The concept of isotonic hypotonic and hypertonic solutions. Hypertonic saline solution: description, indications for use, how to prepare

Bleeding: atonic and hypotonic The most important and most dangerous complications early postpartum period are hypotension and atony of the uterus. To date, it has been established that bleeding that occurs in the first 2 hours of the postpartum period is most often

The loss of body fluid is called dehydration, or dehydration. Dehydration can be physiological (sweating) and pathological (diarrhea, bleeding, etc.). Replenishment of fluid volume is called rehydration, and it can be carried out on an emergency basis intravenous administration large volumes of different solutions, blood and blood plasma, as well as gradually by taking liquids inside. Other routes of administration of fluids are less commonly practiced.
Many sources say that during a cold, especially accompanied by high temperature body, must be taken a large number of liquids. But this is not an entirely accurate statement, and against the background of the body's fight against infection, a large water (liquid) load can be harmful.

What is important to remember before starting additional fluid intake? A few basics water-salt metabolism, which will be discussed next.
You will be absolutely right if you remember the well-known postulate that the human body consists of 75-80% water, but this amount of water is only in newborns and young children. The adult human body contains 60 to 65% (men) and 50 to 60% (women) of water. At an older age percentage water drops slightly. About 85% of the brain is fluid, and bone tissue there is only 10-15% water.

Of all the water contained in the body, 60% of it is inside the cells (in the cytoplasm and nucleus), the rest is outside the cells (extracellular). in blood and lymphatic vessels there is about 20% of the remaining fluid, and the remaining 80% is the fluid of the gastrointestinal tract and interstitial fluid.
The cell membrane, like cells, is not water-soluble, but at the same time, no substance can penetrate the cell if it is not dissolved in water and is not in the form of ions. A number of organic substances for assimilation require a connection with special carrier proteins, as well as the presence of enzymes (enzymes).

In reality, there is no pure water in the human body. We are all, without exception, a reservoir of saline solutions. The presence of salt ions and a number of other substances (carbohydrates, fats and proteins) creates a certain acid-base environment, as well as a specific pressure, which is called osmotic pressure. Osmotic pressure plays important role in the exchange of salt ions (electrolytes) through the cell wall, and all the vital processes of the body are based on it.
Osmosis characterizes the penetration of water through membranes. If the cell is placed in clean water, water molecules will begin to penetrate into the inside of the cell, since there is a certain concentration of salts in the cytoplasm of the cell. In this case, the cell increases in size (swells, swells) and may even die. The absorption of water is a necessary life process (for example, by plant roots from the soil).
On the contrary, if a cell is placed in a solution whose concentration of salt ions is higher than the intracellular concentration, the cell will begin to lose its fluid, that is, shrink in size, because water molecules will be the first to leave the cell.

Probably many of you have heard the word " isotonic”, especially if you had to be treated in a hospital. Isotonic solutions are used for intravenous drips when it is necessary to inject a large amount of liquid or when the drug must be administered into low concentrations And a long period time, as well as for different injections.
The concept of "isotonic" refers to "tone", that is, the osmotic pressure that occurs when there are different concentrations of solutions outside the cell and inside the cell. Moreover, the osmotic pressure does not depend on the type of substance, but on its concentration. "Isotonic" means almost the same osmotic pressure across different sides cell membrane, when water exchange through it is practically not observed or it is in a balanced state. In this case, the cell becomes "open" to ions of minerals and other substances.
The closer the isotonicity of the injected solutions, including through the mouth, the better they are perceived by the human body, which constantly compares all substances on a scale of "self-foreign", and therefore with less aggression.

Physiological sodium chloride or glucose solution has almost the same osmotic pressure as human blood and intracellular fluid, therefore does not cause cell destruction. It quickly replenishes the volume of fluid in the body without seriously disturbing water-electrolyte exchange. At the same time, drugs can be administered through isotonic solutions, the absorption of which is significantly improved.
Hypertonic saline implies a greater concentration of substances, which means a greater osmotic pressure on cell membrane, therefore, with the introduction of such solutions, the cells will begin to lose their own (cytoplasmic) fluid.

Hypotonic solution means a lower concentration, which means a lower osmotic pressure outside the cells, so the first of these solutions to penetrate into the cell will be water molecules.

The figure shows the effect of different types of solutions on the state of erythrocytes. Therefore, when introducing medicinal substances, especially intravenously, their osmolarity must be taken into account.

Now we've come up To a question water regime . In some sources you will find the statement that to maintain health you need to drink at least 8 glasses of water (up to 2 liters of water) per day, however, such a statement is based only on theoretical assumptions, and not on scientific facts.
With food you get up to 1 liter of water. Your body produces 600-700 ml of water as a result of chemical reactions. The body can excrete up to 2-2.5 liters of water in different ways. Excretion of water through the skin (sweating) and the respiratory system (breathing) is largely dependent on your physical activity. The less you move, the less fluid you lose. Therefore, the additional load of the body with water during a sedentary lifestyle (which many older people suffer from) can lead to backlash- a large load on the urinary and cardiovascular system. Water poisoning is quite possible, only few people talk about it.

Recall the features of water exchange. Animals drink water only when they feel thirsty, since in the animal world many processes are rational and are closely related to the instincts of self-preservation. The same can be said about flora: fill a flower pot with water, you'd rather kill it than help it, because the plant will absorb only the amount of water it needs. The feeling of thirst is the best indicator of whether a person needs liquid or not.
Water, entering the body, is not absorbed immediately, that is, even with severe dehydration of the body, its saturation with water in a matter of minutes and even hours will not occur. Water in the human body is primarily involved(the very first link of its use) in body temperature. If the body overheats, excess energy is released through the process of sweating and the body cools down. Therefore, when you are engaged in physical activity or your metabolism is increased (for example, with hyperfunction thyroid gland), you begin to sweat, while losing body fluid, but along with it, a number of salts.
When you sweat, you rarely urinate because your body is already losing water through skin. On the contrary, when you are cold, the body tries to get rid of excess water, heating the "water reservoir" requires a lot of energy, so in cold weather you urinate more often. The absorption of water in the gastrointestinal tract, mainly in the large intestine, takes place at a certain rate, in a certain volume, so excess water is excreted through the intestines, kidneys and skin. By the way, drinking water reduces appetite.

Water is needed for human body . Some nutritionists advise not to wait for the feeling of thirst, because supposedly this can wait until serious dehydration. This is not a completely accurate statement. The feeling of thirst appears with a loss of 0 to 2% of the total volume of body water, and at 2% you want to drink a lot! Symptoms of dehydration (weakness, fatigue, apathy, loss of appetite, difficulty in performing physical activity) appear with a loss of 4% or more of body water. So feeling thirsty (not extreme thirst) is indeed one of the best indicators that our bodies need fluids (not just water).
In children and older people, the process of water exchange and disturbance of water and electrolyte balance are observed more often., although rehydration in children is much faster than in adults.
In children, the pathological loss of water and salts also passes faster, since in them the center of the brain that regulates water-salt and temperature metabolism is still in a state of maturation (therefore, a “causeless” short-term increase in body temperature in young children is a frequent occurrence). Given the fact that the body of children is "more watery", they need regular replenishment of water supplies.
Many parents complain that their children almost constantly ask for something to drink, especially during physical activity or in hot weather. It is important in such cases not to give sugary drinks, which, due to the presence of sugar, lead to a loss of water in the cells of the oral mucosa (simply “dry”), and therefore provoke a feeling of thirst even more.
But it’s one thing to be healthy, it’s another thing when conditions arise that require the restoration of fluid volume and water-salt balance. Under what circumstances is there a rapid loss of water, and with it salts? This is the loss of blood and/or plasma due to bleeding, after extensive burns, due to diarrhea and vomiting due to different reasons(infection, poisoning), as a result of an overdose of diuretics. In other words, any rapid loss of a large amount of liquids leads to a violation of the water-salt balance.
In addition to diseases, dehydration is observed as a result of profuse sweating, which occurs with intense physical activity, overheating, the presence of elevated body temperature (fever), as well as diseases of the thyroid gland.

How to restore water supplies, that is, to carry out rehydration? It is necessary to understand an important fact: against the background of a disease that often debilitates the body, a sharp volumetric administration of liquid can lead to an even worsening of the condition, so there must be a measure in everything, including the amount of liquid! Fluid intake begins with sips of a small amount of water, increasing the frequency of intake. It is very important to monitor urination, which should be observed every 2-3 hours, or even more often. If a person does not urinate within 5-6 hours, load it excess water and liquids are not allowed. Therefore, the first 4-6 hours are control in relation to the amount of fluid administered and require the intake of small doses of water, but in a frequent mode.

What types of liquids should be preferred? Here it is important to return again to the concept of isotonicity, hypertonicity and hypotonicity. Since fluid is injected through gastrointestinal tract, the mucous organs will be the first to contact water molecules digestive system. With vomiting and diarrhea, the removal of water and salts from the cells to the outside is already observed, which means that the cells and tissues are dehydrated. That's why the best option there will be isotonic saline solutions or slightly hypotonic (low osmolar) solutions.

Why you can not use concentrated saline solutions i.e. hypertonic Because this will lead to even greater loss of intracellular water. If hypotonic solutions are administered, they can also lead to rapid swelling fabrics.

Regidron, which for some reason is forgotten or ignored by doctors, is a salt preparation with a slightly reduced osmolarity. Dissolving the contents of the sachet into required quantity water (usually in 1 liter) a solution is obtained that replenishes intracellular water loss not rigidly, and at the same time quickly, due to its hypotonicity.

Why do many salt and other combinations of drugs to restore electrolyte-water balance include sugars(glucose, fructose, lactose) in small amounts? To maintain the equilibrium of the solution and maintain its osmolarity for a certain period of time (usually several hours).
The osmolarity of blood plasma is 280-300 mosm/l and pH 7.37-7.44. Regidron has an osmolarity of 260 mosm / l and a pH of 8.2, which differs slightly from the properties of human fluids, and at the same time promotes the transport of water and salt ions through cell membranes.
Taking a lot of juices to restore the water-salt balance is not recommended, despite the fact that these are liquids, and as many people think, they contain vitamins and minerals, therefore they are useful. Most juices are not 100% natural product, as they are created from a concentrate diluted in water and contain a large number of additives: sugar, dyes, flavors, etc. To obtain an "isotonic solution" of juice or close to it, 1 liter of water must contain 50 g of glucose.
1 liter of different juices may contain different amounts of sugar. For example, 1 l carrot juice contains 40 g of sugar, orange juice- 90-100 g (in fresh juice from oranges - 100-120 g of sugar), fruit drinks - 100-110 g, apple juice- 120 g, cranberry juice - 120-130 g, grape juice- 150 g, grapefruit juice - 90 g of sugar. 1 liter of most canned juices contains 120-150 g of sugar. Many manufacturers add more sugars to juices to increase shelf life.
As such, most juices are hypertonic solutions and can exacerbate dehydration. Doctors often recommend diluting juices by half with water, especially for children.
Teas, including herbal teas, are hypotonic and hypomolar unless sugar or honey is added to them. But, like coffee, teas can contain caffeine and tannin, which are beneficial to the body in small amounts, but against the background of dehydration, and in large quantities can be harmful, disrupting protein metabolism and causing toxicity. Tannin is also included in a number of fruit drinks.

A number of medicinal herbs, when the body is weakened and in a state of dehydration, can have a toxic effect, therefore herbal teas must be taken with great caution.
While sugar can be dosed in teaspoons, the dosage of honey, especially the amount of sugars included in it, is extremely difficult, so it should not be used in cases of dehydration.

How about lean chicken broth? which is recommended for sick people, especially debilitated and dehydrated? The broth is nothing but water solution salts, proteins, a small amount of fats and other substances. Many experimenters have researched the broth for its usefulness, taking into account osmolarity and pH.
Naturally, a broth with a pH close to 7.0-8.0 will be considered the most natural option. But none of the hostesses will take such measurements. However, by connecting folk wisdom cooking with the results of "broth" experiments, as well as with wisdom folk medicine, certain conclusions can be drawn.
If the broth is made from red meat (legs), it is more acidic (i.e. its pH is 5.0-5.8), so white meat (brisket) should be preferred. The more transparent and lighter in color the broth, the more useful it is for assimilation. In 1 liter of broth there should be no more than 2 teaspoons of salt (without top), i.e. no more than 10 g. A smaller amount of salt is acceptable, but you should not completely refuse salt.
How much meat and water is needed? The question is debatable, but usually one brisket per 3 liters of water is enough. It is important to remember that the broth should be transparent and not too saturated in color. Also, the process of preparing the broth should not be long, i. no more than 2 hours on low heat. The more the broth is cooked, the more its pH shifts towards acidity due to the breakdown of proteins, although more palatability.
Some seasonings and additives may change acid-base balance broth (usually alkalize those found in dry seasonings, such as Vegeta, because soda is often included). It is important to consume the broth warm (but not hot) immediately after cooking. The optimal period for taking the broth is the cessation of diarrhea and the absence of fever.

Also healing properties possesses milk, whose pH is very close to that of the intracellular fluid. Therefore, it is not surprising that milk was given to people who were emaciated by the disease, since it is easily digested by most consumers and contains a large amount of useful ingredients.

Thus, the best option replenishment of liquids and salts in a number of conditions will be the intake of ready-made saline solutions, less often solutions of glucose and ordinary water. The combination of different types of fluids is possible after the disappearance of signs of dehydration and during recovery.

Hypertensive - a solution with a higher concentration and a higher osmotic pressure compared to another solution.

hypotonic - a solution having a lower concentration and a lower value of osmotic pressure.

Isotonic solutions are solutions with the same osmotic pressure.

Isotonic ratio

Isotonic van't Hoff coefficient (i) shows how many times the colligative properties of the electrolyte solution are greater than those of the non-electrolyte solution under the same conditions and concentrations.

The concept of isoosmia (electrolyte homeostasis)

Isoosmia - relative constancy of osmotic pressure in liquid media and tissues of the body, due to the maintenance of given level concentrations of substances contained in them: proteins, electrolytes, etc.

Osmolality and Osmolarity biological fluids and perfusion solutions.

Osmotic concentration is the total concentration of all dissolved particles.

Can be expressed as osmolarity (osmol per liter of solution) and how osmolality (osmol per kg of solvent).

Osmol - a unit of osmotic concentration, equal to the osmolality obtained by dissolving one mole of non-electrolyte in one liter of solvent. Accordingly, a non-electrolyte solution with a concentration of 1 mol/l has an osmolarity of 1 osmol/liter.

All monovalent ions (Na +, K +, Cl-) form a number of osmoles in solution, equal to the number of moles and equivalents (electric charges). Divalent ions form in solution each one osmole (and mole), but two equivalents each.

The osmolality of normal plasma is a fairly constant value and is equal to 285-295 mosmol/kg. Of the total plasma osmolality, only 2 mosmol/kg is due to the presence of proteins dissolved in it. Thus, the main components that provide plasma osmolality are Na+ and C1- (about 140 and 100 mosmol/kg, respectively). The constancy of the osmotic pressure of the intracellular and extracellular 1 fluids implies the equality of the molar concentrations of the electrolytes contained in them, despite the differences in the ionic composition inside the cell and in the extracellular space. Since 1976, in accordance with the International System (SI), the concentration of substances in a solution, including osmotic concentration, is usually expressed in millimoles per 1 liter (mmol/l). The concept of "osmolality" or "osmotic concentration" is equivalent to the concept of "molality" or "molal concentration". In essence, the concepts of "milliosmol" and "millimole" for biological solutions are close, although not identical.

Table 1. Normal values osmolality of biological media

R osm of blood = 7.7 atm

The main task of osmoregulation is performed by the kidneys. The osmotic pressure of urine is normally much higher than that of blood plasma, which ensures active transport from the blood to the kidney. Osmoregulation is controlled enzymatic systems. Their disruption leads to pathological processes. At intravenous injections to avoid disturbing the osmotic balance, isotonic solutions should be used. Isotonic to blood saline containing 0.9% sodium chloride. In surgery, the phenomenon of osmosis is used by using hypertonic gauze bandages(gauze is impregnated with 10% sodium chloride solution). In this case, the wound is cleared of pus and infection carriers. Hypertonic solutions are administered intravenously for glaucoma to reduce intraocular pressure due to increased moisture content in the anterior chamber of the eye.

The role of osmosis in biological systems.

Causes turgor (elasticity) of cells.

Provides water entry into cells and intercellular structures, tissue elasticity and preservation certain form organs. Provides transport of substances.

· The osmotic pressure of human blood at 310 K is 7.7 atm, the concentration of NaCl is 0.9%.

Plasmolysis and hemolysis

Plasmolysis - compression, wrinkling of the cell in a hypertonic solution.

Hemolysis - swelling and rupture of the cell in a hypotonic solution.

Ticket 14. Colligative properties of dilute solutions of electrolytes. Isotonic ratio.