Volume expander
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 or during surgery to prevent nausea and vomiting after surgery.[1]
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 rested patient can safely tolerate very low hemoglobin levels, less than 1/3 that of a healthy person.
The body detects the lower hemoglobin 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 their blood. In extreme cases, patients have survived with a hemoglobin level of 2 g/dl, about 1/7 the normal, 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
Types
There are two main types of volume expanders: crystalloids and colloids. Crystalloids are aqueous solutions of mineral salts or other water-soluble molecules. Colloids contain larger insoluble molecules, such as gelatin; blood itself is a colloid. There is no evidence that colloids are better than crystalloids in those who have had trauma, burns, or surgery. Colloids are more expensive than crystalloids. As such, colloids are not recommended for volume expansion in these settings.[2]
Crystalloids
The most commonly used crystalloid fluid is normal
Normal saline
Normal saline (NS) is the commonly used term for a solution of 0.9%
Ringer's solution
1/3 NS 2/3D5
2/3 1/3 is no longer recommended as a maintenance intravenous fluid in children as it is hypotonic and isotonic fluids are preferred.[7]
Glucose (dextrose)
Intravenous sugar solutions, such as those containing 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:
- D5W (5% dextrose in water), which consists of 278 mmol/L dextrose
- D5NS (5% dextrose in normal saline), which, in addition, contains normal saline.
Plasma-lyte
Plasma-Lyte A[8] and Plasma-Lyte 148[9] are buffered crystalloid solutions[8][10] that may be infused intravenously,[9] or used in conjunction with blood products.[8]
Comparison table
Solution | Other Name | [Na+](mmol/L) | [Cl−](mmol/L) | [Glucose](mmol/L) | [Glucose](mg/dl) |
---|---|---|---|---|---|
D5W | 5% Dextrose | 0 | 0 | 278 | 5000 |
2/3 D5W & 1/3 NS | 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 | Change in ICF
|
---|---|---|
D5W | 333 mL | 667 mL |
2/3 D5W & 1/3 NS | 556 mL | 444 mL |
Half-normal saline | 667 mL | 333 mL |
Normal saline
|
1000 mL | 0 mL |
Ringer's lactate | 900 mL | 100 mL |
Colloids
Colloids preserve a high
Hydroxyethyl starch
Hydroxyethyl starch (HES/HAES, common trade names: Hespan, Voluven) is controversial. Its use in those who are very ill is associated with an increased risk of death and kidney problems. Therefore, HES/HAES is not recommended in people with known inflammatory conditions such as renal impairment.[2][12]
Gelofusine
Gelofusine is a colloid volume expander which may be used as a
References
- PMID 30925195.
- ^ PMID 30073665.
- ^ "Choosing between colloids and crystalloids for IV infusion". Nursing Times. 20 November 2017. Retrieved 31 August 2018.
- molarity) NaCl assuming complete dissociation. Physiological dissociation is approximately 1.7 ions per mole, so one normal of NaCl is 1/1.7 = 0.588 molar. This is roughly 4 times more concentrated than medical "normal saline" of 0.154 molar.
- from the original on 6 May 2020.
- PMID 29763209.
- S2CID 1191733.
- ^ PMID 29523397.
- ^ a b ""Baxter PLASMA-LYTE 148 Injection (Multiple Electrolytes Injection, Type 1, USP)" (PDF). accessdata.fda.gov.
- PMID 27896148.
- ^ a b c Gregory S. Martin (2005-04-19). "An Update on Intravenous Fluids". Medscape.
- PMID 23423413.