases, the amount of calories needed increases accordingly. The percentages of total calories provided by carbohydrates, fats and proteins after metabolism are 60-70%, 20-25% and 10-15% respectively.
(i) Protein: After digestion, protein in food is absorbed by the body in the form of amino acids. Normal people need to supply 1-1.5 grams of protein per kilogram of body weight per day, one third of which comes from animal food. It is known that protein is composed of more than 20 different amino acids, eight of which are essential amino acids that cannot be synthesized in the body, and the rest are non-essential amino acids. Certain proteins in milk, protein and meat and globulin in soybeans contain various essential amino acids and are called “complete proteins”.
Protein is an important component of all body tissues. Its main functions are: maintaining the level of hemoglobin and plasma proteins; participating in the renewal and repair of tissues and organs; constituting enzymes, hormones and antibodies, and regulating various physiological functions. The content of nitrogen in protein accounts for about 16%, i.e. 6.25 grams of protein per day contains 1 gram of nitrogen. By measuring the nitrogen content in the urine for 24 hours, we can understand the daily protein consumption of the body. Under normal circumstances, the daily nitrogen excretion in the urine of adults is 4 grams, equivalent to 25 grams of protein, if the amount of excretion is lower than the amount of intake, the body is in a positive nitrogen balance, and vice versa is called negative nitrogen balance.
(ii) Fat: Fat in food is absorbed in the form of fatty acids and lipids. After fat absorption, a part of it is consumed to provide calories, another part is stored as reserve fat under the skin, in the abdominal cavity, in the interstitial muscles and around the kidneys, and a few is stored in the liver cells as phospholipids. The daily supply of fat should not be too much, and the total daily fat of normal adults should not exceed 40-50 grams. The fat intake, in addition to supplying 20-25% of the total daily calories, contains phospholipids and cholesterol, which are components of brain nerve tissue, and can also promote the absorption and utilization of some fat-soluble vitamins (A, D, E and K).
(C) carbohydrates: carbohydrates in food mainly in the form of glucose, fructose, lactose, plethora sugar and a variety of polysaccharides, after digestion and absorption. Most of the carbohydrates in the body are oxidized to produce heat, while another part is stored in muscle and liver cells in the form of glycogen, and a small amount exists in the extracellular fluid. The amount of glycogen stored in the body is very small, about 300 grams in total, and only about 1200 calories can be stored, which is only enough for 12 hours of consumption. The normal adult daily supply of sugar is 400-450 grams, and if the content of protein and fat in food is high, the sugar intake can be reduced accordingly. On the contrary, when the dietary sugar supply heat is sufficient, it is conducive to the synthesis of protein by amino acids, such as when 100-150 grams of sugar is supplied by the vein, 50-75 grams of protein can be saved.
In addition to providing calories and saving protein, carbohydrates are important components of the cytoplasm and nucleus, including ribonucleic acid and deoxyribonucleic acid, which are composed of sugar, phosphate and alkaline groups. And glycoproteins, which are produced by combining sugar and protein, are the components that make up cartilage, bone and cornea. The synthesis of large amounts of liver glycogen enhances the regeneration of liver cells and promotes the metabolism and detoxification of the liver.
(D) vitamins: more than 20 kinds of vitamins are known, most of which cannot be combined in the body and must be provided by food. Vitamins can be divided into two categories: fat-soluble and water-soluble: the former has vitamins A, D, E and K; the latter has vitamin C and B vitamins. Vitamins do not provide calories and do not constitute tissues, but they play an important role in maintaining growth and development and in regulating physiological functions. Patients with normal diet and good digestive function generally do not suffer from vitamin deficiency.
(E) minerals: food is rich in minerals, it only accounts for 4% of body weight, but are essential components of the body, in addition to constitute the raw materials of human bones and teeth, not involved in some important physiological functions. Trace elements are a very small part of the minerals, the content in the body is very small, can not be measured by ordinary methods. It is known that iron, iodine, fluorine, zinc, copper, cobalt, chromium, manganese, molybdenum, selenium, nickel, tin, silicon and alum are 14 kinds of trace elements, which are closely related to the organism and are essential for human body. There is no “stock” of trace elements, and insufficient intake can have certain effects on the body.
Second, the causes of nutritional deficiencies in surgical patients
(A) preoperative nutritional deficiency: most patients due to the impact of the disease itself, there are varying degrees of nutritional disorders before surgery. The reasons for the occurrence of: 1. Insufficient intake and absorption: acute and chronic gastrointestinal obstruction, the intake of nutrients is limited; chronic inflammation of the pancreas and small intestine, seriously affecting the digestion and absorption of nutrients. 2. Excessive consumption and loss: malignant tumors and hyperthyroidism, increased nutrient consumption; external fistula, chronic blood loss, massive burns and serious infections, causing a large number of nutrients constantly lost. In conclusion, each patient’s nutritional status should be determined before surgery. In conclusion, the nutritional status of each patient should be correctly judged before surgery, and those with severe nutritional deficiencies should be corrected in time. There is a lack of accepted, convenient and accurate unified standard for the estimation of nutritional status of inpatients. Clinically, we can use the comparison method between the patient’s hospitalization and standard weight to judge: if there is no edema after the disease and weight loss of 30% or more can be considered as severe malnutrition, and loss of 20% or more is quite severe or moderate malnutrition.
(2) Loss during and after surgery: Surgery itself is a kind of trauma, and the tissue damage and blood loss caused during surgery will definitely cause protein loss. For example, the average amount of protein lost in subtotal thyroidectomy is 75 grams, while the average amount of protein lost in radical breast cancer surgery is twice as much as that in subtotal thyroidectomy. Immediately after surgery, the metabolism in the body is in the catabolic phase, and protein decomposition is accelerated, while the excretion of urinary nitrogen increases significantly, even if a large amount of protein is given, it cannot change the patient’s negative nitrogen balance. The duration of negative nitrogen balance after surgery is closely related to the difficulty, duration and scope of surgery, generally 5-10 days (Table 1-26)
Table 2-26 Amount of nitrogen loss after various types of surgery
Name of surgery
Average nitrogen loss (protein)
Duration
Radical breast cancer surgery
15 g (94 g)
10 days
Inguinal hernia repair
18g (113g)
10 days
Perforated orchiocele excision
49g (306g)
10 days
Gastrectomy
54g (338g)
5 days
Myringotomy + pyloroplasty
75g (469g)
5 days
Cholecystectomy
114g (712g)
10 days
Ulcer perforation repair
136g (850g)
10 days
Third, the surgical patient nutrition supplementation pathway
(a) supplementation through the gastrointestinal tract: there are two methods of oral and tube feeding, diet types are ordinary diet, tube feeding diet and elemental diet.
1. Oral diet: oral intake of food is the most commonly used method, the most economical and convenient, and is also the ideal method. According to the needs of the disease, choose the ordinary diet such as flowing juice, semi-flowing and soft food. When the patient’s appetite is poor, the variety of meals and cooking techniques can be changed appropriately, and some drugs that are helpful for digestion should be added. In chronic diseases, adequate vitamins and electrolytes should also be given.
2. Tube feeding diet: Comatose patients who cannot eat normally and patients with advanced esophageal cancer and gastric cancer with gastrointestinal obstruction can be supplemented with nutrients through gastric tube, stomach or jejunum’s fistula. Currently, the commonly used tube feeding diet is mixed milk with fluid juice or semi-liquid, containing 140 grams of sugar, 35 grams of fat and protein each, and a total of 1015 calories per 1000 ml of mixed milk. The full amount is infused six times a day at regular intervals, and a small amount of other fluids is infused between the two times as appropriate.
3. Elemental diet: In recent years, elemental diet has been widely used clinically as the nutrition liquid for oral and tube feeding, with satisfactory results. The element diet is a kind of powdered frothy non-slag food with relatively balanced chemical composition, which can form a liquid-type stable suspension emulsion after rehydration. The liquid uses L-amino acid as the nitrogen source, glucose and plethora sugar as the energy source, and contains moderate amount of fat, electrolytes, multiple vitamins and trace elements, with more perfect nutritional value. At present, the commonly used commercial elemental diet is divided into two main categories: ① low-fat elemental diet: fat content only accounts for 0.8-2%; ② high-fat elemental diet: fat content accounts for 30%.
The biggest advantage of the elemental diet is that energy and nitrogen source materials can be absorbed without digestion or little digestion, and because it is a dregs-free diet, it can keep the intestinal tract clean, and because the nutrients are more comprehensive, it is suitable for various gastrointestinal diseases and can quickly restore the positive nitrogen balance. The complications of nutritional support therapy with elemental diet are not serious, but nausea, vomiting and diarrhea may occur when the concentration is too high and the speed of injection is too fast, and abdominal cramps may occur in some cases, which can be improved after changing the concentration and speed of diet. Long-term application pay attention to the supplementation of essential fatty acids, vitamins and trace elements to prevent the deficiency of these nutrients.
(B) Supplementation through the external digestive tract: broadly speaking, there are two types of superficial venous route and deep venous route.
1) Superficial intravenous route: nutrients are provided through peripheral superficial intravenous drip. It is mainly used for patients who are on short-term fasting. It is mainly used for short-term fasting patients, and isotonic fluids are fed to provide certain amount of calories and proteins. There are several kinds of nutrient solutions available for input.
(1) 5% or 10% glucose solution: Each 1000 ml of 5% glucose solution can provide 200 calories. Adults use glucose at a rate of 0.5 g/hour/kg, beyond which it is excreted in the urine. 25-50% glucose solution can provide more calories, but the concentration is too high and long-term application can cause phlebitis.
(2) Protein-based solutions: These substances include plasma, albumin solution, hydrolyzed protein and amino acid injection solution, which can provide a certain amount of protein. Reliance on plasma or whole blood transfusion to supplement the lack of protein. Although 5% hydrolyzed protein solution 500 ml can provide 25 grams of protein (equivalent to 4 grams of nitrogen), it is necessary to provide 800 calories of non-protein (equivalent to 4000 ml of 5% glucose solution) to fully utilize these proteins, and the reaction to intravenous drip is also greater, which has been replaced by compound amino acid injection. The currently produced commercial amino acid solution is L-type compounded crystalline amino acid solution, which contains 14-18 amino acids, but all of them contain 8 essential amino acids. The high branched chain amino acid solution contains 45% branched chain amino acids, which has better nitrogen saving effect than the commonly used balanced amino acid solution.
(3) Fat emulsion: 10% fat emulsion can provide 900 calories in 1000ml, which is a more satisfactory amount of heat supply. Fat emulsion can also provide enough essential fatty acids (linoleic acid and linseed oil), which can prevent essential fatty acid deficiency. It is less irritating and does not cause phlebitis when given through peripheral veins for a longer period of time. It can also be mixed with glucose or amino acids and does not cause metabolic disorders due to hypertonic diuresis and high sugar.
2. Deep vein route: The method of nutrient supplementation through superior or inferior vena cava cannula is clinically known as total extra gastrointestinal nutrition (TPN for short). The deep vein catheter is used to infuse a large amount of high-value nutrient solution at a uniform rate, which can provide the body with sufficient calories, amino acids and electrolytes to maintain the positive nitrogen balance, and can replace oral nutrition in long-term application.
(1) Insertion site: superior vena cava is better than inferior vena cava. The subclavian vein can be directly punctured from one side or the diameter head vein or external jugular vein can be incised and silicone catheter can be inserted.
(2) Preparation of nutrition solution: it should include basic nutrition solution, main electrolytes, vitamins and trace elements.
(1) Basic nutrition solution: there are more formulas, commonly used is 50% (or 25%) glucose 250 ml, plus 500 ml of compound amino acid solution (or 5% hydrolyzed protein solution), a total of 750 ml is calculated as one unit, of which the ratio of nitrogen to card should be kept at 1:150-1:200 is better. Start with one unit of nutrient solution per day and gradually increase to 4-6 units per day.
②Major electrolytes: add the daily required electrolytes to each unit of nutrient solution separately on average. The daily electrolyte supplementation dose is: potassium 80-110 milli-equivalent, sodium 125-150 milli-equivalent, magnesium 8-16 milli-equivalent, phosphorus 45-60 milli-equivalent.
③Vitamins: There are now intravenous multivitamin preparations, including water-soluble and fat-soluble vitamins, a total of 12 types, 1-2 doses per day. The daily requirement for adults is VitA: 25,000 units, D: 200 units, E: 10 units, C: 500 mg, C acid: 2.5 mg, Niacin: 150 mg, B2: 10 mg, B1: 15 mg, B6: 40 mg, and pantothenic acid: 15 mg.
Trace elements: For patients on long-term TPN support, it is important to maintain the balance of trace elements, and the daily requirement of trace elements is 0.3 mg of copper, 0.12 mg of iodine, 2.9 mg of zinc, 0.7 mg of manganese, 0.02 mg of chromium, 0.118 mg of selenium, and 1.0 mg of iron. At present, there are a variety of trace elements preparations in the clinic, which are very convenient to use.
(3) Precautions for clinical application
(1) The total daily amount should be mixed and dripped at an even rate within 24 hours. If the total amount of liquid is not enough, it can be supplemented with 5% or 10% glucose solution.
②In order to prevent the obstruction of the nutrition tube, if there is no contraindication, 5-10 mg of heparin can be added to each unit of nutrition solution.
③In the initial stage, 1 unit of insulin can be added for every 10 grams of glucose, and the amount of insulin can be adjusted according to the degree of urine sugar.
④Pay attention to the aseptic effect when preparing nutrition solution, change the infusion bottle and accessories daily, frequently change the dressing of the skin at the entrance of the nutrition tube, and maintain sterility.
⑤ Regularly recheck various electrolytes, blood sugar and urine sugar, liver function and kidney function, and adjust the dose and ratio of various ingredients at any time.
(4) Prevention and control of complications: complications can occur during the application of complete gastrointestinal nutrition, some of which are quite serious and should be detected early and dealt with in time.
Infection is one of the common complications of TPN. The source of infection can come from the skin entrance of the catheter, the catheter and the input high sugar solution. Clinically, the infection mostly presents as sepsis, often forcing the termination of treatment. Measures for prevention: frequent disinfection of the skin entry point of the catheter, daily replacement of the infusion connection system, nutrient solution should be freshly prepared under aseptic operation, and air filtration method and appropriate administration of antibacterial drugs during infusion.
②Metabolic complications: Metabolic disorders can occur if the nutrient solution is improperly prepared during long-term application of TPN. This group of complications includes paper glucose reaction, hyperglycemia and hyperglycemic hyperosmolar non-ketotic coma due to disorders of glucose metabolism, metabolic acidosis due to electrolyte disorders, hypophosphatemia due to hypomagnesemia, etc. The main measure of prevention lies in precise calculation and supplementation of various nutrients required by the patient, while more systematic and comprehensive monitoring should be carried out during the treatment process to provide clues for early detection and early treatment.
(3) Catheter-related complications: During puncture and intubation and infusion of nutrients, some catheter-related complications can occur, such as pneumothorax caused by accidental injury to the pleura during puncture, catheter breakage, twisting and improper catheter position during intubation. Air embolism is a serious condition that can lead to the death of the patient. Air embolism can occur during intubation or when changing infusion accessories. Therefore, vigilance and strict adherence to procedures are necessary to prevent such complications.