1. Water is the largest single constituent of the body

a. Accounts for approximately 60% of the body weight for an adult and 80% for full-term infants

b. Adult body weight is attained by puberty

1) Increased fat stores are found in females; females have less fluid content than do males

2) Fat tissue contains little water and increased body fat content generally comes with aging, accompanied by a decrease in fluid volumes

2. Fluid function

a. Maintains blood volume

b. Regulates body temperature

c. Transports material to and from cells

d. Serves as an aqueous medium for cellular metabolism

e. Assists digestion of food through hydrolysis

f. Acts as a solvent in which solutes are available for cell function

g. Serves as a medium for the excretion of wastes

3. Fluids are normally lost through various routes

a. Kidneys, as urine

b. Skin, as sweat

c. Lungs, as water vapor

d. Gastrointestinal tract, as vomitus and diarrhea

4. Fluid distribution

a. There are two major fluid compartments: intracellular and extracellular

1) Infants have relatively more extracellular fluid (ECF) than do adults

2) Rapid changes occur during the first 6 months of life

3) By age 3 years, intracellular fluid (ICF) decreases to approximately 36%

4) By puberty, the percentage approximates that of an adult

b. ICF

1) Fluid within the cells

2) It constitutes the largest portion of adult total body weight (TBW) at 40% (approximately two thirds); equivalent to approximately 23 L in a 70-kg adult

c. ECF

1) Fluids located outside the cells, with a volume of approximately 12 L in a 70-kg adult

2) The volume of ECF is approximately 5 to 6 L in an average adult

3) It is further divided into interstitial and intravascular fluids

a) Interstitial fluid is the fluid located between cells and accounts for 15% of the TBW

b) Intravascular fluid is located in arteries, veins, and capillaries and accounts for 5% of the TBW

d. Transcellular fluid

1) Includes lymph, gastrointestinal secretions, cerebrospinal fluid, sweat, ocular fluids, and pleural, synovial, and pericardial fluids

5. Fluid transportation

a. Osmosis

1) A passive transport that allows the movement of water freely through the semipermeable membrane

2) The fluid moves in relation to the concentration of the solutes from low solute concentration to higher solute concentration

b. Diffusion

1) A form of passive transport; it is the random movement of molecules and ions from an area of higher concentration to an area of lower concentration

2) Several factors influence diffusion: membrane permeability, size, and number of diffusing molecules or ions, and differences in electrical charges and temperature

c. Filtration

1) Passive transport of solutes and water together through selectively permeable membranes from higher pressure to an area of lower pressure

2) Involves movement of solutes and water in relation to hydrostatic pressure

d. Active transport

1) Requires energy to move the molecules or ions against osmotic pressure to an area of higher concentration

2) Energy source for primary active transport is adenosine triphosphate (ATP)

e. Osmolarity versus osmolality

1) Osmolarity is a measure of solute concentration

a) The concentration of a solution in terms of milliosmoles per liter of solution

b) Used in referring to solutions outside of the body

2) Osmolality is the number of milliosmoles per kilogram of a solution

a) Used to describe fluids inside the body

b) 1 L of water weighs 1 kg

f. Tonicity or osmolarity of infusion solutions

1) Isotonic solutions have the same osmolarity as normal body fluids; 250-375 mOsm/L

2) Hypotonic solutions contain less salt than intracellular space; osmolarity below 250 mOsm/L

3) Hypertonic solutions cause water from within a cell to move to the ECF compartment; osmolarity above 375 mOsm/L

1. Overview

a. Internal chemical balance is necessary for normal bodily function

b. Several organs are responsible for ensuring balance (homeostasis)

2. Renal system

a. Kidneys act as major regulators of the body’s water balance

b. Body’s water balance is controlled by urine output

c. Electrolytes are regulated through retention or excretion of urine

d. Acid-base balance is maintained through excretion of noncarbonic acid and reabsorption of bicarbonate ions

e. Functions in the excretion of metabolic wastes and toxic chemicals

3. Cardiac system

a. Heart and blood vessels are responsible for circulating the blood through the kidneys, enabling urine production

b. Fluid regulation is assisted by the cardiovascular system through fluid volume, pressure sensors, and atrial natriuretic factor

4. Respiratory system

a. Lungs remove 300 to 500 mL of water through exhalation (insensible loss)

b. Assists in the acid-base balance maintenance through regulation of hydrogen ions

5. Endocrine system

a. Regulates the chemical reactions related to metabolism, growth, and reproduction

b. Endocrine glands that control these reactions include the pituitary, adrenal, parathyroid, and thyroid

c. Pituitary gland

1) Signals are received by hypothalamus from the nervous system, and electrolytes are transmitted to the pituitary

2) Antidiuretic hormone (ADH) is secreted by the hypothalamus and stored in the posterior pituitary, and is important for regulating renal water excretion and conservation

d. Adrenal gland

1) Comprised of two components: adrenal cortex and adrenal medulla

2) Of the two components, adrenal cortex (outside layer of the adrenal gland) is more influential in fluid and electrolyte balance

3) Aldosterone, a mineralocorticoid, is secreted by the adrenal cortex

a) It causes potassium excretion

b) It causes fluid volume restoration through sodium retention

4) Cortisol also influences potassium excretion and sodium and fluid retention

e. Parathyroid gland

1) The production of parathyroid hormone affecting the regulation of calcium and phosphate is largely attributable to the effect on bone resorption

2) Increased parathyroid levels result in an increased calcium level and decreased phosphate level; referred to as an inverse proportional relationship

3) Exerts opposite effect with decreased hormone level

f. Thyroid gland

1) Secretes calcitonin to regulate calcium levels

2) Increased calcitonin levels lead to decreased calcium concentration

1. Disease/injury status

a. Renal, cardiac, respiratory, and endocrine system diseases

b. Chronic alcoholism

c. Cancer

d. Massive trauma, including burns and crushing injuries

2. Medications

a. Diuretics

1) Fluid and electrolyte depletion

2) Possible electrolyte excess (dependent on the type of diuretic)

b. Laxatives may lead to potassium deficits

c. Corticosteroids

1) Possible fluid and electrolyte retention

2) Potassium deficit

3) Respiratory and metabolic alkalosis

d. Inappropriate use of intravenous solutions

1) Excessive use of sodium-containing solutions can result in fluid volume excess (FVE) and hypernatremia

2) Administration of electrolyte-free intravenous solutions can lead to electrolyte deficits

3) Use of electrolyte-containing fluids could lead to excesses, depending on the content

3. Fluid status

a. Output exceeding intake may create fluid volume deficits (FVDs) or electrolyte imbalances

b. Abnormal fluid loss through vomitus, gastrointestinal suctioning, fistulas, profuse perspiration, or diarrhea may result in imbalances

c. Patient’s activity and location of activity just before assessment can reveal if imbalance is related to activity level or excessive environmental temperature

4. Age

a. Takes longer and is more difficult for the elderly to regain homeostasis

b. Increased risk of FVD with aging

1) Reduction in total body fluid

2) Diminished renal function

3) Increased difficulty for respiratory system to maintain a normal pH

4) Decreased skin turgor makes it more difficult to determine the fluid status

5) Poor intake or excessive fluid losses may occur because of confusion, decreased thirst threshold, inability to obtain fluids, and diuretic/laxative use (the most common problem is hypernatremia)

6) Osteoporosis is related to calcium deficits

c. The risks of fluid and electrolyte imbalances in children are proportional to their age and include deficits, as well as fluid overload

1) Infants are more vulnerable to FVD because of a greater volume of output to intake

2) Infants’ renal function is not fully developed, which limits the kidneys’ ability to concentrate urine

3) The body surface area is greater for infants and young children

1. Clinical assessment parameters

a. Clinical assessment should be performed on patient admission and monitored on a continuing basis throughout the course of the treatment

b. Shared responsibility with emphasis for nursing staff because of increased patient contact

c. Ongoing documentation

d. Report any unusual or abnormal findings to the licensed independent practitioner (LIP)

2. Fluid intake and output

a. Awareness of intake and output is needed for all patients, especially those with possible fluid and electrolyte imbalances

b. Intake measurement includes all oral fluids, enteral feedings, other tube feedings, and parenteral solutions

c. Individual volumes and the time of day are important for accurate comparison between intake and output and with body weight and should be totaled for a 24-hour period

d. Output measurement includes urine, diarrhea, fistula drainage, vomitus, and any drainage obtained through suctioning

e. Other fluid losses are important but not as easily measured

1) Perspiration, respirations (particularly hyperventilation and respirator use), and drainage from lesions

2) Document and quantify as much as possible, particularly in situations in which strict intake and output are required

3) Time of day influences the findings

f. Comparison of intake and output totals is important

1) When the total intake is greater than the output, fluid volume overload is possible

2) When output exceeds intake, FVD is possible

3) Electrolyte imbalances are a possible effect of FVDs or excesses

4) Notify the LIP regarding abnormal findings

3. Renal system

a. Urine volume and concentration are the indicators of homeostasis

1) Urine volume is the important component of the total output for a patient

2) Low urine volume may indicate FVD

3) High urine volume may suggest FVE

b. Urine concentration also may indicate fluid imbalances

1) Urine is more concentrated with FVD

2) Urine is less concentrated with FVE and functioning renal and endocrine (ADH and aldosterone levels) systems

3) Document the findings and report the abnormalities to the LIP

4. Skin appearance and temperature

a. Skin turgor or tissue turgor

1) Is assessed by pinching the skin and observing the results on release of the skin

2) With normal fluid balance, skin quickly returns to its normal position

3) With FVD, skin remains slightly elevated for several seconds

4) Assessment sites for checking skin turgor include over the forearm, dorsum of the hand, forehead, and sternum, with the latter two areas generally considered the best sites

5) Possible exceptions include checking skin turgor in infants; the best sites in infants are the abdominal area and the medial aspects of the thighs

b. Appearance and temperature of the skin

1) May be affected by fluid and electrolyte imbalances

2) Pale skin may result from peripheral vasoconstriction secondary to FVD

3) Warm, flushed skin may occur from vasodilation, as found with metabolic acidosis

4) Skin temperature may indicate imbalances

a) With hypovolemia, skin may be cool to the touch

b) With hypernatremic dehydration, skin temperature may be elevated

5. Special senses

a. The eyes, mouth, and tongue are also key indicators of fluid volume imbalances

b. Normally, the tongue reveals one longitudinal furrow

1) Increase in number of furrows is indicative of reduced tissue volume related to FVD

2) With hypernatremia, the tongue may appear red and swollen

c. Thirst: the presence or absence of thirst may indicate a fluid imbalance

1) Ensures an adequate fluid volume as long as thirst is present, fluid is available, and losses are not abnormally high

2) Is normally present but may be altered by certain conditions

a) Nausea

b) Vomiting

c) Altered states of consciousness

d) Inability to respond

e) Increasing age (older adult)

d. Tearing and salivation

1) Normally present, may be absent when there is a deficit in fluid volume

2) A tearless cry or the lack of salivation in an infant older than 3 months is a good indicator of FVD (becomes obvious with a fluid loss of greater than 5% of the TBW)

e. Appearance of the oral cavity

1) Normally, the oral mucous membranes are moist

2) Possibly altered in individuals who breathe mainly through the mouth

3) Sticky, dry mucous membranes may be indicative of FVD or hypernatremia

6. Cardiovascular system

a. Edema develops when excessive fluid accumulates in the interstitial space

1) Localized edema may occur as a result of inflammation

2) Generalized edema may result from excessive sodium and water retention or from altered capillary hemodynamics

3) Is more visible in dependent areas, such as the feet and ankles

4) Edema in the back and buttocks is common in patients confined to bed

5) Edema is often classified according to the severity of the swelling

a) Peripheral edema is best measured daily in the same area using a tape measure

b) Degree of pitting is best assessed over a bony prominence when there is cellular swelling

b. Central venous pressure

1) Measurement of mean right atrial pressure

2) Readings should be taken with the patient in the same position each time

3) Low readings may be related to a decrease in fluid volume

4) High readings may be related to an increase in blood volume

c. Other cardiovascular indicators

1) Changes in the circulating volume of fluid are detected by the observation of the neck and hand veins

2) In a dependent position and in the presence of a FVD, neck veins are flat and filling of hand veins is delayed

3) With increased plasma volume, emptying of hand veins is delayed and neck veins appear engorged

7. Body weight

a. Body weight is used as an indicator of fluid status

b. One kilogram of body weight gained or lost is equal to approximately 1 L of fluid

c. Weight loss may be the result of several factors

1) Can occur from loss of tissue associated with malnutrition

2) Is often indicative of fluid loss

a) Rapid fluid loss of 2% of the TBW is indicative of mild FVD

b) A loss of 5% is indicative of moderate deficit

c) A loss of 8% is indicative of severe deficit

3) Severe FVD is not always signaled by a loss of body weight, particularly when the fluid is pulled from the vascular system and trapped in a space or cavity, such as in third spacing

d. Rapid weight gain often indicates an increased fluid volume

1) Gain can occur in any fluid compartment

a) Overload in vascular space as a result of excessive administration of intravenous fluids or an excess of sodium

b) Body’s inability to excrete fluid (e.g., renal disease and ascites)

2) Percentage of weight gain indicates severity of the excess

a) Rapid weight gain of 2% indicates mild FVE

b) 5% weight gain indicates moderate FVE

c) 8% weight gain indicates severe FVE

e. Daily weight recordings are used for comparisons to detect losses or gains

1) Weight taken at the same time every day

2) Best time is in the morning after voiding and before eating

3) For accuracy, same type of scales should be used and same type of clothing should be worn each day

4) Dry clothing should be worn to prevent additional nonbody weight

5) Findings should be recorded in a manner that allows for easy day-to-day comparison of losses or gains

8. Neurological system

a. Changes may occur in sensorium, including levels of awareness, orientation, and consciousness from acid-base and electrolyte imbalances

1) Degree of changes is directly related to severity of imbalance

2) Restlessness and confusion may result from FVD

b. Disturbances in neuromuscular excitability may occur as a result of electrolyte imbalances

1) Increased excitability is seen with calcium and magnesium deficits

2) Depressed neuromuscular activity is seen with excesses of calcium and magnesium

c. Neuromotor symptoms result from metabolic alkalosis, which decreases calcium ionization

1) Tingling of fingers and toes

2) Hypertonic muscles

3) Dizziness

d. Chvostek’s and Trousseau’s signs are useful in determining calcium and magnesium imbalances

1) Chvostek’s sign is elicited by tapping facial nerve slightly anterior to ear lobe

2) Positive Chvostek’s sign is indicated by unilateral contraction of facial and eyelid muscles

3) Trousseau’s sign is created by inflating blood pressure cuff placed on the upper arm to a level above systolic pressure

4) Positive Trousseau’s sign is indicated by hand spasm, resulting from decreased blood supply

9. Vital signs

a. Temperature

1) Elevated temperature may result in loss of fluids and electrolytes from excessive sweating

2) May increase with FVD

3) May decrease with hypovolemia

b. Pulse

1) Increased heart rate in an attempt to maintain cardiac output with a FVD; pulse is usually weak with FVD and full and bounding with FVE

2) Increased heart rate may result from potassium and magnesium deficits and sodium excess

3) Decreased heart rate may result from severe hyperkalemia or hypermagnesemia

4) Irregularities in heart rate with potassium imbalances or magnesium deficit

5) Electrocardiogram (ECG) changes (e.g., irregularity) are possible with potassium, calcium, and magnesium excesses or deficits

c. Respirations

1) Increased respiratory rate may lead to increased fluid loss

2) FVD is possible from increased production of respiratory secretions

3) Shortness of breath and moist crackles seen with FVE

4) Mechanical ventilation is associated with fluid gain

5) Deep, rapid respirations are indicative of respiratory alkalosis or compensation for metabolic acidosis

6) Slow, shallow respirations are indicative of respiratory acidosis or compensation for metabolic alkalosis

d. Blood pressure

1) Increased blood pressure with FVE

2) Decreased blood pressure with FVD

3) Decreased blood pressure with magnesium excess from decreased vascular resistance

4) Changes in blood pressure with sodium imbalances secondary to fluid volume levels

5) Postural hypotension possible with hypokalemia

1. Serum osmolality

a. Used to measure the number of solutes in blood

b. Primarily affected by the serum sodium content

c. Used in assessment of hydration status and hyponatremia

d. Concentration increases with dehydration, hyperglycemia, and elevated blood urea nitrogen (BUN)

e. Concentration decreases with FVE

f. Normal range: 280 to 300 mOsm/kg

2. Hematocrit

a. Measures the percentage of red blood cells as compared with the plasma in whole blood

b. Normal range is 37% to 51% for males and 35% to 47% for females

c. Decreases with FVE

d. Increases in dehydration

3. BUN

a. Measures the amount of urea, the end product of protein metabolism, found in the serum

1) Formed in the liver

2) Picked up by the circulating blood

3) Excreted through the renal system

b. Normal adult level: 5 to 20 mg/dL

c. Low BUN may result from overhydration, infusion therapy, and low protein intake

d. Increased BUN levels result from dehydration, excessive protein intake, diabetes mellitus, gastrointestinal bleeding, trauma, and renal disease

4. Serum creatinine

a. Measurement of the serum level of creatinine, a by-product of muscle catabolism, is directly proportional to the muscle mass

b. Circulates in the blood, is filtered by glomeruli, and is not reabsorbed by the renal tubules

c. Generally not affected by diet or fluid levels and is a more sensitive indicator of renal disease

d. Normal adult level: 0.6 to 1.6 mg/dL

5. Serum electrolytes

a. Measures the electrolytes found in the body

1) Sodium

2) Potassium

3) Calcium

4) Magnesium

5) Phosphorus

6) Chloride

7) Bicarbonate

b. Affected by fluid and electrolyte intake and excretion

6. Arterial blood gases (ABGs)

a. Measurement of pH, PaCO₂, PaO₂, bicarbonate, and base excess levels

b. Used to evaluate acid-base balance

7. Urinary specific gravity

a. Measures the quantity and nature of particles in the urine

b. Normal value is 1.003 to 1.030

c. Affected by hydration status, renal status, and the number and size of particles in urine; large molecules, such as glucose, protein, and radiologic contrast media, will elevate the results out of proportion to actual concentration

8. Urine osmolality

a. Measures the number of particles, ions, and molecules in urine

b. Not overly influenced by the size of the molecules

c. Urine osmolality in conjunction with serum osmolality is generally considered a more accurate indication of renal concentrating ability than is the specific gravity measurement

1. Description

a. An increase in the fluid volume of the extracellular compartment

b. Can occur in the intravascular or interstitial compartments, or both

c. Generally, the same proportion of water and electrolytes is retained

2. Etiology

a. Intake of sodium and water

1) Excessive intake of intravenous solutions

a) Rapid administration of solutions

b) Continuous or excessive use of sodium-containing solutions leading to water retention

2) Ingestion of sodium-containing foods in patients with renal or cardiac disease resulting in increased thirst and fluid intake

3) Oral or intravenous medications containing sodium may lead to fluid retention

b. Conservation of water and sodium

1) Abnormal ADH production or increased aldosterone, such as occurs after surgery

2) Circulating intravascular volume often decreased with congestive heart failure, renal diseases, and cirrhosis of the liver

a) Subsequent renin and aldosterone production leads to increased water and sodium conservation

3) Corticosteroid therapy will increase water and sodium retention

c. Fluid shifts

1) Shift of fluid from interstitial to vascular space may increase FVE

2) Possible during the treatment of burns or with the use of hypertonic intravenous solutions or medications

d. Inability to excrete fluids

1) Secondary to renal disease resulting in decreased renal function leading to decreased output

2) Continuous fluid ingestion then leads to an intake that exceeds output

3. Signs and symptoms (dependent on severity and location of excess)

a. Elevated blood pressure

b. Increased pulse rate, bounding

c. Possible third heart sound (S3 or ventricular gallop)

d. Increased central venous pressure

e. Distended neck veins

f. Engorged peripheral veins with slowed hand vein emptying

g. Pulmonary edema

1) Shortness of breath

2) Moist crackles

3) Increased respirations

h. Body weight increases as fluid increases in the extracellular compartment (exception: if fluid excess is caused by fluid shift between compartments)

i. Peripheral edema, possibly pitting edema in dependent areas, such as the feet and ankles

1) Determined by applying pressure for several seconds

2) If edema present, the indention from finger pressure remains

3) Severity is measured by the size of indention and the length of time required for the indention to disappear

j. Ascites

1) Subsequent shortness of breath as a result of increased pressure on diaphragm

2) Drop in cardiac output as a result of poor right ventricle filling

4. Diagnostic data

a. Hematocrit: decreased as a result of hemodilution

b. ABGs: decreased oxygen content, decreased PaCO₂, and increased pH

c. Chest X-ray: pulmonary vascular congestion

d. Serum sodium and osmolality: possibly decreased as a result of excessive fluid retention, particularly if renal disease is present

e. BUN and creatinine levels: increased with renal or cardiac failure

f. Urinary specific gravity: decreased as kidneys try to excrete excessive fluid

5. Treatment

a. Elimination of precipitating factors and return of ECF to a normal level

b. Sodium and water restriction

c. Diuretic therapy

6. Nursing interventions

a. Assess vital signs with focus on bounding pulse, body weight, and edema

b. Monitor intake and output

c. If diuretic therapy is used, document the response

d. Observe for any signs of overcorrection resulting in a FVD

e. Monitor for symptoms of related conditions (e.g., pulmonary edema and ascites) such as constant irritating cough, difficulty in breathing, neck and hand vein engorgement, and lung crackles

1. Description

a. Decreased fluid volume in the extracellular compartment

b. With fluid loss, electrolytes are lost, further complicating the body’s ability to retain water

c. May be related to acid-base, fluid, or electrolyte imbalances

2. Etiology

a. Abnormal fluid loss

1) Gastrointestinal tract is the most common route

a) Vomiting

b) Suctioning

c) Diarrhea

d) Fistulas

e) Laxative abuse

2) Fluid lost through the skin

a) Insensible fluid loss is used as the mechanism to regulate the temperature within the body

b) Elevated temperatures as a result of illness or strenuous activity cause body to dissipate heat, resulting in increased fluid loss

c) Any breaks in the skin, such as burns and wounds, allow fluid to escape the body

3) Hemorrhage causes rapidly decreasing fluid volume in the intravascular space

a) Surgery

b) Trauma

c) Bleeding disorders

d) Accidental disconnection of administration set from the vascular access device

4) Renal disease or the use of diuretics

5) Fluid shifting from one area to another, where it cannot be readily used by the body (third spacing)

a) Ascites

b) Internal bleeding

c) Burns

d) Fluid trapped in bowel or body cavities, such as the pleural, pericardial, or peritoneal spaces

b. Decreased intake

1) Failure to prescribe or deliver adequate amounts of intravenous solutions

2) Lack of available fluids, such as with infants or older adults who are physically unable to get to a fluid source

3) Alteration of the thirst mechanism; older adults have a decreased sense of thirst and may not seek adequate replacement

4) Difficulty communicating the need for fluid

a) Infants

b) Comatose patients

3. Signs and symptoms (directly related to severity of the deficiency)

a. Weight loss particularly with rapid fluid loss, except with third spacing

b. Decreased central venous pressure, slow hand filling, decreased blood pressure, and postural hypotension

c. Flattened jugular veins in the supine position

d. Neurological indicators such as muscle weakness, dizziness, lethargy, and confusion from decreased tissue perfusion

e. Weak, rapid pulse in an attempt to maintain an adequate circulating volume within the vascular system

f. Decreased urine output as the body tries to conserve fluid (in hypovolemic states, urinary output typically is <30 mL/hour)

g. Decreased skin turgor

h. Soft, small tongue with several longitudinal furrows, instead of the normal one furrow

i. Pinched facial expression

j. Soft, sunken eyes

k. With severe losses, patient may go into shock

1) Cool, clammy extremities

2) Diaphoresis

3) Sharp drop in urine output

4) Coma

4. Diagnostic data

a. Serum BUN: increased above 20 mg/dL

b. Hematocrit: increased (unless deficit is caused by bleeding)

c. Serum electrolytes, serum osmolality and acid-base balance: dependent on the cause of deficit and the type of fluid lost

d. Urinary specific gravity: increased

e Urinary osmolality increased

5. Treatment

a. Correction of the cause of the deficit

b. Restoration of the ECF level

c. Initially, fluid replacement with an isotonic electrolyte solution, such as lactated Ringer’s

d. Replacement rate is dependent on the severity of the deficit

e. Once volume replacement is achieved, replacement solutions are chosen to provide free water to assist the kidneys in excreting wastes. Fluid challenge may be considered if oliguria is present to determine the cause

1) Intravenous solutions are administered according to a specific plan

2) Patient is monitored closely

a) Increased urinary output indicates that oliguria was related to the hypovolemia

b) No change in the output possibly indicates the cause to be renal failure or decreased cardiac function

6. Nursing interventions

a. Assess vital signs, urinary output, hemodynamic pressures, laboratory findings, and body weight

b. Use caution in fluid replacement to avoid fluid overload

c. Monitor the rate of infusion administration

d. With rehydration, look for a drop in hematocrit that may necessitate blood administration

1. Overview

a. The main cation in the ECF

b. Important physiologic functions

1) Controls water distribution

2) Maintains the volume of ECF

3) Promotes irritability of nerve and muscle tissue

4) Transmits nerve impulses

5) Maintains acid-base balance

c. Normal serum sodium value: 135 to 145 mEq/L

2. Hyponatremia

a. Definition

1) Serum sodium deficit

2) Level below 135 mEq/L

b. Etiology

1) Excessive intake of water

a) Administration of excessive water or dextrose-containing intravenous solutions resulting in water excess (edema) and dilution of sodium concentration

b) Excessive fluid intake as a result of a chronic psychiatric disorder, psychogenic polydipsia, resulting in dilutional hyponatremia

c) Syndrome of inappropriate antidiuretic hormone (SIADH): inappropriate secretion of ADH resulting in excessive water retention

2) Excessive sodium loss

a) Diuretics

b) Adrenal insufficiency resulting in stimulation of the ADH and increased water retention leading to hyponatremia

c) Excessive sweating, such as occurs in children with cystic fibrosis, increasing loss of sodium

c. Signs and symptoms (dependent on the cause and rate of onset)

1) A decrease in serum osmolality may result in fluid being pulled into the cells. Overhydration of brain cells (Na⁺ < 115 mEq/L) results in nausea, vomiting, focal weakness, muscular twitching or cramps, confusion, and coma

2) Deficit caused by water gain results in same symptoms of hypervolemia

a) Weight gain

b) Peripheral edema and fingerprinting

3) Deficit caused by fluid loss results in signs and symptoms of hypovolemia

a) Hypotension

b) Dizziness

d. Diagnostic data

1) Serum sodium level: below 135 mEq/L

2) Serum osmolality: decreased below 280 mOsm/L

3) Urine sodium and specific gravity: increased with SIADH and decreased with excessive sodium losses

4) Hematocrit: above normal when FVD is present

e. Treatment

1) Dependent on etiology

2) Deficit as a result of loss of fluids

a) Sodium and fluid replacement is done orally or with isotonic intravenous solutions

b) Hypertonic sodium chloride (3%) intravenous solutions are used for extremely low sodium levels

3) Deficit related to fluid gain

a) Diuretics to excrete excess fluid

b) Hypertonic sodium chloride solutions along with loop diuretics are used for severe hyponatremia

4) Deficit as a result of SIADH

a) Removal of cause

b) Diuretics

c) Fluid restriction

d) Medication to inhibit the action of ADH (chronic SIADH)

f. Nursing interventions

1) Assess patient for clinical signs and symptoms

2) Monitor laboratory values

3) Monitor intake and output and daily weight

4) Administer medications and intravenous solutions as ordered

5) Document observations and interventions, especially when administering hypertonic sodium chloride

6) Notify the LIP of abnormal findings

3. Hypernatremia

a. Definition

1) Serum sodium excess

2) Serum level above 145 mEq/L

b. Etiology

1) Excessive sodium

a) Intravenous administration of sodium-containing solutions or medications

b) Decreased excretion of sodium, such as with primary aldosteronism

2) Increased water loss

a) Burns

b) Diaphoresis

c) Increased insensible fluid loss from the lungs

d) Impaired thirst or inability to get water (normally with hypernatremia, thirst response is initiated and thirst satisfied by fluid intake, which replaces volume deficit)

e) Osmotic diuresis, such as from administration of mannitol or elevated glucose level

f) Diabetes insipidus (a lack of functioning ADH)

c. Signs and symptoms (many related to FVD)

1) Moderate imbalance first evident by restlessness, fatigue, and weakness; more prominent signs develop as cells become more dehydrated