Medical-Surgical Nursing Chapter 6.pdf

Fluid, Electrolyte, and Acid-Base Balance 6 http://evolve.elsevier.com/Linton/medsurg Objectives 1. Describe the extracellular and intracellular fluid compartments. 2. Describe the composition of the extracellular and intracellular body fluid compartments. 3. Discuss the mechanisms of fluid trans...

Fluid, Electrolyte, and Acid-Base Balance 6 http://evolve.elsevier.com/Linton/medsurg Objectives 1. Describe the extracellular and intracellular fluid compartments. 2. Describe the composition of the extracellular and intracellular body fluid compartments. 3. Discuss the mechanisms of fluid transport and fluid balance. 4. Identify the causes, signs and symptoms, and treatment of fluid imbalances. 5. Describe the major functions of the major electrolytes: sodium, potassium, calcium, magnesium, and chloride. 6. Identify the causes, signs and symptoms, and treatment of electrolyte imbalances. 7. List data to be collected for the focused assessment of fluid and electrolyte status. 8. Discuss the medical treatment and nursing management of persons with fluid and electrolyte imbalances. 9. Explain why older persons are at increased risk for fluid and electrolyte imbalances. 10. List the four types of acid-base imbalances. 11. Identify the major causes of each acid-base imbalance. 12. Explain the medical treatment and nursing management of acid-base imbalances. Key Terms acid acid-base balance active transport base diffusion (dĭ-FYŪ-zhŭn) electrolyte (ĕ-LĔK-trō-līt) extracellular fluid (ĕks-tră-SĔL-ū-lăr) filtration (f ĭl-TRĀ-shŭn) fluid volume deficit fluid volume excess homeostasis (hō-mē-ō-STĀ-sĭs) intracellular fluid (ĭn-tră-SĔL-yū-lăr) osmolality (ŏz-mō-LĂL-ĭ-tē) osmolarity (ŏz-mō-LĀR-ĭ-tē) osmosis (ŏz-MŌ-sĭs) selectively permeable membrane (sĕ-LĔK-tĭv-lē PĔR-mē-ăb’l MĔM-brān) Maintaining the correct amount and distribution of body fluids and electrolytes and the correct pH of body fluids is essential for survival. The body constantly makes adjustments to maintain this balance. Unfortunately, many disease processes and medical interventions pose actual or potential threats to patients’ fluid and electrolyte balances. Therefore, nurses must understand the basic principles of fluid and electrolyte and acid-base balance to maintain homeostasis and to detect and correct imbalances. This chapter offers a review of key concepts. Homeostasis is necessary for cells to be able to carry out their work. Body fluids are in constant motion, maintaining healthy living conditions for body cells. The process of homeostasis involves the delivery of essential elements such as oxygen and glucose to the cells and the removal of wastes such as carbon dioxide from the cells. When the body does not maintain homeostasis, the cells cannot function properly and illness or death results.! HOMEOSTASIS Body fluids are classified as intracellular or extracellular, depending on their location. Intracellular fluid is fluid within a cell and extracellular fluid is fluid outside the cell. Most of the body’s fluids are found within the cell. Extracellular fluids are found in the blood vessels in the form of plasma or serum (called intravascular fluid); in the fluid surrounding the cells (called interstitial fluid), including lymph fluid; and elsewhere, such as in digestive Approximately 50% to 60% of the human body is composed of water. To maintain internal balance, the body must be able to regulate the fluids within it. The tendency to maintain relatively constant conditions as in the fluid compartments is called homeostasis. All organs and structures of the body are involved in the maintenance of homeostasis. BODY FLUID COMPARTMENTS 85 86 UNIT III Pathology Processes and Effects Table 6.1 Total Body Fluids Intracellular MEN (%) 40 WOMEN (%) 36 INFANT (%) 40 Extracellular 20 18 35 Total body fluids 60 54 75 secretions, sweat, and cerebrospinal fluid. Extracellular fluid is mainly responsible for the transport of nutrients and wastes throughout the body. The distribution of total body fluids varies by age and gender (Table 6.1).! COMPOSITION OF BODY FLUIDS WATER Water makes up the largest portion of the body weight. The percentage of body weight that is water is affected by age, sex, and amount of body fat. A person’s percentage of body water usually decreases with advancing age. Women have a lower percentage of body water than do men throughout the adult years because women have more fat than men and fat cells contain less water than other cells. Obese people have a relatively lower percentage of body water because of their increased number of fat cells.! SOLUTES In addition to water, body fluids contain solutes (dissolved substances) such as electrolytes and nonelectrolytes. Table 6.2 Electrolyte Composition of Extracellular and Intracellular Fluids ELECTROLYTE Sodium (Na+) EXTRACELLULAR FLUID (mEq/L) 130–145 INTRACELLULAR FLUID (mEq/L) 14 Potassium (K+) 3.5–5.1 140 Chloride (Cl–) 98–107 4–6 Bicarbonate (HCO3–) 24 12 5 1–8 1.5–2.5 6–30 2 40–95 Calcium (Ca2+) Magnesium (Mg2+) Phosphate (HPO4–) Electrolytes can move from one fluid compartment to another. However, the normal concentration of specific electrolytes is different in the two compartments (Table 6.2). Sodium Sodium (Na+) is the most abundant electrolyte in the body and the primary electrolyte in the extracellular fluid. It plays a major role in the regulation of body fluid volumes, muscular activity, nerve impulse conduction, and acid-base balance. To remember the role of sodium in water distribution, think “water goes where sodium is.” For example, a person whose sodium level is too high will retain water. We can promote the elimination of excess water by giving a diuretic that promotes excretion of sodium.! Potassium Electrolytes An electrolyte is defined as a substance that develops an electrical charge when dissolved in water. Examples of electrolytes are sodium, potassium, calcium, chloride, bicarbonate, and magnesium. When these substances are dissolved in water, they break up into small particles called ions, which have either a positive (+) or a negative (−) charge. Ions that have a positive electrical charge are called cations. Examples of cations are sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+). Ions that have a negative charge are called anions. Examples of anions are chloride (Cl−), bicarbonate (HCO3−), and phosphate (HPO4−). Electrolytes maintain a balance between positive and negative charges. For every positively charged cation, a negatively charged anion can be found. In every fluid compartment of the body, the cations and anions combine to balance one another. This process keeps the body cells in homeostasis. The concentration of an electrolyte in a solution or body fluid compartment is measured in milliequivalents per liter (mEq/L). Milliequivalents indicate the chemical activity or combining power of ions. Hydrogen is used as a standard for comparing chemical activities of electrolytes. One milliequivalent of an electrolyte has the same chemical combining power as 1 mEq of hydrogen. Potassium (K+) is found mainly in the intracellular fluid and is the major intracellular cation. Because it is so abundant within the cell, it plays an important role in maintaining fluid osmolarity and volume within the cell. Potassium is essential for normal membrane excitability, a critical factor in the transmission of nerve impulses. It is also needed for protein synthesis, for the synthesis and breakdown of glycogen, and to maintain plasma acid-base balance.! Chloride Chloride (Cl−) is an extracellular anion that is usually bound with other ions, especially sodium or potassium. Its major functions are to regulate osmotic pressure between fluid compartments and to assist in regulating acid-base balance.! Calcium Calcium (Ca2+) is usually combined with phosphorus to form the mineral salts of the bones and teeth. Of the total calcium in the body, 99% is concentrated in the bones and teeth and 1% is in the extracellular fluid. Calcium is ingested through the diet and absorbed through the intestine. Calcium and phosphorus have a reciprocal relationship, meaning that if one falls, the other typically rises; if one rises, the other falls. In addition to maintaining strong teeth and bones, calcium promotes normal transmission of nerve Fluid, Electrolyte, and Acid-Base Balance CHAPTER 6 impulses and helps to regulate normal muscle contraction and relaxation. Constant regulation of calcium levels takes place in the body. If the serum calcium level falls, additional calcium is absorbed in the intestine, reabsorbed through the kidneys, or taken from the bones. If more calcium is needed in the bones, it is taken from the bloodstream and also reabsorbed through the kidneys.! Magnesium Magnesium (Mg2+) is a cation that is found in bone (50%–60%), intracellular fluid (39%–49%), and extracellular fluid (1%). After potassium, magnesium is the most abundant cation in intracellular fluid; therefore it is vital to cellular function. Magnesium plays a role in the metabolism of carbohydrates and proteins, the storage and use of intracellular energy, and neural transmission. Magnesium is important in the functioning of the heart, nerves, and muscles. Approximately 30% to 40% of magnesium ingested through the diet is absorbed, mainly through the small intestine. Magnesium is excreted through the kidneys, and the rate of excretion is regulated by sodium and calcium excretion, extracellular fluid volume, and parathyroid hormone.! Nonelectrolytes Although most of the solutes in the body are electrolytes, other substances are dissolved in the body fluids as well. Examples are urea, protein, glucose, creatinine, and bilirubin. These solutes do not carry an electrical charge and are measured in milligrams per deciliter (mg/dL).! TRANSPORT OF WATER AND ELECTROLYTES MEMBRANES The intracellular and extracellular fluid compartments are separated by selectively permeable membranes that control movement of water and certain solutes. Selective permeability maintains the unique composition of each compartment of the body while allowing for the transport of nutrients and wastes to and from cells. For example, selectively permeable membranes surround cells to separate fluid in the cells from fluid in the tissues. Some solutes cross membranes more easily than others. Small molecules and water move freely across membranes whereas larger molecules such as protein move less readily.! TRANSPORT PROCESSES Water and solutes are transported between intracellular and extracellular fluid compartments by one or more of the following processes: (1) diffusion, (2) active transport, (3) filtration, and (4) osmosis. Diffusion Diffusion is the random movement of particles in all directions. The natural tendency is for a substance to 87 move from an area of higher concentration to an area of lower concentration. One example is the movement of oxygen from the alveoli to the pulmonary capillaries. The concentration of oxygen in the alveoli is greater than in the capillaries, therefore oxygen diffuses into the capillaries and is transported through the bloodstream to other parts of the body. The term facilitated diffusion is used when a carrier protein transports the molecules through membranes toward an area of lower concentration. This process does not require energy.! Active Transport Carrier proteins can transport substances from an area of lower concentration to an area of equal or greater concentration. This process, which requires expenditure of energy, is called active transport. Many solutes, such as sodium, potassium, glucose, and hydrogen, are actively transported across cell membranes. An example of active transport is the sodium pump. The concentration of sodium is highest in extracellular fluid. Therefore excess sodium cannot leave the cell by diffusion. Active transport “pumps” the excess sodium out of the cell into the extracellular fluid.! Filtration Filtration is the transfer of water and solutes through a membrane from an area of high pressure to an area of low pressure. This pressure is known as hydrostatic pressure and is a combination of pressures from the force of gravity on the fluid and the pumping action of the heart. Filtration is a necessary process for moving fluid out of the capillaries into the tissues and for filtering plasma through the kidneys.! Osmosis Osmosis is the movement of water across a membrane from a less concentrated solution to a more concentrated solution. It involves the movement of water only, but sometimes the force of movement across the membrane carries some solutes along. If a fluid compartment has less water and more sodium, water from another compartment moves to the more concentrated compartment by osmosis to create a better fluid balance.! OSMOLALITY Osmolality refers to the concentration of a solution de- termined by the number of dissolved particles per kilogram of water. A higher osmolality means that the concentration of salt, or any other solute, is higher in the water because the solution contains less water. Osmolality controls water movement and distribution in body fluid compartments by regulating the concentration of fluid in each compartment. When solutes such as electrolytes are added to water, the volume is expanded to include both the water and the solutes. The osmolality of intracellular fluid and extracellular fluid tends to equalize because of the constant 88 UNIT III Pathology Processes and Effects shifting of water. A change in osmolality of intracellular fluid affects the osmolality of extracellular fluid and vice versa. The osmolality of intracellular fluid is maintained primarily by potassium and the osmolality of the extracellular fluid is maintained primarily by sodium. The normal range of osmolality of the body fluids is between 280 and 294 milliosmoles per kilogram (mOsm/kg). You will see the term osmolarity also used to refer to the concentration of particles in body water. Osmolarity refers to the concentration of particles per liter of solution. For the study of body fluids, measuring liters of fluid is more practical than measuring kilograms; therefore you will see clinical studies of fluids using the term osmolarity rather than osmolality.! REGULATORY MECHANISMS Regulation of fluid balance requires the constant adjustment of fluid volume, distribution, and composition. This process is accomplished by the kidneys and circulatory system, which are influenced by the sympathetic nervous system, specific hormones, and the thirst center. KIDNEYS The kidneys are the main regulators of fluid balance. They control extracellular fluid by adjusting the concentration of specific electrolytes, the osmolality of body fluids, the volume of extracellular fluid, blood volume, and pH. Kidney function is delicately controlled by hormones and other coordinating mechanisms (see Chapter 41 for a review of renal structure and function). The nephron is the functioning unit of the kidney. Each nephron is made up of a glomerulus and tubules. The glomerulus is the filtering portion of the nephron and the tubule is responsible for secretion and reabsorption. The nephrons conduct the work of the kidney through the processes of filtration, reabsorption, and secretion. Filtration A primary activity of the kidney is filtration. Blood plasma entering the kidney via the renal artery is delivered to the glomerulus. Approximately 20% of the plasma is filtered into the glomerular capsule. This fluid is called filtrate. Most of the remaining plasma leaves the kidney through the renal vein. The filtrate then moves through the tubules, where it is transformed into urine by the processes of tubular reabsorption and secretion.! Tubular Reabsorption Tubular reabsorption is a process by which most of the glomerular filtrate is returned to the circulation. Water and selected solutes move from the tubules into the capillaries. Waste products remain in the tubules for excretion whereas most water and sodium are reabsorbed into the bloodstream. Tubular reabsorption is important for adjusting the volume and composition of the filtrate and for preventing excessive fluid loss through the kidneys.! Tubular Secretion Tubular secretion is the last phase in the work of the kidneys. During this phase, the filtrate is transformed into urine. Various substances, among them drugs, hydrogen ions, potassium ions, creatinine, and histamine, pass from the blood into the tubules. This process eliminates some excess substances to maintain fluid and electrolyte balance as well as metabolic waste products.! HORMONES Hormones that have a major effect on fluid volume and balance are renin, aldosterone, antidiuretic hormone (ADH), and atrial natriuretic factor (ANF). Renin is a hormone that is secreted when blood volume or blood pressure falls. Renin activates angiotensinogen, a substance secreted by the liver, to form angiotensin I. Angiotensin-converting enzyme then converts angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor that also stimulates the release of aldosterone, with subsequent sodium and water retention. Aldosterone is released by the adrenal glands in response to the hormone renin. Aldosterone acts on the kidney tubules to increase the reabsorption of sodium and decrease the reabsorption of potassium. Because the retention of sodium causes water retention, aldosterone acts as a volume regulator. The release of aldosterone from the adrenal gland is stimulated by many factors, including increased potassium levels and decreased sodium levels in the blood. ADH is produced by the hypothalamus and is secreted into the general circulation by the posterior pituitary gland. It causes the capillaries to reabsorb more water so that urine is more concentrated and less volume is excreted. An increase in plasma osmolality (plasma is more concentrated) stimulates the release of ADH into the bloodstream to replenish needed fluid in the body. Other factors that stimulate the release of ADH are related to stress situations such as hypotension, pain, surgery, and certain medications. ANF is a hormone released by the atria in response to stretching of the atria by increased blood volume. ANF stimulates excretion of sodium and water by the kidneys, decreased synthesis of renin, decreased release of aldosterone, and vasodilation. The effect of these actions is to reduce blood volume and to lower blood pressure.! THIRST An additional regulatory mechanism is thirst, which regulates fluid intake. Increased plasma osmolality stimulates osmoreceptors in the hypothalamus to Fluid, Electrolyte, and Acid-Base Balance CHAPTER 6 trigger the sensation of thirst. In other words, more sodium and less water in the body make a person thirsty. Additional fluids are consumed and the kidneys conserve water until plasma osmolality returns to normal.! 89 FLUID GAINS Liquids AMOUNT (mL) 1000 FLUID LOSSES Lungs AMOUNT (mL) 400 Food (solid) 1200 Skin 400 H2O of oxidation (metabolic production) 300 Kidneys (urine) 1500 the kidneys, skin, lungs, and gastrointestinal tract. The usual adult urine volume is between 1 and 2 liters per day (L/day), or 1 milliliter per kilogram of body weight per hour. In the kidneys, water loss varies largely with the amount of solute excreted and with the level of ADH. Water and electrolyte (sodium, chloride, and potassium) losses through the skin occur by sweating. Water loss through the lungs occurs by evaporation at a rate of 300 to 400 milliliters per day (mL/day). In a hot, dry environment, water loss via the skin and lungs increases. In the gastrointestinal tract, the usual loss of fluid is approximately 100 to 200 mL/day. The bulk of fluid secreted into the gastrointestinal tract is reabsorbed in the small intestine. Water loss through the skin, lungs, and intestinal tract is referred to as insensible loss. Fig. 6.1 diagrams the regulation of body fluid volume.! Daily total intake 2500 Intestines (feces) 200 AGE-RELATED CHANGES AFFECTING FLUID BALANCE Daily total output 2500 FLUID GAINS AND LOSSES In a healthy adult, the 24-hour fluid intake and output are approximately equal (Table 6.3). Fluids are gained by drinking and eating and are lost through 24-Hour Intake and Output of Body Fluids Table 6.3 Multiple factors place the older person at risk for fluid and electrolyte imbalances. The aging kidney is slower Regulation of body fluid volume ADH release (inhibited) Hypervolemia Excess fluid volume Hypovolemia Deficient fluid volume Inhibits Stimulates Aldosterone release (inhibited) Thirst (inhibited) Thirst (stimulated) ADH release (stimulated) Aldosterone release (stimulated) Contribute to Contribute to Increased urination of dilute urine Decreased urination of concentrated urine Normal fluid volume restored Fig. 6.1 Regulation of body fluid volume depends on aldosterone, antidiuretic hormone (ADH), and thirst. (From Black JM, Hawks JH, Keene AM: Medical-surgical nursing: clinical management for continuity of care, ed 8, Philadelphia, 2009, Saunders.) 90 UNIT III Pathology Processes and Effects to adjust to changes in acid-base, fluid, and electrolyte balance. The older adult often has a reduced sense of thirst and therefore may be in a state of chronic dehydration because of inadequate fluid intake. Total body water declines with age, with the greatest loss being from the intracellular fluid compartment. Therefore an older person has limited reserves with which to maintain fluid balance when abnormal losses occur. You must monitor fluid status in the older person and be alert for signs and symptoms of imbalances, including disorientation, confusion, constipation, and falls resulting from postural hypotension. The health history may reveal many chronic conditions, such as heart failure and renal insufficiency, which are more common among older adults and place them at risk for fluid and electrolyte imbalances. Drugs such as antihypertensives, diuretics, and antacids used to treat these and other conditions can also contribute to imbalances. In addition, chronic conditions that affect mobility or mental status may interfere with adequate fluid intake. Some factors that contribute to acute fluid deficits are trauma, infection, fever, influenza or cold, NPO (nothing by mouth) status, and drug therapies (diuretics, antidepressants, sedatives). In addition to the general assessment data, it is especially important to document fluid intake patterns, medications, mental status, and recent weight changes. Components of the physical examination are described later in this chapter. Note that skin turgor is a less reliable indicator of fluid status in older persons than in younger individuals, because some loss of skin elasticity normally occurs with increased age. Assessing turgor on the sternum or forehead is advised for better accuracy in the older person. Serum electrolytes should be the same for all adults, so any abnormalities of such in the older person should be investigated. No prescription for a specific daily fluid intake exists because body weight, health state, activity level, and environment all affect individual requirements. The common belief that 8 glasses per day are required has no scientific basis. Current guidelines from the Institute of Medicine advise that adult men should take in 3 L/day, and adult women should take in 2.2 liters daily. Some sources recommend an intake of 30 mL/kg/day with a minimum of 1.5 L/day. Residents at long-term care facilities are at high risk for inadequate fluid intake because of physiologic, functional, cognitive, and environmental factors. However, fluid intake should be increased gradually in the older adult, because the heart and kidneys adapt more slowly to changes in fluid volume. An individual with cardiac or renal disease sometimes has fluid restrictions because of fluid retention. Put On Your Thinking Cap! Measure your fluid intake and output for 24 hours. If they are not equal, list possible explanations for the difference. ! FOCUSED ASSESSMENT OF FLUID AND ELECTROLYTE BALANCE HEALTH HISTORY A complete health history helps to determine whether patients have any conditions that may contribute to fluid or electrolyte imbalances. Conditions that have great potential for disrupting fluid balance are vomiting, diarrhea, kidney diseases, diabetes, salicylate poisoning, burns, congestive heart failure, cerebral injuries, ulcerative colitis, and hormonal imbalances. Other risk factors include the intake of drugs such as diuretics and cathartics and medical interventions such as gastric suctioning. Anticipate fluid and electrolyte imbalances in patients who are at risk. Patient complaints that may be associated with fluid imbalances are fatigue, palpitations, dizziness, edema, muscle weakness or cramps, dyspnea, and confusion. Because electrolyte disturbances produce nonspecific symptoms, they can be confirmed only with laboratory tests.! PHYSICAL EXAMINATION Vital Signs Assessment of pulse, respiration, temperature, and blood pressure can detect indicators of changes in both fluid and electrolyte balance, as shown in Box 6.1. Box 6.1 Vital Sign Changes With Fluid and Electrolyte Imbalances PULSE • Increased rate with fluid volume deficit, sodium deficit, or magnesium deficit • Decreased rate with magnesium excess or potassium deficit • Weak quality, irregular rhythm, and rapid rate suggest severe potassium excess or sodium deficit • Bounding quality with fluid volume excess, which often results in circulatory overload.! RESPIRATION • Fluid volume excess can cause pulmonary edema with dyspnea and tachypnea. • Changes in respiratory function are noted also with acid-base imbalances. Slow, shallow respirations with intermittent periods of apnea occur in severe metabolic alkalosis. Deep, rapid respirations indicate metabolic acidosis.! TEMPERATURE • Fever increases the metabolic rate, causing fluid loss it also increases the respiratory rate, which increases loss of water vapor from the lungs. • Temperature may be subnormal with fluid volume excess ! BLOOD PRESSURE • A fall in systolic pressure of more than mm g when the patient changes from the lying to the standing position or from the lying to the sitting position usually indicates fluid volume deficit • Fluid volume excess that expands blood volume raises the blood pressure. Fluid, Electrolyte, and Acid-Base Balance CHAPTER 6 Body temperature variations can be associated with excess or deficit fluid volume. Also fever poses a risk of water and electrolyte loss associated with sweating and an increased metabolic rate. Blood pressure is directly related to blood volume. The pulse rate and quality may change in response to blood volume alterations. Because electrolytes affect the conduction of impulses, electrolyte changes can affect heart rate and rhythm. Respirations are minimally affected by electrolyte changes. However, rapid respirations increase water loss. Also excess fluid volume can lead to heart failure and pulmonary edema with shortness of breath. Measuring blood pressure with the patient lying, sitting, and standing can detect positional differences that may reflect inadequate blood volume.! 91 Skin Skin characteristics Skin color, moisture, turgor, and temperature all reflect fluid balance. Dry, flushed skin is associated with dehydration. Pale, cool, clammy skin is associated with the severe fluid volume deficit that occurs with shock. Moist, edematous tissue, especially in dependent areas, may be seen with excess fluid volume.! Facial characteristics The patient who is severely dehydrated usually has a pinched, drawn facial expression. Soft eyeballs and sunken eyes accompany a severe fluid volume deficit. Puffy eyelids and fuller cheeks suggest excess fluid volume.! Skin turgor Intake and Output An accurate record of intake and output is essential to determine whether the patient’s intake is equal to output. All fluids entering or leaving the body should be noted, as explained in Box 6.2. A changing urine output may reflect attempts by the kidneys to maintain or restore balance or it may reflect a problem that causes fluid disturbances. In addition to urine volume, urine characteristics also give clues to fluid balance. Clear, pale urine in a healthy person suggests the excretion of excess water whereas dark, concentrated urine indicates that the kidneys are retaining water.! Body Weight Measurement of body weight is a good indicator of fluid loss or retention (Box 6.3). One liter of fluid weighs 2.2 lb. Therefore, retention of 1 liter of fluid is reflected as a weight gain of 2.2 lb (1 kg). A patient can accumulate up to 10 lb (4.5 kg) of fluid before pitting edema is evident. To monitor fluid status, weigh the patient daily on the same scale, at the same time of day, and wearing the same type of clothing.! Box 6.2 Focused Assessment of Intake and Output • Many serious fluid and electrolyte imbalances can be averted by carefully monitoring records of fluid intake and output. • If the total intake is substantially less than the total output, the patient is in danger of fluid volume deficit • If the total intake is substantially more than the total output, the patient is in danger of fluid volume excess. • Intake should include all fluids taken into the body: oral fluids, foods that are liquid at room temperature, intravenous fluids, subcutaneous fluids, fluids instilled into drainage tubes or irrigants, tube feeding solutions, water given through feeding tubes, and enema solutions. • utput measures include urine, vomitus, diarrhea, drainage from fistulas, drainage from suction machines, excessive perspiration, and drainage from excisions normal adult urine output is 40–80 mL/h. Skin turgor is best measured by pinching the skin over the sternum, the inner aspects of the thighs, or the forehead. In patients who are dehydrated, skin flattens more slowly after the pinch is released. The term tenting is sometimes used to describe skin that does not flatten promptly after being gently pinched into a tent shape. The skin of older people generally has a slower return to normal, so assuming a fluid deficit based only on poor skin turgor would be inappropriate in the older person.! Edema Edema reflects water and sodium retention, which can result from excessive reabsorption or inadequate excretion of sodium, as may occur with kidney failure. Inspect and palpate the skin for edema. Test for edema by pressing the skin that lies over the tibia, fibula, sacrum, or sternum. Edema is described as pitting if a depression remains in the tissue after pressure is applied with a fingertip. Pitting edema is evaluated on a fourpoint scale, ranging from 1+ edema (barely detectable pit) to 4+ edema (deep and persistent pit that is approximately 1 inch or 2.54 cm deep). Edema can be so severe that pitting is not possible. The tissue becomes so full that fluid cannot be displaced when pressed. Edematous tissue that feels hard is known as brawny edema. After a radical mastectomy, Box 6.3 Focused Assessment of Body Weight The use of body weight as an accurate index of fluid balance is based on the assumption that the patient’s dry weight remains relatively stable. Even under starvation conditions, an individual loses no more than 1⁄3 to 1⁄2 lb dry weight per day. A rapid loss of body weight occurs when the total fluid intake is less than the total fluid output. A rapid gain of body weight occurs when total fluid intake is more than the total fluid output. Rapid loss Rapid gain MILD MODERATE SEVERE 2% 2% 5% 5% deficit 8% = excess Rapid gain or loss of 1 kg (2.2 lb) of body weight is approximately equivalent to the gain or loss of 1 liter of fluid. 92 UNIT III Pathology Processes and Effects brawny edema commonly occurs because the removal of axillary nodes allows fluid to accumulate in the affected arm.! Mucous Membranes Tongue turgor In a normal person, the tongue has one longitudinal furrow. A person with deficient fluid volume has additional longitudinal furrows, and the tongue is smaller as a result of fluid loss. Sodium excess causes the tongue to appear red and swollen.! Moisture of the oral cavity A dry mouth may be the result of deficient fluid volume or mouth breathing. Normally, saliva is pooled in the area where the cheek and the gum meet. Dryness in this area usually indicates a true fluid volume deficit. However, dry mouth is a common side effect of many medications.! Veins The appearance of the jugular veins in the neck and the veins in the hands can suggest either a deficient or excess fluid volume. Neck vein distention Distention of the jugular veins can indicate excess fluid volume. Inspect the neck veins by having the patient recline with the head of the bed elevated at a 30- to 45-degree angle. If the jugular veins can be seen more than 3 cm above the sternal angle, then excess fluid volume is most likely present. Deficient fluid volume may be detected by examining the jugular neck veins with the patient lying down. If no distention occurs, then deficient fluid volume is most likely present.! Hand veins Observation of hand veins can also be helpful in evaluating the patient’s fluid volume. Elevate the hands and then note how long it takes for the veins to empty. Veins usually empty in 3 to 5 seconds. Next, place the hands in a dependent position and note the time needed for the veins to fill. Veins usually fill in 3 to 5 seconds. If the volume is decreased, veins take longer than 3 to 5 seconds to fill. When the fluid volume is increased, veins take longer than 3 to 5 seconds to empty. The nursing assessment of fluid and electrolyte status is summarized in Box 6.4.! DIAGNOSTIC TESTS AND PROCEDURES A variety of laboratory tests may be performed to assess fluid and electrolyte status and to determine whether they are within the normal range (Table 6.4). Various references report slightly different ranges of normal. Clinical laboratories typically report the normal range along with patient results, therefore you do not need to memorize these ranges. Box 6.4 Focused Assessment of Fluid and Electrolyte Status HEALTH HISTORY Present Illness Vomiting, diarrhea, burns, head injury! Past Health History Renal or cardiac disease, diabetes, inflammatory bowel disease, adrenal or thyroid disease! Current Drugs Diuretics, salicylates, antacids, potassium or calcium supplements! Family History Diabetes, cardiac disease! Review of Systems Fatigue, palpitations, dizziness, edema, dyspnea, confusion! Functional Assessment Change in activity tolerance, mental alertness! PHYSICAL EXAMINATION General Survey: Alertness, orientation, posture Vital Signs: Pulse rate/rhythm/quality respiratory rate/ pattern blood pressure in lying, sitting, and standing positions temperature Weight: Present compared with usual Skin: Color, moisture, turgor, temperature Facial Characteristics: Expression, firmness of eyeballs, edema of eyelids or cheeks Edema: Presence, location, pitting, or brawny Mucous Membranes: Tongue turgor, moisture of the oral cavity Veins: Jugular vein distention, hand vein emptying and refilling time Urine Studies Urine pH The kidneys can change the acidity or alkalinity of the urine by excreting hydrogen (H+) ions. Urine pH is a measure of hydrogen ions in the urine. It is useful for determining whether the kidneys are responding appropriately to metabolic acid-base imbalances. The normal range is 4.5 to 8.0; however, fresh urine is usually acidic (∼6.0). Urine tends to be most acidic in the morning (after a fast) and more alkaline after meals. Diet is a factor in that a person who consumes large amounts of citrus fruits and vegetables tends to have alkaline urine whereas a person who eats a lot of meat tends to have acidic urine. A urine specimen that is not tested within 4 hours of collection may become alkaline, therefore urine pH should be measured within 1 to 2 hours of collection. If the specimen cannot be tested promptly, it should be refrigerated.! Urine specific gravity Urine specific gravity (SpG) is a measure of urine concentration. In most instances, normal urine SpG is between 1.016 and 1.022 in adults. Fluid, Electrolyte, and Acid-Base Balance CHAPTER 6 Table 6.4 93 Normal Values Related to Fluid and Electrolyte and Acid-Base Balance URINE Urine pH 4.6–6.8 BLOOD Arterial blood pH Urine specific gravity 1.016–1.022 NA Urine osmolality (random specimen) 250–1200 mOsm/kg H2O Serum osmolality 285–300 mOsm/kg Urine sodium 40–220 mEq/24 h or SI = 40–220 mmol/24 h Serum sodium 136–145 mEq/L Urine potassium 25–125 mEq/24 h Serum potassium 3.5–5.1 mEq/L Urine chloride 40–220 mEq/24 h or SI: 40–220 mmol/24 h Serum chloride 98–107 mEq/L Urine phosphorus 0.4–1.3 g/24 h Serum phosphorus 2.8–4.5 mg/dL Urine magnesium 6.0–10.0 mEq/L or SI: 3–5 mmol/day Serum magnesium Age 21–59 years: 1.6–2.6 mg/dL Age 60–90 years: 1.6–2.4 mg/dL Urine creatinine Male: 1–2 g/day Female: 0.8–1.8 g/day Serum calcium (total) Ages 18–60 years: 8.6–10.0 mg/dL Ages 60+ years: 8.8–10.2 Serum creatinine Female: 0.6–1.1 mg/dL Male: 0.7–1.3 mg/dL 7.35–7.45 Serum bicarbonate Arterial 21–28 mEq/L Venous 24–28 mm Hg or SI: 24–28 mmol/L From Malarkey, LM, McMorrow, ME: Saunders nursing guide to laboratory and diagnostic tests, ed 2, St. Louis, 2012, Elsevier-Saunders. SpG is a good indicator of fluid balance. A high SpG indicates that the urine is highly concentrated, usually as a result of deficient fluid volume. A low SpG indicates that the urine contains a large amount of water in relation to solutes, usually as a result of excess fluid volume. The SpG also reflects renal function. If the kidneys are not functioning properly, they may fail to concentrate or dilute urine as needed to maintain extracellular fluid balance. The presence of x-ray dyes, glucose, or protein in the urine can cause an increased SpG that may be misleading; that is, the patient may not really have a deficient fluid volume. As people age, their kidneys are less efficient at conserving water by concentrating urine. Therefore the older person may produce relatively dilute urine (low or normal SpG) even when they are dehydrated.! is required. The patient is instructed to void, discard the specimen, record the time, and start collecting all urine thereafter for 24 hours. The specimen must be refrigerated. During the specimen collection period, the patient should maintain good hydration, should not engage in vigorous exercise, and should avoid high-protein foods, coffee, tea, and cola drinks. Be aware that many drugs, including cephalosporin antibiotics, can alter test results. For best interpretation, serum creatinine clearance should be assessed as well. Also the laboratory needs to know the patient’s height, weight, and age. The normal creatinine clearance for men is 85 to 125 mL/min/1.73 m2 of body surface area; for women, it is 75 to 115 mL/min/1.73 m2 of body surface area. The range decreases with age.! Urine osmolality Osmolality measures the number of dissolved particles in a solution. This information provides a more precise measurement of the kidney’s ability to concentrate urine than does the SpG. For the most accurate interpretation, a serum osmolality should be done simultaneously with the SpG. Dilute urine has a low osmolality and generally reflects renal excretion of excess water. Low osmolality is also apparent when kidneys are unable to conserve water by concentrating urine. Concentrated urine has a high osmolality and generally indicates renal conservation of water. It can also be present when the kidneys are failing because the volume of urine secreted declines.! Urine creatinine clearance Urine creatinine clearance tests are used to detect glomerular damage in the kidney. A 24-hour specimen Urine sodium Urine sodium reflects sodium intake and fluid volume status. When the intake of sodium is high, the kidneys will increase the excretion of sodium in the urine. When large amounts of fluids are taken in or sodium intake is restricted, the urine is more dilute, thus the urine sodium falls. The urinary excretion of sodium is normally highest during the day. The normal urine sodium is 75 to 200 mEq/L. If collected over a period of 24 h, the normal range is 40 to 220 mEq/24 hours or SI = 40 to 220 mmol/24 h.! Urine potassium Urine potassium is a measure of renal tubular function. A 24-hour specimen is most meaningful because the urinary excretion of potassium is highest at night and lowest during the day. Therefore a random sample would 94 UNIT III Pathology Processes and Effects not truly represent function of the renal tubules. The normal value is 25 to 125 mEq/24 hours.! Blood Studies Serum hematocrit The hematocrit is the percentage of blood volume that is composed of red blood cells. An increased hematocrit is seen with deficient fluid volume and dehydration because the blood is more concentrated. A low hematocrit is consistent with excess fluid volume because of dilution. The normal range for hematocrit is 40% to 54% for men and 38% to 47% for women.! Serum creatinine Creatinine is a metabolic waste product. The serum creatinine level is a better indicator of renal function than the blood urea nitrogen. A high level of creatinine in the blood indicates poor renal function. The normal range is 0.6 to 1.1 mg/dL for females and 0.7 to 1.3 mg/dL for males. Even small changes in the serum creatinine can be significant.! Blood urea nitrogen Blood urea nitrogen (BUN) provides a measure of renal function. Normal is 5 to 20 mg/dL for adults under 60 years of age and 8 to 23 mg/dL for adults over 60 years of age. A high BUN is associated with deficient fluid volume and possibly impaired renal function; conversely, a low BUN is associated with excess fluid volume.! Serum osmolality Serum osmolality is a measure of blood concentration. High serum osmolality is related to a deficient fluid volume, and low serum osmolality is related to excess fluid volume. The normal range is 285 to 300 mOsm/kg.! Serum albumin Albumin is a plasma protein that helps to maintain blood volume by creating colloid osmotic pressure. The normal range for serum albumin is 3.5 to 5.5 g/dL. Low serum albumin allows water to shift into the interstitial compartment, which reduces blood volume and creates edema.! Serum electrolytes Normal values for serum sodium, potassium, chloride, and calcium are shown in Table 6.4.! FLUID IMBALANCES FLUID VOLUME DEFICIT Fluid volume deficit occurs when water is less than normal in the body. The two types of fluid volume deficits are isotonic extracellular fluid deficit (hypovolemia) and hypertonic extracellular fluid deficit (dehydration). A fluid volume deficit may result from decreased intake, abnormal fluid losses, or both. Examples of abnormal fluid losses are the loss of water as a result of excessive bleeding, severe vomiting and diarrhea, and severe burns. The signs and symptoms of fluid volume deficit vary depending on how suddenly the deficit develops and how severe it is. Symptoms are not as apparent with deficits that are mild and have a gradual onset but are quite dramatic when the loss is severe and the onset is abrupt. In general, the body attempts to compensate for fluid volume deficits by decreasing urine output. The heart rate increases to maintain blood flow to body tissues. The blood pressure may fall because of the reduced blood volume. Treatment varies somewhat according to the cause of a fluid volume deficit and the severity of symptoms. Nursing care should be based on specific patient problems, which might include the following: • Fluid volume deficit/loss, potential for fluid volume deficit related to inadequate fluid intake, excessive fluid loss, high blood glucose, inadequate ADH production or effect, high fever, altered capillary permeability • Acute confusion related to decreased cerebral tissue perfusion • Constipation related to excessive reabsorption of water from stool in the colon • Decreased activity tolerance related to decreased blood volume, decreased tissue perfusion • Hyperthermia related to infectious process, decreased fluid volume • Potential for injury related to decreased level of consciousness • Potential for disrupted tissue integrity related to poor tissue turgor • Inadequate circulation related to decreased cardiac output secondary to decreased blood volume The characteristics, causes, assessment findings, treatment, and nursing care for each type of fluid volume deficit are outlined in Table 6.5.! FLUID VOLUME EXCESS An increase in body water is called fluid volume excess. The two types of fluid volume excess are extracellular fluid excess (isotonic fluid excess) and intracellular water excess (hypotonic fluid excess). Fluid volume excess may result from renal or cardiac failure with retention of fluid, increased production of ADH or aldosterone, overload with isotonic intravenous fluids, or the administration of 5% dextrose in water (D5W) after surgery or trauma. The body attempts to compensate for fluid volume excess by increasing the filtration and excretion of sodium and water by the kidneys and decreasing the production of ADH. As with fluid volume deficit, the severity of the symptoms in fluid volume excess depends on how quickly the condition develops. Severe fluid volume excess can cause or aggravate heart failure and pulmonary edema. Nursing care varies somewhat according to the cause of a fluid volume excess and the severity of symptoms. Care should be based on appropriate patient problem statements, which might include the following: • Fluid volume excess related to fluid retention, excess or hypotonic intravenous fluid administration • Acute confusion related to cerebral edema • Activity intolerance, inadequate oxygenation related to pulmonary edema Fluid, Electrolyte, and Acid-Base Balance CHAPTER 6 Table 6.5 95 Fluid Volume Deficit Definition Etiology ISOTONIC EXTRACELLULAR FLUID DEFICIT (HYPOVOLEMIA) Deficiency of both water and relative electrolytes HYPERTONIC EXTRACELLULAR FLUID DEFICIT (DEHYDRATION) Deficiency of water without electrolyte deficiency Decreased fluid intake related to inability to obtain or ingest fluids Excessive fluid loss related to vomiting, diarrhea Shifting of fluid into interstitial space (third spacing) related to increased capillary permeability Increased water loss related to high blood glucose as in uncontrolled diabetes mellitus, inadequate ADH production or renal response to ADH, high fever, excessive sweating Decreased fluid intake with continued intake of electrolytes, as with concentrated tube feedings Focused Assessment Findings Blood pressure Hypotension Hypotension Pulse Weak, rapid Weak, rapid Respirations Rapid Rapid Temperature Decreased Increased Weight Loss Loss Tissue turgor Normal or edema Poor Mucous membranes Moist Dry Blood cells Hgb, Hct, RBCs increased Hgb, Hct, RBCs increased Urine output Decreased Decreased or increased Thirst Normal Thirsty Treatment Correction of underlying cause Water and electrolyte replacement. Antiemetics, antidiarrheals. Oral and intravenous fluids. Correction of underlying cause Water replacement. Oral and intravenous fluids. Hypoglycemic agents, ADH, antipyretics. Nursing care Protect edematous tissue with third spacing. Assist with rising and ambulating if patient is dizzy. Keep hourly records of intake and output expect intake to exceed output at first Be alert for fluid excess (rising pulse and blood pressure, dyspnea) caused by excessive fluid replacement. Monitor blood glucose if patient has diabetes. Assist with oral hygiene. Assist with rising and ambulating if patient is dizzy. Keep hourly records of intake and output expect intake to exceed output at first Be alert for fluid excess (rising pulse and blood pressure, dyspnea) caused by excessive fluid replacement. ADH, Antidiuretic hormone Hct, hematocrit Hgb, hemoglobin RBCs, red blood cells. • Potential for injury related to decreased level of consciousness • Potential for disrupted skin tissue integrity related to edema • Inadequate circulation related to reduced cardiac output with heart failure The causes, assessment findings, treatment, and nursing care of the patient with fluid volume excess are outlined in Table 6.6.! The two electrolytes that cause the majority of problems when an imbalance exists are sodium and potassium. replacement; the use of distilled water to irrigate body cavities; and excessive secretion of ADH. Increased ADH secretion is associated with severe stress, some head injuries, and a condition called syndrome of inappropriate antidiuretic hormone secretion (SIADH). Other disorders that put the patient at risk for hyponatremia include congestive heart failure, liver cirrhosis, and nephrotic syndrome. Sodium normally holds water in the extracellular compartment. When serum sodium is low, water can enter cells more freely. This shift of fluids is most significant in relation to brain cells. The accumulation of fluid in brain cells produces the most important physiologic effects of hyponatremia. HYPONATREMIA (SODIUM DEFICIT) Hyponatremia is lower-than-normal sodium in the blood serum. It can be an actual deficiency of sodium or an increase in body water that dilutes the sodium excessively. Causes include excessive intake of water without sodium; excessive loss of sodium, as with vomiting, diarrhea, or diaphoresis with only water Focused Assessment If hyponatremia is suspected or the patient is at risk, monitor for signs and symptoms, which include headache, muscle weakness, fatigue, apathy, confusion, abdominal cramps, and orthostatic hypotension. Take blood pressure readings with the patient lying or sitting and then standing to determine whether a drop ELECTROLYTE IMBALANCES 96 UNIT III Pathology Processes and Effects Table 6.6 Fluid Volume Excess EXTRACELLULAR FLUID EXCESS Isotonic Fluid Excess INTRACELLULAR WATER EXCESS Hypotonic Fluid Excess Definition Excess of both water and electrolytes. Major symptoms are caused by increased blood volume. Excess of body water without excess electrolytes. Major symptoms are caused by cerebral edema. Etiology Retention of water and electrolytes related to kidney disease overload with isotonic IV fluids verhydration in presence of renal failure administration of D5W after surgery or trauma Focused Assessment Findings Blood pressure Increased Increased systolic Pulse Bounding, increased rate Decreased rate Respirations Increased rate, crackles, dyspnea Increased rate Weight Gain Gain Edema Extremities: dependent, pitting Puffy eyelids Cerebral Neck veins Distended Normal Mucous membranes Moist Moist Blood Hgb, Hct, RBCs decreased by dilution Hgb, Hct, RBCs normal or decreased Mental status Irritability, confusion, lethargy Irritability, confusion, lethargy Hand vein engorgement Present Absent Pupils Sluggish response to light with cerebral edema Sluggish response to light with cerebral edema Treatment Correction of underlying cause. Restriction of water and sodium intake. Diuretics to promote fluid elimination, digitalis to improve cardiac output. Renal dialysis if kidney failure is a factor. Correction of underlying cause. Restricted water intake. IV and oral fluids with electrolytes. Demeclocycline (Declomycin) to decrease kidney response to ADH. Nursing care Give drugs and IV fluids as ordered. Monitor Give drugs and IV fluids as ordered. Explain for excess diuresis. Explain and enforce fluid and enforce fluid restriction. Offer ice restriction ffer ice chips use small fluid chips, provide oral hygiene, serve only containers, let patient help design plan for fluid fluids allowed with meal trays, let patient intake. If patient is not confused, allow to swish design plan for fluid intake. If patient is not fluids in mouth and spit out without swallowing. confused, allow to swish fluids in mouth and Explain salt restriction obtain dietary consult spit out without swallowing. If confused, for teaching (see Box 6.5). Protect edematous take safety precautions: side rails up, bed in tissue: turn and reposition q2h. Inspect for low position, call light in reach, check often. signs of skin breakdown. If dyspneic: Elevate Seizure precautions per agency policy. head of bed 30 degrees or for comfort, loosen restrictive clothing, oxygen as ordered. ADH, Antidiuretic hormone D5W, dextrose in water Hct, hematocrit Hgb, hemoglobin IV, intravenous q2h, every hours RBCs, red blood cells. in pressure is significant. A drop in systolic blood pressure of more than 20 mm Hg indicates orthostatic hypotension.! diuretic therapy, drugs such as tolvaptan (Samsca) and conivaptan (Vaprisol), which block the action of ADH, or demeclocycline may be ordered.! Medical Treatment The usual treatment for hyponatremia is restriction of fluids while the kidneys excrete excess water. Intravenous normal saline or Ringer’s lactate may be ordered. If sodium falls below 115 mEq/L, hypertonic sodium may be ordered. The diuretic furosemide (Lasix) may be ordered because of its ability to promote water loss that exceeds the sodium loss. A balanced diet usually provides adequate sodium, but patients with moderate or severe hyponatremia may need sodium replacement therapy. If the patient has SIADH, which can be chronic or acute, an effort is made to determine and correct the cause. In addition to fluid management and NURSING CARE OF THE PATIENT WITH HYPONATREMIA You can help to prevent hyponatremia in patients with feeding tubes by using normal saline rather than water for irrigation. For patients with hyponatremia, administer prescribed medications and intravenous fluids and monitor the response to these. Measure fluid intake and output, assess mental status, and monitor laboratory test results. If the patient is confused, take safety measures to prevent injury. If the patient who has hyponatremia has low blood pressure or postural hypotension, assist with ambulation.! Fluid, Electrolyte, and Acid-Base Balance CHAPTER 6 Box 6.5 97 Guidelines for Sodium Restriction Salt substitutes containing potassium chloride should be recommended only if approved by the physician. Potassium is generally contraindicated for patients with renal disease. Salt-free, herb-based seasoning products are readily available in most grocery stores and should be suggested instead. • Instruct patients/clients on reading the Nutrition Facts food label for sodium content of foods. • Encourage patients to prepare food at home without adding salt and to limit eating in restaurants. • Recommend baked products, using sodium-free baking powder, potassium bicarbonate (instead of sodium bicarbonate or baking soda), and salt-free shortening in place of those containing sodium. • Avoid obviously salted foods such as bouillon, soup and gravy bases, canned soups and stews bread and rolls with salt toppings, salted crackers salted nuts or popcorn, potato chips, pretzels, and other salted snack foods. Avoid buying vegetables prepared in sauce. • Avoid smoked or cured meats, such as bacon, bologna, cold cuts, other processed meats, chipped or corned beef, frankfurters, ham, koshered or kosher-style meats, and canned meat poultry. • Avoid salted and smoked fish such as cod, herring, and sardines. • Avoid sauerkraut, olives, pickles, relishes, kimchi, and other vegetables prepared in brine, tomato, and vegetable cocktail juices. • Avoid seasonings such as celery salt, garlic salt, Worcestershire sauce, fish sauce and soy sauce Reduced sodium versions of items like soy sauce can still be very high in sodium. • Serve cheeses in limited amounts Swiss cheese and cream cheese are relatively low in sodium. • Monitor the sodium content of various medications, including over-the-counter brands. The front of the food package can be used to identify foods that may contain less sodium, but it is important to understand terminology such as salt/sodium-free (<5 mg per serving), very low sodium (<36 mg per serving), low sodium (<141 mg per serving), reduced sodium (25% less sodium than original product), light in sodium or lightly salted (at least 50% or less sodium added than in the regular product), and no-salt added or unsalted (not necessarily sodium-free). Seasoning without salt: Flavorings or seasonings will make food more appetizing. For example: • Fish, meat, vegetables: lemon, vinegar • Meat: onion, garlic, green pepper, nutmeg, ginger, dry mustard, sage, cumin, marjoram, and curry without salt • Meat and poultry: cranberry sauce, applesauce, jelly • Vegetables: onion, mint, ginger, mace, dill seed, parsley, green peppers, fresh mushrooms • Unsalted cottage cheese: minced onion, chopped chives, raw green pepper, grated carrots, chopped parsley, crushed pineapple From Mahan LK, Raymond JL: Krause’s food and the nutrition care process, 14th ed, St. Louis, 2017, Elsevier, 1037–1038. HYPERNATREMIA (SODIUM EXCESS) Hypernatremia refers to a higher-than-normal concentration of sodium in the blood. It is a very serious imbalance that can lead to death if not corrected. Hypernatremia can occur alone or in combination with extracellular fluid volume deficit. The high level of sodium in the serum and other extracellular fluids causes water to shift out of the cells, which creates cellular dehydration. Hypernatremia occurs when loss of water or retention of sodium is excessive. Some causes of hypernatremia are vomiting, diarrhea, diaphoresis (profuse sweating), and insufficient ADH. Signs and symptoms of hypernatremia are thirst, a flushed skin, dry mucous membranes, a low urine output, restlessness, an increased heart rate, convulsions, and postural hypotension. Medical Treatment Medical intervention focuses on oral or intravenous replacement of water to restore balance. The aim is to restore the fluid balance slowly to prevent cerebral edema resulting from excessive dilution of extracellular fluid. If the patient has an extracellular fluid volume deficit as well, intravenous fluids with decreasing amounts of sodium may be ordered. A low-sodium diet is often prescribed.! NURSING CARE OF THE PATIENT WITH HYPERNATREMIA Encourage patients with hypernatremia to drink water for hydration. Closely monitor the infusion of intravenous fluids, especially when the patient’s cardiac or renal function is abnormal. Patient education is important. Teach the patient with hypernatremia to track daily intake and output and to recognize the signs and symptoms of fluid retention or depletion. Advise patients of any dietary restrictions. If a low-sodium diet is prescribed, patients should avoid foods that are high in sodium: ketchup, monosodium glutamate (Accent), mustard, pickles, olives, ham, most canned foods, artificial sweeteners, laxatives, cough medications, and some antacids. Box 6.5 provides guidelines for patients who need to restrict their sodium intake.! HYPOKALEMIA (POTASSIUM DEFICIT) Hypokalemia is low serum potassium. Causes include vomiting, diarrhea, nasogastric suction, inadequate dietary intake of potassium, diabetic acidosis, excessive aldosterone secretion, and drugs such as potassium-wasting diuretics and corticosteroids. Because potassium is necessary for normal cellular function, deficiencies may result in gastrointestinal, renal, cardiovascular, and neurologic disturbances. Most important is the effect on myocardial cells, which tends to cause abnormal, and potentially fatal heart rhythms. 98 UNIT III Pathology Processes and Effects Signs and symptoms of hypokalemia are anorexia, abdominal distention, vomiting, diarrhea, muscle cramps, weakness, dysrhythmias (abnormal cardiac rhythm