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Intravenous Fluid
Selection
CHAPTER
LEARNING OBJECTIVES
By the end of this chapter, you should be able to: Describe and differentiate colloid and crystalloid IV fluids Understand osmosis as it pertains to water movement with IV therapy Define tonicity and the actions of isotonic, hypotonic, and hypertonic crystalloids in the body Identify the three most common IV solutions used in the prehospital setting, and classify them as isotonic, hypotonic, or hypertonic Describe how an IV fluid is packaged and important informa- tion located on the label of the IV fluid
KEY TERMS
5% Dextrose in water —A carbohydrate solution that uses glucose (sugar) as the solute dissolved in sterile water. Five percent dextrose in water is packed as an isotonic solution but becomes hypotonic once in the body because the glucose (solute) dissolved in sterile water is metabolized rapidly by the body’s cells. Colloid solutions —IV fluids containing large proteins and molecules that tend to stay within the vascular space (blood vessels). Crystalloid solutions —IV fluids containing varying concentrations of electrolytes. D 5 W —See 5% dextrose in water. Extracellular space —Space outside the cells consisting of the intravas- cular and interstitial spaces.
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CHAPTER 3 Intravenous Fluid Selection 21
Hypertonic crystalloid —A crystalloid solution that has a higher concen- tration of electrolytes than the body plasma.
Hypotonic crystalloid —A crystalloid solution that has a lower concen- tration of electrolytes than the body plasma.
Intracellular space —Space within the cells.
Intravascular volume —Volume of blood contained within the blood vessels.
Intravenous fluids —Chemically prepared solutions that are adminis- tered to a patient through the IV site.
Isotonic crystalloid —A crystalloid solution that has the same concen- tration of electrolytes as the body plasma.
Lactated Ringer’s —An isotonic crystalloid solution containing the solutes sodium chloride, potassium chloride, calcium chloride, and sodium lactate, dissolved in sterile water (solvent).
LR —See Lactated Ringer’s.
Normal saline solution —An isotonic crystalloid solution that contains sodium chloride (salt) as the solute, dissolved in sterile water (solvent). The specific concentration for normal saline solution is 0.9%.
NS —See Normal saline solution.
NSS —See Normal saline solution.
Osmosis —The movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. This movement of water allows the equalization of the solute-to-solution ratio across the membrane.
Oxygen-carrying solutions —Chemically prepared solutions that can carry oxygen to the cells.
Plasma —Fluid surrounding the cells of the body.
Ringer’s lactate —See Lactated Ringer’s.
Solute —Particles that are dissolved in the sterile water (solvent) of an IV fluid.
Solvent —The liquid portion of an IV solution that the solute(s) dissolves into. The most common solvent is sterile water.
Total body water —Water contained within the cells, around the cells, and in the bloodstream. Water comprises about 60% of the body’s weight.
Case Study You are staffing a first aid center for the city’s 5-kilometer run for charity. With the temperature at 96 oF and the humidity at 92%, the first aid center is overwhelmed with patients suffering from dehy- dration. Because IV therapy is within your scope of practice, the lead physician instructs you to start an IV and administer IV fluid to a 32-year-old female who is seriously dehydrated and extremely weak.
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CHAPTER 3 Intravenous Fluid Selection 23
On Target
Although colloids are an effective IV solution for increasing a patient’s blood volume, their expense and specific storage requirements limit their use in the prehospital setting.
On Target
IV fluids are comprised of solutes dissolved in a solvent.
Together, the solvent (water) and solutes (electrolytes, proteins, or other molecules dissolved in the water) create the IV solution. Consider a cup of coffee to which sugar is added for sweetness. The coffee is the solvent, which dissolves the solute sugar.
Intravenous Fluids
IV fluids come in four different forms:
- Colloids
- Crystalloids
- Blood and blood products
- Oxygen-carrying solutions
Understanding these IV fluids is important because each has a different impact on the body and particular indications for use:
- Colloid Solutions. Colloid solutions are IV fluids that contain solutes in the form of large proteins or other similarly sized molecules. The pro- teins and molecules are so large that they cannot pass through the walls of the capillaries and onto the cells. Accordingly, colloids remain in the blood vessels for long periods of time and can significantly increase the intravascular volume (volume of blood). The proteins also have the ability to attract water from the cells into the blood vessels. However, although the movement of water from the cells into the bloodstream may be beneficial in the short term, continual movement in this direc- tion can cause the cells to lose too much water and become dehydrated. Colloids are useful in maintaining blood volume, but their use in the field is limited. Colloids are expensive, have specific storage require- ments, and have a short shelf life. This makes their use more suitable in the hospital setting. However, familiarity is important because in a mass casualty incident the EMT may be required to assist with the ad- ministration of colloids either in a field hospital or during the transport of critically injured patients. Commonly used colloid solutions include plasma protein fraction, salt poor albumin, dextran, and hetastarch. To learn more about colloidal solutions, the EMT should consult a critical care or paramedic textbook.
- Crystalloid Solutions. Crystalloid solutions are the primary fluid used for prehospital IV therapy. Crystalloids contain electrolytes (e.g., sodium, potassium, calcium, chloride) but lack the large proteins and molecules found in colloids. Crystalloids come in many preparations and are classified according to their “tonicity.” A crystalloid’s tonicity describes the concentration of electrolytes (solutes) dissolved in the water, as compared with that of body plasma (fluid surrounding the cells). When the crystalloid contains the same amount of electrolytes as the plasma, it has the same concentration and is referred to as “isotonic” ( iso, same; tonic, concentration). If a crystal- loid contains more electrolytes than the body plasma, it is more concen- trated and referred to as “hypertonic” ( hyper, high; tonic, concentration).
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Consider the example of coffee and sugar. The more sugar that is added to the coffee, the more concentrated the sugar becomes relative to the amount of coffee, and the sweeter tasting the coffee becomes. Conversely, when a crystalloid contains fewer electrolytes than the plasma, it is less concentrated and referred to as “hypotonic” ( hypo, low; tonic, concentration). The less sugar a cup of coffee contains, the lower its concentration or tonicity, and the less sweet the coffee may taste. Depending on their concentration, crystalloids can affect the distribu- tion of water within the body. To better understand this, the EMT must first know what total body water (TBW) is. TBW describes the entire amount of water contained within the body and accounts for approxi- mately 60% of body weight. It is distributed among the intracellular and extracellular compartments. The intracellular space is the space within all the body cells ( intra, within; cellular, cell). The extracellular space is the space outside the cells ( extra, outside; cellular, cells). The extracellular compartment can be further divided into the intravascular space (space within the blood vessels) and the interstitial space (space between the cells but not within the blood vessels) (Figure 3.1). The different compartments are separated by membranes through which the body water can easily pass. As a general rule, body water is pulled toward the solution with a higher concentration of dissolved molecules. The movement of water across a semipermeable membrane that selectively allows certain structures to pass while inhibiting others (i.e., a capillary wall or cellular wall) is known as osmosis. The osmotic movement of water occurs as the body attempts to create a balance be- tween the different solute concentrations that exist on either side of a semipermeable membrane. What this means is that the water will easily cross the semipermeable membrane from the side that has a lower con- centration of particles to the side that has a higher concentration of particles. The net movement of water stops when each side of the mem- brane becomes equal in its concentration of water and particles. With this in mind, isotonic, hypertonic, and hypotonic IV fluids cause the following shifts of body water:
- Isotonic. Isotonic crystalloids have a tonicity equal to the body plasma. When administered to a normally hydrated patient, isotonic crystalloids do not cause a significant shift of water between the
24 CHAPTER 3 Intravenous Fluid Selection
On Target
Isotonic crystalloids have a tonicity that is equal to the plasma in the body. When admin- istering an isotonic crystalloid, the fluid will distribute evenly between the intravas- cular space and cells.
Figure 3-1. Locations of intra- cellular, interstitial, and intravascular spaces in a capillary bed.
Oxygenated blood
Arteriole
Cells
Venule
Deoxygenated blood Blood flow from an artery
Blood flow levelsof CO 2 to a vein
CO2 CO 2
CO (^2) CO
O
O
O
O
levels of O 2
levels of O 2
levels of O 2
Cells
Capillary
On Target
Through osmosis, water is pulled from an area of lower solute concentra- tion to an area of higher solute concentration.
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On Target
The isotonic fluids 0.9% NSS and LR are the most common IV fluids used in the prehospital setting.
26 CHAPTER 3 Intravenous Fluid Selection
cellular dehydration. The EMS system’s medical director will determine which crystalloids will be used for prehospital IV therapy. The most common isotonic solutions used in prehospital care are
- Lactated Ringer’s. Lactated Ringer’s (LR) is an isotonic crystalloid that contains sodium chloride, potassium chloride, calcium chlo- ride, and sodium lactate in sterile water.
- Normal saline solution. Normal saline solution (NSS) is an isotonic crystalloid that contains 0.9% sodium chloride (salt) in sterile water.
- 5% Dextrose in water. 5% Dextrose in water (D 5 W) is packaged as an isotonic carbohydrate (sugar solution) that contains glucose (sugar) as the solute. D 5 W is useful in keeping a vein open by de- livering a small amount of the fluid over a long period of time and/or supplying sugar, which is used by the cells to create energy. However, once D 5 W enters the body, the cells rapidly consume the glucose. This leaves primarily water and causes IV fluid to become hypotonic in relation to the plasma surrounding the cells. Accordingly, the now hypotonic solution causes an osmotic shift of water to and from the bloodstream and into the cells. In the prehospital setting, LR and NSS are commonly used for fluid replacement because of their immediate ability to expand the volume of circulating blood. However, over the course of about 1 hour, approxi- mately two-thirds of these IV fluids eventually leave the blood vessels and move into the cells. Some authorities recommend that for every 1 liter of blood lost, 3 liters of an isotonic crystalloid be administered for replacement. This is only a guide, and the volume of IV fluid ad- ministered should be based on medical direction or local protocol, as well as the patient’s clinical response to fluid administration.
- Blood and Blood Products. Blood and blood products (e.g., platelets, packed red blood cells, plasma) are the most desirable fluids for replacement. Unlike colloids and crystalloids, the hemo- globin (in the red blood cells) carries oxygen to the cells. Not only is the intravascular volume increased, but the fluid administered can also transport oxygen to the cells. Blood, however, is a precious commodity and must be conserved to benefit the people most in need. Its use in the field is generally limited to aeromedical services or mass casualty incidents. The universal compatibility of O-negative blood makes it the ideal choice for administration in emergent situ- ations. To learn more about blood and blood products, consult a critical care or paramedic textbook.
- Oxygen-Carrying Solutions. Oxygen-carrying solutions are synthetic fluids that carry and deliver oxygen to the cells. These fluids, which re- main experimental, show promise for the prehospital care of patients who have experienced severe blood loss or are otherwise suffering from hypovolemia. It is hoped that oxygen-carrying solutions will be similar to crystalloid solutions in cost, storage capability, and ease of administration, and be capable of carrying oxygen, which presently can only be accomplished by blood or blood products.
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Intravenous Fluid Packaging
Most IV fluids are packaged in soft plastic or vinyl bags of various sizes (10, 50, 100, 250, 500, 1,000, 2,000, and 3,000 milliliters) (Figure 3.5). The EMT will most likely be using 250-, 500-, and 1,000-milliliter bags. Some IV solutions are premixed with medications that are not compatible with plastic or vinyl and must be packaged in glass bottles. Glass bottles are not common to prehospital IV therapy but may be encountered during interfacility or critical care transports. Every IV fluid container must contain a label. The label provides im- portant information that you must examine before administering the fluid to a patient. This information includes
- Type of IV fluid (by name and by type of solutes contained within).
- Amount of IV fluid (expressed in milliliters or “mL”).
- Expiration date.
Always carefully read the label to ensure you are administering the correct IV solution. Many different IV fluids are packaged in similar contain- ers, including those containing premixed medications. Administering an in- appropriate IV fluid may be detrimental or even fatal to the patient, resulting in disciplinary and/or legal action. Like any other medication, IV solutions have a shelf life and must not be used after their expiration date (Figure 3.6). The IV fluid container contains a medication injection site and admin- istration set port. Both ports are located on the bottom of the IV bag when
CHAPTER 3 Intravenous Fluid Selection 27
Figure 3-5. Different volumes of IV bags are used in the prehospital evironment.
On Target
To ensure the right pa- tient receives the right IV fluid, it is imperative that the EMT reads the label of the IV container prior to preparing and administering the fluid!
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SUMMARY
There are several different types of fluids used for IV therapy. Depending on their specific type and makeup, IV fluids can cause the shift and redis- tribution of body water between the intracellular and extracellular com- partments. Therefore, it is important for the EMT to have a basic understanding of the different IV fluids and to choose the fluid most appropriate to the patient’s needs. Because most IV fluids are packaged in similar-looking plastic bags, it is imperative for the EMT to carefully examine the label on the bag to ensure the right fluid has been selected. Administering an inappropriate IV fluid can result in undesirable compli- cations, as well as a less than optimal patient outcome.
REVIEW QUESTIONS
- All IV fluids have the same impact within the body.
A. True B. False
- In a fluid used for IV therapy, the sterile water into which electrolytes, proteins, or other materials are dissolved is referred to as the A. tonicity. B. solvent. C. solute. D. concentration.
- Which of the following are types of IV solutions?
A. Colloids B. Crystalloids C. Blood D. All of the above are types of IV solutions
- An IV solution contains the electrolyte sodium. Which of the follow- ing statements is true concerning the sodium? A. The sodium is the solution. B. The sodium is the solute. C. The sodium is the solvent. D. All of the above are true concerning the sodium.
- You are administering an IV solution that contains large proteins and molecules. As such, what category of IV solution are you administering? A. Extravascular solution B. Crystalloid solution C. Colloid solution D. Hypotonic crystalloid solution
CHAPTER 3 Intravenous Fluid Selection 29
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30 CHAPTER 3 Intravenous Fluid Selection
- The most commonly administered IV fluid given prehospitally is a colloid solution. A. True B. False
- A crystalloid solution typically contains sterile water and ____________. A. proteins B. blood C. oxygen crystals D. electrolytes
- Which of the following best describes a hypertonic solution? A. Concentration higher than the body plasma B. Concentration lower than the body plasma C. Contains less electrolytes than the body plasma D. Contains more oxygen crystals than the body plasma
- Match the following IV solutions to their description: ____ Hypertonic crystalloid A. Concentration the same as the body plasma ____ Isotonic crystalloid B. Concentration less than the body plasma ____ Hypotonic crystalloid C. Concentration greater than the body plasma
- Identify the crystalloid solution. A. Hetastarch B. Lactated Ringer’s C. Blood D. Oxygen-carrying solution
- The most commonly used fluids for prehospital IV therapy are A. colloids, crystalloids, and blood B. lactated Ringer’s, blood, and 5% dextrose in water (D 5 W) C. blood, 5% dextrose in water (D 5 W), and sterile water D. Normal saline solution and lactated Ringer’s
- It is important to read the label on every IV bag because A. different IV solutions are packaged similarly. B. the label contains the expiration date of the IV fluid. C. the name of the IV solution is on the label. D. all of the above are reasons why the EMT should read the label on every IV bag.
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