Fluid and Electrolytes Balance

Fluid and Electrolytes: Balance and Distribution

Copyright © 2007, 2004, 2000, Mosby, Inc., an affiliate of Elsevier Inc. All Rights Reserved.

Homeostasis



State of equilibrium in body



Naturally maintained by adaptive responses



Body fluids and electrolytes are maintained within narrow limits


Water Content of the Body



60% of body weight in adult



45% to 55% in older adults



70% to 80% in infants



Varies with gender, body mass, and age


Changes in Water Content with

Age


Fig. 17-1

Compartments



Intracellular fluid (ICF)



Extracellular fluid (ECF)



Intravascular (plasma)



Interstitial



Transcellular


Fluid Compartments of the Body


Fig. 17-2

Intracellular Fluid (ICF)



Located within cells



42% of body weight


Extracellular Fluid (ECF)



One third of body weight



Between cells (interstitial fluid), lymph, plasma, and transcellular fluid


Transcellular Fluid



Part of ECF



Small but important



Approximately 1 L


Transcellular Fluid



Includes fluid in



Cerebrospinal fluid



Gastrointestinal tract



Pleural spaces



Synovial spaces



Peritoneal fluid spaces


Electrolytes



Substances whose molecules dissociate into ions (charged particles) when placed into water



Cations: positively charged



Anions: negatively charged


Measurement of Electrolytes



International standard is millimoles per liter (mmol/L)



U.S. uses milliequivalent (mEq)



Ions combine mEq for mEq


Electrolyte Composition



ICF



Prevalent cation is K +



Prevalent anion is PO

4

3

-



ECF



Prevalent cation is Na +



Prevalent anion is Cl

-


Mechanisms Controlling Fluid and Electrolyte Movement



Diffusion



Facilitated diffusion



Active transport



Osmosis



Hydrostatic pressure



Oncotic pressure


Diffusion



Movement of molecules from high to low concentration



Occurs in liquids, solids, and gases



Membrane separating two areas must be permeable to diffusing substance



Requires no energy


Diffusion

Fig. 17-4

Facilitated Diffusion



Movement of molecules from high to low concentration without energy



Uses specific carrier molecules to accelerate diffusion


Active Transport



Process in which molecules move against concentration gradient



Example: sodium–potassium pump



External energy required


Sodium–Potassium Pump

Fig. 17-5

Osmosis



Movement of water between two compartments by a membrane permeable to water but not to solute



Moves from low solute to high solute concentration



Requires no energy


Osmosis


Fig. 17-6

Osmotic Pressure



Amount of pressure required to stop osmotic flow of water



Determined by concentration of solutes in solution


Hydrostatic Pressure



Force within a fluid compartment



Major force that pushes water out of vascular system at capillary level


Oncotic Pressure



Osmotic pressure exerted by colloids in solution (colloidal osmotic pressure)



Protein is major colloid


Fluid Movement in Capillaries



Amount and direction of movement determined by



Capillary hydrostatic pressure



Plasma oncotic pressure



Interstitial hydrostatic pressure



Interstitial oncotic pressure


Fluid Shifts



Plasma to interstitial fluid shift results in edema



Elevation of hydrostatic pressure



Decrease in plasma oncotic pressure



Elevation of interstitial oncotic pressure


Fluid Shifts



Interstitial fluid to plasma



Fluid drawn into plasma space with increase in plasma osmotic or oncotic pressure



Compression stockings decrease peripheral edema


Fluid Movement between

ECF and ICF



Water deficit (increased ECF)



Associated with symptoms that result from cell shrinkage as water is pulled into vascular system


Fluid Movement between

ECF and ICF



Water excess (decreased ECF)



Develops from gain or retention of excess water


Fluid Spacing



First spacing



Normal distribution of fluid in ICF and

ECF



Second spacing



Abnormal accumulation of interstitial fluid (edema)


Fluid Spacing



Third spacing



Fluid accumulation in part of body where it is not easily exchanged with

ECF


Regulation of Water Balance



Hypothalamic regulation



Pituitary regulation



Adrenal cortical regulation



Renal regulation


Regulation of Water Balance



Cardiac regulation



Gastrointestinal regulation



Insensible water loss


Hypothalamic Regulation



Osmoreceptors in hypothalamus sense fluid deficit or increase



Stimulates thirst and antidiuretic hormone (ADH) release



Result in increased free water and decreased plasma osmolarity


Pituitary Regulation



Under control of hypothalamus, posterior pituitary releases ADH



Stress, nausea, nicotine, and morphine also stimulate ADH release


Adrenal Cortical Regulation



Releases hormones to regulate water and electrolytes



Glucocorticoids

•

Cortisol



Mineralocorticoids

• Aldosterone


Factors Affecting

Aldosterone Secretion

Fig. 17-9


Renal Regulation



Primary organs for regulating fluid and electrolyte balance



Adjusting urine volume

•

Selective reabsorption of water and electrolytes

• Renal tubules are sites of action of ADH and aldosterone


Effects of Stress on

F&E Balance

Fig. 17-10


Cardiac Regulation



Natriuretic peptides are antagonists to the RAAS



Produced by cardiomyocytes in response to increased atrial pressure



Suppress secretion of aldosterone, renin, and ADH to decrease blood volume and pressure


Gastrointestinal Regulation



Oral intake accounts for most water



Small amounts of water are eliminated by gastrointestinal tract in feces



Diarrhea and vomiting can lead to significant fluid and electrolyte loss


Insensible Water Loss



Invisible vaporization from lungs and skin to regulate body temperature



Approximately 600 to 900 ml/day is lost



No electrolytes are lost


Gerontologic Considerations



Structural changes in kidneys decrease ability to conserve water



Hormonal changes lead to decrease in ADH and ANP



Loss of subcutaneous tissue leads to increased loss of moisture


Gerontologic Considerations



Reduced thirst mechanism results in decreased fluid intake



Nurse must assess for these changes and implement treatment accordingly


Fluid and Electrolyte

Imbalances



Common in most patients with illness



Directly caused by illness or disease

(burns or heart failure)



Result of therapeutic measures

(IV fluid replacement or diuretics)


Extracellular Fluid Volume

Imbalances



ECF volume deficit (hypovolemia)



Abnormal loss of normal body fluids

(diarrhea, fistula drainage, hemorrhage), inadequate intake, or plasma-to-interstitial fluid shift



Treatment: replace water and electrolytes with balanced IV solutions


Extracellular Fluid Volume

Imbalances



Fluid volume excess (hypervolemia)



Excessive intake of fluids, abnormal retention of fluids (CHF), or interstitial-to-plasma fluid shift



Treatment: remove fluid without changing electrolyte composition or osmolality of ECF


Nursing Management

Nursing Diagnoses



Hypovolemia



Deficient fluid volume



Decreased cardiac output



Potential complication: hypovolemic shock






Hypervolemia



Excess fluid volume



Ineffective airway clearance



Risk for impaired skin integrity



Disturbed body image



Potential complications: pulmonary edema, ascites



Nursing Implementation



I&O



Monitor cardiovascular changes



Assess respiratory status and monitor changes



Daily weights



Skin assessment






Neurologic function



LOC



PERLA



Voluntary movement of extremities



Muscle strength



Reflexes


Electrolyte Disorders

Signs and Symptoms

Electrolyte

Sodium (Na)

Excess

Hypernatremia

Thirst

CNS deterioration

Increased interstitial fluid

Deficit

Hyponatremia


Potassium (K) Hyperkalemia

Ventricular fibrillation

ECG changes

CNS changes

Hypokalemia

Bradycardia

ECG changes

CNS changes


Electrolyte Disorders

Signs and Symptoms

Electrolyte

Calcium (Ca)

Excess

Hypercalcemia

Thirst


Increased interstitial fluid

Magnesium (Mg) Hypermagnesemia

Loss of deep tendon reflexes

(DTRs)

Depression of CNS

Depression of neuromuscular function

Deficit

Hypocalcemia

Tetany

Chvostek’s, Trousseau’s signs

Muscle twitching

CNS changes

ECG changes

Hypomagnesemia

Hyperactive DTRs

CNS changes


Sodium



Imbalances typically associated with parallel changes in osmolality



Plays a major role in



ECF volume and concentration



Generation and transmission of nerve impulses



Acid–base balance



NV: 135-145 mEq/L


Hypernatremia



Elevated serum sodium occurring with water loss or sodium gain



Causes hyperosmolality leading to cellular dehydration



Primary protection is thirst from hypothalamus


Hypernatremia



Manifestations



Thirst, lethargy, agitation, seizures, and coma



Impaired LOC



Produced by clinical states



Central or nephrogenic diabetes insipidus


Hypernatremia



Serum sodium levels must be reduced gradually to avoid cerebral edema






Risk for injury



Potential complication: seizures and coma leading to irreversible brain damage






Treat underlying cause



If oral fluids cannot be ingested, IV solution of 5% dextrose in water or hypotonic saline



Diuretics


Hyponatremia



Results from loss of sodiumcontaining fluids or from water excess



Manifestations



Confusion, nausea, vomiting, seizures, and coma






Risk for injury



Potential complication: severe neurologic changes






Caused by water excess



Fluid restriction is needed



Severe symptoms (seizures)



Give small amount of IV hypertonic saline solution (3% NaCl)






Abnormal fluid loss



Fluid replacement with sodiumcontaining solution


Potassium



Major ICF cation



Necessary for



Transmission and conduction of nerve and muscle impulses



Maintenance of cardiac rhythms



Acid–base balance


Potassium



Sources



Fruits and vegetables (bananas and oranges)



Salt substitutes



Potassium medications (PO, IV)



Stored blood



NV: 3.5-5.0 mEq/L


Hyperkalemia



High serum potassium caused by



Massive intake



Impaired renal excretion



Shift from ICF to ECF



Common in massive cell destruction



Burn, crush injury, or tumor lysis


Hyperkalemia



Manifestations



Weak or paralyzed skeletal muscles



Ventricular fibrillation or cardiac standstill



Abdominal cramping or diarrhea







Risk for injury



Potential complication: dysrhythmias






Eliminate oral and parenteral K intake



Increase elimination of K (diuretics, dialysis, Kayexalate)






Force K from ECF to ICF by IV insulin or sodium bicarbonate



Reverse membrane effects of elevated ECF potassium by administering calcium gluconate IV


Hypokalemia



Low serum potassium caused by



Abnormal losses of K + via the kidneys or gastrointestinal tract



Magnesium deficiency



Metabolic alkalosis


Hypokalemia



Manifestations



Most serious are cardiac



Skeletal muscle weakness



Weakness of respiratory muscles



Decreased gastrointestinal motility







Risk for injury









KCl supplements orally or IV



Should not exceed 10 to 20 mEq/hr



To prevent hyperkalemia and cardiac arrest


Calcium



Obtained from ingested foods



More than 99% combined with phosphorus and concentrated in skeletal system



Inverse relationship with phosphorus


Calcium



Bones are readily available store



Blocks sodium transport and stabilizes cell membrane



Ionized form is biologically active



NV: 4.5-5.5 mg/dl



NV: (total) 9-11 mg/dl


Calcium



Functions



Transmission of nerve impulses



Myocardial contractions



Blood clotting



Formation of teeth and bone



Muscle contractions


Calcium



Balance controlled by



Parathyroid hormone



Calcitonin



Vitamin D


Hypercalcemia



High serum calcium levels caused by



Hyperparathyroidism (two thirds of cases)



Malignancy



Vitamin D overdose



Prolonged immobilization


Hypercalcemia



Manifestations



Decreased memory



Confusion



Disorientation



Fatigue



Constipation






Risk for injury









Excretion of Ca with loop diuretic



Hydration with isotonic saline infusion



Synthetic calcitonin



Mobilization


Hypocalcemia



Manifestations

 Positive Trousseau’s or Chvostek’s sign



Laryngeal stridor



Dysphagia



Tingling around the mouth or in the extremities


Hypocalcemia



Low serum Ca levels caused by



Decreased production of PTH



Acute pancreatitis



Multiple blood transfusions



Alkalosis



Decreased intake


Tests for Hypocalcemia

Chvostek’s – contraction of facial muscles in response to a light tap over the facial nerve in front of the ear

Trousseau’s sign - carpal spasm induced by inflating a blood pressure cuff above the systolic pressure for a few minutes

Fig. 17-15






Risk for injury



Potential complication: fracture or respiratory arrest






Treat cause



Oral or IV calcium supplements



Not IM to avoid local reactions



Treat pain and anxiety to prevent hyperventilation-induced respiratory alkalosis


Phosphate



Primary anion in ICF



Essential to function of muscle, red blood cells, and nervous system



Deposited with calcium for bone and tooth structure



NV: 2.8-4.5 mg/dl



Phosphate



Involved in acid–base buffering system, ATP production, and cellular uptake of glucose



Maintenance requires adequate renal functioning



Essential to muscle, RBCs, and nervous system function


Hyperphosphatemia



High serum PO

4

3

caused by



Acute or chronic renal failure



Chemotherapy



Excessive ingestion of phosphate or vitamin D





Manifestations



Calcified deposition in soft tissue such as joints, arteries, skin, kidneys, and corneas



Neuromuscular irritability and tetany





Management



Identify and treat underlying cause



Restrict foods and fluids containing

PO

4

3

-



Adequate hydration and correction of hypocalcemic conditions


Hypophosphatemia



Low serum PO

4

3

caused by



Malnourishment/malabsorption



Alcohol withdrawal



Use of phosphate-binding antacids



During parenteral nutrition with inadequate replacement





Manifestations



CNS depression



Confusion



Muscle weakness and pain



Dysrhythmias



Cardiomyopathy





Management



Oral supplementation



Ingestion of foods high in PO

4

3

-



IV administration of sodium or potassium phosphate


Magnesium



50% to 60% contained in bone



Coenzyme in metabolism of protein and carbohydrates



Factors that regulate calcium balance appear to influence magnesium balance


Magnesium



Acts directly on myoneural junction



Important for normal cardiac function



NV: 1.5-2.5 mEq/L


Hypermagnesemia



High serum Mg caused by



Increased intake or ingestion of products containing magnesium when renal insufficiency or failure is present


Hypermagnesemia



Manifestations



Lethargy or drowsiness



Nausea/vomiting



Impaired reflexes



Respiratory and cardiac arrest


Hypermagnesemia



Management



Prevention



Emergency treatment

•

IV CaCl or calcium gluconate



Fluids to promote urinary excretion


Hypomagnesemia



Low serum Mg caused by



Prolonged fasting or starvation



Chronic alcoholism



Fluid loss from gastrointestinal tract



Prolonged parenteral nutrition without supplementation



Diuretics


Hypomagnesemia



Manifestations



Confusion



Hyperactive deep tendon reflexes



Tremors



Seizures



Cardiac dysrhythmias


Hypomagnesemia



Management



Oral supplements



Increase dietary intake



Parenteral IV or IM magnesium when severe


IV Fluids



Purposes

1.

Maintenance

• When oral intake is not adequate

2.

Replacement

• When losses have occurred


IV Fluids



Hypotonic



More water than electrolytes

•

Pure water lyses RBCs



Water moves from ECF to ICF by osmosis



Usually maintenance fluids


IV Fluids



Isotonic



Expands only ECF



No net loss or gain from ICF


IV Fluids



Hypertonic



Initially expands and raises the osmolality of ECF



Require frequent monitoring of

•

Blood pressure

•

Lung sounds

•

Serum sodium levels


D5W



Isotonic



Provides 170 cal/L



Free water



Moves into ICF



Increases renal solute excretion


D5W



Used to replace water losses and treat hyponatremia



Does not provide electrolytes


Normal Saline (NS)



Isotonic



No calories



More NaCl than ECF



30% stays in IV (most)



70% moves out of IV


Normal Saline (NS)



Expands IV volume



Preferred fluid for immediate response



Risk for fluid overload higher



Does not change ICF volume



Blood products



Compatible with most medications


Lactated Ringer’s



Isotonic



More similar to plasma than NS



Has less NaCl



Has K, Ca, PO

4

3

-

, lactate (metabolized to HCO

3

-

)



Expands ECF


D5 ½ NS



Hypertonic



Common maintenance fluid



KCl added for maintenance or replacement


D10W



Hypertonic



Provides 340 kcal/L



Free water



Limit of dextrose concentration may be infused peripherally


Plasma Expanders



Stay in vascular space and increase osmotic pressure



Colloids (protein solutions)



Packed RBCs



Albumin



Plasma


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