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Various liquids are input during anesthesia work.
In principle, the closer the type of liquid input is to plasma, the more perfect it is.
One of the most important indicators is isotonicity.
Everyone is very familiar with the concept of osmotic pressure, that is, for semipermeable membranes with different aqueous solutions on both sides, in order to prevent water from permeating from the low concentration side to the high concentration side, the minimum additional pressure applied on the high concentration side is called osmosis.
In short, if the osmotic pressure inside and outside the cell is not equal, cell dehydration or cell edema will occur.
Why is it called isotonic saline when the concentration of sodium chloride solution is 0.
9%? Can the osmotic pressure of any liquid be obtained by simple calculation? Let us do it one by one.
In 1886, van't Hoff derived a rule based on experimental data: For dilute solutions, the osmotic pressure is proportional to the concentration and temperature of the solution, and its proportional constant is the constant R in the equation of state of the gas.
This law is called Van der Hoover's law.
The equation is expressed as follows: πV=nRT or π=cRT where π is the osmotic pressure of the dilute solution, in KPa; V is the volume of the solution; n is the amount of solute; c is the concentration of the solution, in mol/ L; R is the gas constant, 8.
31kPa·L·K-1/mol; T is the absolute temperature.
The above formula looks complicated.
In fact, only one conclusion is needed: at the same temperature, the osmotic pressure of the solution is proportional to the number of solute particles (number of molecules or ions) contained in the solution per unit volume, and is proportional to the number of solute particles.
Nature has nothing to do.
For example, the osmotic pressure of 0.
1 mol/L glucose solution and 0.
1 mol/L sucrose solution is equal, but it is half the osmotic pressure of 0.
1 mol/L sodium chloride solution, because sodium chloride can be completely dissociated into sodium ions and Chloride.
In the human body, the normal osmotic pressure of plasma is 280-320mmol/L, with an average of 300 mmol/L.
Because the body temperature changes very little, the total molar concentration of plasma (mmol/L) can be used instead of osmotic pressure (kPa).
300 mmol/L is equivalent to about 770 kPa.
In addition, osmolarity can often be seen.
Commonly used units are Osm/L and mOsm/L, and 1mOsm/L=1mmol/L, and the two units are interchangeable.
The following is a simple calculation of the osmotic pressure of the most commonly used liquid in clinical practice: 1.
A 0.
9% sodium chloride solution refers to the solute contained in 1L of sodium chloride 9g converted into molar concentration = 9 (g)/58.
5 (g/mol) = 153.
8 mmol/L Because the sodium chloride solution can be completely dissociated, the solution osmotic pressure=153.
8*2=307.
7mmol/L This value is within the normal plasma osmotic pressure range but slightly higher, this is also said to be 0.
9% sodium chloride osmotic pressure In fact, it is a bit high, and the osmotic pressure of 0.
85% sodium chloride may be more appropriate.
2.
5% glucose solution means that 1L solution contains 50g glucose, so the molar concentration=50/180=0.
278mol/L.
Note that glucose cannot be dissociated in water, so the osmotic pressure of the solution=0.
278mol/L=278mmol/L 5% glucose solution It is an isotonic solution, but because glucose can be quickly oxidized through the cell membrane, plasma osmotic pressure cannot be maintained after infusion, and it is an isotonic tension-free solution. 3.
The formula of sodium lactate Ringer’s commonly used sodium lactate Ringer’s solution per 1000ml contains 3.
1g sodium lactate, 6g sodium chloride and 0.
3g potassium chloride, and 0.
2g calcium chloride 2×3.
1/112+2×6/58.
5+2×0.
3 /74.
5+3×0.
2/147=272.
6mmol/L belongs to isotonic pressure and at the same time avoids acidosis caused by excessive chloride ion concentration.
4.
5% sodium bicarbonate solution is often used to correct acidosis.
The size of the alkaline solution is 12.
5g: 250ml The osmotic pressure is 2×12.
5×4/84=1190.
5mmol/L.
This solution is hypertonic and nearly 4 times that of plasma? ! This solution is only used to correct acidosis.
A small amount can achieve the correction goal.
It cannot be used to supplement blood volume.
The alkali solution used for rehydration is commonly used in isotonic 1.
4% sodium bicarbonate solution.
5, hydroxyethyl starch 130/0.
4 chlorination Sodium injection 500ml solution mainly contains macromolecular polystarch 30g and sodium chloride 4.
5g polystarch.
The average molecular weight of polystarch is 130,000, so the osmotic pressure is 60/130000+2×9/58.
5=308.
2mmol/L.
It is still an isotonic solution.
Note It is wrong to use it for the dehydration treatment of cerebral edema.
6.
The commonly used specification of mannitol injection is 250ml: 50g osmotic pressure is 4×50/182=1098.
9mmol/L.
The most commonly used tissue dehydration drug has both high osmotic pressure and osmotic pressure.
It is far more important to master the calculation method of sexual diuresis than to memorize the results.
Understanding the principles can give us a deeper understanding of clinical work, and share some tips, hope to gain you! Recommendation: How to evaluate the bleeding in children and the estimated blood transfusion.
What is the appropriate intraoperative inspired oxygen concentration?
In principle, the closer the type of liquid input is to plasma, the more perfect it is.
One of the most important indicators is isotonicity.
Everyone is very familiar with the concept of osmotic pressure, that is, for semipermeable membranes with different aqueous solutions on both sides, in order to prevent water from permeating from the low concentration side to the high concentration side, the minimum additional pressure applied on the high concentration side is called osmosis.
In short, if the osmotic pressure inside and outside the cell is not equal, cell dehydration or cell edema will occur.
Why is it called isotonic saline when the concentration of sodium chloride solution is 0.
9%? Can the osmotic pressure of any liquid be obtained by simple calculation? Let us do it one by one.
In 1886, van't Hoff derived a rule based on experimental data: For dilute solutions, the osmotic pressure is proportional to the concentration and temperature of the solution, and its proportional constant is the constant R in the equation of state of the gas.
This law is called Van der Hoover's law.
The equation is expressed as follows: πV=nRT or π=cRT where π is the osmotic pressure of the dilute solution, in KPa; V is the volume of the solution; n is the amount of solute; c is the concentration of the solution, in mol/ L; R is the gas constant, 8.
31kPa·L·K-1/mol; T is the absolute temperature.
The above formula looks complicated.
In fact, only one conclusion is needed: at the same temperature, the osmotic pressure of the solution is proportional to the number of solute particles (number of molecules or ions) contained in the solution per unit volume, and is proportional to the number of solute particles.
Nature has nothing to do.
For example, the osmotic pressure of 0.
1 mol/L glucose solution and 0.
1 mol/L sucrose solution is equal, but it is half the osmotic pressure of 0.
1 mol/L sodium chloride solution, because sodium chloride can be completely dissociated into sodium ions and Chloride.
In the human body, the normal osmotic pressure of plasma is 280-320mmol/L, with an average of 300 mmol/L.
Because the body temperature changes very little, the total molar concentration of plasma (mmol/L) can be used instead of osmotic pressure (kPa).
300 mmol/L is equivalent to about 770 kPa.
In addition, osmolarity can often be seen.
Commonly used units are Osm/L and mOsm/L, and 1mOsm/L=1mmol/L, and the two units are interchangeable.
The following is a simple calculation of the osmotic pressure of the most commonly used liquid in clinical practice: 1.
A 0.
9% sodium chloride solution refers to the solute contained in 1L of sodium chloride 9g converted into molar concentration = 9 (g)/58.
5 (g/mol) = 153.
8 mmol/L Because the sodium chloride solution can be completely dissociated, the solution osmotic pressure=153.
8*2=307.
7mmol/L This value is within the normal plasma osmotic pressure range but slightly higher, this is also said to be 0.
9% sodium chloride osmotic pressure In fact, it is a bit high, and the osmotic pressure of 0.
85% sodium chloride may be more appropriate.
2.
5% glucose solution means that 1L solution contains 50g glucose, so the molar concentration=50/180=0.
278mol/L.
Note that glucose cannot be dissociated in water, so the osmotic pressure of the solution=0.
278mol/L=278mmol/L 5% glucose solution It is an isotonic solution, but because glucose can be quickly oxidized through the cell membrane, plasma osmotic pressure cannot be maintained after infusion, and it is an isotonic tension-free solution. 3.
The formula of sodium lactate Ringer’s commonly used sodium lactate Ringer’s solution per 1000ml contains 3.
1g sodium lactate, 6g sodium chloride and 0.
3g potassium chloride, and 0.
2g calcium chloride 2×3.
1/112+2×6/58.
5+2×0.
3 /74.
5+3×0.
2/147=272.
6mmol/L belongs to isotonic pressure and at the same time avoids acidosis caused by excessive chloride ion concentration.
4.
5% sodium bicarbonate solution is often used to correct acidosis.
The size of the alkaline solution is 12.
5g: 250ml The osmotic pressure is 2×12.
5×4/84=1190.
5mmol/L.
This solution is hypertonic and nearly 4 times that of plasma? ! This solution is only used to correct acidosis.
A small amount can achieve the correction goal.
It cannot be used to supplement blood volume.
The alkali solution used for rehydration is commonly used in isotonic 1.
4% sodium bicarbonate solution.
5, hydroxyethyl starch 130/0.
4 chlorination Sodium injection 500ml solution mainly contains macromolecular polystarch 30g and sodium chloride 4.
5g polystarch.
The average molecular weight of polystarch is 130,000, so the osmotic pressure is 60/130000+2×9/58.
5=308.
2mmol/L.
It is still an isotonic solution.
Note It is wrong to use it for the dehydration treatment of cerebral edema.
6.
The commonly used specification of mannitol injection is 250ml: 50g osmotic pressure is 4×50/182=1098.
9mmol/L.
The most commonly used tissue dehydration drug has both high osmotic pressure and osmotic pressure.
It is far more important to master the calculation method of sexual diuresis than to memorize the results.
Understanding the principles can give us a deeper understanding of clinical work, and share some tips, hope to gain you! Recommendation: How to evaluate the bleeding in children and the estimated blood transfusion.
What is the appropriate intraoperative inspired oxygen concentration?
