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Fluids and Electrolytes

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1 Fluids and Electrolytes
Chapter 14 Fluids and Electrolytes

2 Homeostasis Maintaining relatively constant conditions as in fluid compartments To maintain internal balance, body must be able to regulate fluids All organs and structures of the body involved in homeostasis What percent of the human body is composed of water? 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 results.

3 Homeostasis cont’d Intracellular fluid Extracellular fluid
Fluid within a cell Most of the body’s fluids found within the cell Extracellular fluid Fluid outside the cell Intravascular fluid In blood vessels in the form of plasma or serum Interstitial fluid In fluid surrounding cells, including lymph Which fluid is mainly responsible for the transport of nutrients and wastes throughout the body?

4 Water Largest portion of body weight
Percentage affected by age, sex, body fat Percentage of body water decreases with age Females have a lower percentage of body water than males throughout adult years because women have more fat than men and fat cells contain less water than other cells Obese have a lower percentage of body water because of the increased number of fat cells

5 Solutes Electrolyte Substance that develops an electrical charge when dissolved in water Examples: sodium, potassium, calcium, chloride, bicarbonate, and magnesium Maintain balance between positive and negative charges For every positively charged cation, there is a negatively charged anion Cations and anions combine to balance one another How is the concentration of an electrolyte in a solution or body fluid compartment measured? Hydrogen is used as a standard for comparing the chemical activities of electrolytes.

6 Solutes cont’d Sodium (Na)
Most abundant electrolyte; primary electrolyte in extracellular fluid Major role in regulating body fluid volumes, muscular activity, nerve impulse conduction, and acid-base balance

7 Solutes cont’d Potassium (K)
Found mainly in the intracellular fluid; the major intracellular cation Important in maintaining fluid osmolarity and volume within the cell Essential for normal membrane excitability— a critical factor in transmitting nerve impulses Needed for protein synthesis, for the synthesis and breakdown of glycogen, and to maintain plasma acid-base balance

8 Solutes cont’d Chloride (Cl)
An extracellular anion that is usually bound with other ions, especially sodium or potassium Functions are to regulate osmotic pressure between fluid compartments and assist in regulating acid-base balance

9 Solutes cont’d Calcium (Ca)
Usually combined with phosphorus to form the mineral salts of the bones and teeth Of total body calcium, 99% concentrated in the bones and teeth; 1% is in the extracellular fluid Ingested through the diet and absorbed through the intestine Promotes transmission of nerve impulses; helps regulate muscle contraction and relaxation How does calcium regulation take place in the body?

10 Solutes cont’d Magnesium (Mg2+)
A cation found in bone (50% to 60%), intracellular fluid (39% to 49%), and extracellular fluid (1%) Plays a role in the metabolism of carbohydrates and proteins, the storage and use of intracellular energy, and neural transmission Important in heart, nerve, and muscle function How much of the magnesium ingested through the diet is absorbed? Magnesium is excreted through the kidneys, and the rate of excretion is regulated by sodium and calcium excretion, extracellular fluid volume, and parathyroid hormone.

11 Solutes cont’d Nonelectrolytes
Other substances dissolved in the body fluids Urea, protein, glucose, creatinine, and bilirubin These solutes do not carry an electrical charge

12 Transport of Water and Electrolytes
Membranes Selectively permeable membranes Separate fluid compartments and control movement of water and certain solutes Maintain unique composition of each compartment of the body while allowing transport of nutrients and wastes to and from cells Some solutes cross membranes more easily than others What is an example of selective permeability? Small molecules and water move freely across membranes, whereas larger molecules such as protein move less readily.

13 Transport Processes Diffusion
The random movement of particles in all directions is for a substance to move from an area of higher natural tendency concentration to an area of lower concentration Facilitated diffusion A carrier protein transports the molecules through membranes toward an area of lower concentration

14 Transport Processes cont’d
Active transport Carrier proteins transport substances from an area of lower concentration to an area of equal or greater concentration Requires expenditure of energy Many solutes, such as sodium, potassium, glucose, and hydrogen, are actively transported across cell membranes How does a sodium pump function?

15 Transport Processes cont’d
Filtration Transfer of water and solutes through a membrane from an area of high pressure to an area of low pressure Hydraulic pressure A combination of pressures from the force of gravity on the fluid and the pumping action of the heart Needed to move fluid out of capillaries into tissues and filter plasma through the kidneys

16 Transport Processes cont’d
Osmosis Movement across a membrane from a less concentrated to a more concentrated solution Involves movement of water only; sometimes force of movement across membrane carries 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

17 Osmolality Concentration of solution determined by number of dissolved particles per kg water Controls water movement and distribution by regulating the concentration of fluid in each body fluid compartment The osmolality of intracellular fluid and extracellular fluid tends to equalize because of the constant shifting of water A higher osmolality means there is a higher concentration of a solute in the water because the solution contains less water. What is the normal osmolality of body fluid? Osmolarity refers to the concentration of particles per liter of solution.

18 Regulatory Mechanisms

19 Kidneys Main regulators of fluid balance
Control extracellular fluid by adjusting the concentration of specific electrolytes, osmolality of body fluids, the volume of extracellular fluid, blood volume, and pH The nephron is the functioning unit of the kidney Glomerulus is the filtering portion of the nephron, and the tubule is responsible for secretion and reabsorption Nephrons conduct work of the kidney through filtration, reabsorption, and secretion

20 Kidneys cont’d Filtration
Blood plasma entering the kidney via the renal artery is delivered to the glomerulus About 20% of plasma filtered into glomerular capsule Most remaining plasma leaves kidney through the renal vein Filtrate then moves through the tubules, where it is transformed into urine by tubular reabsorption and secretion

21 Kidneys cont’d Tubular reabsorption
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 tubules for excretion, whereas most water and sodium is reabsorbed into the bloodstream Adjusts volume and composition of the filtrate; prevents excessive fluid loss through kidneys

22 Kidneys cont’d Tubular secretion
The last phase in the work of the kidneys The filtrate is transformed into urine Various substances—drugs, hydrogen ions, potassium ions, creatinine, and histamine—pass from the blood into the tubules Process eliminates some excess substances to maintain fluid and electrolyte balance, as well as metabolic waste products

23 Hormones Renin Aldosterone
Hormone secreted when blood volume or blood pressure falls Causes the release of aldosterone with subsequent sodium and water retention Aldosterone Acts on kidney tubules to increase reabsorption of sodium and decrease reabsorption of potassium Because the retention of sodium causes water retention, aldosterone acts as a volume regulator

24 Hormones cont’d Antidiuretic hormone (ADH)
Causes capillaries to reabsorb more water, so urine is more concentrated and less volume is excreted Atrial natriuretic factor (ANF) Hormone released by the atria in response to stretching of the atria by increased blood volume Stimulates excretion of sodium and water by the kidneys, decreased synthesis of renin, decreased release of aldosterone, and vasodilation Reduces blood volume and lowers blood pressure Where is ADH produced? An increase in plasma osmolality stimulates the release of ADH into the bloodstream to replenish needed fluid in the body.

25 Thirst Regulates fluid intake
Increased plasma osmolality stimulates osmoreceptors in the hypothalamus to trigger the sensation of thirst More sodium and less water in the body make a person thirsty Additional fluids consumed; kidneys conserve water until osmolality returns to normal

26 Regulation of body fluid volume depends on aldosterone, antidiuretic hormone (ADH), and thirst.

27 Fluid Gains and Losses In healthy adult, 24-hour fluid intake and output approximately equal Fluids gained by drinking and eating and lost through the kidneys, skin, lungs, and gastrointestinal tract The usual adult urine volume is between 1 and 2 L/day, or 1 ml/kg of body weight per hour In kidneys, water loss varies largely with the amount of solute excreted and with the level of antidiuretic hormone

28 Fluid Gains and Losses cont’d
Losses through the skin occur by sweating Water loss through the lungs by evaporation at 300 to 400 ml/day In the gastrointestinal tract, the usual loss of fluid is about 100 to 200 ml/day Where is the bulk of fluid secreted into the GI tract reabsorbed?

29 Age-Related Changes Affecting Fluid Balance
Aging kidney slower to adjust to changes in acid-base, fluid, and electrolyte balances Older adult often has a reduced sense of thirst and therefore may be in a state of chronic dehydration Total body water declines with age; greatest loss from the intracellular fluid compartment

30 Age-Related Changes Affecting Fluid Balance cont’d
Older person has limited reserves to maintain fluid balance when abnormal losses occur Antihypertensives, diuretics, and antacids can also contribute to imbalances Unless contraindicated, fluid requirements for older adults, based on ideal body weight, are 30 ml/kg for ages 55 to 65 and 25 ml/kg for 65 years and older What symptoms may occur in the older adult with fluid imbalances? Chronic conditions that affect mobility or mental status may interfere with adequate fluid intake.

31 Assessment of Fluid and Electrolyte Balance
Health history Determines if patient has conditions that contribute to fluid or electrolyte imbalances Vomiting, diarrhea, kidney diseases, diabetes, salicylate poisoning, burns, congestive heart failure, cerebral injuries, ulcerative colitis, and hormonal imbalances; the intake of drugs, such as diuretics and cathartics; and medical interventions, such as gastric suctioning Complaints of fatigue, palpitations, dizziness, edema, muscle weakness or cramps, dyspnea, and confusion may be associated with fluid imbalances

32 Assessment of Fluid and Electrolyte Balance cont’d
Vital signs Pulse, respiration, temperature, and blood pressure can indicate changes in fluid and electrolyte balance. Temperature variations can be associated with fluid volume excess or deficit. Pulse rate and quality may change in response to blood volume alterations; electrolyte changes can affect heart rate and rhythm. Blood pressure is directly related to blood volume. Respirations are minimally affected by electrolyte changes. Fever poses a risk of water and electrolyte loss associated with sweating and an increased metabolic rate. How should blood pressure be measured in the older adult?

33 Assessment of Fluid and Electrolyte Balance cont’d
Intake and output Accurate records are essential to determine whether the patient’s intake is equal to output All fluids entering or leaving the body should be noted 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 Urine characteristics also give clues to fluid balance Clear, pale urine in a healthy person suggests the excretion of excess water, whereas darker, concentrated urine indicates the kidneys are retaining water

34 Assessment of Fluid and Electrolyte Balance cont’d
Skin Characteristics Moisture, turgor, and temperature reflect fluid balance. Dry, flushed skin—dehydration. Pale, cool, clammy skin—severe fluid volume deficit that occurs with shock. Moist, edematous tissue seen with excess fluid volume Facial characteristics Severely dehydrated patient has a pinched, drawn facial expression. Soft eyeballs and sunken eyes indicate severely deficient fluid volume. Puffy eyelids and fuller cheeks suggest excess fluid volume

35 Assessment of Fluid and Electrolyte Balance cont’d
Skin turgor 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 Edema Reflects water and sodium retention, which can result from excessive reabsorption or inadequate secretion of sodium, as may occur with kidney failure Pitting depression remains in the tissue after pressure is applied with a fingertip What does the term tenting mean? Pitting edema is evaluated on a four-point scale, ranging from +1 edema (barely detectable pit) to +4 edema (deep and persistent pit that is approximately 1 inch [2.54 cm] deep).

36 Assessment of Fluid and Electrolyte Balance cont’d
Mucous membranes Tongue turgor In well person, tongue has one longitudinal furrow. Fluid volume deficit causes additional longitudinal furrows, and the tongue is smaller. 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. Veins Appearance of the jugular veins in the neck and the veins in the hands can suggest either a fluid volume deficit or excess.

37 Diagnostic Tests and Procedures
Urine studies Urine pH Determines if kidneys are responding appropriately to metabolic acid-base imbalances Urine specific gravity A measure of urine concentration A good indicator of fluid balance Osmolality Measures the number of dissolved particles in a solution Provides more precise measurement of kidneys’ ability to concentrate urine What is the normal pH of urine? Specific gravity? Osmolarity? 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. The specific gravity also reflects renal function. Dilute urine has a low osmolality and generally reflects renal excretion of excess water. Concentrated urine has a high osmolality and generally indicates renal conservation of water.

38 Diagnostic Tests and Procedures cont’d
Urine creatinine clearance tests Detect glomerular damage in the kidney A 24-hour specimen is required Urine sodium Sodium intake and fluid volume status Urine potassium A measure of renal tubular function What instructions should the patient be given during a urine creatinine clearance test? Normal creatinine clearance for adult males is 85 to 125 mL/min/1.73 m2 of body surface area; for females, it is 75 to 115 mL/min/1.73 m2 of body surface area. The normal urine sodium is 75 to 200 mEq/L. The normal value is 25 to 123 mmol/24 hr.

39 Diagnostic Tests and Procedures cont’d
Blood studies Serum hematocrit Percentage of blood volume composed of red blood cells Serum creatinine A metabolic waste product Indicator of renal function Blood urea nitrogen (BUN) A measure of renal function What is the normal range for hematocrit? Serum creatinine? Blood urea nitrogen? The serum creatinine level is a better indicator of renal function than the blood urea nitrogen.

40 Diagnostic Tests and Procedures cont’d
Serum albumin A plasma protein that helps maintain blood volume by creating colloid osmotic pressure Serum electrolytes Sodium, potassium, chloride, and calcium Low serum albumin allows water to shift into the interstitial compartment, which reduces blood volume and creates edema. What is the normal range for serum albumin? Electrolytes?

41 Fluid Imbalances Decreased intake, abnormal fluid losses, or both
Deficient fluid volume Less water than normal in the body Isotonic extracellular fluid deficit Hypovolemia Hypertonic extracellular fluid deficit Dehydration Decreased intake, abnormal fluid losses, or both Examples: loss of water from excessive bleeding, severe vomiting/diarrhea, severe burns The signs and symptoms of fluid volume deficit vary depending on how suddenly the deficit develops and how severe it is. What nursing diagnoses may be used for fluid volume deficit?

42 Fluid Imbalances cont’d
Excess fluid volume An increase in body water Extracellular fluid excess Isotonic fluid excess Intracellular water excess Hypotonic fluid excess From renal or cardiac failure with retention of fluid, increased production of antidiuretic hormone or aldosterone, overload with isotonic IV fluids, or administration of dextrose 5% in water (D5W) after surgery or trauma 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. What nursing diagnoses may be used for fluid volume excess?

43 Electrolyte Imbalances

44 Hyponatremia Lower than normal sodium in the blood serum
Can be actual deficiency of sodium or increase in body water that dilutes the sodium excessively Assessment Symptoms: headache, muscle weakness, fatigue, apathy, confusion, abdominal cramps, and orthostatic hypotension Take blood pressures with the patient lying or sitting and then standing to determine if a significant drop What is syndrome of inappropriate antidiuretic hormone secretion (SIADH)? Disorders that put the patient at risk for hyponatremia include congestive heart failure, liver cirrhosis, and nephrotic syndrome.

45 Hyponatremia cont’d Medical treatment Nursing care
The usual treatment is restriction of fluids while the kidneys excrete excess water Diuretic: furosemide (Lasix) Sodium replacement therapy Nursing care Administer prescribed medications and IV fluids Measure fluid intake and output and assess mental status A balanced diet usually provides adequate sodium, but patients with moderate or severe hyponatremia may need sodium replacement therapy. How can you prevent hyponatremia in patients with feeding tubes?

46 Hypernatremia Higher than normal concentration of sodium in the blood
Very serious imbalance; can lead to death if not corrected Occurs when excessive loss of water or excessive retention of sodium Signs and symptoms Thirst, flushed skin, dry mucous membranes, low urine output, restlessness, increased heart rate, convulsions, and postural hypotension What are some causes of hypernatremia?

47 Hypernatremia cont’d Medical treatment Nursing care
Oral or IV replacement of water to restore balance A low-sodium diet often prescribed Nursing care Encourage patients with hypernatremia to drink water Closely monitor the infusion of IV fluids Teach patient to track daily intake and output and to recognize the signs and symptoms of fluid retention or depletion What foods should be avoided for a patient on a low-sodium diet?

48 Hypokalemia Low serum potassium
May result in gastrointestinal, renal, cardiovascular, and neurologic disturbances Can cause abnormal, potentially fatal, heart rhythm Signs and symptoms Anorexia, abdominal distention, vomiting, diarrhea, muscle cramps, weakness, dysrhythmias (abnormal cardiac rhythms), postural hypotension, dyspnea, shallow respirations, confusion, depression, polyuria (excessive urination), and nocturia What are some causes of hypokalemia? The effect on myocardial cells is important because it tends to cause abnormal and potentially fatal heart rhythms.

49 Hypokalemia cont’d Medical treatment Nursing care
Potassium replacement by the IV or oral route Nursing care Monitoring at-risk patients for decreased bowel sounds, a weak and irregular pulse, decreased reflexes, and decreased muscle tone Cardiac monitors may be used to detect dysrhythmias Administer oral or IV potassium Urine output should be no less than 30 ml/hr

50 Hyperkalemia High serum potassium
Patients at risk: decreased renal function, in metabolic acidosis, taking potassium supplements A serious imbalance because of the potential for life-threatening dysrhythmias Signs and symptoms Explosive diarrhea and vomiting; muscle cramps and weakness, paresthesia, irritability, anxiety, abdominal cramps, and decreased urine output Potassium is plentiful in common foods, so it is easy for people on normal diets to take in adequate amounts. How can traumatic injuries cause hyperkalemia?

51 Hyperkalemia cont’d Medical treatment Nursing care
Correct the underlying cause Restrict potassium intake Polystyrene sulfonate (Kayexalate) Intravenous calcium gluconate Nursing care Patients with low urine output or those taking potassium-sparing diuretics must be monitored carefully for signs and symptoms Carefully monitor flow rate of IV fluids, which should not exceed 10 mEq/hr through peripheral veins Screen the results of laboratory studies Temporary effects may be obtained by the intravenous administration of insulin and glucose or sodium bicarbonate to promote the shifting of potassium into the cells. What instructions should be given to the patient taking potassium supplements?





56 Chloride Imbalance Usually bound to other electrolytes; therefore, chloride imbalances accompany other electrolyte imbalances Hyperchloremia Usually associated with metabolic acidosis Hypochloremia Usually occurs when sodium is lost because chloride most frequently bound with sodium

57 Calcium Imbalance Regulated by the parathyroid glands
Hypocalcemia results from diarrhea, inadequate dietary intake of calcium or vitamin D, and multiple blood transfusions (banked blood contains citrates that bind to calcium), in addition to some diseases, including hypoparathyroidism Hypercalcemia results from a high calcium or vitamin D intake, hyperparathyroidism, and immobility that causes stores of calcium in the bones to enter the bloodstream


59 Magnesium Imbalance Hypomagnesemia: decreased gastrointestinal absorption or excessive gastrointestinal loss, usually from vomiting and diarrhea, or increased urinary loss Hypermagnesemia occurs most often with excessive use of magnesium-containing medications or intravenous solutions in patients with renal failure or preeclampsia of pregnancy

60 Acid-Base Disturbances




64 Respiratory Acidosis Respiratory system fails to eliminate the appropriate amount of carbon dioxide to maintain the normal acid-base balance Caused by pneumonia, drug overdose, head injury, chest wall injury, obesity, asphyxiation, drowning, or acute respiratory failure Medical treatment Improve ventilation, which restores partial pressure of carbon dioxide in arterial blood (Paco2) to normal What are the common clinical signs and symptoms of respiratory acidosis? Underlying respiratory conditions are treated to eliminate the cause of respiratory acidosis.

65 Respiratory Acidosis cont’d
Nursing care Assess Paco2 levels in the arterial blood Observe for signs of respiratory distress: restlessness, anxiety, confusion, tachycardia Intervention Encourage fluid intake Position patients with head elevated 30 degrees Paco2 directly reflects the degree of respiratory dysfunction.

66 Respiratory Alkalosis
Low Paco2 with a resultant rise in pH Most common cause of respiratory alkalosis is hyperventilation Medical treatment Major goal of therapy: treat underlying cause of condition; sedation may be ordered for the anxious patient What aspect of the respirations is a key observation for a patient with respiratory alkalosis? Clinical signs and symptoms include increased respiratory and heart rates, an anxious appearance, irritability, dizziness, light-headedness, muscle weakness, and tingling or numbness of the fingers.

67 Respiratory Alkalosis cont’d
Nursing care Intervention In addition to giving sedatives as ordered, reassure the patient to relieve anxiety Encourage patient to breathe slowly, which will retain carbon dioxide in the body

68 Metabolic Acidosis Body retains too many hydrogen ions or loses too many bicarbonate ions; with too much acid and too little base, blood pH falls Causes are starvation, dehydration, diarrhea, shock, renal failure, and diabetic ketoacidosis Signs and symptoms: changing levels of consciousness, headache, vomiting and diarrhea, anorexia, muscle weakness, cardiac dysrhythmias Medical treatment: treat the underlying disorder Signs and symptoms vary according to the underlying cause and the severity of the acid-base disturbance. Mechanical ventilation may be necessary, especially in patients who are comatose.

69 Metabolic Acidosis cont’d
Nursing care Assessment of the patient in metabolic acidosis should focus on vital signs, mental status, and neurologic status Emergency measures to restore acid-base balance. Administer drugs and intravenous fluids as prescribed. Reassure and orient confused patients

70 Metabolic Alkalosis Increase in bicarbonate levels or a loss of hydrogen ions Loss of hydrogen ions may be from prolonged nasogastric suctioning, excessive vomiting, diuretics, and electrolyte disturbances Signs and symptoms: headache; irritability; lethargy; changes in level of consciousness; confusion; changes in heart rate; slow, shallow respirations with periods of apnea; nausea and vomiting; hyperactive reflexes; and numbness of the extremities

71 Metabolic Alkalosis cont’d
Medical treatment Depends on the underlying cause and severity of the condition

72 Metabolic Alkalosis cont’d
Nursing care Assessment Take vital signs and daily weight; monitor heart rate, respirations, and fluid gains and losses Keep accurate intake and output records, including the amount of fluid removed by suction Assess motor function and sensation in the extremities; monitor laboratory values, especially pH and serum bicarbonate levels

73 Metabolic Alkalosis cont’d
Intervention To prevent metabolic alkalosis, use isotonic saline solutions rather than water for irrigating nasogastric tubes because the use of water for irrigation can result in a loss of electrolytes Provide reassurance and comfort measures to promote safety and well-being



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