Disorders of Fluid, Electrolyte, and Acid-Base Balance

Question 1

Define electrolytes

Answer 1

Substances that dissolve in a solution to form a charged particle (an ion)

Question 2

What is the #1 rule regarding the exchange of anions and cations?

Answer 2

Cations (+) and anions (-) are attracted to each other. A cation can be exchanged for a different cation (H+ for K+) and an anion can be exchanged for a different anion (Cl- for HCO3-)

Question 3

what is mEqL?

Answer 3

milliequivalents per liter (one of the measurements for electrolytes)

Question 4

Why is the total concentration gradient between the intracellular and extracellular fluid equal?

Answer 4

Osmosis

Question 5

Define osmolarity

Answer 5

osmolar concentration in 1 L of solution

Question 6

Define tonicity

Answer 6

Tension on cell due to water movement across the membrane
Isotonic, hypotonic, hypertonic

Question 7

What happens to cells placed in a hypotonic solution?

Answer 7

They swell (solution has a lower osmolarity than the ICF of the cell and water moves towards the area with more particles)

Question 8

What happens to cells placed in a hypertonic solution?

Answer 8

They shrivel (the hypertonic solution has a higher osmolality than the ICF, causing water to move out of the cell to dilute the particles outside the cell)

Question 9

What are the compartments of the ECF?

Answer 9

1. Plasma compartment
2. Interstitial compartment
3. Transcellular compartment (CSF and fluids in body cavities)

Question 10

What is third space?

Answer 10

Large amounts of fluid enter the transcellular compartment (this fluid is not available for exchange with the other ECF compartments readily)

Question 11

Capillary filtration pressure

Answer 11

Pushes water out of the capillary and into interstitial space

Question 12

Capillary colloidal osmotic pressure

Answer 12

Pulls water back into the capillary

Question 13

Interstitial hydrostatic pressure

Answer 13

Opposes water movement out of the capillary

Question 14

Interstitial colloidal osmotic pressure

Answer 14

Pulls water out of the capillary and into the interstitial space

Question 15

Physiologic mechanisms that lead to edema

Answer 15

(1) increase the capillary filtration pressure
(2) decrease the capillary colloidal osmotic pressure
(3) increase capillary permeability
(4) produce obstruction to lymph flow

Question 16

examples of edema caused by Increased Capillary pressure

Answer 16

Increased vascular volume (e.g., heart failure, kidney disease)

Venous obstruction (e.g., thrombophlebitis)

Liver disease with portal vein obstruction

Acute pulmonary edema

Question 17

Examples of edema due to Decreased Colloidal Osmotic pressure

Answer 17

Increased loss of plasma proteins (e.g., protein- losing kidney diseases, extensive burns)

Decreased production of plasma proteins (liver disease, malnutrition)

Question 18

Causes of edema due to Increased Capillary permeability

Answer 18

Inflammation
Allergic reactions (e.g., hives, angioneurotic edema)

Malignancy (e.g., ascites, pleural effusion)
Tissue injury and burns

Question 19

Causes of edema due to Obstruction of Lymphatic Flow

Answer 19

Malignant obstruction of lymphatic structures

Surgical removal of lymph nodes

Question 20

Pitting edema

Answer 20

• accumulation of interstitial fluid exceeds the absorptive capacity of tissue gel.
• tissue water becomes mobile and can be moved with pressure by a finger.

Question 21

Nonpitting edema

Answer 21

• swollen area becomes firm and discolored
• occurs when plasma proteins accumulate in tissue spaces and coagulate.
• most commonly seen in areas of localized infection or trauma.

Question 22

Assessment of edema

Answer 22

• daily weight (1 L of water weighs 2.2 pounds)
• visual assessment
• measurement of the affected part
• application of finger pressure to assess for pitting edema evaluated on a scale of +1 (minimal) to +4 (severe)

Question 23

Treatment for edema

Answer 23

• if swelling involves vital structure: correcting or controlling the cause and preventing tissue injury.
• lower extremities: elevating the feet.
• Diuretic therapy to treat edema associated with an increase in ECF volume.
• Serum albumin levels can be measured, and albumin administered intravenously to raise the plasma colloidal osmotic pressure when edema is caused by hypoalbuminemia.
• Elastic support stockings increase resistance to outward movement of fluid from the capillary into the tissue spaces. prescribed for patients with venous or lymphatic obstruction
• Moderate to severe lymphedema: light-pressure massage designed to increase lymph flow by encouraging opening and closing of lymph vessel valves; compression garments or pneumatic compression pumps; range-of-motion exercises; and skin care to prevent infection

Question 24

Ascites

Answer 24

accumulation of fluid in peritoneal cavity

Question 25

Effusion

Answer 25

Movement of fluid into serous cavities

Question 26

Hydrothorax

Answer 26

fluid in pleural cavity

Question 27

Where is edema life threatening?

Answer 27

brain larynx lungs

Question 28

What is the main determinant of water and sodium balance in the body?

Answer 28

effective circulating blood volume monitored by stretch recepotors in vascular system: causes thirst and stimulates posterior pituitary to release ADH

Question 29

Sodium concentration in ECF

Answer 29

135-145 mEq/L (mmol/L)

Question 30

Ideal sodium intake per day

Answer 30

500 mg

Question 31

Where do most sodium losses occur?

Answer 31

Kidneys

Question 32

How does the sympathetic NS and renin-angiotensin-aldosterone system contribute sodium balance?

Answer 32

* *sympathetic nervous system: adjusts* glomerular filtration rate in response to changes in blood volume. Also regulates renal reabsorption of sodium and renin release. * *renin-angiotensin-aldosterone system:* * Angiotensin II acts on renal tubules to increase sodium reabsorption * constricts renal blood vessels= decreases glomerular filtration rate and slows renal blood flow so less sodium is filtered and more is reabsorbed. * Angiotensin II regulates *aldosterone from* adrenal cortex. Aldosterone increases sodium reabsorption by the kidneys and increases potassium elimination (gotta trade one for the other due to positive charges)

Question 33

How is thirst controlled?

Answer 33

hypothalamus: *osmoreceptors* in thirst center in hypothalamus respond to changes in ECF osmolality Stimuli: * cellular dehydration caused by increase in ECF osmolality * decrease in effective circulating volume * production of angiotensin II by renin-angiotensin mechanism in the kidney increases in response to low blood pressure (backup thirst mechanism)

Question 34

Hypodipsia

Answer 34

Inability to detect thirst due to head trauma/disease affecting the hypothalamus

Question 35

Polydipsia

Answer 35

Excessive thirst

Question 36

mechanism of action of ADH

Answer 36

* exerts effects through vasopressin receptors in collecting tubules of kidney. * *aquaporins* are inserted into the tubular membrane. * increased water permeability allows water from the urine filtrate to be reabsorbed into the blood, making the urine more concentrated

Question 37

Does nicotine increase or decrease ADH? Alcohol?

Answer 37

Nicotine increases ADH alcohol decreases ADH

Question 38

diabetes insipidus

Answer 38

* caused by deficiency of adh or decreased renal response to adh * inability to concentrate urine, so large amounts of water leave through the kidneys = a lot of pee * strong sensation of thirst, polyuria, bedwetting, drink 2-20 L of water per day * central (neurogenic: autoimmune or vascular disease affects hypothalamus) or nephrogenic (defects in vasopressin receptor synthesis)

Question 39

Syndrome of Inappopriate Antidiuretic Hormone

Answer 39

failure of negative feedback system that regulates release and inhibition of ADH ADH secretion continues even when serum osmolality is decreased, causing water retention and dilutional hyponatremia. caused by medications and many diseases including tumors, HIV, TB, head injury, and other infections