Unit #6: Fluids, Electrolytes, Acid-Base Homeostasis/Imbalances

Question 1

Distribution of body fluids within compartments/spaces in infants and adults.

Answer 1

• Extracellular (outside of cell)

- Intracellular (inside of cell).

Question 2

What is extracellular body fluid made up of?

Answer 2

Rich in sodium, chloride, and bicarbonate ions. It is low in potassium, magnesium and phosphate ions.

Question 3

What is intracellular body fluid made up of?

Answer 3

Rich in potassium, magnesium, phosphates, and proteins.

Question 4

What are the homeostatic mechanisms the body uses to control fluid balance? (Osmosis)

Answer 4

If particle concentration of interstitial fluid is higher than inside the cell, water will move out of the cell by osmosis from the cells to the interstitial fluid to equalize the osmolality of the two compartments. Vice versa will occur if there is a higher particle concentration inside the cell.

Question 5

What are the homeostatic mechanisms the body uses to control fluid balance? (Sweating)

Answer 5

Fluid is excreted through the skin as visible sweat (which may or may not occur) or insensible perspiration (which always occurs).

Question 6

What are the homeostatic mechanisms the body uses to control fluid balance? (Urination)

Answer 6

Largest volume of fluid is excreted by urine.

Question 7

What is Antidiuretic Hormone (ADH) role in urine excretion?

Answer 7

• Factors that increase release of ADH into the blood include increased concentratedness, decreased circulating fluid volume, pain, nausea, and different stressors.
• Causes reabsorption of water that dilutes the blood and other body fluids)
• This decrease in water decreases urine volume and makes the urine more concentrated, thus decreasing fluid excretion.

Question 8

What is Aldosterone’s role in urine excretion?

Answer 8

• Activated by a decrease in circulating fluid volume and an increased concentration of potassium ions in the plasma
• Causes the renal tubules to reabsorb sodium and water, which expands the extracellular fluid volume (decreases fluid excretion)
• Decreased secretion of aldosterone causes a larger urine volume.

Question 9

What is Natriuretic Peptides role in urine excretion?

Answer 9

• Promote fluid excretion in the urine.
• When the vascular volume increases, the heart stretches, and more NP are released to cause renal excretion of the excess fluid.
• When the vascular volume decreases, the heart is less stretched and therefore, fewer NP is released and the kidneys excrete less fluid.

Question 10

Explain the movement of fluids and electrolytes between the body fluid compartments.

Answer 10

-Fluid distribution between the vascular and interstitial compartments is the net result of filtration across permeable capillaries.

Question 11

What is the effect of interstitial fluid osmotic pressure on fluid movement?

Answer 11

Inward-pulling force of particles in the interstitial fluid)

Question 12

What is the effect of capillary hydrostatic pressure on fluid movement?

Answer 12

Outward push of vascular fluid against the capillary walls

Question 13

What is the etiology and clinical manifestations of: extracellular fluid volume deficit?

Answer 13

• Caused by the removal of a sodium-containing fluid from the body
• Another example is fluid that accumulates rapidly in the bowel during an acute intestinal obstruction (no longer part of the extracellular fluid and signs/symptoms of fluid deficit occurs.
• Clinical manifestation: Sudden weight loss, postural blood pressure decrease, decreased skin turgor,

Question 14

What is the etiology and clinical manifestations of: extracellular fluid volume excess?

Answer 14

• The amount of extracellular fluid is abnormally increased
• Both the vascular and interstitial areas have too much isotonic fluid.
• Caused by additional or retention of saline (salt water in the same concentration as normal saline).
• Clinical manifestation: Sudden weight gain, edema, bounding pulse, dyspnea (difficulty breathing).

Question 15

What is the etiology and clinical manifestations of: clinical dehydration

Answer 15

Etiology: common in individuals who have vomited and diarrhea and do not know how to replace salt and water that is exiting the body. Removal of the saline portion of this fluid causes ECV deficit, and removal of extra water from the body causes hypernatremia.

Clinical manifestation: Sudden weight loss, light-headedness, sunken fontanels (infants), decreased skin turgor, hard stool, thirst, confusion, coma, hypovolemic shock.

Question 16

What is the etiology and clinical manifestations of: clinical dehydration

Answer 16

Etiology: common in individuals who have vomited and diarrhea and do not know how to replace salt and water that is exiting the body. Removal of the saline portion of this fluid causes ECV deficit, and removal of extra water from the body causes hypernatremia.

Clinical manifestation: Sudden weight loss, light-headedness, sunken fontanels (infants), decreased skin turgor, hard stool, thirst, confusion, coma, hypovolemic shock.

Question 17

What is the etiology and clinical manifestations of: interstitial fluid volume – edema

Answer 17

-An excess of fluid in the interstitial compartment.
-An increase in the forces that tend to move fluid from the capillaries into the interstitial compartment or a decrease in forces that tend to move fluid from the interstitial compartment into the capillaries will cause edema
Causes:
- Increased Capillary Hydrostatic Pressure (may be a cause of ECV excess)
-Increased Interstitial Fluid Osmotic Pressure
-Blocked Lymphatic Drainage
-Decreased Capillary Osmotic Pressure

Question 18

Define the term: Acid

Answer 18

• Low pH indicates a large amount of hydrogen ions, meaning that the solution is acidic.
• An acid releases hydrogen ions. The more hydrogen ions present, the more acidic the solution.
• Normal adult blood pH ranges from 7.35-7.45.

Question 19

Identify and describe the 3 main/major mechanisms to regulate the acid-base status of the body: Buffers

Answer 19

• Chemicals that help to control the pH of body fluids.
• First line of defense against pH imbalances
• Each buffer system consists of a weak acid, which releases hydrogen ions when the fluid is too alkaline, and a base, which takes up hydrogen ions when the fluid is too acidic.

Question 20

What are the different types of buffer systems?

Answer 20

-Different buffer systems include: bicarbonate buffer (most important in extracellular fluid), phosphate buffer (in intracellular fluid/urine), hemoglobin buffer (inside erythrocytes), and protein buffers ( in intracellular fluid/blood).

Question 21

Identify and describe the 3 main/major mechanisms to regulate the acid-base status of the body: Respiratory Contribution

Answer 21

• Body cells continually produce carbon dioxide. CO2 + Water make carbonic acid, which is present in the blood.
• The lungs excrete CO2 and water from the bod therefore, is effective at removing carbonic acid from the body.
• Respiratory system regulates how much carbonic acid is in the blood by altering rate and depth of respirations.
• Rate/depth of respirations are influenced by chemoreceptors that sense Paco2, Pa02, and pH of blood.
• If too little carbonic acid is in the blood, rate and depth of respirations are slowed.

Question 22

When does hyperventilation occur?

Answer 22

When there is a decreased pH and increase Paco2

Question 23

When does hypoventilation occur?

Answer 23

When there is an increase pH and a decreased Paco2

Question 24

Identify and describe the 3 main/major mechanisms to regulate the acid-base status of the body: Renal Contribution

Answer 24

• The kidneys can excrete any acid from the body except for carbonic acid (excreted by the lungs)
• Acids in the body except for carbonic acid are called metabolic acids and are called this because body cells continually produce them during normal metabolism
• Kidneys normally excrete metabolic acids
• If a metabolic acid starts to accumulate in the blood, the kidneys increase their acid excretion mechanisms to correct the problem. Kidneys will slow down their acid excretion mechanism if there is a metabolic deficiency in the blood.

Question 25

What is the etiology for metabolic acidosis?

Answer 25

Excess of any acid, except carbonic acid

• Can be caused by increased acid; decreased base; or combination of the 2
• Decrease in the 20:1 ratio of bicarbonate to carbonic acid
• Common Causes of Metabolic Acidosis (E.G. increase in acid from: ketoacidosis, burns, tissue anoxia, intake of acids, oliguric renal failure; decrease in base from: diarrhea, GI suction or drain.

Question 26

What is the clinical manifestations of metabolic acidosis?

Answer 26

Headache, abdominal pain, CNS depress (confusion, lethargy, stupor, coma)

Question 27

What is the compensatory response for metabolic acidosis?

Answer 27

Hyperventilation is the compensatory response. Low blood pH stimulates peripheral chemoreceptors, which then stimulate ventilatory neurons in the brainstem (results in increased rate/depth of respirations

Question 28

What is the etiology for respiratory acidosis?

Answer 28

Excess carbonic acid (CO2 + H2O)

• Factors making respiratory excretion of carbonic acid difficult cause this imbalance (E.G. COPD, pneumonia, asthma, pulmonary edema, obstructive sleep apnea (impaired gas exchange); Guillain-Barré, chest injury/surgery, respiratory muscle weak related to hypokalemia, respiratory muscle fatigue (impaired neuromuscular function); respiratory depression from drugs like opioids, central sleep apnea (impaired respiratory control in brainstem)
• Hypoxia in patients with COPD

Question 29

What is the clinical manifestation of respiratory acidosis?

Answer 29

• Headache because of dilation of blood vessels in brain
• Tachycardia
• Cardiac dysrhythmias
• Neurological abnormalities like blurred vision, tremors, vertigo, disorientation, and somnolence (sleepiness)

Question 30

What is the compensatory response for respiratory acidosis?

Answer 30

Increased renal excretion of metabolic acid is the compensatory response (mechanism requires several days to be effective)
-Although the kidneys cannot excrete carbonic acid, their ability to excrete more metabolic acid changes the ratio of bicarbonate ions to carbonic acid in favourable direction so that the pH moves toward normal.

Question 31

What is the etiology for respiratory alkalosis?

Answer 31

When have carbonic acid deficit (as occurs with Hyperventilation) get too much CO2 exhaled therefore get decreased carbonic acid
- (Causes Respiratory Alkalosis) E.G. hypoxemia because need O2 therefore get hyperventilation; acute pain; anxiety; prolonged sobbing; alcohol withdrawal; stimulation of brainstem with salicylate overdose, meningitis, head injury, or gram-negative sepsis leads to increased respiratory rate and decreased CO2.

Question 32

What is the clinical manifestation for respiratory alkalosis?

Answer 32

-Happens because of increased neuromuscular excitement (paresthesia leads to numb & tingle fingers & around mouth), confusion because increased pH causes dysfunction of brain cells, cerebral vasoconstriction therefore decreased blood flow to brain cells & confusion; decreased Ca++ therefore increased neuromuscular excitement.

Question 33

What is the compensatory response for respiratory alkalosis?

Answer 33

Decreased renal excretion of metabolic acid is the compensatory response. As metabolic acid accumulates in the blood, the bicarbonate ion concentration decreases because bicarbonate ions are used for buffering.