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Chapter 13, Fluid and Electrolyte Imbalances

Sodium Na+

Reference Range
136-145 mEq/L
Main cation of the ECF that maintains ECF osmolarity

Sodium Na+ function

Major extracellular cation (+)
Maintenance of plasma and interstitial osmolarity
Generation and transmission of action potentials
Maintenance of acid-base balance
Maintenance of electroneutrality

Potassium K+

Reference Range
3.5-5.0 mEq/L
98% of body's total potassium is inside of the cells
Maintains action potentials in excitable membranes

Potassium K+ function

Major intracellular cation (+)
Regulation of intracellular osmolarity
Maintenance of electrical membrane excitability
maintenance of plasma acid-base balance
Regulates protein synthesis
Regulating glucose use and storage
Potassium control also occurs thru kidney function/80% of potassium removed is done so thru the kidney
Kidney excretion of potassium is enhanced by aldosterone

Calcium Ca2+

Reference Range
9.0-10.5 mg/dL
Calcium enters the body by dietary intake and absorption through the intestinal tract. Absorption requires the active form of Vit D.

Calcium Ca2+ function

Cofactor in blood clotting cascade
Excitable membrane stabilizer
Adds strength/density to bones and teeth
Essential element in cardiac, skeletal, & smooth muscle contraction

Chloride Cl-

Reference Range
98-106 mEq/L

Chloride Cl- function

Maintenance of plasma acid-base balance
Maintenance of plasma electroneutrality
Formation of hydrochloric acid

Magnesium Mg2+

Reference Range
0.65-1.05 mEq/L

Magnesium Mg2+ function

Excitable membrane stabilizer
Essential element in cardiac skeletal and smooth muscle contraction
Cofactor in blood clotting cascade
Cofactor in carbohydrate metabolism
Cofactor in DNA and protein synthesis

Phosphorus P

Reference Range
3.0-4.5 mg/dL
Major intracellular anion

Phosphorus P function

Intracellular anion (-)
Activtion of B complex vitamins
Formation of adenosine triphosphate and other high energy substances
Cofactor in carbohydrate, protein, and lipid metabolism

Hyponatremia, definition

Serum sodium (Na+) level below 136 mEq/L.
Reduced excitable depolarization & cellular swelling.
Osmolarity of ECF is lower than that of the ICF & water moves into the cell, causing swelling.
125 mEq/L - nausea and vomiting
120 mEq/L - HA, lethargy, obtundation
115 mEq/L - seizure and coma
neuromuscular = general muscle weakness
intestinal changes = increased motility, nausea/diarrhea/cramping
cardiovascular = w/decreased plasma volume a rapid, weak and thready pulse w/periphreal pulses hard to palpate.

Hyponatremia, common causes

Most common cause is excessive use of diuretics
Excessive sweating, diuretics (high ceiling), wound drainage, decreased secretion of aldosterone, hyperlipidemia, renal disease, NPO status, low salt diet.
Excessive hypotonic fluids
Psychogenic polydipsia, freshwater submersion accident, renal failure (nephrotic syndrome) irrigation with hypotonic fluids, syndrome of inappropriate antidiuretic hormone secretion, hyperglycemia, heart failure

Interventions for hyponatremia

Priority = monitoring client for hypernatremia & fluid overload
Reduce doses of any drug that increase sodium loss
Occuring w/fluid deficit, IV Saline infusions prescribed
Severe hyponatremia, treat w/sm. volume infusions of hyprtonic (2%-3%) saline.


"Hypocalcemia is defined as a serum calcium concentration <8.5-9 mg/dL (or ionized calcium <4.2 mg/dL). Symptoms of hypocalcemia usually occur when ionized levels fall to <2.5 mg/dL.
Muscle spasms/charley horses
Tingling and numbness in hands and feet
Positive Trousseau's and Chvosek's signs
HR slower or faster than normal w/slight thready pulse
Severe case = prolonged QT and ST iintervals on EKG
Inc. peristaltic activity w/hyperactive bowel sounds
Loss of bone density in severe cases


"In marked hyperglycemia, ECF osmolality rises and exceeds that of ICF, since glucose penetrates cell membranes slowly in the absence of insulin, resulting in movement of water out of cells into the ECF.


Serum Na+ greater than 146 mEq/L
Lethargy, weakness, irritability that progresses to seizure, coma and death. Usually occurs in adults with altered mental status or no access to water

Calcium, Ionized Serum Calcium

Levels 1.17-1.29 mmol/L
Ionized calcium is that calcium which is not bound to albumin/proteins
Free calcium is the active form and must be kept in a narrow range in the ECF

Calcium, bound calcium decreases when...

Serum albumin drops

Calcium, a high albumin level causes....

Bound Calcium to increase

Calcium, acidosis decreases Calcium binding which...

Allows more ionized calcium

What hormone releases more calcium when needed?

Parathyroid (PTH) hormone increases serum calcium levels by releasing free calcium from bone storage sites,stimulating activation to help increase intestinal absorption of dietary calcium, inhibiting kidney calcium excretion and stimulating kidney calcium re-absorption.

Lactose intolerance

Caused by a deficiency of the enzyme lactase. Occurs in 75% to 90% of all Asians, African Americans, and American Indians.


Total serum level above 10.5mg/dL . Normal excitable tissues become less sensitive to normal stimuli.
Manifestations =
Causes faster clotting times
Increased HR and BP w/mild case of hyperCa+
Severe imbalance depresses elec. conduction & slows HR
Shortened QT intervals
Severe muscle weakness & decr. deep tendon reflexes
Altered LOC, confusion, lethargy, coma
Decreased peristalsis, constipation, anorexia, N/V, ab pain
Bowel sounds hypo-active or absent

Hypercalcemia - Interventions

Eliminate calcium from diet
Monitor neurological status
Strain urine and observe passage of calculi
Increase fluids 3000-4000 po a day
provide small frequent meals
maintain airway

Hypercalcemia - causes

Excessive oral intake of calcium & antacids
Excessive oral intake of Vitamin D
Renal failure
Use of thiazide diuretics
Malignancy = direct invasion, cancer of breast, lung, prostate, osteoclastic bone and multiple myeloma)
Renal disease which prevents Ca excretions

Extracellular fluid (ECF)

Fluid outside of the cells
Contains about 1/3 (15L) of the body's total body water

Intracellular fluid (ICF)

Fluid inside of the cells
Contains about 2/3's (25L) of total body water.

Interstitial fluid (part of ECF)

Fluid between cells, sometimes called the third space
Consists of blood lymph, bone, and connective tissue water

Transcellular fluids (part of ECF)

Fluids in special body spaces that include cerebrospinal fluid, synovial fluid, peritoneal fluid, and pleural fluid.


Most important and common substance in the body, maes up about 55% to 60% of total body weight for healthy younger adults and 50-55% of total weight for older adults.

Obligatory Urine Output

400 to 600 mL of urine per day needed to excrete toxic waste products

Insensible water loss

water loss from the skin, lungs, and stool. Insensible water loss in about 500-1000 mL/day. For every degree in body temp insensible water loss increases by about 10%.

Normal daily Inputs

Drink 1500 mL water
Food 750-800 mL of water in food
Metabolic 350 mL of water
Total 2600

Normal daily Outputs

Urine 1500 mL/water
Feces 100 mL/water
Lungs 400 mL/water
Skin 600 mL/water
Total 2600


Hormone secreted by the adrenal cortex whenever sodium level in the ECF is decreased. Prevents both water and sodium loss. Acts on kidney nephrons, triggering them to reabsorb sodium and water from the urine back into the blood. Increases blood osmolarity and blood volume.

ADH Antidiuretic hormone (vasopressin)

Acts directly on kidney tubules and collecting ducts, making them more permeable to water. More water is reabsorbed by these tubules and returned to the blood decreasing blood osmolarity by making it more dilute.

Natriuretic peptides (NPs)

Hormones sereted by special cells that line the atria of the heart (ANP) and ventricles of the heart (BNP) Secreted in response to increased blood volume and BP, which stretch the heart tissue. Creates effects that are opposite to aldosterone. Outcome is decreased circulating blood volume and decreased blood osmolarity.

Dehydration, actual

Caused by too little intake of fluid of too great a loss of fluid

Dehydration, relative

When dehydration occurs without an actual loss of water, as wehn water shifts from the plasma into the interstitial space.

Dehydration, isotonic

Most common type of dehydration. Fluid is lost only in the ECF space, including both the plasma and the interstitial spaces. No shift of fluids between spaces, so intracellular fluid (ICF) volume remains normal. Circulating blood volume is decreased &hypovolemia) and leads to inadequate tissue perfusion.


Isotonic ECF deficit
Occurs when water and electrolyetes are lost or unavailable to circulation (second or third spaces)
May be from abrupt decrease in fluid intake, acute loss of secretions, or excretions.

What is the best indicator of fluid losses or gains?

Daily weights...
1 L of water weights 2.2 pounds (1 kg)
Weight change of 1 lb. corresponds to fluid volume change of about 500 mL.

Hypovolemia manifestations

HR incr. in attempt to maintain blood pressure w/less volume
Peripheral pulses are weak & difficult to find
BP also decreases as well as pulse pressure decreases
Orthostatic hypotension possible with position changes
Risk for falling increases
Neck veins normally distended when pt. in supine position
Neck & hand veins are flat
Skin changes can indicate dehydration
Alterations in mental status
Ofter pt. has low grade fever

Hypervolemia management

Prevention is best way
Guide fluid therapy with CVP level or pulmonary wedge pressure
Diuretics, High ceiling such as furosimide
increase oncotic pressure

What are the two most important areas to monitor during rehydration?

Pulse rate and quality and urine output.


Fluid overload, overhydration or excess of body fluid. Excessive intake, or inadaquate excretion. When severe, can lead to heart failure and pulmonary edema. Patients often have pitting edema.


Substances in body fluids that carry an electrical charge. Cations have a positive charge and anions have a negative charge. Bod fluids are electrochemically neutral.

Who is most at risk for severe electrolyte imbalances?

Older patients
Patients with chronic renal or endocrine disorders
patients who are mentally impaired
patients who are taking drugs that alter fluid and electrolyte levels


True solutions capable of passing through a semipermeable membrane such as common intravenous therapy solutions/0.9% saline, 5% dextrose, 0.45% saline, and others


blood, plasma, albumin, synthetics

Foods highest in potassium are:

Meat, fish, and many vegetables and fruits.
Lowest in eggs, bread, and cereal grains.


When serum potassium is below 3.5 mEq/L. Cell membranes of all excitable tissues, such as nerve and muscle, are less response to normal stimuli.

Hypokalemia, causes

Inappropriate or excessive use of drugs such as diuretics
Digitalis, corticosteroids
Increased secretion of aldosterone
Cushing's syndrome
Diarrhea, vomiting, wound drainage, NPO
Renal disease, excessive diaphoresis

Hypokalemia, manifestations

Skeletal muscle weakness results in shallow respirations
Overall skeletal muscle weakness
flaccid paralysis, hand grasps weak,
Pulse us thready and weak, palpation difficult, pulse rate can change from slow to fast
Altered mental status, confusion, coma,
Smooth muscle contractions in intestine are decreased
Hypoactive bowel sounds
EKG changes, ST segment depression, flat or inverted T waves

Dilute KCL

Cannot be given straight push or will cause cardiac arrest. Potassium is a severe tissue irritant and is never given by IM or subcutaneous injection.


Serum potassium level higher than 5.0 mEq/L
Excitable tissue responds to less intense stimuli and may discharge spontaneously. Heart is sensitive to potassium increases.

Hyperkalemia, common causes

Excessive ingestion of potassium rich foods
Salt substitutes
potassium chloride, rapid infusion of potassium containing IV solution. Bolus IV potassium injections.
Renal insufficiency
Shift of potassium out of the cell as seen in acidosis

Hyperkalemia, manifestations

Bradycardia, hypotension and ECG chanages of tall, peaked T waves, proonged PR intervals, flat or absent P waves, and wide QRS complexes. Ectopic beats may appear w/increased potassium levels.
Skeletal muscles twitch in early stages of hyperkalemia
Muscle twitching changes to weakness
Followed by flaaccid paralysis
Increased motility in intestinal, diarrhea, andspastic colonic activity
Bowel sounds are hyperactive, rushes and gurgles
Frequent watery bowel movements


Serum phosphorus level below 3.0 mEq/L.
Most effects of hypophosphatemia are R/T decreased energy metabolism and imbalances of other electrolytes and body fluids.
Decreases in serum phosphorus = increases in serum calcium

Hypophosphatemia manifestations

Decreased stroke volume and decreased cardiac output
Peripheral pulses are slow, difficult to find
Weak skeletal muscles
respiratory failure
bone density is decreased leading to fractures and changes in bone shape. Irritability may lead to seizures as progresses.


Serum phosphorus level above 4.5 mEq/L.
Increased membrane excitability
Neuromuscular irritability
Muscle weakness, tetany
Hypocalcemia usually present as calcium and phosphorus exist in the blood in a balanced reciprocal relationship. When one increases the other decreases.


Serum magnesium level below 1.2 mEq/L.
Effects are caused by increased membrane excitability and accompanying serum calcium and potassium imbalances.
chronic alcoholism, diarrhea, prolonged TPN, drugs including aminoglycosides and diuretics, pancreatitis


Serum level above 2.1 mEq/L.
Magnesium is a membrane stabilizer. When excess occurs, excitable membranes are less excitable and need stronger stimulus to respond.
Renal failure and excessive fluid losses
Bradycardia, peripheral vasodilations, hypotension. Prolonged PR interval w/widened QRS complex.
Drowsy or lethargic
Deep tendon muscle reflexes depressed
Respiratory muscles become weak making breathing difficult

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