Volume expander
Encyclopedia
A volume expander is a type of intravenous therapy
that has the function of providing volume for the circulatory system
. It may be used for fluid replacement
.
The body automatically detects the lower haemoglobin level, and compensatory mechanisms start up. The heart
pumps more blood with each beat. Since the lost blood was replaced with a suitable fluid, the now diluted blood flows more easily, even in the small vessels. As a result of chemical changes, more oxygen is released to the tissues. These adaptations are so effective that if only half of the red blood cells remain, oxygen delivery may still be about 75 percent of normal. A patient at rest uses only 25 percent of the oxygen available in his blood. In extreme cases, patients have survived with a haemoglobin level of 2 g/dl, about 1/7 the norm, although levels this low are very dangerous.
With enough blood loss, ultimately red blood cell levels drop too low for adequate tissue oxygenation, even if volume expanders maintain circulatory volume. In these situations, the only alternatives are blood transfusions, packed red blood cells, or oxygen therapeutics (if available). However in some circumstances, hyperbaric oxygen therapy
can maintain adequate tissue oxygenation even if red blood cell levels are below normal life-sustaining levels.
s of mineral salts or other water-soluble molecules. Colloids contain larger insoluble molecules, such as gelatin
; blood
itself is a colloid.
loss caused by trauma
, surgery
, or some other problem. It increases the blood volume
, allowing red blood cell
s to continue to deliver oxygen
to the body.
, a solution of sodium chloride
at 0.9% concentration, which is close to the concentration in the blood (isotonic
). Ringer's lactate or Ringer's acetate is another isotonic solution often used for large-volume fluid replacement. A solution of 5% dextrose in water, sometimes called D5W, is often used instead if the patient is at risk for having low blood sugar
or high sodium
. The choice of fluids may also depend on the chemical properties of the medications being given.
Intravenous fluids must always be sterile
.
contains 28 mmol/L lactate, 4 mmol/L K+ and 1.5 mmol/L Ca2+. It is very similar - though not identical to - Hartmann's Solution
, the ionic concentrations of which differ.
Ringer's acetate consists of 28 mmol/L acetate, 4 mmol/L K+ and 1.5 mmol/L Ca2+.
of NaCl
, about 300 mOsm/L. Less commonly, this solution is referred to as physiological saline or isotonic saline, neither of which is technically accurate. NS is used frequently in intravenous drips (IVs) for patients who cannot take fluids orally and have developed or are in danger of developing dehydration
or hypovolemia
. NS is typically the first fluid used when hypovolemia is severe enough to threaten the adequacy of blood circulation, and has long been believed to be the safest fluid to give quickly in large volumes. However, it is now known that rapid infusion of NS can cause metabolic acidosis
.
s, such as with glucose
(also called dextrose), have the advantage of providing some energy, and may thereby provide the entire or part of the energy component of parenteral nutrition.
Types of glucose/dextrose include:
Intravenous therapy
Intravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...
that has the function of providing volume for the circulatory system
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...
. It may be used for fluid replacement
Fluid replacement
Fluid replacement or fluid resuscitation is the medical practice of replenishing bodily fluid lost through sweating, bleeding, fluid shifts or other pathologic processes. Fluids can be replaced via oral administration , intravenous administration, rectally, or hypodermoclysis, the direct injection...
.
Physiology
When blood is lost, the greatest immediate need is to stop further blood loss. The second greatest need is replacing the lost volume. This way remaining red blood cells can still oxygenate body tissue. Normal human blood has a significant excess oxygen transport capability, only used in cases of great physical exertion. Provided blood volume is maintained by volume expanders, a quiescent patient can safely tolerate very low haemoglobin levels, less than 1/3 that of a healthy person.The body automatically detects the lower haemoglobin level, and compensatory mechanisms start up. The heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
pumps more blood with each beat. Since the lost blood was replaced with a suitable fluid, the now diluted blood flows more easily, even in the small vessels. As a result of chemical changes, more oxygen is released to the tissues. These adaptations are so effective that if only half of the red blood cells remain, oxygen delivery may still be about 75 percent of normal. A patient at rest uses only 25 percent of the oxygen available in his blood. In extreme cases, patients have survived with a haemoglobin level of 2 g/dl, about 1/7 the norm, although levels this low are very dangerous.
With enough blood loss, ultimately red blood cell levels drop too low for adequate tissue oxygenation, even if volume expanders maintain circulatory volume. In these situations, the only alternatives are blood transfusions, packed red blood cells, or oxygen therapeutics (if available). However in some circumstances, hyperbaric oxygen therapy
Hyperbaric oxygen therapy
Hyperbaric medicine, also known as hyperbaric oxygen therapy , is the medical use of oxygen at a level higher than atmospheric pressure. The equipment required consists of a pressure chamber, which may be of rigid or flexible construction, and a means of delivering 100% oxygen...
can maintain adequate tissue oxygenation even if red blood cell levels are below normal life-sustaining levels.
Types
There are two main types of volume expanders; crystalloids and colloids. Crystalloids are aqueous solutionSolution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
s of mineral salts or other water-soluble molecules. Colloids contain larger insoluble molecules, such as gelatin
Gelatin
Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...
; blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
itself is a colloid.
Colloids
Colloids preserve a high colloid osmotic pressure in the blood, while, on the other hand, this parameter is decreased by crystalloids due to hemodilution. Therefore, they should theoretically preferentially increase the intravascular volume, whereas crystalloids also increase the interstitial volume and intracellular volume. However, there is still controversy as to the actual difference in efficacy due to this difference in action. Another difference is that crystalloids generally are much cheaper than colloids.Hydroxyethyl starch
Hydroxyethyl starch (HES/HAES, common trade names: Hespan, Voluven) is one of the most frequently used colloids. An intravenous solution of hydroxyethyl starch is used to prevent shock following severe bloodBlood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
loss caused by trauma
Physical trauma
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
, surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
, or some other problem. It increases the blood volume
Blood volume
Blood volume is the volume of blood in the circulatory system of an individual.-Humans:A typical adult has a blood volume of approximately between 4.7 and 5 liters, with females generally having less blood volume than males....
, allowing red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...
s to continue to deliver oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
to the body.
Crystalloids
The most commonly used crystalloid fluid is normal salineSaline (medicine)
In medicine, saline is a general term referring to a sterile solution of sodium chloride in water but is only sterile when it is to be placed intravenously, otherwise, a saline solution is a salt water solution...
, a solution of sodium chloride
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
at 0.9% concentration, which is close to the concentration in the blood (isotonic
Isotonic
The term isotonic may refer to;*Isotonic for the term associated with muscle contraction*An isotone in nuclear physics*Sports drinks are sometimes designed in an isotonic way to assist athletes rehydrate while balancing electrolytes...
). Ringer's lactate or Ringer's acetate is another isotonic solution often used for large-volume fluid replacement. A solution of 5% dextrose in water, sometimes called D5W, is often used instead if the patient is at risk for having low blood sugar
Blood sugar
The blood sugar concentration or blood glucose level is the amount of glucose present in the blood of a human or animal. Normally in mammals, the body maintains the blood glucose level at a reference range between about 3.6 and 5.8 mM , or 64.8 and 104.4 mg/dL...
or high sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
. The choice of fluids may also depend on the chemical properties of the medications being given.
Intravenous fluids must always be sterile
Sterilization (microbiology)
Sterilization is a term referring to any process that eliminates or kills all forms of microbial life, including transmissible agents present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media...
.
Ringer's solution
Lactated Ringer's solutionLactated Ringer's solution
Lactated Ringer's solution is a solution that is isotonic with blood and intended for intravenous administration. It may also be given subcutaneously....
contains 28 mmol/L lactate, 4 mmol/L K+ and 1.5 mmol/L Ca2+. It is very similar - though not identical to - Hartmann's Solution
Hartmann's Solution
Hartmann's solution or compound sodium lactate is a crystalloid solution that is most closely isotonic with blood and intended for intravenous administration.Hartmann's IV Infusion is used toreplace body fluid and mineral salts...
, the ionic concentrations of which differ.
Ringer's acetate consists of 28 mmol/L acetate, 4 mmol/L K+ and 1.5 mmol/L Ca2+.
Normal saline
Normal saline (NS) is the commonly-used term for a solution of 0.91% w/vPercentage solution
"Percentage solution" is an ambiguous term which is used to describe a solution with the unit "%". It may refer to:* Mass fraction if mass/mass is meant...
of NaCl
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
, about 300 mOsm/L. Less commonly, this solution is referred to as physiological saline or isotonic saline, neither of which is technically accurate. NS is used frequently in intravenous drips (IVs) for patients who cannot take fluids orally and have developed or are in danger of developing dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
or hypovolemia
Hypovolemia
In physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...
. NS is typically the first fluid used when hypovolemia is severe enough to threaten the adequacy of blood circulation, and has long been believed to be the safest fluid to give quickly in large volumes. However, it is now known that rapid infusion of NS can cause metabolic acidosis
Metabolic acidosis
In medicine, metabolic acidosis is a condition that occurs when the body produces too much acid or when the kidneys are not removing enough acid from the body. If unchecked, metabolic acidosis leads to acidemia, i.e., blood pH is low due to increased production of hydrogen by the body or the...
.
Glucose (dextrose)
Intravenous sugar solutionIntravenous sugar solution
An intravenous sugar solution is a solution with a sugar used for intravenous therapy, where it may function both as a volume expander and a means of parenteral nutrition.-Types:...
s, such as with glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
(also called dextrose), have the advantage of providing some energy, and may thereby provide the entire or part of the energy component of parenteral nutrition.
Types of glucose/dextrose include:
- D5W (5% dextrose in water), which consists of 278 mmol/L dextrose
- D5NS (5% dextrose in normal saline), which, in addition, contains normal saline.
Comparison table
| Solution | Other Name | [Na+](mmol/L) | [Cl-](mmol/L) | [Glucose](mmol/L) | [Glucose](mg/dl) |
|---|---|---|---|---|---|
| D5W Intravenous sugar solution An intravenous sugar solution is a solution with a sugar used for intravenous therapy, where it may function both as a volume expander and a means of parenteral nutrition.-Types:... |
5% Dextrose | 0 | 0 | 278 | 5000 |
| 2/3D & 1/3S | 3.3% Dextrose / 0.3% saline | 51 | 51 | 185 | 3333 |
| Half-normal saline | 0.45% NaCl | 77 | 77 | 0 | 0 |
| Normal saline | 0.9% NaCl | 154 | 154 | 0 | 0 |
| Ringer's lactate | Lactated Ringer | 130 | 109 | 0 | 0 |
| D5NS | 5% Dextrose, Normal Saline | 154 | 154 | 278 | 5000 |
| Solution | Change in ECF Extracellular fluid Extracellular fluid usually denotes all body fluid outside of cells. The remainder is called intracellular fluid.In some animals, including mammals, the extracellular fluid can be divided into two major subcompartments, interstitial fluid and blood plasma... |
Change in ICF |
|---|---|---|
| D5W | 333 mL | 667 mL |
| 2/3D & 1/3S | 556 mL | 444 mL |
| Half-normal saline | 667 mL | 333 mL |
| Normal saline | 1000 mL | 0 mL |
| Ringer's lactate | 900 mL | 100 mL |