Learning Objectives
By the end of this section, you will be able to:
- Discuss the pathophysiology and clinical manifestations of hypovolemia and hypervolemia
- Describe the diagnostics and laboratory values related to hypovolemia and hypervolemia
- Apply nursing concepts to and plan associated nursing care for patients with hypovolemia and hypervolemia
- Evaluate the efficacy of nursing care for patients with hypovolemia and hypervolemia
- Describe the medical therapies that apply to the care of those experiencing hypovolemia and hypervolemia
- Identify the appropriate fluid replacement method for various fluid disturbances
The importance of maintaining a normal fluid balance within the body cannot be overstated. Both excessive and inadequate amounts of fluid can alter the body’s homeostasis and become life-threatening if left untreated. These imbalances are common in many different medical conditions, which nurses must be able to effectively monitor and actively treat to restore overall fluid balance and homeostasis.
Hypovolemia
A decrease in fluid volume in the intravascular space, known as hypovolemia, occurs when fluid loss is greater than fluid intake, resulting in a deficient volume of fluid in the body. Dehydration, often misconstrued for hypovolemia, is a decrease in extracellular fluid that can cause hypovolemia. Hypovolemia may occur on its own, affecting only the body’s overall fluid balance, or in combination with other imbalances, such as those involving electrolytes or acids and bases.
Pathophysiology of Hypovolemia
The underlying pathophysiology of hypovolemia involves mechanisms that increase fluid loss from the body and often are coupled with limited fluid intake needed to replenish lost fluids. Common causes of hypovolemia include
- burns
- excessive diaphoresis
- excessive urine loss (from diabetes insipidus or diabetes mellitus)
- fever
- malnutrition
- poor oral fluid intake
- prolonged diarrhea or vomiting
- severe hemorrhage
Certain risk factors may predispose some individuals to experiencing hypovolemia. These risk factors include
- chronic disease (e.g., diabetes mellitus, kidney disease)
- exercising or working outdoors in hot weather
- old age
- using diuretic medication
- young age (e.g., infants, children)
Assessment and Diagnostics of Hypovolemia
Hypovolemia can develop quickly and become life-threatening if not assessed and treated swiftly. Nurses can perform several important assessments to determine the patient’s overall fluid status and confirm the presence of hypovolemia. These assessments and their expected findings are described in Table 10.3.
| Assessment | Findings Associated with Hypovolemia |
|---|---|
| Physical assessment |
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| Intake and output |
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| Daily weights |
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| Vital signs |
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| Laboratory values |
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There are no diagnostic tests specifically for hypovolemia. This diagnosis is based on clinical manifestations, assessment findings, trends in laboratory values, and the patient’s physiological response to treatment with fluid resuscitation, which is described in more detail in the following sections.
Nursing Care of Patients with Hypovolemia
First and foremost, effective nursing care for patients with hypovolemia begins with early detection of the condition. The nurse should be mindful of subtle changes in assessment findings or laboratory value trends that may indicate the development or worsening of a fluid deficit. Once the diagnosis has been made, the main goals of nursing care include restoring fluid balance to an optimal level, maintaining homeostasis, and preventing the development of complications such as hypovolemic shock, a life-threatening condition in which the heart cannot get enough blood and oxygen to tissues and organs.
Recognizing and Analyzing Cues
Because of the body’s internal compensatory mechanisms, patients with hypovolemia may be asymptomatic at first. This highlights the importance of assessing for subtle changes in condition that may indicate the early development of a fluid deficit. Some of these early signs include
- confusion due to decreased perfusion to the brain
- hypotension, because the lack of fluid results in lower-than-normal blood pressure within blood vessels
- thirst, including dry mucous membranes
Prioritizing Hypotheses, Generating Solutions, and Taking Action
If the nurse observes signs and symptoms that are indicative of a fluid deficit, one of the first actions they should take is to gather more information and assessment data. If they have not been done already, the nurse should begin to measure and document the patient’s intake and output to monitor for a steadily decreasing urine output, another potential early clinical manifestation of hypovolemia. Daily weights should be ordered to measure and monitor overall fluid balance. If possible, the nurse should also obtain laboratory values such as serum creatinine, blood urea nitrogen (BUN), and urine specific gravity, because these tests can provide more information about the patient’s overall fluid status and condition. Additionally, it is important for the nurse to take proactive actions to prevent the worsening of the condition. For example, if the patient’s fluid loss stems from excessive vomiting, the nurse should ensure the patient has appropriate antiemetic medications available to prevent further fluid loss and keep the patient’s condition from deteriorating. Fluid replenishment should be initiated intravenously if the patient cannot tolerate oral intake.
Evaluation of Nursing Care for Patients with Hypovolemia
After diagnosing and initiating treatment for hypovolemia, the nurse should evaluate patient outcomes to determine whether treatment was effective and if further intervention is necessary.
After treatment, the nurse should monitor the patient for signs indicating that the patient’s fluid imbalance has been corrected. Signs that would indicate an improvement in condition include
- adequate blood pressure (specifically, a systolic blood pressure >100 mm Hg)
- clear, lighter-colored urine
- decreased confusion
- improved level of consciousness
- improved urine output (at minimum, 30 mL/h)
- moist mucous membranes
- normal capillary refill time and improved skin turgor
- normalized laboratory values (e.g., BUN, creatinine)
- vital signs within normal ranges
Medical Therapies and Related Care
The main aspect of medical treatment for a fluid deficit involves the replacement of lost fluid back into the body. Sometimes it is enough to encourage the patient to consume more fluids orally, especially water. However, in more severe cases, medical treatment with intravenous (IV) fluid therapy may be necessary.
The purpose of IV therapy for treating hypovolemia is to replace fluids to replenish blood volume. Using a peripheral IV catheter or central line, IV fluids are injected via a vein directly into the patient’s bloodstream, where they act rapidly in the body to restore fluid volume. This treatment allows large amounts of fluids to be administered quickly to restore significant fluid volume losses, such as those experienced with severe hemorrhage and trauma. Once the fluid enters the vein, there is no way to terminate the action. Therefore, it is important to properly prepare the IV fluid, correctly calculate the dose and rate, and administer it safely to the patient. It is important to note that IV fluid administration is considered a medical intervention and requires an order from the provider prior to the initiation of therapy.
Types of IV Solutions for Therapy
Intravenous fluid therapy is administered to restore fluid volume in the intravascular compartment or within the blood vessels. However, IV fluids can also be used to facilitate the movement of fluid between compartments. The three types of IV fluids are isotonic, hypotonic, and hypertonic, and they vary on the basis of their tonicity, or composition and concentration of dissolved particles. An isotonic solution contains the same number of dissolved solutes compared with blood. A hypotonic solution contains fewer dissolved solutes than blood contains. A hypertonic solution contains more dissolved solutes than blood contains. Table 10.4 describes characteristics of each category of IV fluid. Figure 10.8 illustrates the osmotic effects of each type of fluid on red blood cells.
| Characteristic | Isotonic Fluid | Hypotonic Fluid | Hypertonic Fluid |
|---|---|---|---|
| Tonicity | Contains the same number of solutes compared with blood | Contains fewer solutes than blood contains | Contains more solutes than blood contains |
| Fluid movement | No net movement of fluid | Fluid moves into cells (can cause cellular swelling) | Fluid moves out of cells (can cause cellular shrinking) |
| Situations used | Fluid replacement in states such as:
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| Nursing considerations |
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| Examples |
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Clinical Safety and Procedures (QSEN)
Safe Administration of IV Fluid Therapy
When initiating or changing a bag of IV fluids or medications, it is important to remember the following points:
- IV fluids are a medication. Verify the provider’s orders and check that the patient does not have an allergy to the medication. Perform the six rights of medication administration three times, as you would when giving any other medication. Check the type of fluid and the expiration date, and verify the fluid is free of discoloration and sediment. Check the expiration date when obtaining a new tubing administration set.
- Examine the bag to ensure it is intact and not leaking. There may be moisture on the inside of the plastic IV bag storage container; this is normal.
- Verify the infusion rate of IV fluids is appropriate based on the patient’s age, size, preexisting medical conditions, and prescribed indication. If a manual calculation is needed to set the IV flow rate, calculate the rate, then double-check the calculated rate with another registered nurse.
- IV tubing administration sets require routine replacement to prevent infection. Follow agency policy regarding initiating tubing change before initiating a new bag of fluid or medication.
- If administration-set tubing is present, trace the tubing from the patient to its point of origin to make sure you are accessing the correct port.
- Assess the IV site. Inspect for redness, swelling, or tenderness that could be a sign of irritation, inflammation, or infection.
- Ensure the IV site is patent when initiating new fluid or medication. Aspirate for blood return and flush the IV catheter according to agency policy.
Hypervolemia
Fluid volume overload, known as hypervolemia, occurs when an increased amount of fluid is retained in the intravascular compartment, resulting in an excess fluid volume. This condition may occur on its own, affecting overall fluid balance, or in combination with other imbalances, such as those involving electrolytes or acids and bases.
Pathophysiology of Hypervolemia
The underlying pathophysiology of hypervolemia involves mechanisms that increase fluid retention in the body. Common causes of hypervolemia include
- excessive consumption of fluids or salts
- heart failure
- kidney failure
- liver cirrhosis
Clinical Manifestations
Hypervolemia can quickly become life-threatening if not detected and treated early. Common clinical manifestations of hypovolemia include
- ascites, or fluid retention in the abdominal cavity
- bounding pulses
- crackles in the lungs
- jugular venous distension (JVD)
- pitting edema, or swelling, in dependent tissues and extremities due to fluid accumulation in the interstitial space (Figure 10.9 and Table 10.5)
- Weight gain
Assessment and Diagnostics
There are several key assessments that nurses can perform to determine the patient’s overall fluid status and confirm the presence of hypervolemia. These assessments and their expected findings are described in Table 10.5.
| Assessment | Findings Associated with Hypervolemia |
|---|---|
| Physical assessment |
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| Intake and output |
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| Daily weights |
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| Vital signs |
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| Laboratory values |
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A useful test used for diagnosing hypervolemia is a chest X-ray, because it may visualize fluid congestion in the lungs. However, there are no specific diagnostic tests for hypervolemia. As with hypovolemia, the diagnosis is made on the basis of clinical manifestations and assessment findings, laboratory value trends, and the patient’s physiological response to treatment.
Nursing Care of the Patient with Hypervolemia
Effective nursing care for patients with excess fluid volume begins with early detection of the imbalance. The nurse should monitor for subtle changes in condition that may indicate the development or worsening of fluid overload. Once the diagnosis has been made, the main goals of nursing care include removing excess fluid, maintaining homeostasis, and preventing the development of complications such as pulmonary edema, a life-threatening condition in which the respiratory system no longer functions effectively due to excessive fluid accumulation in the lungs.
Recognizing and Analyzing Cues
In the early stages of hypervolemia, the body is usually able to compensate for the increased fluid volume. Eventually, however, the major organs involved in fluid filtration and excretion become tired, resulting in fluid excess. Some of the earliest signs of hypervolemia the nurse should monitor for include
- confusion or headache, due to increased perfusion to the brain
- edema in the extremities, which occurs as fluid leaks from intravascular space into the interstitial tissues
- polyuria, as the body attempts to compensate for excessive fluid by excreting more as urine
Prioritizing Hypotheses, Generating Solutions, and Taking Action
If the nurse observes signs symptoms are indicative of hypervolemia, more information and data should be gathered to aid in the diagnosis. Similar to hypovolemia, it is important that the nurse begin accurately measuring and documenting intake and output. In some cases, one of the first signs of fluid excess is a steadily increasing urine output as the body attempts to compensate and remove excess fluid. It is also important for the nurse to take proactive actions to prevent worsening of the condition. For example, if the patient is experiencing severe pitting edema, the nurse should implement measures such as elevating the affected extremity above heart level or applying compression stockings to lessen the amount of edema present. Daily weights are another measurement intervention to enable accurate fluid balance and monitoring.
Evaluation of Nursing Care for Patients with Hypervolemia
After diagnosis of and initiation of treatment for hypervolemia, it is important for the nurse to evaluate patient outcomes to determine whether treatment was effective and if further intervention is necessary.
After treatment, the nurse should monitor the patient for signs indicating their fluid imbalance has been corrected. Signs that would indicate an improvement in condition include
- decreased confusion
- improved edema or ascites
- normal hourly urine output (approximately 30 mL/h)
- normalized laboratory values (e.g., BUN, hemoglobin)
- pulse oximetry greater than 92% and normal lung sounds
- vital signs within normal ranges
Medical Therapies and Related Care
If the fluid overload is occurring secondary to IV fluid therapy, simply stopping the fluid infusion and initiating a fluid restriction may be adequate to restore normal fluid balance. In more severe cases of hypervolemia, however, the use of diuretic medications or invasive procedures such as dialysis may be necessary. Potential treatment options for hypervolemia are displayed in Table 10.6.
| Treatment | Rationale | Nursing Considerations |
|---|---|---|
| Fluid and sodium restriction |
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| Pharmacologic therapy: diuretics | Indicated for excess fluid removal:
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| Dialysis |
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