Week 11 Flashcards
Exam 4
Intracellular fluid (ICF)
is all the fluid within cells
Extracellular fluid (ECF)
Extracellular fluid (ECF) is all the fluid outside the cells.
What is included in ECF
ECF includes the interstitial fluid, the intravascular fluid, and the various transcellular fluids
Sodium concentration is regulated by:
The sodium concentration is regulated by the renal effects of aldosterone
Water balance is regulated primarily by:
antidiuretic hormone (ADH)
What percent of ECF does sodium account for?
Sodium (Na+) accounts for 90% of the ECF cations (positively charged ions)
What are the major anions?
- Chloride
- Bicarbonate
What acts to regulate water balance?
- Sodium
- Chloride
- Bicarbonate
How do sodium, chloride and bicarbonate act to regulate water balance?
Sodium in concert with chloride and bicarbonate, the two major anions (negatively charged ions), acts to regulate water balance by contributing to extracellular osmotic forces.
The serum sodium concentration is normally:
135 to 145 mEq/L
How is the serum sodium concentration normally maintained?
By renal tubular reabsorption within the kidney in response to neural and hormonal influences.
What does aldosterone regulate?
Hormonal regulation of sodium (and potassium) balance is mediated by aldosterone,
Where is aldosterone secreted from?
Secreted from the adrenal cortex.
Aldosterone is a component of what system?
renin-angiotensin-aldosterone system
Aldosterone secretion is influenced by a number of factors, including:
Circulating blood volume, blood pressure, and plasma concentrations of sodium and potassium
Where is renin released from:
Secreted by the juxtaglomerular cells of the kidney,
When is renin released?
When the circulating blood volume or blood pressure is reduced, renin is released.
What is another reason renin may be released?
Renin also is released when sodium levels are depressed or potassium levels are increased.
Once released, renin stimulates the formation of what?
Angiotensin I
Angiotensin I
an inactive polypeptide, from angiotensinogen
Where is angiotensinogen secreted by?
Secreted by the liver
Where are Angiotensin-converting enzyme (ACE) found?
Angiotensin-converting enzyme (ACE), found primarily in pulmonary vessels and to a lesser extent in endothelial and renal epithelial cells.
What does the Angiotensin-converting enzyme (ACE) do?
Converts angiotensin I to angiotensin II , a potent vasoconstrictor.
What does vasoconstriction do to blood pressure and renal perfusion?
Vasoconstriction elevates blood pressure and restores renal perfusion.
What does Angiotensin II stimulate?
Angiotensin II also stimulates both the secretion of aldosterone from the adrenal cortex and antidiuretic hormone from the posterior pituitary.
What does aldosterone promote?
Aldosterone promotes sodium and water reabsorption, in addition to the excretion of potassium within the renal tubules.
What is the major anion and provides electroneutrality?
Chloride
Natriuretic peptides are produced by what?
Are hormones primarily produced by the myocardium.
Natriuretic peptides cause what?
Natriuretic peptides cause vasodilation and increase sodium and water excretion, decreasing blood pressure.
Water balance is regulated by what?
Water balance is regulated by the secretion of ADH, also known as vasopressin .
Where is ADH is produced by what? What is it secreted by?
ADH is produced in the posterior pituitary
Sodium imbalances occur with what?
Sodium imbalances occur with gains or losses of body water.
Water imbalances develop with what?
Water imbalances develop with gains or losses of salt.
Isotonic fluid loss causes what?
Isotonic fluid loss causes hypovolemia.
Isotonic fluid excess is causes what?
Isotonic fluid excess causes hypervolemia.
Hypertonic fluid alterations occur when?
Hypertonic fluid alterations develop when the osmolality of the ECF is elevated above normal
What are the most common causes of hypertonic fluid alterations?
The most common causes are:
- hypernatremia (increased concentration of ECF sodium) or a
- deficit of ECF water,
- or both.
Hypernatremia
Increased concentration of ECF sodium
Dehydration
water deficit
When does hypernatremia occur?
Hypernatremia occurs when serum sodium levels exceed 145 mEq/L.
When does hypernatremia occur?
Hypernatremia occurs when serum sodium levels exceed 145 mEq/L.
Increased levels of serum sodium cause what?
hypertonicity
Water is redistributed osmotically to the hypertonic extracellular space, causing intracellular dehydration.
Hypernatremia can occur in what three forms:
- Isovolemic
- Hypovolemic
- Hypervolemic
Isovolemic (euvolemic) hypernatremia:
- most common
It occurs when a deficit of free water is accompanied by normal or near-normal body sodium concentration.
Water deficiency w/o sodium loss
Most common causes of Isovolemic (euvolemic) hypernatremia are:
The most common causes include inadequate water intake, excessive sweating (sweat is hypotonic), fever, vomiting, diarrhea, burns, or respiratory tract infections.
Hypovolemic hypernatremia
occurs when a loss of sodium is accompanied by a relatively greater loss of body water.
Common causes of hypovolemic hypernatremia:
Common causes include use of loop diuretics (diuretics that inhibit sodium and chloride reabsorption in the kidney loop of Henle) or renal failure in which the kidneys fail to concentrate urine and excrete a large volume of urine.
Hypervolemic hypernatremia
It occurs when an increase in total body water is accompanied by a greater increase in total body sodium level, resulting in hypervolemia.
Causes of hypervolemic hypernatremia:
One cause is infusion of hypertonic saline solutions in an effort to replace sodium in cases of salt depletion
Other causes include oversecretion of adrenocorticotropic hormone (ACTH) or aldosterone, as might occur with Cushing syndrome or adrenal hyperplasia.
What accompanies hypernatremia and why?
Because chloride follows sodium, hyperchloremia, often accompanies hypernatremia.
Hyperchloremia
defined as an elevation of serum chloride concentration greater than 105 mEq/L,
In addition to hyperchloremia, what occurs with hypernatremia?
Plasma bicarbonate deficits, as would occur with metabolic acidosis also occur.
Clinical manifestations of hypernatremia?
Central nervous system signs are the most serious signs of hypernatremia and are related to alterations in membrane potentials and shrinking of brain cells (sodium cannot cross brain capillaries because of their tight endothelial junctions)
What are the tests that determine hypernatremia?
Serum sodium levels are greater than 145 mEq/L and urine specific gravity is greater than 1.030.
Treatment for isovolemic hypernatremia:
give oral water, IV dextrose 5% in water, or 0.45% normal saline.
Treatment for hypovolemic hypernatremia
is to give oral fluids or isotonic salt-free IV fluid (5% dextrose in water) until the serum sodium level returns to normal.
Treatment for hypervolemic hypernatremia
Treatment for hypervolemic hypernatremia is to administer loop diuretics.
Hypotonic fluid imbalances occur when
Hypotonic fluid imbalances occur when the osmolality of the ECF is less than 280 mOsm
Most common cause of hypotonic fluid imbalance:
The most common causes are sodium deficit or water excess.
Hyponatremia
Hyponatremia develops when the serum sodium concentration falls below 135 mEq/L.
What does hyponatremia result from:
Hyponatremia results from a loss of sodium, inadequate intake of sodium, or sodium dilution secondary to excess water.
Isovolemic hyponatremia
Isovolemic hyponatremia occurs when there is loss of sodium without a significant loss of water (pure sodium deficit).
Common causes of isovolemic hyponatremia:
Causes include water retention secondary to the syndrome of inappropriate antidiuretic hormone (SIADH), hypothyroidism, pneumonia, and glucocorticoid deficiency.
Hypervolemic hyponatremia
occurs when the total body sodium level increases.
The increase of sodium in hypervolemic hyponatremia leads to what?
The increased sodium leads to an increase in total body water and the dilution of sodium in the extracellular space.
Causes of hypervolemic hyponatremia;
Causes include congestive heart failure, cirrhosis of the liver, and nephrotic syndrome.
Edema typically is present in these cases.
Hypovolemic hyponatremia
Hypovolemic hyponatremia occurs with a loss of total body water and a greater loss of body sodium.
*extracellular volume is decreased
Causes of hypovolemic hyponatremia
Causes include prolonged vomiting, severe diarrhea, inadequate secretion of aldosterone (adrenal insufficiency), and renal losses from diuretics.
Dilutional hyponatremia (water intoxication)
occurs with an oral intake of a large amount of free water or with inappropriate IV administration of 5% dextrose in water (D5W) to replace fluid loss. The net effect in either case is to dilute sodium.
Hypochloremia,
a serum chloride level of less than 97 mEq/L
What occurs secondary to hyponatremia or elevated bicarb concentration?
Hypochloremia
What is the serum sodium level of hyponatremia?
Serum sodium concentration is less than 135 mEq/L,
Clinical manifestations of hyponatremia:
Clinical manifestations are related to impaired nerve conduction and neurologic changes
The most life-threatening consequence is cerebral edema and increased intracranial pressure.
What is a major intracellular electrolyte?
Potassium (K+)
Total body potassium content:
4000mEq
The ICF concentration of potassium
150 to 160 mEq/L
The concentration of potassium gradient is maintained by:
his concentration gradient is maintained by an active transport system, the sodium-potassium adenosinetriphosphatase pump (Na+-K+ ATPase pump)
Potassium maintains what?
Potassium also influences the intracellular electrical status in relation to hydrogen (H+) and sodium.
Potassium maintains the resting membrane potential, as reflected in the conduction of nerve impulses
Other roles of potassium
- facilitating glycogen and glucose deposition in liver and skeletal muscle cells,
- maintaining normal cardiac rhythm, and having a role in the contraction of both skeletal and smooth muscle
What is the most significant regulator of potassium balance?
the kidney is the most significant regulator of potassium balance.
What regulates potassium levels?
aldosterone,
Insulin
Sodium
epinephrine
Hypokalemia
Potassium deficiency
develops when the serum potassium concentration falls to less than 3.5 mEq/L.
How are changes in potassium balance reflected?
Changes in the potassium balance are reflected—although not always accurately—by the plasma concentration.
Factors contributing to development of hypokalemia:
Factors contributing to the development of hypokalemia include a reduced intake of potassium, an increased movement of potassium into the cells, and increased losses of potassium.
Potassium loss is also associated with:
Potassium loss from total body stores can also be caused by gastrointestinal and renal disorders.
Diarrhea, intestinal drainage tubes, fistulae, and laxative abuse all can result in hypokalemia.
What else is associated with potassium loss?
Vomiting or continuous nasogastric suctioning often is associated with potassium depletion.
What does severe potassium loss result in?
Severe potassium loss results in neuromuscular and cardiac disorders.
What does potassium loss do to neuromuscular excitability?
Neuromuscular excitability decreases, causing skeletal muscle weakness, smooth muscle atony, cardiac dysrhythmias, glucose intolerance, and impaired urinary concentrating ability.
How do symptoms of potassium loss occur in relation to depletion?
Symptoms occur in proportion to the rate of potassium depletion. The body can accommodate slow losses of potassium.
Potassium adaptation
Refers to the ability of the body to adapt to increased levels of potassium intake over time.
How should Potassium be increased?
A sudden increase in potassium may be fatal. If the potassium intake is increased slowly, renal excretion increases, maintaining the potassium balance.
Hypokalemia
Potassium deficiency
What is the level for potassium deficiency (hypokalemia)
develops when the serum potassium concentration falls to less than 3.5 mEq/L.
ADD MORE SLIDES ABOUT HYPOKALEMIA
Hyperkalemia
Hyperkalemia is defined as an ECF potassium concentration greater than 5.5 mEq/L.
Why would increase in body potassium be RARE?
Increases in the total body potassium level are relatively rare, largely because of efficient renal excretion.
Hyperkalemia may be caused by:
Hyperkalemia may be caused by an increased intake, a shift of potassium from cells to the ECF, decreased renal excretion, or drugs that decrease renal potassium excretion.
Drugs that cause hyperkalemia:
- ACE inhibitors
- Angiotensin receptor blockers
- Aldosterone antagonists
Times when hyperkalemia can occur?
- Short term potassium loading
- Cell trauma or changes to cell membrane permeability (ICF–>ECF)
-insulin deficiency
With acidosis, how do ECF H+ and K+ behave? What does this mean?
With acidosis, ECF hydrogen ions shift into cells in exchange for ICF potassium and sodium.
Means hyperkalemia and acidosis often occur simultaneously.
What else stimulates the movement of potassium into the cell?
Insulin
Mild presentation of hyperkalemia:
increased neuromuscular irritability may manifest as restlessness, intestinal cramping, and diarrhea.
Severe hyperkalemia results in:
Severe hyperkalemia decreases the resting membrane potential resulting in muscle weakness, loss of muscle tone, and paralysis.
HYPOKALEMIA AND HYPERKALEMIA ON A ECG
I DONT KNOW ANYTHING CAUSE I AM STUPID
In general, what is the management plan of hyoerkalemia:
Management of hyperkalemia includes both treating the underlying cause and reversing the excessive potassium concentration.
Calcium gluconate
used to decrease the negativity of the threshold potential when serum potassium levels are dangerously high
How to lower serum levels of potassium in hyperkalemia:
- Administer glucose and insulin
- Sodium bicarb
- Dialysis
- ORal or rectal administration of potassium binding agents (Kayexalate)
How does administering glucose and change Potassium levels?
Administration of glucose, an insulin secretagogue (a substance that causes another substance to be secreted), facilitates the movement of potassium into the cells.
pH of what is neutral for biologic fluids?
7.35 to 7.45
What is normal arterial pH?
7.35 to 7.45
Body acids form as the end result to whaat?
Body acids form as the end products of protein, carbohydrate, and fat metabolism; these acids can release hydrogen ion.
Base
A base is a substance that accepts hydrogen ions
An acid
an acid is a substance that donates hydrogen ions.
Body acids exist in what two forms:
- Volatile
- Nonvolatile
volatile acids
(substances that can be eliminated as carbon dioxide [CO2] gas)
nonvolatile acids
(substances that can be eliminated only by the kidney).
The sole volatile acid formed in the body is
The sole volatile acid formed in the body is carbonic acid (H2CO3), a weak acid, which means that it does not easily release its hydrogen ion.
The body has three mechanisms to maintain the acid–base balance:
(1) physiologic (chemical) buffer systems (bicarbonate, phosphate, hemoglobin, and protein), the first line of defense;
(2) respiratory acid–base control, the second line of defense; and
(3) renal acid–base control, the third line of defense.
Buffer systems
resist changes in pH and maintain pH within the normal range.
The important intracellular buffers are
phosphate and protein.
