Fundametals of Nursing: Fluid, Electrolyte, and Acid–Base Balance Flashcards

Terms Definitions
Describe intracellular fluid (ICF)
ICF is the fluid within cells 40% of the adult's body weight.
Describe Extracellular fluid (ECF)
The fluid outside the cells 20% of the body weight. 75% interstitial fluids & 25% intravascular (plasma)
List the major homeostatic mechanisms in fluid balance
Skin: perspiration

Lungs: regulate O2 & CO2 of the blood; crucial in maintaining acid–base balance

Kidneys: selectively retain electrolytes, water, excrete wastes & excesses, acid base balance

GI: water and nutrients that enter the body through this route
Describe the Hormonal control of fluid balance
Antiduretic hormone:
Active passport
Requires the cell to spend energy, usually in the form of ATP. Examples include transport of large molecules (non-lipid soluble) and the sodium-potassium pump
Diffusion is the net movement of a substance (liquid or gas) from an area of higher concentration to one of lower concentration.
Filtration is the passage of fluid through a permeable membrane. Passage is from an area of high pressure to one of lower pressure.
Diffusion of water molecules across a membrane in response to differences in solute concentration. Water moves from areas of high-water/low-solute concentration to areas of low-water/high-solute concentration. Diffusion of water across a semi-permeable barrier such as a cell membrane, from high water potential (concentration) to lower water potential (concentration).
Hypertonic solutions
Are those in which more solute (and hence lower water potential) is present
Hypertonic solutions
A solution having a high concentration of solute.
Isotonic solutions
Have equal (iso-) concentrations of substances. Water potentials are thus equal, although there will still be equal amounts of water movement in and out of the cell, the net flow is zero.
Excessive retention of water and sodium in ECF in near-equal proportions results in a condition termed fluid volume excess
Signs and symptoms of Hypervolemia
Bounding pulse, elevated BP, respiratory changes, edema, weight gain, increased urine output, heart failure.
Nursing interventions for hypervolemia
Monitor I & O, weight
place in a fowler's position. O2, restrict fluids & sodium.
Define electrolytes
Substances capable of breaking into electrically charged ions when dissolved in a solution
Sodium (Na+):
Chief electrolyte of ECF influential in many chemical reactions particularly in nervous & muscle tissue cells.
Controls & regulates the volume of body fluids
Maintains water balance throughout the body
Is the primary regulator of ECF volume
Sources and Losses Sodium (Na+):
2,400 mg (approx. 1 tsp) Sodium found in many foods; typically present in large amounts, particularly in processed foods.

Eliminated primarily by the kidneys; small amounts lost in feces and perspiration
Na+2 Less than 135mEq/L

Sodium deficit in ECF caused by a loss of sodium or a gain of water. Due to the decrease in sodium, fluid moves by osmosis from the less concentrated ECF compartment to the ICF space. This shift of fluid can lead to swelling of the cells and cerebral edema. Seizures and permanent neurological damage can result from severe hyponatremia
Cuases of Hyponatremia
NPO, excessive diaphoresis, diuretics, GI suction, fresh water near drowning, decreased aldasterone, fluid overload
Signs and symptoms of Hyponatremia
Na+2 levels less than; 135mEq/L
Fluid excess or deficit, mental status changes, weakness & vomiting
Nursing interventions for hyponatremia:
Monitor I & O, weight, restrict fluids, admister diuretics/steroids
Na+2 greater than 145mEq/L

Hypernatremia refers to a surplus of sodium in ECF that can result from excess water loss or an overall excess of sodium. Because of the increased extracellular osmotic pressure, fluids move from the cells, causing them to shrink and leaving them without sufficient fluid. The cells of the central nervous system are especially affected, and signs of neurological impairment may result from severe hypernatremia.
Causes of Hypernatremia
Renal failure, excssive intake of sodium, dehydration, acute/chronic illness, IV fluids
Signs and symptoms of Hypernatremia
Sodium levels greater than 145mEq/L, thirst, mentatl status changes, seizures, muscle weakness, respiratory compromise
Nursing interventions for hypernatremia:
Treat fluid imbalance 1st, monitor I & O, weight, administer diuretics, restrict sodium, dialysis, treat cause.
Potassium (K+):
Major cation of ICF working in reciprocal fashion with sodium (eg, an excessive intake of sodium resulting in an excretion of potassium, and vice versa)chief regulator of cellular enzyme activity and cellular water content
Plays a vital role in such processes as the transmission of electric impulses, particularly in nerve, heart, skeletal, intestinal, and lung tissue; protein and carbohydrate metabolism; and cellular building
Assists in regulation of acid-base balance by cellular exchange with H+
Sources and Losses of Potassium (K+):
50 to 100 mEq daily
Leading food sources: bananas, peaches, melons, potatoes.

Potassium excreted primarily by the kidneys (no effective method of conserving potassium); deficits occur if potassium excretion in excess without being replaced simultaneously.

Gastrointestinal (GI) secretions contain potassium in large quantities; also some in perspiration and saliva
K+ less than 3.5mEq/L

When the extracellular potassium level falls, potassium moves from the cell, creating an intracellular potassium deficiency. Sodium and hydrogen ions are then retained by the cells to maintain isotonic fluids. These electrolyte shifts influence normal cellular functioning, the pH of ECF, and the functions of most body systems, including the cardiovascular system. Skeletal muscles are generally the first to demonstrate a potassium deficiency.
Causes of Hypokalemia:
Severe loss of GI fluids; NG suction. gastric lavage, prolonged vomiting diarrhea, diaphoresis, diuresis, drugs; diuretics, steroids, insulin
Signs and symptoms of Hypokalemia:
K+ levels bellow 3.5mEq/L, muscle weakness, shallow respirations, mental status changes, weak irregular pulse, ECg changes, cramping, N/V, respiatory arrest
Nursing interventions for Hypokalemia:
Treat cuase, offer potassium rich foods/replacement, educate pt.
Refers to an excess of potassium in ECF. Although this condition occurs less frequently than hypokalemia, it can be hazardous. Nerve conduction as well as muscle contractility can be affected. A variety of cardiac irregularities may result, including cardiac arrest if hyperkalemia is not corrected.
Causes of Hyperkalemia:
Overuse of potassium based salt substitute/potassium supplements, potasium sparing diretics, renal failure, massive tissue truma, metabolic acidosis
Signs and symptoms of Hyperkalemia:
k+ level above 5mEq/L, muscle twiching, cramps, diarrhea, low BP, cardiac dysrhythmia & arrest
Nursing Interventions for hyperkalemia:
Limit potassium intake, administer medications as ordered
Refers to a calcium deficit in ECF.
Signs and symptoms of hypocalcemia
Common signs of hypocalcemia include numbness and tingling of fingers, muscle cramps, and tetany.
Causes of Hypocalcemia
Common causes related to a calcium deficit involve inadequate calcium intake, impaired calcium absorption, and excessive calcium loss.
Refers to an excess of calcium in ECF.
Signs and symptoms of Hypercalcemia
Hypercalcemia is an emergency situation because the condition often leads to cardiac arrest.
Causes of Hypercalcemia
Ca+ levels above 5.5 mEq/L
Two major causes of hypercalcemia are cancer and hyperparathyroidism.
Respiratory Acidosis
Excess buildup of CO2 in the blood, occurs secondary to problems that cause hypoventalation:
CNS deoression, airwway resistance, loss of lung resistance, neuromuscular disease, mechanical ventalation.
Signs and symptoms of respiratory acidosis:
pH: Less than 7.35
pCO2: More than 45
Dyspnea, hypoxia, restlessness, drowsiness, dizziness, tachycardia & tachypnea, diaohoresis, seizures
Nursing interventions of respiratory acidosis:
Administration of bronchodialtors, semi fowlers position, assess airway, monitor for less than 12 breaths per minute.
Repiratory alkalosis:
Low circulating CO2 levels in the blood from hyperventalation secondary to hypoxia, pulmonary emboli, pain, anxiety
Signs and symptoms of Repiratory alkalosis:
pH: greater than 7.45
pCO2: less than 35
HYPERVENTALATION, dizziness, anxiety, epigastric pain, tetany, seziures
Nursing interventions of respiratory alkalosis:
Monitor: rspiratory rate/depth, encourage rebreathing, try to relax, reduce stimuli
Metabolic acidosis:
Exess production of acid or rapid excretion of HCO3. Mtabolic system primary problem, respiratory system atempts to compensate
Signs and symptoms of Metabolic acidosis:
pH:less than 7.35
HCO3: Less than 22
CO2: may be normal
Kassmaul breathing (deep, rapid respirations), Confusion, headache, lethargy, arrythmia, hot flushed skin, abdominal pain
List the three major homeostatic regulators of hydrogen ions.
(1) buffer systems, (2) respiratory mechanisms, and (3) renal mechanisms
Define buffer
A buffer is a substance that prevents body fluids from becoming overly acidic or alkaline.
What are the body's three buffer systems:
(1) the carbonic acid–sodium bicarbonate buffer system, (2) the phosphate buffer system, and (3) the protein buffer system
Respiratory Control of H+ Balance
The lungs are the primary controller of the body's carbonic acid supply. Due to the huge surface area from which CO2 can readily diffuse, the lungs can bring about rapid changes in H+ when needed. Carbon dioxide, constantly produced by cellular metabolism (carbonic acid [H2CO3] yields CO2 and H2O), is excreted by exhalation

Short term/rapid response
Renal Control of H+ Balance/Bicarbonate Formation
the kidneys excrete or retain hydrogen ions and form or excrete bicarbonate ions in response to the pH of the blood. In the presence of acidosis, the kidneys excrete hydrogen ions and form and conserve bicarbonate ions, thus raising the pH to the normal range. If alkalosis is present, the kidneys retain hydrogen ions and excrete bicarbonate ions in an effort to return to a balanced state.
Acid–base regulation by the kidneys occurs more slowly than that which occurs by the carbonic acid–sodium bicarbonate system or by respiratory regulation
Third-space fluid shift
refers to a distributional shift of body fluids into potential body spaces such as the pleural,
peritoneal (ascites), or pericardial areas; joint cavities; the bowel; or interstitial spaces. The fluid moves out of the intravascular spaces (plasma) to any of these spaces. Once trapped in these spaces, the fluid is not easily exchanged with ECF
Respiratory acidosis:
↓ pH < 7.35 ↑ PaCO Normal HCO3-
Respiratory alkalosis:
↑ pH > 7.45 ↓ PaCO2 Normal HCO3-
Metabolic acidosis:
↓ pH < 7.35 ↑ HCO3-Normal PaCO2
Metabolic alkalosis:
↑ pH > 7.45 ↓ HCO3-Normal PaCO2
When interpreting ABGs, follow these necessary steps:
1. Determine whether the pH is alkalotic or acidotic.

2. Check for the cause of the change in pH. Is it respiratory (PaCO2) or metabolic (HCO3-)? In respiratory acid–base imbalances, the pH and PaCO2 values are inversely abnormal (move in opposite directions):

3. Determine whether the body is compensating for the pH change. When the problem is respiratory, the renal system assists in compensation either by increasing or by decreasing HCO3-. In contrast, the respiratory system assists in compensating for a metabolic acid–base imbalance by regulating CO2 levels. When compensation occurs, the PaCO2 and the HCO3-will always point in the same direction. The focus of compensation efforts is to return the pH to the normal range:
Compensation is classified as Absent if:
pH abnormal
One component abnormal
Second component within normal range
Compensation is classified as Partial if:
pH abnormal
One component abnormal
Second component beginning to change
Compensation is classified as Complete if:
pH within normal range
One component abnormal
Second changed to move pH within normal range
When assessment data point to fluid and electrolyte problems amenable to nursing therapy, they receive one of three diagnostic labels:
Excess Fluid Volume
Deficient Fluid Volume
Risk for Imbalanced Fluid Volume
Outcome Identification and Planning in Fluid and Electrolyte Disturbances
Maintain an approximate balance between fluid intake and fluid output (average about 2500 mL fluid intake and output over 3 days)

Maintain a urine specific gravity within normal range (1.010–1.025)

Practice self-care behaviors to promote fluid, electrolyte, & acid–base balance

Identify signs and symptoms of recurrence of imbalance with need to notify the physician
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