Chapter 4 Alterations In Fluid And Electrolyte Balance

Question 1

Water balance:

Answer 1

Determined by osmotic gradients established by sodium concentrations

Antidiuretic hormone (ADH) regulates water balance

Question 2

Sodium balance

Answer 2

Sodium accounts for 90% of the ECF cations

Question 3

Sodium functions:

Answer 3

Maintains extracellular osmolarity

Maintains resting membrane potential (RMP) and required for depolarization

Question 4

Regulation of Plasma Sodium

Answer 4

Effects of aldosterone secretion on sodium reabsorption in renal tubules

Note: aldosterone secretion is regulated by the renin-angiotensin-aldosterone system

Question 5

Isotonic alterations in sodium and water balance

Answer 5

Changes in total body water (TBW) accompanied by proportional changes in electrolytes

Question 6

Causes of isotonic alterations in sodium and water balance:

Answer 6

Fluid overload

Hypovolemia

Question 7

What is fluid overload?

Answer 7

Administration of intravenous normal saline solutions or hypersecretion of aldosterone (hyperaldosteronism)

Question 8

What is hypovolemia?

Answer 8

Hyposectretion of aldosterone (hyperaldosterone), sweating (if sodium and water losses are equal)

Question 9

Water…

Answer 9

Follows sodium

Question 10

Hypotonic alterations- Hyponatremia causes:

Plasma sodium <135

ON EXAM

Answer 10

Vomiting, gastric suctioning
Inadequate sodium intake (rare, but can occur w/ individuals on low sodium diet)
Excessive oral water intake
Excess ADH secretion (syndrome of inappropriate ADH-SIADH)

Question 11

Fluid overload: Increased aldosterone causes:

Answer 11

Increased sodium and water retention

Question 12

Hypovolemia: decreased aldosterone causes

Answer 12

Decreased sodium and water retention

Question 13

Hyponatremia pathophysiology

ON EXAM

Answer 13

Shift of water from ECF to cytoplasm

Hyperpolarization of the RMP of neurons

Question 14

Hyponatremia: clinical manifestations related to neuronal swelling and/or hyperpolarization

NOT ON EXAM

Answer 14

Lethargy and confusion, seizures, coma

Gait disturbances, falls (especially in the elderly)

Question 15

Clinical manifestations related to fluid overload in dilutional hyponatremia

ON EXAM

Answer 15

Weight gain

Edema

Question 16

Hypertonic Alterations- Hypernatremia causes:

Plasma sodium > 145

Answer 16

Pure dietary sodium excess (rare unless patient has renal dysfunction)
Administration of hypertonic saline solutions
Insufficient water intake/dehydration
Decreased ADH secretion (diabetes insipidus)

Question 17

Hypernatemia pathophysiology

Answer 17

Shift of water from cytoplasm to ECF

Hypopolarization of the RMP of neurons

Question 18

Hypernatremia clinical manifestations due to neuronal dehydration and hypopolarization

PROBS NOT ON EXAM

Answer 18

Restlessness, irritability

Convulsions/seizures

Question 19

Hypernatremia clinical manifestations due to systemic dehydration

ON EXAM

Answer 19

Thirst
Low blood pressure and increased heart rate (tachycardia)
Dry mucous membranes
Poor skin turgor
Weight loss
Decreased urine output and concentrated urine

Question 20

Potassium balance:

Answer 20

Major intracellular electrolyte (150-160)

Plasma concentrations= 3.5 - 5.5

Question 21

Regulation of plasma potassium by the kidneys:

Answer 21

Potassium normally secreted by renal tubules and excreted in urine

PROBS WONT BE ON EXAM (BELOW)
Regulated by aldosterone: aldosterone stimulates potassium excretion by kidneys

Question 22

Important functions of potassium balance

Answer 22

Maintains RMP and required for repolarization

Necessary for insulin dependent glucose uptake by all cells (except brain)

Question 23

Hypokalemia common causes:

Plasma levels <3.5
(In general, lowered plasma K+ is indicative of a loss of total body K+. However, low plasma K+ can be caused by shifts of K+ from the ECF to the ICF)

Answer 23

Gastrointestinal (diarrhea)
Renal losses (diuresis)
***Shift of K+ from ECF to ICF (insulin administration)

Question 24

Hypokalemia pathophysiology:

Answer 24

Effects of decreased total body K+ on RMP

Question 25

Hyperkalemia common causes: Plasma levels > 5.5 ON EXAM

Answer 25

Renal failure Increased potassium intake (oral overdose uncommon, possible with intravenous administration) *** shift of K+ from ICF to ECF (cell trauma/death, insulin deficiency)

Question 26

Hyperkalemia pathophysiology:

Answer 26

Effects of increased total body K+ on RMP Mild to moderate hyperkalemia- increased muscular excitability

Question 27

Severe hyperkalemia-

Answer 27

Cells unable to repolarize