Nursing Care of Patients With Fluid, Electrolyte, and Acid-Base Imbalances PDF

4068_Ch06_069-089 15/11/14 12:46 PM Page 70 6 Nursing Care of Patients With Fluid, Electrolyte, and Acid–Base Imbalances KEY TERMS acidosis (as-ih-DOH-sis) alkalosis (al-kah-LOH-sis) anion (AN-eye-on) antidiuretic (AN-tee-DYE-yuh-RET-ik) cation (KAT-eye-on) dehydration (DEE-hye-DRAY-shun) diffusi...

4068_Ch06_069-089 15/11/14 12:46 PM Page 70 6 Nursing Care of Patients With Fluid, Electrolyte, and Acid–Base Imbalances KEY TERMS acidosis (as-ih-DOH-sis) alkalosis (al-kah-LOH-sis) anion (AN-eye-on) antidiuretic (AN-tee-DYE-yuh-RET-ik) cation (KAT-eye-on) dehydration (DEE-hye-DRAY-shun) diffusion (dih-FEW-zhun) dysrhythmia (dis-RITH-mee-yah) edema (eh-DEE-mah) electrolytes (ee-LEK-troh-lites) extracellular (EX-trah-SELL-yoo-lar) filtration (fill-TRAY-shun) hydrostatic (HYE-droh-STAT-ik) hypercalcemia (HYE-per-kal-SEE-mee-ah) hyperkalemia (HYE-per-kuh-LEE-mee-ah) hypermagnesemia (HYE-per-MAG-nuh-SEE-mee-ah) hypernatremia (HYE-per-nuh-TREE-mee-ah) hypertonic (HYE-per-TAWN-ik) hyperventilation (HYE-per-VEN-tih-LAY-shun) hypervolemia (HYE-per-voh-LEE-mee-ah) hypocalcemia (HYE-poh-kal-SEE-mee-ah) hypokalemia (HYE-poh-kuh-LEE-mee-ah) hypomagnesemia (HYE-poh-MAG-nuh-SEE-mee-ah) hyponatremia (HYE-poh-nuh-TREE-mee-ah) hypotonic (HYE-poh-TAWN-ik) hypovolemia (HYE-poh-voh-LEE-mee-ah) interstitial (IN-tur-STISH-uhl) intracellular (IN-trah-SELL-yoo-ler) intracranial (IN-trah-KRAY-nee-uhl) intravascular (IN-trah-VAS-kyoo-ler) isotonic (EYE-so-TAWN-ik) osmolarity (OZ-moh-LAR-it-ee) osmosis (ahs-MOH-sis) osteoporosis (AHS-tee-oh-por-OH-sis) semipermeable (SEM-ee-PER-mee-uh-bull) transcellular (trans-SELL-yoo-lar) 70 BRUCE K. WILSON LEARNING OUTCOMES 1. Identify the purposes of fluids and electrolytes in the body. 2. List the signs and symptoms of common fluid imbalances. 3. Predict patients who are at the highest risk for dehydration and fluid excess. 4. Identify data to collect in patients with fluid and electrolyte imbalances. 5. Describe therapeutic measures for patients with fluid and electrolyte disturbances. 6. Identify the education needs of patients with fluid imbalances. 7. Categorize common causes, signs and symptoms, and treatments for sodium, potassium, calcium, and magnesium imbalances. 8. Identify foods that have high sodium, potassium, and calcium contents. 9. Give examples of common causes of acidosis and alkalosis. 10. Compare how arterial blood gases change for each type of acid–base imbalance. 4068_Ch06_069-089 15/11/14 12:46 PM Page 71 Chapter 6 Nursing Care of Patients With Fluid, Electrolyte, and Acid–Base Imbalances Have you ever wondered why you get thirsty? The body is continually changing, and water supports these changes. Approximately 60% of a young adult’ s body weight is w ater. Older people are less than 50% w ater, and infants are between 70% and 80% water. Fat cells do not contain water, so people with a higher percentage of fat cells have a lower percentage of water. In addition to w ater, body fluids also contain solid substances that dissolve, called solutes. Some solutes are electrolytes and some are nonelectrolytes. Electrolytes are chemicals that can conduct electricity when dissolv ed in water. Examples of electrolytes are sodium, potassium, calcium, magnesium, acids, and bases; these are discussed later in this chapter. Nonelectrolytes do not conduct electricity; examples include glucose and urea. FLUID BALANCE Fluids are located in various compartments within the body. Fluid inside the cells is referred to as intracellular fluid (ICF), and fluid outside the cells is called extracellular fluid (ECF). ECF can be further di vided into three types: interstitial fluid, intravascular fluid, and transcellular fluid (Fig. 6.1). Interstitial fluid is the w ater that surrounds the body’ s cells and includes lymph. Intravascular fluid, or blood plasma, is the fluid within arteries, veins, and capillaries. Fluids and electrolytes mo ve between the interstitial fluid and the intravascular fluid. Transcellular fluids are those in specific compartments of the body, such as cerebrospinal fluid, digestive juices, and synovial fluid in joints. Control of Fluid Balance The primary control of water in the body is through pressure sensors in the vascular system that stimulate or inhibit the release of antidiuretic hormone (ADH) from the pituitary 71 gland. A diuretic is a substance that causes the kidne ys to excrete more fluid. ADH works in just the opposite w ay. ADH causes the kidne ys to retain fluid. If fluid pressures within the vascular system decrease, more ADH is released, and water is retained. If fluid pressures increase, lessADH is released, and the kidneys eliminate more water. Movement of Fluids and Electrolytes in the Body Fluids and electrolytes move in the body by active and passive transport systems. Active transport depends on the presence of adequate cellular adenosine triphosphate (A TP) for energy. The most common examples of active transport are the sodium-potassium pumps. These pumps, located in the cell membranes, cause sodium to mo ve out of the cells and potassium to move into the cells when needed. In passive transport, no energy is expended specifically to move the substances. General body mo vements aid passive transport. The three passive transport systems are diffusion, filtration, and osmosis. Diffusion is the movement of a substance from an area of higher concentration to an area of lower concentration. If you pour cream into a cup of coffee, the movement of the molecules will eventually cause the cream to be dispersed throughout the beverage. If you stir the coffee, this process occurs at a faster rate. Body mo vement assists passive transport, like stirring the coffee. It causes diffusion to occur at a faster rate. Filtration is the mo vement of both w ater and smaller molecules through a semipermeable membrane. A semipermeable membrane works like a screen that keeps larger substances on one side and permits only smaller molecules to filter to the other side of the membrane. Filtration is promoted by hydrostatic pressure differences between areas. Hydrostatic pressure, sometimes called water-pushing pressure, is the force that water exerts. In the body, filtration is important for the movement of water, nutrients, and waste products in the capillaries. The capillaries serve as semipermeable membranes allowing water and smaller substances to move from the vascular system to the interstitial fluid, but larger molecules and red blood cells remain inside the capillary walls. Osmosis is the movement of water from an area of lower substance concentration to an area of higher concentration. • WORD • BUILDING • Intracellular Intravascular Interstitial Transcellular FIGURE 6.1 Normal distribution of total body water. electrolyte: electro—electricity + lyte—dissolve intracellular: intra—within + cellular—cell extracellular: extra—outside of + cellular—cell interstitial: inter—between + stitial—tissue intravascular: intra—within + vascular—blood vessel transcellular: trans—across + cellular—cell antidiuretic: anti—against + diuretic—urination diffusion: diffuse—spread, scattered filtration: filter—strain through semipermeable: semi—half or part of + permeable—passing through hydrostatic: hydro—water + static—standing osmosis: osmo—impulse + osis—condition 4068_Ch06_069-089 15/11/14 12:46 PM Page 72 72 UNIT TWO Understanding Health and Illness The substances exert an osmotic pressure sometimes called water-pulling pressure. The term osmolarity refers to the concentration of the substances in body fluids. The normal osmolarity of blood is between 270 and 300 milliosmoles per liter (mOsm/L). Another term for osmolarity is tonicity. Fluids or solutions can be classified as isotonic, hypotonic, or hypertonic. A fluid that has the same osmolarity as the blood is called isotonic. For example, a 0.9% (normal) saline solution is isotonic to the blood and is often used as a solution for intravenous (IV) therapy. A solution that has a lower osmolarity than blood is called hypotonic. When a hypotonic solution is gi ven to a patient, the water in the solution lea ves the blood and other ECF areas and enters the cells. Hypertonic solutions exert greater osmotic pressure than blood. When a hypertonic solution is given to a patient, water leaves the cells and enters the bloodstream and other ECF spaces. Fluid Gains and Fluid Losses Water is very important to the body for cellular metabolism, blood volume, body temperature regulation, and solute transport. Although people can survive without food for se veral weeks, they can survi ve only a fe w days without w ater. Thirst is the major indicator that a healthy adult needs more water. Water is gained and lost from the body every day. In addition to liquid intake, some fluid is obtained from solid foods. When too much fluid is lost, the brain’s thirst mechanism tells the individual that more fluid intak e is needed. Older adults are more prone to fluid def icits because they have a diminished thirst reflex and their kidneys do not function as effectively. An adult loses as much as 2500 mL of sensible and insensible fluid each day. Sensible losses are those of which the person is aware, such as urination. Insensible losses may occur without the person recognizing the loss. Perspiration and water lost through respiration and elimination of feces are examples of insensible losses. FLUID IMBALANCES Fluid imbalances are common in all clinical settings. Older people are at the highest risk for life-threatening complications that can result from either fluid deficit, more commonly called dehydration, or fluid e xcess. Infants are at risk for fluid deficit because they take in and excrete a large proportion of their total body water each day. Dehydration Although there are se veral types of dehydration, only the most common type is discussed in this chapter. Dehydration occurs when there is not enough fluid in the body, especially in the blood (intravascular area). Pathophysiology and Etiology The most common form of dehydration results from loss of fluid from the body, resulting in decreased blood volume. This decrease is referred to as hypovolemia. Hypovolemia occurs when the patient is hemorrhaging or when fluids from other parts of the body are lost. F or example, severe vomiting and diarrhea, severely draining wounds, and profuse diaphoresis (sweating) can cause dehydration (Box 6-1). Hypovolemia can also occur when fluid from the intravascular space moves into the interstitial fluid space.This process is called third spacing. Examples of conditions in which third spacing is common include burns, liver cirrhosis, and extensive trauma. As described previously in this chapter, the body initially attempts to compensate for fluid loss by a number of mechanisms. If the cause of dehydration is not resolved or the patient is not able to replace the fluid, a state of dehydration occurs. Prevention You can help pre vent dehydration by identifying patients who have the highest risk for developing this condition and intervening quickly to correct the cause. High-risk patients include older adults, infants, children, and any patient with one of the conditions listed in Box 6-1. Also see “Gerontological Issues—Dehydration.” Adequate hydration is another important interv ention to help prevent dehydration. You should encourage patients to drink adequate fluids. Adults need 30 mL/kg/day of fluids. If a patient is unable to tak e enough fluid by mouth, alternate routes may be necessary. Gerontological Issues Dehydration As a person ages, total body water decreases from 60% to 50% of total body weight. The age-related decrease in total body water is secondary to an increase in body f at and a decrease in thirst sensation. These factors increase the risk of developing dehydration. Manifestations of dehydration in an older adult are different from typical manifestations in a younger person and may include altered mental status, lightheadedness, and syncope. These occur because a patient with hypovolemia has an inadequate circulatory volume and, therefore, oxygen supply to the brain. Signs and Symptoms Thirst is the initial symptom e xperienced by otherwise healthy adults in response to hypovolemia. As the percentage of water in the blood goes down, the percentage of other substances goes up, resulting in the thirst response. As the blood volume decreases, • WORD • BUILDING • isotonic: iso—equal + tonic—strength hypotonic: hypo—less than + tonic—strength hypertonic: hyper—more than + tonic—strength dehydration: de—down + hydration—water hypovolemia: hypo—less than + vol—volume + emia—blood 4068_Ch06_069-089 15/11/14 12:46 PM Page 73 Chapter 6 Box 6-1 Nursing Care of Patients With Fluid, Electrolyte, and Acid–Base Imbalances Common Causes of Dehydration Cecostomy Diabetes insipidus Diarrhea Diuretic therapy Draining abscesses Draining fistulas Fever Frequent enemas Gastrointestinal suction Hemorrhage Ileostomy Long-term nothing-by-mouth (NPO) status Profuse diaphoresis (sweating) Severely draining wounds Systemic infection Vomiting the heart pumps the remaining blood faster but not as powerfully, resulting in a rapid, weak pulse and low blood pressure. The body pulls water into the vascular system from other areas, resulting in decreased tear formation, dry skin, and dry mucous membranes. A dehydrated person will have poor skin turgor. Turgor is considered to be poor if the skin is pinched and a small “tent” or wrinkle remains (called tenting). A dehydrated person’s temperature increases because the body is less able to cool itself through perspiration. Temperature may not appear elevated in an older person because an older adult’s normal body temperature is often lower than a younger person’s. Urine output decreases and the urine becomes more concentrated as water is conserved. Dehydration should be considered in any adult with a urine output of less than 30 mL per hour . The urine may appear darker because it is less diluted. The patient becomes constipated as the intestines absorb more water from the feces. A major method of evaluating dehydration is weight loss. A pint of w ater (16 ounces) weighs approximately 1 pound. Symptoms of dehydration in older p ersons may be atypical (see “Gerontological Issues—Dehydration”). 73 brain, kidneys, and heart must be adequately supplied with blood (perfused) to function properly. The body protects these organs by decreasing blood flow to other areas. When these organs no longer receive their minimum requirements, death results. LEARNING TIP The magic fluid number is 30: healthy adults should drink approximately 30 mL of fluid per kilogram of body weight per day, and they should urinate at least 30 mL per hour. This is just a basic rule of thumb and will vary based on individual circumstances. Diagnostic Tests A patient with dehydration usually has an elevated blood urea nitrogen (BUN) level and elevated hematocrit. Both values are increased because there is less water in proportion to the solid substances being measured. The specific gravity of the urine also increases as the kidneys attempt to conserve water, resulting in a more concentrated urine. Therapeutic Measures The goals of therapeutic measures are to replace fluids and resolve the cause of dehydration. In a patient with moderate or severe dehydration, IV therapy is used. Isotonic fluids that have the same osmolarity as blood, such as normal saline, are typically administered. BE SAFE! BE VIGILANT! Use at least two ways to identify patients. For example, use the patient’s name and date of birth. This is done to make sure that each patient gets the correct medicine and treatment (© The Joint Commission, 2013. Reprinted with permission.). Note: The patient’s room number or physical location is not used as an identifier. LEARNING TIP Do you remember your grandmother saying, “A pint’s a pound the world around”? It’s a great way to remember how much fluid loss is represented by each lost pound. Complications If dehydration is not treated, lack of sufficient blood volume causes organ function to decrease and e ventually fail. The Nursing Process for the Patient Experiencing Dehydration Nurses can play a major role in identifying and caring for patients who are dehydrated. DATA COLLECTION. Assess the patient for signs and symptoms of dehydration. All the classic signs and symptoms may not be present. When assessing an older patient for skin turgor (tenting), assess the skin over the forehead or sternum. The skin over 4068_Ch06_069-089 15/11/14 12:46 PM Page 74 74 UNIT TWO Understanding Health and Illness these areas usually retains elasticity and is therefore a more reliable indicator of skin tur gor. Also check mucous membranes, which should be moist. Weight is the most reliable indicator of fluid loss or gain. A loss of 1 to 2 pounds or more per day suggests w ater loss rather than fat loss. The patient in the hospital setting should be weighed every day. The patient in the nursing home or home setting should be weighed at least three times a week if the patient is at risk for fluid imbalance. Weigh the patient before breakfast using the same scale each time. Intak e and output (I&O) are also typically measured (see “Cultural Considerations”). NURSING DIAGNOSES, PLANNING, AND IMPLEMENTATION. The primary nursing diagnosis and interv entions for the patient with dehydration may include: Risk for Deficient Fluid Volume or Deficient Fluid Volume related to fluid loss or inadequate fluid intake. EXPECTED OUTCOME: The patient will be adequately hydrated as evidenced by stable weight, moist mucous membranes, and elastic skin turgor. • Monitor daily weights and I&O so problems can be detected and corrected early. • Plan with the patient and other members of the health care team the type and timing of fluid intake. Planning with the patient increases the likelihood that the plan will be followed. • Offer fluids often to the confused patient since he or she may not drink independently. • Correct the underlying cause of the fluid deficit, so it does not recur. • Be careful not to overhydrate the patient, so fluid excess does not occur. See Box 6-2 for best practices for maintaining oral hydration in older people. EVALUATION. The patient who is adequately hydrated will have elastic skin turgor, moist mucous membranes, and stable weight. Patient Education The patient, family, and significant others need to be taught the importance of reporting early signs and symptoms of dehydration to a physician or other health care pro vider (HCP). At home or in the nursing home, infections often cause fever and sepsis, a serious condition in which the infection invades the bloodstream. The body attempts to decrease the temperature through perspiration. The patient becomes dehydrated as a result and can become increasingly ill. CRITICAL THINKING Mrs. Levitt ■ Mrs. Levitt is a 92-year-old widow who has been living in the nursing home where you w ork for 4 years. Today she mentions that her urine smells bad and that her heart feels lik e it is beating f aster than usual. You suspect that she is becoming dehydrated. You check her urine and find that it is a dark amber color and has a strong odor. Her heart rate is 98 beats per minute, blood pressure 126/74 mm Hg, respiratory rate 20 per minute, and temperature 99.2°F (37.3°C). 1. What other data should you collect, and what results do you expect? 2. Which interventions should you provide at this time? 3. How should you document your findings? 4. What other team members should be informed of your plan for Mrs. Levitt? 5. How will you know if she is improving? Suggested answers are at the end of the chapter. Fluid Excess Fluid excess, sometimes called overhydration, is a condition in which a patient has too much fluid in the body . Most of the problems related to fluid e xcess result from too much fluid in the bloodstream or from dilution of electrolytes and red blood cells. Pathophysiology and Etiology The most common result of fluid excess is hypervolemia in which there is excess fluid in the intravascular space. Healthy • WORD • BUILDING • hypervolemia: hyper—more than + vol—volume + emia—blood Cultural Considerations Muslims who celebrate Ramadan fast for 1 month from sunup to sundown. Although the ill are not required to fast, ill Muslims may still wish to do so. Fasting may include not taking fluids and medications during daylight hours. Therefore, the nurse may need to alter times for medication administration, including intramuscular medication. Special precautions may need to be taken to prevent dehydration in Muslim patients. 4068_Ch06_069-089 15/11/14 12:46 PM Page 75 Chapter 6 Box 6-2 Nursing Care of Patients With Fluid, Electrolyte, and Acid–Base Imbalances Best Practice Recommendations for Maintaining Oral Hydration in Older People • A fluid intake sheet is the best method of monitoring daily fluid intake. • Urine specific gravity may be the simplest, most accurate method to determine patient hydration status. • Evidence of a dry furrowed tongue and mucous membranes, sunken eyes, confusion, and upper body muscle weakness may indicate dehydration. • Regular presentation of fluids to bedridden older people can maintain adequate hydration status. • Owing to the observation that medication time can be an important source of fluids, fluids should be encouraged at this time. Source: Adapted from Joanna Briggs Best Practice Recommendations: Maintaining Oral Hydration in Older People, 5:6, 2001. Retrieved June 15, 2013, from http://connect.jbiconnectplus.org /ViewSourceFile.aspx?0=4319 adult kidneys can compensate for mild to moderate hyper volemia. The kidneys increase urinary output to rid the body of the extra fluid. Sometimes, however, the kidneys cannot keep up with the excess fluid. Conditions that can cause e xcessive fluid intake are poorly controlled IV therapy, excessive irrigation of wounds or body cavities, and excessive ingestion of water. Conditions that can result in inadequate excretion of fluid include renal (kidney) failure, heart failure, and the syndrome of inappropriate antidiuretic hormone. These conditions are discussed elsewhere in this book. in the feet and legs may be present. The skin is pale and cool. The kidneys increase urine output, and the urine appears diluted, almost like water. The patient rapidly gains weight. In severe fluid excess, the patient develops moist crackles in the lungs, dyspnea, and ascites (excess peritoneal fluid). Complications Acute fluid excess typically results in congestive heart failure. As the fluid builds up in the heart, the heart is not able to properly function as a pump. The fluid then backs up into the lungs, causing a condition known as pulmonary edema. Other major organs of the body cannot recei ve adequate oxygen, and organ failure can lead to death. Diagnostic Tests In the patient experiencing fluid excess, BUN and hematocrit levels tend to decrease from hemodilution. The plasma content of the blood is proportionately increased compared with the solid substances. The specific gravity of the urine also diminishes as the urinary output increases. Therapeutic Measures Once the patient’s breathing has been supported, the goal of treatment is to rid the body of excessive fluid and resolve the underlying cause of the excess. Drug therapy and diet therapy are commonly used to decrease fluid retention. POSITIONING. To facilitate ease in breathing, the head of the patient’s bed should be in semi-Fowler’s or high Fowler’s position (Fig. 6.2). These positions allow greater lung expansion and thus aid respiratory effort. Once the patient has been properly positioned, oxygen therapy may be necessary. OXYGEN THERAPY. Oxygen therapy is typically used to ensure adequate perfusion of major or gans and to minimize dyspnea. If the patient has a history of chronic obstructi ve pulmonary disease, such as emphysema or chronic bronchitis, Prevention One of the best w ays to pre vent fluid e xcess is to a void excessive fluid intake. For example, you should monitor the patient receiving IV therapy for signs and symptoms of fluid excess. In at-risk patients, an electronic infusion pump or a quantity-limiting device, such as a burette, should be used to control the rate of infusion. Also monitor the amount of fluid used for irrigations. For example, when a patient’s stomach is being irrigated (gastric lavage), be sure an excessive amount of fluid is not absorbed. Signs and Symptoms The vital sign changes seen in the patient with fluid e xcess are the opposite of those found in patients with dehydration. The blood pressure is elevated, pulse is bounding, and respirations are increased and shallo w. The neck veins may become distended, and pitting edema (excess water in tissues) • WORD • BUILDING • edema: swelling 75 FIGURE 6.2 Patient in high Fowler’s position with oxygen. 4068_Ch06_069-089 15/11/14 12:46 PM Page 76 76 UNIT TWO Understanding Health and Illness be cautious if you need to administer more than 2 L per minute of oxygen. At higher oxygen doses, the patient may lose the stimulus to breathe and may suffer respiratory arrest. Monitor pulse oximetry and respiratory rate carefully. DRUG THERAPY. Diuretics are commonly administered to rapidly rid the body of excess water. A diuretic is a drug that increases elimination by the kidneys. The drug of choice for fluid excess when the patient has adequately functioning kidneys is usually a loop diuretic such as furosemide (Lasix). Loop diuretics cause the kidneys to excrete sodium and water. Sodium (Na+) and water tend to move together in the body. Potassium (K+), another electrolyte, is also lost, which can lead to a potassium def icit, which is discussed later in this chapter. Furosemide may be given by the oral, intramuscular, or IV route. The oral route is used most commonly for mild fluid excess. IV furosemide is administered by a registered nurse (RN) or HCP for severe fluid excess. The patient should be gin diuresis within 30 minutes after receiving IV furosemide. If not, another dose is given. Strict I&O should be monitored, as well as daily weight, when a patient is receiving IV furosemide. DIET THERAPY. Mild to moderate fluid restriction may be necessary, as well as a sodium-restricted diet. In collaboration with the dietitian, a HCP prescribes the specific restriction necessary, usually a 1- to 2-g sodium restriction for severe excess. Different diuretics result in dif fering electrolyte elimination. Specific diet therapy depends on the medications the patient is receiving and the patient’s underlying medical problems. Nursing Process for the Patient Experiencing Fluid Excess The nurse plays a pivotal role in the care of a patient with fluid excess. Prompt action is needed to pre vent life-threatening complications. DATA COLLECTION. Observe a patient who is at high risk for fluid excess and monitor fluid I&O carefully. If the patient is drinking adequate amounts of fluid (1500 mL per day or more) but is voiding in small amounts, the fluid is being retained by the body. Assess for edema; if it is pitting, a f inger pressed against the skin over a bony area such as the tibia leaves a temporary indentation. For patients in bed, check the sacrum for edema. For patients in the sitting position, check the feet and le gs. Also assess lung sounds because e xcess fluid accumulation in the lungs can cause crackles (see Chapter 29). As mentioned earlier, weight is the most reliable indicator of fluid gain. Weigh at-risk patients daily . A gain of 1 to 2 pounds or more per day indicates fluid retention e ven though other signs and symptoms may not be present. NURSING DIAGNOSES, PLANNING, AND IMPLEMENTATION. Excess Fluid Volume related to excessive fluid intake or inadequate excretion of body fluid EXPECTED OUTCOME: Patient will return to a normal hydration status as evidenced by return to weight that is normal for patient, absence of edema, and clear lung sounds. • Report any increase in weight to the HCP. Increased weight indicates fluid retention. • Implement fluid restriction as ordered to reduce excess intake. Work with the patient and RN to determine how it should be implemented. For example, if a patient is on a 1000 mL per day fluid restriction, you might plan for 150 mL with each meal, 450 mL to be given to the patient to use as he or she likes during the day and 100 mL to be used during the night. Be sure to include the patient in your planning, and remember to reserve enough fluid for swallowing medications. Post a sign in the patient’s room so other caregivers know how much fluid the patient can have. • Administer diuretics as ordered, and monitor patient response. Be sure to monitor potassium in patients receiving potassium-losing loop or thiazide diuretics. Diuretics promote diuresis. • Report urinary output below 30 mL per hour to the HCP or RN because this may signify increasing renal complications. EVALUATION. If interventions have been effective, the patient will return to his or her normal weight with clear lung sounds and no edema. Many patients must remain on drug and diet therap y after hospital discharge to prevent the problem from recurring. Patient Education In collaboration with the dietitian, instruct the patient, family, or other caregiver about any fluid or sodium restrictions to prevent further problems (see “Nutrition Notes”). Highsodium foods to avoid are listed in Table 6.1. Nutrition Notes Reducing Sodium Intake Many foods, such as dairy products, grain products, and some vegetables, are naturally high in sodium, b ut the major sources of dietary sodium are salted and processed foods, including baked goods and condiments. F or example, American cheese has more sodium than cheddar, and cured ham has more than fresh pork. Drinking water may contain signif icant amounts of sodium, particularly if it is softened or mineral water. Because of the numerous hidden sources of sodium, patients on low-sodium diets benefit from education by a dietitian. The adequate intake (AI) of sodium is • 1.5 g daily for adults through age 49 • 1.3 g daily for those aged 50 to 70 • 1.2 g daily for those aged 71 and older The upper tolerable intak e level (UL) for sodium is 2.3 g daily, which is contained in slightly more than a teaspoon of salt. None of these amounts applies to those losing large amounts of sweat daily or to unacclimatized persons exercising in a hot environment. 4068_Ch06_069-089 15/11/14 12:46 PM Page 77 Chapter 6 Nursing Care of Patients With Fluid, Electrolyte, and Acid–Base Imbalances Specific definitions for reduced-sodium food products have been adopted. Note that serving size is an important variable. • Salt or sodium free: <5 mg sodium per serving • Very low sodium: <35 mg sodium per serving (per 100 g if main dish) • Low sodium: <140 mg sodium per serving (per 100 g if main dish) Teaching about diuretic therap y is essential to pre vent electrolyte imbalances. If a potassium-losing diuretic is prescribed, teach the patient to eat foods that are high in potassium (Table 6.2). The patient’s serum potassium level must be periodically monitored by a HCP or home care nurse. If it becomes too low, an oral potassium supplement is needed. The patient or caregiver also needs to be taught common signs and symptoms of fluid e xcess that should be reported TABLE 6.1 COMMON FOOD SOURCES OF SODIUM* 77 to a physician or other HCP. Of special importance is weight gain. A patient at high risk for fluid excess should be weighed at least three times a week in the home or nursing home, at the same time each day, and on the same scale. Weight gain should be reported. TABLE 6.2 FOOD SOURCES OF POTASSIUM* Food, Standard Amount Sweet potato, baked, 1 potato (146 g) Potassium (mg) 694 Calories 131 Beet greens, cooked, 1/2 cup 655 9 Potato, baked, flesh, 1 potato (156 g) 610 145 Yogurt, plain, nonfat, 8-oz container 579 127 Prune juice, 3/4 cup 530 136 Soybeans, green, cooked, 1/2 cup 485 127 Bananas, 1 medium 422 105 Spinach, cooked, 1/2 cup 419 21 Tomato juice, 3/4 cup 417 31 Tomato sauce, 1/2 cup 405 39 Food Group Frozen vegetables Serving Size 1 oz Range (mg) 95–210 Frozen pizza, plain, cheese 4 oz 450–1200 Frozen vegetables, all types 1/2 cup 2–160 Milk, nonfat, 1 cup 382 83 Salad dressing, regular fat, all types 2 tbsp 110–505 Pork chop, center loin, cooked, 3 oz 382 197 Salsa 2 tbsp 150–240 Apricots, dried, uncooked, 1/4 cup 378 78 Soup (tomato), reconstituted 8 oz 700–1260 Cantaloupe, 1/4 medium 368 47 Tomato juice 8 oz (1 cup) 340–1040 1% or 2% milk, 1 cup 366 102–122 Potato chips† 1 oz (28.4 g) 120–180 Kidney beans, cooked, 1/2 cup 358 112 Tortilla chips† 1 oz (28.4 g) 105–160 Orange juice, 3/4 cup 355 85 Pretzels† 1 oz (28.4 g) 290–560 Split peas, cooked, 1/2 cup 355 116 *Ranges of sodium content are for selected foods available in the retail market. This table is provided to exemplify the importance of reading the food label to determine the sodium content of food, which can vary by several hundreds of milligrams in similar foods. †All snack foods are regular flavor, salted. Note: None of the examples provided was labeled “low sodium.” Source: Agricultural Research Service Nutrient Database for Standard Reference, Release 17, and recent manufacturers’ label data from retail market surveys. Serving sizes were standardized to be comparable among brands within a food. Pizza and bread slices vary in size and weight across brands. *Food sources of potassium ranked by milligrams of potassium per standard amount, also showing calories in the standard amount. (The adequate intake for adults is 4700 mg/day of potassium.) Source: Nutrient values from Agricultural Research Service (ARS) Nutrient Database for Standard Reference, Release 17. Foods are from ARS single nutrient reports, sorted in descending order by nutrient content in terms of common household measures. Food items and weights in the single nutrient reports are adapted from those in the 2002 revision of U.S. Department of Agriculture Home and Garden Bulletin No. 72, Nutritive Value of Foods. Mixed dishes and multiple preparations of the same food item have been omitted from this table. 4068_Ch06_069-089 15/11/14 12:46 PM Page 78 78 UNIT TWO Understanding Health and Illness CRITICAL THINKING 160 Mr. Peters 140 ■ Mr. Peters is a 32-year -old man with a congenital heart problem. He has been recovering from congestive heart failure and fluid excess. Today his blood pressure is higher than usual, and his pulse is bounding. He is having trouble breathing and presses the call light for your assistance. 120 1. What should you do first when you assess Mr. Peters’s condition? 2. What questions should you ask him? 3. What objective data should you collect? 4. What should you do with your findings? mEq/liter 100 80 60 40 20 Suggested answers are at the end of the chapter. 0 ELECTROLYTE BALANCE Natural minerals in food become electrolytes or ions in the body through digestion and metabolism. Electrolytes are usually measured in milliequivalents per liter (mEq/L) or in milligrams per deciliter (mg/dL). Electrolytes are one of two types: cations, which carry a positive electrical charge, and anions, which carry a negative electrical charge. Although there are many electrolytes in the body, this chapter discusses the most important ones, including sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+). These electrolytes are maintained in different concentrations inside the cell and outside the cell because of pumps in the cell wall (Fig. 6.3). ELECTROLYTE IMBALANCES At times, a patient may experience problems because of too much or too little of an electrolyte. In general, if a patient experiences a deficit of an electrolyte, the electrolyte is replaced either orally or intra venously. If the patient e xperiences an excess of an electrolyte, treatment focuses on getting rid of the excess, often via the kidneys. The underlying cause of the imbalance must also be treated. The most important aspects of nursing care are preventing and assessing electrolyte imbalances. You must be vigilant in w atching for signs of imbalance in high-risk patients. Serum electrolytes are measured on a regular basis. As a general rule, patients should be checked for electrolyte imbalance when there is a change in their mental state (either increased irritability or decreased responsi veness) or when muscle function changes. Patient education is another important nursing role. Sodium Imbalances The normal level of serum sodium is 135 to 145 mEq/L. Because sodium is the major cation in the blood, it helps Potassium Sodium Extracellular Calcium Magnesium Intracellular FIGURE 6.3 Extracellular and intracellular electrolytes. maintain serum osmolarity. Therefore, sodium imbalances are often associated with fluid imbalances, described ear lier in this chapter. Sodium is also important for cell function, especially in the central nerv ous system. The two sodium imbalances are hyponatremia (sodium deficit) and hypernatremia (sodium excess). Hyponatremia Hyponatremia occurs when the serum sodium le vel is less than 135 mEq/L. PATHOPHYSIOLOGY AND ETIOLOGY. Many conditions can lead to either an actual or a relative decrease in sodium. In an actual decrease, the patient has inadequate intak e of sodium or excessive sodium loss from the body. As the percentage of sodium in the ECF decreases, water is pulled by osmotic pressure into the cells. In a relati ve decrease, the sodium is not lost from the body but may leave the intravascular space and move into the interstitial tissues (third spacing). Another cause of a relative decrease occurs when the plasma volume increases (fluid e xcess), causing a dilutional effect. The percentage of sodium compared with the fluid is diminished. PREVENTION. Additional sodium is commonly administered to patients at high risk for hyponatremia (Box 6-3), usually by the IV route. Individuals who have high fevers or who engage in strenuous exercise or physical labor, especially in the • WORD • BUILDING • cation: cat—descending + ion—carrying anion: an—without + ion—carrying hyponatremia: hypo—less than + natr—sodium + emia—blood hypernatremia: hyper—more than + natr—sodium + emia—blood 4068_Ch06_069-089 15/11/14 12:46 PM Page 79 Chapter 6 Box 6-3 Nursing Care of Patients With Fluid, Electrolyte, and Acid–Base Imbalances Conditions that Place Patients at High Risk for Hyponatremia Nothing by mouth (NPO) Excessive diaphoresis (sweating) Diuretics Gastrointestinal suction Syndrome of inappropriate antidiuretic hormone Excessive ingestion of hypotonic fluids Freshwater near-drowning Decreased aldosterone heat, need to replace both sodium and w ater. Hyponatremia is especially dangerous for the older patient. SIGNS AND SYMPTOMS. Unfortunately, the signs and symp- toms of hyponatremia are v ague and depend somewhat on whether a fluid imbalance accompanies the hyponatremia. The patient with sodium and fluid def icits has signs and symptoms of dehydration (discussed previously). The patient with a sodium deficit and relative fluid excess has signs and symptoms associated with fluid excess. With more severe sodium deficit, the patient experiences mental status changes, including disorientation, confusion, and personality changes. This occurs because the low sodium and decrease in osmolarity cause more “water-pushing pressure,” which causes water to collect in and around the brain and increase pressure (cerebral edema). Weakness, nausea, vomiting, and diarrhea may also occur. See “Gerontological Issues—Confusion.” Gerontological Issues Confusion Often older clients who e xperience a change in their electrolyte levels will present with sudden une xplained confusion. By referring the situation to the RN or HCP as soon as the situation occurs, blood w ork for an electrolyte panel can be conducted and the older patient can be provided the needed electrolytes via IV therap y, which may quickly relieve the confused state. Because older patients’ cardiovascular systems are very sensitive to quick fluid shifts, IV infusions should only be provided at the rate prescribed by the HCP. COMPLICATIONS. In severe hyponatremia, respiratory arrest or coma can lead to death. The patient who also has fluid 79 excess may develop pulmonary edema, another life-threatening complication. DIAGNOSTIC TESTS. The primary diagnostic test is a serum sodium level, which is lower than the normal value when hyponatremia is present. The serum osmolarity also decreases in patients with hyponatremia. Other laboratory results may be af fected if the patient e xperiences an ac_ companying fluid imbalance. Serum chloride (Cl ), an anion, is often depleted when sodium decreases because these two electrolytes commonly combine as NaCl (salt in solution, or saline). THERAPEUTIC MEASURES. Therapeutic measures focus on resolving the underlying cause of hyponatremia and replacing the lost sodium. The HCP orders IV saline for patients who have hyponatremia without fluid excess. For patients who have a fluid excess, a fluid restriction is often ordered. Diuretics that rid the body of fluid but do not cause sodium loss may also be used. For patients with cerebral edema, steroids may be prescribed to reduce intracranial swelling. I&O are strictly monitored, and the patient is weighed daily. Also implement interventions to keep the patient safe if mental status is affected. Hypernatremia Hypernatremia occurs when the serum sodium level is above 145 mEq/L. PATHOPHYSIOLOGY AND ETIOLOGY. A serum sodium in- crease may be an actual increase or a relative increase. In an actual increase, the patient recei ves too much sodium or is unable to excrete sodium, as seen in renal failure. In a relative increase, the amount of sodium does not change, b ut the amount of fluid in the intravascular space decreases. Therefore, the percentage of sodium (solid) is increased in relationship to the amount of plasma (water). In mild hypernatremia, most e xcitable tissues, such as muscle and neurons of the brain, become more stimulated. The patient becomes irritable and has tremors. In se vere cases, these tissues fail to respond. PREVENTION. Prevention of hypernatremia is not as simple as prevention of hyponatremia. Most patients have a sodium excess as a result of an acute or chronic illness. Patients with a potential for electrolyte imbalance must al ways have their IV fluids carefully regulated. SIGNS AND SYMPTOMS. Thirst is usually one of the f irst symptoms to appear. If you eat salty foods, such as potato chips, the amount of sodium in the body increases, and you become thirsty. Other signs and symptoms of hypernatremia are vague and nonspecific until severe excess is present. Like the patient with a sodium def icit, the patient e xperiencing sodium excess has mental status changes, such as agitation, confusion, and personality changes—but this time, the cause is too little fluid in the brain tissues. Seizures may also occur. • WORD • BUILDING • intracranial: intra—within + cranial—cranium (skull) 4068_Ch06_069-089 15/11/14 12:46 PM Page 80 80 UNIT TWO Understanding Health and Illness At first, muscle twitches and unusual contractions may be present. Later, skeletal muscle weakness occurs that can lead to respiratory failure if it affects the diaphragm. If fluid deficit or fluid excess accompanies the hypernatremic state, the patient also has signs and symptoms associated with these imbalances. COMPLICATIONS. A patient with severe hypernatremia may become comatose or ha ve respiratory arrest as sk eletal muscles weaken. DIAGNOSTIC TESTS. The most reliable diagnostic test is the serum sodium level, which indicates an increase above the normal level. Serum osmolarity may also increase. If the patient has a fluid imbalance, other laboratory v alues, such as BUN, hematocrit, and urine specific gravity, are also affected (see earlier discussion). THERAPEUTIC MEASURES. If a fluid imbalance accompanies hypernatremia, it is treated first. For example, fluid replacement without sodium in a patient with dehydration should correct a relati ve sodium e xcess. If the kidne ys are not excreting adequate amounts of sodium, diuretics may help if the kidneys are functional. If the kidneys are not functioning properly, dialysis may be ordered (see Chapter 37). I&O and daily weights are strictly monitored. The cause of hypernatremia is also treated in an attempt to prevent further episodes of this imbalance. F or some patients, a sodium-restricted diet is prescribed. Potassium Imbalances Potassium is the most common electrolyte in the ICF compartment. Therefore, only a small amount, 3.5 to 5 mEq/L, is found in the bloodstream. Small changes in this laboratory value cause major changes in the body. Potassium is especially important for cardiac muscle, skeletal muscle, and smooth muscle function. If the serum potassium level falls, the body attempts to compensate by moving potassium from the cells into the bloodstream. The two potassium imbalances are hypokalemia (potassium deficit) and hyperkalemia (potassium excess). Hypokalemia is the most commonly occurring imbalance. Hypokalemia Hypokalemia occurs when the serum potassium le vel falls below 3.5 mEq/L. PATHOPHYSIOLOGY AND ETIOLOGY. Most cases of hypokalemia result from inadequate intake of potassium or excessive loss of potassium through the kidne ys. Hypokalemia most often occurs as a result of medications. Potassium-losing diuretics (e.g., furosemide [Lasix]), digitalis preparations (e.g., digoxin [Lanoxin]), and corticosteroids (e.g., prednisone [Deltasone]) are examples of drugs that cause increased e xcretion of potassium from the body . Potassium may also be lost through the gastrointestinal (GI) tract, which is rich in potassium and other electrolytes. Se vere vomiting, diarrhea, and prolonged GI suction cause hypokalemia (see “P atient Perspective”). Major surgery and hemorrhage can also lead to potassium deficit. Patient Perspective Patricia I take hydrochlorothiazide for my high blood pressure. Since it can make me lose potassium, I also take a potassium supplement. So I thought I was all set. But recently I ate something that did not agree with me, and I had diarrhea for a couple of days. One morning as I was driving to work, I felt so weak it made me frightened. I drove back home and asked my husband to drive me to work. I arrived safely, but as I walked down the hallway, I again felt so weak I had to sit down. I felt like I could not put one foot in front of the other. I kept thinking, “This is all in my head.” I decided maybe I was dehydrated from the diarrhea, so I drank a bottle of Gatorade and a glass of orange juice. Slowly I began to feel a bit better, and I made it through the day. After work I had to take my daughter to the doctor, so I asked about my symptoms. I was sent to the lab where I had my potassium level checked, and it was 3.1! Normal is 3.5 to 5 mEq/L. Mine must have been even lower before I drank the juice and Gatorade. I learned that I probably lost a lot of potassium because of the diarrhea. I also learned that low potassium made my muscles weak and could have affected my heart function. Next time I have diarrhea, I plan to call my doctor. PREVENTION. Most patients having major surgery receive potas- sium supplements in their IV fluids to prevent hypokalemia. For patients receiving drugs known to cause hypokalemia, foods high in potassium may prevent a deficit (see Table 6.2). Patients receiving digitalis must be closely monitored because digitalis can cause hypokalemia, which in turn can enhance the action of digitalis and cause digitalis toxicity. SIGNS AND SYMPTOMS. Many body systems are affected by a potassium imbalance. Muscle cramping or muscle f atigue can occur with either a deficit or an excess of potassium. Vital signs change because the respiratory and cardiovascular systems need potassium to function properly. Diminished skeletal muscle activity results in shallow, ineffective respirations. The pulse is typically weak, irre gular, and thready because the heart muscle is depleted of potassium. A major danger is an irregular heartbeat (dysrhythmia), which can lead to cardiac arrest. Orthostatic (postural) hypotension may also be present. • WORD • BUILDING • hypokalemia: hypo—less than + kal—potassium + emia—blood hyperkalemia: hyper—more than + kal—potassium + emia— blood dysrhythmia: dys—bad or disordered + rhythmia—measured motion 4068_Ch06_069-089 15/11/14 12:46 PM Page 81 Chapter 6 Nursing Care of Patients With Fluid, Electrolyte, and Acid–Base Imbalances The nervous system is usually affected as well. The patient experiences changes in mental status follo wed by lethargy. The motility of the GI system is slo wed, causing nausea, vomiting, abdominal distention, and constipation. Vomiting may further increase potassium loss. COMPLICATIONS. If not corrected, hypokalemia can result in death from dysrhythmia, respiratory f ailure and arrest, or coma. The patient must be treated promptly before these complications occur. DIAGNOSTIC TESTS. The primary laboratory test is to obtain a serum potassium le vel. The patient’s electrocardiogram (ECG) may sho w cardiac dysrhythmias associated with potassium deficit. In addition to a decrease in the serum potassium level, the patient may have an acid–base imbalance known as metabolic alkalosis, which commonly accompanies hypokalemia. In metabolic alkalosis, the serum pH of the blood increases (>7.45) so that the blood is more alkaline than usual. Acid–base imbalances are discussed later in this chapter. THERAPEUTIC MEASURES. The goal of treatment is to replace potassium in the body and resolv e the underlying cause of the imbalance. For mild to moderate hypokalemia, oral potassium supplements are given. For severe hypokalemia, IV potassium supplements are given. Because the kidne ys eliminate e xcess potassium, potassium should be administered only after the patient has voided. Potassium is a potentially dangerous drug, especially when administered intravenously. In too high a concentration, it causes cardiac arrest. Only IV solutions that are premixed and carefully labeled should be used. Potassium is ne ver given by IV push. The patient’s laboratory values must be monitored carefully to prevent giving too much potassium. Teach the patient about the side effects of oral potassium and precautions associated with potassium administration. Box 6-4 summarizes the precautions the patient should be aware of when taking oral potassium supplements. Hyperkalemia Hyperkalemia is a condition in which the serum potassium level exceeds 5 mEq/L. It is rare in a person with healthy kidneys. PATHOPHYSIOLOGY AND ETIOLOGY. Hyperkalemia may result from an actual increase in the amount of total body potassium or from the mo vement of intracellular potassium into the blood. Overuse of potassium-based salt substitutes or excessive intake of oral or IV potassium supplements can cause hyperkalemia. Use of potassium-sparing diuretics (e.g., spironolactone [Aldactone]) may also contrib ute to hyperkalemia. Patients with renal f ailure are at risk for hyper kalemia because the kidneys cannot excrete potassium. Movement of potassium from the cells into the blood and other ECF is common in massive tissue trauma and metabolic acidosis. Metabolic acidosis is an acid–base imbalance commonly seen in patients with uncontrolled diabetes mellitus. Acid–base imbalances are discussed later in this chapter. Box 6-4 81 Tips for Patients Taking Oral Potassium Supplements • Do not substitute one potassium supplement for another. • Dilute powders and liquids in juice or other desired liquid to improve taste and to prevent gastrointestinal irritation. Follow manufacturer’s recommendations for the amount of fluid to use for dilution, most commonly 4 oz per 20 mEq of potassium. • Do not drink diluted solutions until mixed thoroughly. • Do not crush potassium tablets, such as Slow-K or K-tab tablets. Read manufacturer’s directions regarding which tablets can be crushed. • Take slow-release tablets with 8 oz of water to help them dissolve. • Do not take potassium supplements if taking potassiumsparing diuretics such as spironolactone or triamterene. • Do not use salt substitutes containing potassium unless prescribed by the HCP. • Take potassium supplements with meals. • Report adverse effects, such as nausea, vomiting, diarrhea, and abdominal cramping, to the HCP. • Have frequent laboratory testing for potassium levels as recommended by the HCP. Source: Adapted from Lee, C. A., Barrett, C. A., & Ignatavicius, D. D. (1996). Fluids and electrolytes: A practical approach (4th ed.). Philadelphia: F. A. Davis. PREVENTION. For patients receiving potassium supplements, hyperkalemia can be prevented by monitoring serum electrolyte values and the patient’ s signs and symptoms and adjusting the dose accordingly. SIGNS AND SYMPTOMS. Most cases of hyperkalemia occur in patients who are hospitalized or those undergoing therapeutic measures for a chronic condition. The classic manifestations are muscle twitches and cramps, later follo wed by profound muscular weakness; increased GI motility (diarrhea); slo w, irregular heart rate; and decreased blood pressure. Cardiac dysrhythmias and respiratory failure can occur in severe hyperkalemia, causing death. COMPLICATIONS. DIAGNOSTIC TESTS. In addition to an elevated serum potassium level, an irregular ECG is associated with hyperkalemia. If the patient also has metabolic acidosis, the serum pH falls below 7.35. THERAPEUTIC MEASURES. For mild, chronic hyperkalemia, dietary limitation of potassium-rich foods may be helpful. • WORD • BUILDING • alkalosis: alkal—alkaline + osis—condition acidosis: acid—acidic + osis—condition 4068_Ch06_069-089 15/11/14 12:46 PM Page 82 82 UNIT TWO Understanding Health and Illness Potassium supplements are discontinued, and potassium-losing diuretics are given to patients with healthy kidneys. For patients with renal problems, a cation exchange resin, such as sodium polystyrene sulfonate (Kaye xalate), is administered either orally or rectally. This drug releases sodium and absorbs potassium for excretion through the feces and out of the body. In cases in which cellular potassium has mo ved into the bloodstream, administration of glucose and insulin can facilitate the movement of potassium back into the cells. During treatment of moderate to se vere hyperkalemia, the patient should be in the hospital on a cardiac monitor. Calcium Imbalances Calcium is a mineral that is primarily stored in bones and teeth. A small amount is found in ECF. The normal value for serum calcium is 9 to 11 mg/dL, or 4.5 to 5.5 mEq/L. Minimal changes in serum calcium levels can have major negative effects in the body. Calcium is needed for the proper function of excitable tissues, especially cardiac muscle. The two calcium imbalances are hypocalcemia and hypercalcemia. Hypocalcemia Hypocalcemia occurs when the serum calcium le vel falls below 9 mg/dL, or 4.5 mEq/L. PATHOPHYSIOLOGY AND ETIOLOGY. Although calcium deficit can be acute or chronic, most patients develop hypocalcemia slowly as a result of chronic disease or poor intake. The woman who is postmenopausal is most at risk for hypocalcemia. As a woman ages, calcium intak e typically declines. The parathyroid glands recognize this decrease and stimulate bone to release some of its stored calcium into the blood for replacement. The result is a condition known as osteoporosis, in which bones become porous and brittle and fracture easily. The woman who is postmenopausal has a decreased le vel of estrogens, hormones that help pre vent bone loss in the younger woman. Immobility or decreased mobility also contributes to bone loss in many patients. The patients at highest risk for osteoporosis are thin, petite, Caucasian women. Hypocalcemia can also result from inadequate absorption of calcium from the intestines, as seen in patients with Crohn’s disease, a chronic inflammatory bo wel disease. Insufficient intake of vitamin D prevents calcium absorption as well. Conditions that interfere with the production of parathyroid hormone, such as partial or complete sur gical removal of the thyroid or parathyroids, can also cause hypocalcemia. Finally, patients with hyperphosphatemia (usually those with renal failure) often experience hypocalcemia. Calcium and phosphate have an inverse relationship. When one of these electrolytes increases, the other tends to decrease and vice versa. • WORD • BUILDING • hypocalcemia: hypo—less than + calc—calcium + emia—blood hypercalcemia: hyper—more than + calc—calcium + emia— blood osteoporosis: osteo—bone + porosis—porous PREVENTION. In the United States, the typical daily calcium intake is less than 550 mg. The AI of calcium for adults ages 19 to 50 is 1000 mg; theAI for adults over age 50 is 1200 mg. Hypocalcemia can be prevented by consuming calciumrich foods and by taking calcium supplements.These supplements can be purchased over the counter in any pharmacy or large food store. An inexpensive source of calcium for patients who do not require vitamin D supplementation is calcium carbonate (Tums), which provides 240 mg of elemental calcium in each tablet. P atients should be cautioned not to routinely take high doses of calcium without checking with their primary care provider (see “Evidence-Based Practice”). EVIDENCE-BASED PRACTICE Clinical Question Are there problems associated with taking too much supplemental calcium? Evidence Studies conducted in Sweden discovered that women who had long-term calcium intakes from all sources above 1400 mg/day had higher death rates from all causes (Michaëlsson, Melhus, Lemming, Wolk, & Byberg, 2013). Implications for Nursing Practice When patients take calcium supplements, teach them how to calculate their total calcium intake and that too much calcium can be as harmful as too little calcium. Teach patients to consult with their providers before beginning calcium supplements. REFERENCE Michaëlsson, K., Melhus, H., Lemming, E., Wolk, A., & Byberg, L. (2013). Long term calcium intake and rates of all cause and cardiovascular mortality: Community based prospective longitudinal cohort study. The British Journal of Medicine, 346, f228. Vitamin D supplementation may be required in addition to calcium for patients whose sun exposure is limited. The sun’s ultraviolet light causes the skin to manufacture vitamin D. SIGNS AND SYMPTOMS. Chronic hypocalcemia is usually not diagnosed until the patient breaks a bone, usually a hip.Acute hypocalcemia, which can occur after sur gery or in patients with acute pancreatitis, has several signs and symptoms. These include increased and irre gular heart rate, mental status changes, hyperactive deep tendon reflexes, and increased GI motility, including diarrhea and abdominal cramping. Two classic signs that can be used to assess for hypocalcemia are Trousseau’s sign and Chvostek’s sign. To test for Trousseau’s sign, inflate a blood pressure cuff around the patient’s upper arm for 1 to 4 minutes. In a patient with hypocalcemia, the hand and fingers become spastic and go into palmar flexion (Fig. 6.4). A positive Chvostek’s sign 4068_Ch06_069-089 15/11/14 12:46 PM Page 83 Chapter 6 Nursing Care of Patients With Fluid, Electrolyte, and Acid–Base Imbalances 83 DIAGNOSTIC TESTS. The patient with hypocalcemia has a lowered serum