I. What is insulin? What does insulin do and how does it relate to blood sugar?
At the back of the human stomach, next to the duodenum, there is a long organ called the pancreas. There are many cell groups in the pancreas, which are scattered in different parts of the pancreas, like small islands in the lake and sea, so they are called islets. The islets are very small and can be seen under a microscope 〖The islets contain four types of cells: α cells that secrete glucagon, β cells that secrete insulin, and D cells that secrete growth hormone. Among them, β cells are the most numerous, accounting for about 60%-80% of islet cells. The hormone secreted by them is called insulin, which is composed of 51 amino acids, a small molecular protein with molecular weight of 57340, and is the main blood sugar-lowering hormone in the body.
Insulin is an endocrine hormone secreted by pancreatic islets in the pancreas, and it acts like a key that can open the door of cells. Insulin is the only hormone that allows glucose in the blood to enter the cells to be oxidized and produce energy, which is necessary to supply the energy needs of life.
Insulin is a very important hormone in the human body that lowers blood sugar. The secretion of insulin is regulated by blood glucose concentration, and its secretion is proportional to blood glucose level, which means that the higher the blood glucose, the more insulin is secreted. After a normal person eats, food is digested in the gastrointestinal tract and then absorbed into the blood through the intestines. After eating food containing more sugar, the glucose absorbed from the intestine into the blood gradually increases, the blood glucose level rises, and insulin secretion also increases rapidly. In a healthy person, blood glucose and insulin secretion generally reach their peak 1 hour after a meal and drop to the level of fasting in 2 hours.
Insulin is synthesized in pancreatic β-cells, and the precursor of insulin is insulinogen, which is hydrolyzed by protease in β-cells and broken down into insulin and C-peptide, which is secreted outside the β-cells and enters the blood circulation. Because C peptide is secreted into blood as an equal molecule with insulin, and the clinical measurement of plasma insulin is easily affected by other factors, the secretion status of endogenous insulin can be understood indirectly by measuring the plasma C peptide level.
Classification of insulin
1.Classification by source
Porcine insulin: It is extracted from pig pancreas and has an amino acid difference with human insulin, which is easy to produce antibodies.
Human insulin: Produced by genetic engineering or by biochemical conversion, it is made by replacing alanine with threonine in the beta chain on porcine insulin. Due to the difference in composition between porcine and bovine insulin and human insulin, antibodies to insulin are more likely to be produced in the patient’s body after injection, resulting in a gradual decrease in the potency of insulin, while human insulin does not produce antibodies.
Synthetic insulin analogues: The pharmacokinetic properties of insulin are affected by changing the structure of insulin molecules and other principles. It includes ultra-short-acting insulin analogues and ultra-constant-acting insulin analogues.
2.Classification by purity
Regular insulin: abbreviated as RI, containing insulin purity up to 90%, but also contains other impurities.
Single component insulin: abbreviated as MC, is ordinary insulin after molecular screening, the purity of insulin can reach 99.9%, so the dosage can be reduced.
3.Classification by duration of action and effect
Short-acting insulin: abbreviated as RI
Domestic: common insulin
Imported: Novolin R, Eugenol R
The effect starts 15-30 minutes after injection, the peak effect is 1-3 hours after injection, and the duration is 5-7 hours.
Features: fast acting, short duration, easy to adjust dose, can be used alone.
Medium-acting insulin: abbreviated as NPH
Domestically produced.
Imported: Novolin N
It takes effect 2-4 hours after injection, with peak at 6-10 hours after injection and duration of 18-24 hours.
Features: slow acting, suitable for those with poor fasting blood sugar control after using short-acting insulin, also can be combined with oral hypoglycemic drugs.
Premixed medium and long-acting insulin: abbreviated as mix, premixed human insulin 30R, 50R, 70, produced by NOVO Denmark Novo and Lilly America Eli Lilly. Among them: 30R: 30% is short-acting insulin, 70% is intermediate-acting insulin; 50R: 50% is short-acting insulin, 50% is intermediate-acting insulin
Long-acting insulin: abbreviated as PZI.
Domestic: fish protein zinc insulin, in which the ratio of fish protein to insulin is 2:1.
It takes effect 4-6 hours after injection, with peak effect at 10-15 hours and duration of 28-36 hours.
Characteristics; slow action, weak and long-lasting hypoglycemic effect, often irregular absorption, dose is not easy to adjust, so it is generally not used alone, often mixed with short-acting insulin and then injected. After mixing with short-acting insulin, the excess fisetin contained in it can rapidly bind with it and make the short-acting insulin long-acting, so this should be taken into account when calculating the actual effect in the body after mixing the two. Therefore, if you want to increase the dose of PZI, you must also increase the dose of RI by the same amount. For example, if you want to increase PZI from 2U to 4U, and the original injected dose is RI 10U + PZI 4U, you should change it to RI 12U + PZI 4U, so that the former is actually RI 8U + PZI 4U and the latter is RI 8U + PZI 8U in the body, and the RI dose remains unchanged, but only the dose of PZI is increased.
l Ultra-short-acting insulin analogues and ultra-regular-acting insulin analogues: Novalis insulin analogues (menadione insulin)
Third, what kind of patients should choose insulin therapy?
1.
Type 1 diabetes: insulin must be injected daily to sustain life because of almost complete loss of pancreatic islet function.
2.
Patients with type 2 diabetes mellitus who are significantly wasted can choose insulin therapy to restore ideal weight.
3.
Type 2 diabetic patients whose blood glucose control is still unsatisfactory after a long period of strict dietary control, suitable physical exercise and adequate treatment with various oral hypoglycemic drugs can choose insulin treatment for a period of time, and then switch to oral hypoglycemic drug treatment after their blood glucose is satisfactorily controlled and their pancreatic islet function is restored.
4.
Diabetic patients who have ketoacidosis, non-ketotic hyperosmolar diabetic coma and lactic acidosis should be treated with insulin (short-acting) regardless of the treatment originally used.
5.
If the chronic complications of diabetes mellitus are serious, such as unbearable pain of lower limbs caused by peripheral neuropathy, lower limb ulcers, gangrene and severe liver and kidney failure, insulin treatment should be chosen.
6.
Insulin therapy should be selected when diabetes is complicated by various acute infections or acute aggravation of chronic infections, trauma, surgery, fracture, anesthesia and acute cardiovascular and cerebrovascular pathologies (such as cardiovascular and cerebrovascular accidents and other cases).
7.
When a diabetic woman is pregnant or a gestational diabetic patient, insulin therapy should be chosen to prevent fetal malformation, giant fetus and the occurrence of neonatal hypoglycemia.
IV. Insulin administration methods
1.Syringe
1ml syringe: blue heart, can be used for various subcutaneous injections and intradermal injections.
Features: the needle is thicker and needs to be manually converted into units (4 U/0.1ml, only 400 u/10ml branches of insulin can be pumped), each time there is a large waste (consumption of about 2U/time), short life span and needs to be replaced each time (glass ones need to be sterilized each time).
BD’s insulin syringe: red cap, used only for insulin injection.
Features: sharp needles, easy to calculate, graduated units for insulin injection units (there are insulin syringes that can pump 40 U/1ml sticks, and there are also insulin syringes that can pump 100 U/1ml sticks of two kinds, and the two cannot be mixed), less waste.
Insulin injection pen: pen-shaped insulin syringe, shaped like a pen, the core of the pen is equipped with insulin is a round storage bottle.
Features: accurate injection dose, sharp needle, basically painless, portable, ready to use, easy to operate, no batteries, no waste, the refill is designed for the pen 300 U/3ml a insulin. (For diabetic patients who inject insulin, especially poor vision, can be used to confirm the insulin dose by hearing)
Needleless insulin syringe.
2.Insulin pump
It is a mechanical pump, a high-tech injection product, also called artificial pancreas, which can simulate the normal insulin secretion by the pancreas by inputting a small amount of insulin every hour.
Features: small, light and handy, portable, can be continuously infused, simulating normal pancreatic secretion. The additional amount of insulin can be given directly through the button on the pump during mealtime, which can make the patient’s blood glucose reach the normal blood glucose range and greatly improve the quality of life.
V. Choosing the injection site?
Subcutaneous injection is the most commonly used insulin injection method, which is to inject insulin into the subcutaneous adipose tissue, that is, the fat layer between the dermis and the muscle of the skin. The insulin injected into the subcutaneous layer will be absorbed by the bloodstream part by part, and the common sites available for injection are
1.Front outer part of upper arm
2.Lateral front of thigh
3.Hips
4, abdomen, below the belt (except around the navel).
However, the absorption of insulin in the above parts is different, with the absorption in the abdomen > thigh > upper arm, and the absorption of insulin in the active parts is the fastest, compared to the abdomen, which is less active and the absorption is the most stable; while the upper arm exerts more force during labor, the blood flow is faster, and the insulin is absorbed faster than usual when injecting in this part, which is more likely to cause the occurrence of hypoglycemia.
Points to note.
1, because insulin injection is long-term, and long-term injection in one part of the site will cause hard nodules caused by poor absorption and increased blood glucose, therefore, when injecting should be planned to rotate the injection site, you can plan to rotate the injection area in a single cell, each interval of two fingers or more, to avoid multiple injections in the same area, resulting in subcutaneous hard nodules, affecting the absorption of insulin.
2. After each injection, lightly press the injection site and do not rub the injection site to avoid rapid absorption of insulin, which may affect the regulation of blood sugar.
3.Insulin should be injected into the patient’s body immediately after pumping to prevent the pumping time from being too long and not injected into the body, causing failure.
4.Check the injection site frequently and gently press each injection site with your finger or palm. If there are lumps, ruptures, epidermal depressions or pains, skin color changes, etc., you should consult your doctor.
VI. Steps of insulin injection?
1.Preparation of supplies: insulin, syringe (or insulin injection pen), sterilized swab (iodine, alcohol), dry swab.
2. Steps.
Wash your hands and clean them.
Sterilize the insulin bottle, inject an equal amount of air, extract the number of units to be injected, cover the protective cap to avoid soiling the needle, and set aside. Use the insulin injection pen to directly rotate to and display the number of units of insulin dose to be injected and sterilize the needle.
Choose the injection site, sterilize, then inject and press again.
3. Caution.
Before using insulin, check the medicine bottle, pay attention to the expiration date and whether the bottle seal is undamaged.
If you use medium or long-acting insulin or premixed insulin, you should gently roll the vial on the palm of your hand and never shake the vial to prevent failure or reduced effectiveness.
When using a mixture of short-acting and long-acting insulin, the short-acting insulin should be drawn first, followed by the long-acting insulin.
Patients injecting insulin should have regular and quantitative meals to prevent hypoglycemia.
The needle should not be withdrawn too quickly, otherwise it will cause a drop of insulin to flow out of the needle and cause the injected insulin to be inaccurate. In addition, avoid injecting in places with hard knots, redness, edema, etc.
VII. Preservation of insulin
Preservation of insulin.
1. The used insulin can be stored in the refrigerator at 4℃, avoiding direct sunlight, high temperature (>35℃) and freezing (forbidden to freeze, it will become invalid after freezing). Generally speaking, a bottle of insulin is valid for 2-3 years.
2. After opening the cap, the validity of subcutaneous injection is three months, which can be stored at room temperature. The expiration date of unopened insulin can be noted, generally speaking, the expiration date of one bottle of insulin is 2-3 years.
3.Insulin stored at room temperature for less than six months (without opening the cap)
4, insulin in use on weekdays can be placed at room temperature, it is best not to take out the insulin from the refrigerator for direct injection, it is easy to cause local allergic reactions. The vial can be warmed up in your hands and then injected by suction when it is close to your body temperature.
VIII. What are the possible side effects of insulin injection?
1. Hypoglycemia: Hypoglycemic reaction may occur due to large insulin injection dose, failure to eat on time or too little food or too much activity after insulin injection, or diarrhea and other reasons without timely adjustment of insulin dose (hypoglycemic reaction treatment is omitted).
2, allergic reactions: a few patients may have allergic reactions to impure insulin or preservatives in insulin solution (such as toluene, etc.), manifested as skin itching and rash, etc. Treatment: replace pure human insulin or local injection, or switch to aspiration therapy or take desensitization therapy under the guidance of doctors.
3, subcutaneous fat atrophy: sometimes patients injected with porcine insulin can have subcutaneous fat atrophy and skin depression at the injection site, which is a kind of perversion reaction to porcine insulin. Treatment: replace the pure insulin or local oxygen at the injection site, physiotherapy, massage can make it slowly recover.
4, skin infection: due to the lack of strict disinfection caused by the injection of local skin redness, swelling, heat and pain, and even abscess infection. The treatment is to pay attention to skin cleaning and local disinfection of the injection, to keep the injection needle sterile, and not to let the injection needle touch any unsterilized items.
5, local hard nodules: caused when injecting in one site for a long time, the injection site should be changed frequently or local hot compresses should be applied.
6.Insulin edema: Very few people can have severe water and sodium retention and high edema after insulin injection, at this time, they should go to hospital promptly to exclude other causes of edema. Some people can use diuretics to reduce swelling and continue to reduce the dose edema will gradually disappear.
IX. What are the factors affecting the role of insulin?
1, the type of insulin: short-acting, medium-acting, and long-acting work differently, high concentration works slowly but strongly, low concentration works quickly but weakly.
2, the dose of insulin: the larger the dose, the longer the onset and duration of action.
3, the concentration of insulin: the higher the concentration, the slower the onset of action, and the fast and slow absorption of insulin varies from patient to patient. (U100 means high concentration, insulin 100 U/1ml, U40 means low concentration, insulin 40 U/1ml, two different insulin syringes can not be mixed).
4, the injection site of insulin: abdominal wall injection is faster absorbed than anterolateral femoral injection; more muscle activity is faster absorbed than less active places.
5, insulin injection route: intravenous injection is faster than intramuscular injection, intramuscular injection is faster than subcutaneous injection.
6, the purity of insulin: the higher the purity, the smaller the demand for insulin.
7, insulin antibodies: injection of insulin secreted by the pancreas of animals, more likely to produce insulin antibodies, a large number of antibodies can be combined with the insulin injected into the body to make it ineffective, so the amount of insulin for people with more antibodies will become increasingly large and less effective.
8, liver and kidney function: When the liver and kidney function is not complete, it can affect the clearance of insulin, make the half-life of insulin prolong, make the free insulin level in the blood circulation increase, and lead to serious hypoglycemia. Therefore, insulin dosage should be greatly reduced in renal failure, and medium and long-acting insulin should not be used.
9, stress factors: when the body is in a state of mental tension and stress (such as trauma, surgery), the secretion of stress hormones such as catecholamines that antagonize insulin increases, making insulin less effective and increasing blood glucose, when insulin dosage needs to increase (skeletal muscle sensitivity to insulin also decreases). For example, when fever and illness reduce activity, blood glucose will rise, when appropriate, the amount of insulin injections on weekdays should be increased.
10, the amount of physical activity: physical activity or exercise increases, which can increase the body’s sensitivity to insulin, thus reducing insulin dosage.
11.In addition, the choice of syringe, injection technique, drug delivery method and the site of injection will affect the effect of insulin.