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Chapter 13

Assessment and Care of Patients with Fluid and Electrolyte Imbalances

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Homeostasis

Extracellular fluid Intracellular fluid Interstitial fluid Transcellular fluids

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Clinical Significance: Blood Pressure

Blood pressure is an example of hydrostatic filtering forces. It moves whole blood from the heart to capillaries where filtration can occur to exchange water, nutrients, and waste products between the blood and the tissues.

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Blood Pressure

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Clinical Significance: Edema

Edema develops with changes in normal hydrostatic pressure differences.

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Fluid Balance

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Clinical Significance: Diffusion

Diffusion is important in the transport of most electrolytes and particles through cell membranes.

Sodium pumps. Glucose cannot enter most cell

membranes without the help of insulin.

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Clinical Significance: Osmosis and Filtration

The thirst mechanism is an example of how osmosis helps maintain homeostasis.

The feeling of thirst is caused by the activation of cells in the brain that respond to changes in ECG osmolarity.

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Fluid Balance

Fluid intake Fluid loss:

Minimum amount of urine needed to excrete toxic waste products is 400 to 600 mL

Insensible water loss

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Hormonal Regulation of Fluid Balance

Aldosterone Antidiuretic hormone Natriuretic peptides

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Dehydration

Fluid intake is less than what is needed to meet the body’s fluid needs, resulting in a fluid volume deficit.

Consideration for older adults.

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Collaborative Care—Dehydration

Assessment History Physical assessment/clinical

manifestations: Cardiovascular changes Respiratory changes Skin changes Neurologic changes Renal changes

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Dehydration: Laboratory Assessment

Elevated hemoglobin Elevated hematocrit Elevated serum osmolarity Elevated glucose Elevated protein Elevated BUN Elevated electrolytes Hemoconcentration

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Dehydration: Interventions Patient safety Fluid replacement Drug therapy

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Fluid Overload

Excess of body fluid. Most problems caused

by overhydration are related to fluid volume excess in the vascular space or to dilution of specific electrolytes and blood components.

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Collaborative Care—Fluid Overload

Assessment Patient safety Pulmonary edema Drug therapy Nutrition therapy Monitoring of I&O

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Sodium (135 to 145 mmol/L)

Sodium level is vital for skeletal muscle contraction, cardiac contraction, nerve impulse transmission, and normal osmolarity and volume of the ECF.

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Hyponatremia

Sodium level below 136 mEq/L Cerebral changes Neuromuscular changes Intestinal changes Cardiovascular changes

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Hyponatremia Interventions

The priority for nursing care of the patient with hyponatremia is monitoring the patient’s response to therapy and preventing hypernatremia and fluid overload.

Drug therapy. Nutrition therapy.

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Hypernatremia

Serum sodium level over 145 mEq/L Nervous system changes Skeletal muscle changes Cardiovascular changes

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Hypernatremia Interventions

Priorities for nursing care of the patient with hypernatremia include monitoring the patient's response to therapy and preventing hyponatremia and dehydration.

Drug therapy. Nutrition therapy.

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Potassium (3.5 to 5.0 mEq/L)

Depolarization and generation of action potentials, as well as regulating protein synthesis and glucose use and storage

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Hypokalemia

Serum potassium level below 3.5 mEq/L Can be life threatening because every

body system is affected Respiratory changes Musculoskeletal changes Cardiovascular changes Neurologic changes Intestinal changes

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Hypokalemia Interventions

The priorities for nursing care of the patient with hypokalemia are ensuring adequate oxygenation and patient safety for falls prevention, preventing injury from potassium administration, and monitoring the patent's response to therapy.

Drug therapy. Nutrition therapy. Safety measures. Respiratory monitoring.

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Hyperkalemia

Serum potassium greater than 5.0 mEq/L. Cardiovascular changes are the most

severe problems from hyperkalemia and are the most common cause of death in patients with hyperkalemia.

Neuromuscular changes. Intestinal changes.

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Hyperkalemia Interventions

Drug therapy—Kayexalate, insulin Cardiac monitoring Health teaching

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Calcium (9.0 to 10.5 mg/dL)

Calcium is a mineral with functions closely related to those of phosphorus and magnesium.

Absorption of dietary calcium requires the active form of vitamin D.

Calcium is stored in the bones. Parathyroid hormone. Thyrocalcitonin.

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Hypocalcemia

Total serum calcium level below 9.0 mg/dL Cultural considerations Women’s health considerations Neuromuscular changes

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Hypocalcemia (Cont’d)

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Hypocalcemia (Cont’d)

Cardiovascular changes Intestinal changes Skeletal changes

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Hypocalcemia Interventions

Drug therapy Nutritional therapy Environmental management—seizure

precautions Injury prevention strategies

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Hypercalcemia

Total serum calcium level above 10.5 mg/dL.

Effects of hypercalcemia occur first in excitable tissues.

All systems are affected.

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Hypercalcemia (Cont’d)

Cardiovascular changes are the most serious and life-threatening problems of hypercalcemia.

Neuromuscular changes. Intestinal changes.

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Hypercalcemia Interventions

Drug therapy—IV 0.9% sodium chloride, furosemide, calcium chelators, phosphorus, calcitonin, bisphosphonates, and prostaglandin synthesis inhibitors

Dialysis Cardiac monitoring

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Phosphorus (3.0 to 4.5 mg/dL)

Most phosphorus can be found in the bones.

Phosphorus is needed for activating vitamins and enzymes, forming adenosine triphosphate, and assisting in cell growth and metabolism.

Food sources include meats, fish, dairy products, and nuts.

Plasma levels of calcium and phosphorus exist in a balanced reciprocal relationship.

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Hypophosphatemia

Serum phosphorus level below 3.0 mEq/L. Most of the effects of hypophosphatemia

are related to decreased energy metabolism and imbalances of other electrolytes and body fluids.

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Hypophosphatemia (Cont’d)

Manifestations are most apparent in the cardiac, musculoskeletal, and hematologic systems and the CNS.

Cardiac changes. Musculoskeletal changes—

rhabdomyolysis. CNS changes.

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Hypophosphatemia Interventions

Oral replacement of phosphorus Vitamin D supplements IV phosphorus Nutrition therapy—increasing the intake of

phosphorus-rich foods while decreasing the intake of calcium-rich foods

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Hyperphosphatemia

Serum phosphorus level above 4.5 mEq/L. Problems caused by hyperphosphatemia

center on the hypocalcemia that results when serum phosphorus levels increase.

Does not cause many direct problems with body function.

Causes include renal insufficiency, certain cancer treatments, increased phosphorus intake, and hypoparathyroidism.

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Hyperphosphatemia Interventions

Because calcium and phosphorus ions exist in the blood in a balanced reciprocal relationship, management of hyperphosphatemia entails the management of hypocalcemia.

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Magnesium (1.3 to 2.1 mg/dL)

Magnesium is critical for skeletal muscle contraction, carbohydrate metabolism, ATP formation, vitamin activation, and cell growth.

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Hypomagnesemia

Serum magnesium level below 1.2 mEq/L. Effects of hypomagnesemia are caused by

increased membrane excitability and the accompanying serum calcium and potassium imbalances.

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Hypomagnesemia (Cont’d)

Neuromuscular changes. CNS changes. Intestinal changes. Interventions for hypomagnesemia:

Drugs—IV magnesium sulfate

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Hypermagnesemia

Serum magnesium level above 2.1 mEq/L. When magnesium excess occurs,

excitable membranes are less excitable and need a stronger-than-normal stimulus to respond.

Cardiac changes. CNS changes. Neuromuscular changes. Respiratory changes.

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Hypermagnesemia Interventions

Magnesium-free IV fluids Furosemide Calcium

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Chloride (98 to 106 mEq/L)

Imbalances of chloride usually occur as a result of other electrolyte imbalances.

Usually corrected by interventions for correcting other electrolyte or acid-base problems.