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HAN 202 > Fluid, Electrolyte and Acid/Bases > Flashcards

Fluid, Electrolyte and Acid/Bases Flashcards

1
Q

body water content

A
  • infants- 73% or more water (low body fat, low bone mass)
  • adult males- 60% water
  • adult females- 50% water (higher fat content, less skeletal muscle mass)
  • water content declines to about 45% in old age
  • daily recommended amount- 8 cups
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2
Q

total body water

A
  • 40L - 60% body weight
  • intracellular fluid- 25L- 40%
  • interstitial fluid- 12L- 80 of ECF
  • extracellular fluid- 15L- 20% body weight
  • plasma- 3L- 20% ECF
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3
Q

extracellular and intracellular fluids

A
  • each fluid compartment has a distinctive pattern of electrolytes
  • ICF- major cation is K and major anion is HPO42-
  • ECF- major cation is Na and major anion is Cl
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4
Q

fluid movement among compartments

A
  • regulated by osmotic and hydrostatic pressures
  • water moves freely by osmosis
  • osmolarities of all body fluids are almost always equal
  • change in solute concentration of any compartment leads to net water flow
  • increase in ECF solate -> water moves out of cells
  • decrease in ECF solate -> water moves into cells
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5
Q

regulation of water intake

A
  • thirst mechanism is the driving force for water intake
  • the hypothalamic thirst center osmoreceptors are stimulated by:
  • increase in osmolality of 1-2% activates receptors
  • angiotensin 2 or baroreceptor input
  • dry mouth - less saliva
  • substantial decrease in blood volume or pressure
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6
Q

regulation of water output

A
  • obligatory water losses:
  • insensible water loss- from lungs and skin
  • feces
  • minimum daily sensible water loss of 500 ml in urine to excrete wastes
  • body water and Na content are regulated in tandem by mechanisms that maintain cardiovascular function and blood pressure
  • thirst is not always a reliable indicator of need (the last straw)
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7
Q

regulation of water output: influence of ADH

A
  • hypothalamic osmoreceptors trigger or inhibit ADH release (inc in ECF solute concentration)
  • decrease in ADH -> dilute urine and decrease volume of body fluids
  • increase ADH -> concentrated urine
  • conserves water in body
  • water reabsorption in collecting ducts is proportional to ADH release
  • other factors may trigger ADH release via large changes in blood volume or pressure
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8
Q

electrolyte balance

A
  • electrolytes are salt, acids, and bases
  • salts enter the body by ingestion and are lost via perspiration, feces, and urine
  • salts:
  • controlling fluid movement, osmotic relations between cells
  • excitability; neuromuscular excitability
  • secretory activity
  • membrane permeability
  • eat a meal high in salt will cause a temporary increase in blood volume
  • electrolyte balance usually refers only to salt balance
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9
Q

central role of sodium

A
  • most abundant cation in the ECF (90-95%)
  • highest in blood plasma
  • exerts the most significant osmotic pressure
  • regulation of sodium linked to BP
  • sodium is a water magnet
  • aldosterone regulates salt
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10
Q

regulation of sodium balance: aldosterone

A
  • if blood volume and BP is low then aldosterone is released
  • renin-angiotensin mechanism is the main trigger for aldosterone release
  • granular cells of JGA secrete renin in response to:
  • sympathetic nervous system stimulation
  • decrease filtration osmolality
  • decrease stretch (due to decreased blood pressure)
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11
Q

regulation of sodium balance: ANP atrial natriuretic peptide

A
  • released by atrial cells in response to stretch (if BP is high)
  • decrease BP and blood volume:
  • decrease ADH, renin and aldosterone production
  • increase excretion of sodium and water
  • promotes vasodilation
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12
Q

cardiovascular system baroreceptors

A
  • if an increase in blood volume and pressure:
  • baroreceptors alert the cardiovascular centers in brain
  • sympathetic nervous system impulses to the kidneys decline
  • afferent arterioles dilate
  • GFR increases
  • Na and water output increase (less reabsorption)
  • blood volume and pressure decrease
  • baroreceptors provide information on the fullness or volume of the circulation that is critical for maintaining CV homeostasis
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13
Q

regulation of potassium balance

A
  • importance of potassium:
  • affects RMP (resting metabolic potential) in neurons and muscle cells (especially cardiac muscle)
  • K balance is controlled by the kidney
  • over 80% of K is reabsorbed at the prox tubule
  • potassium is part of bodys buffer system
  • shift of H+ shift in and out of cells induce corresponding shifts in K in the opposite direction to maintain cation balance
  • Na is reabsorbed at collecting ducts never excreted, K can be excreted at ducts
  • the collecting ducts control the amount of K secreted back into filtrate
  • ***high K content of ECF favors secretion of K
  • when K levels are low, the kidneys conserve K by reducing its excretion
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14
Q

influence of aldosterone on potassium balance

A
  • stimulates K secretion (and Na reabsorption)
  • increased K in the adrenal cortex causes:
  • release of aldosterone
  • potassium secretion
  • amount of K in ECF determines how much will be secreted in kidney
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15
Q

regulation of caclium

A
  • calcium role in ECF- neuromuscular excitability, blood clotting, cell membrane permeability, secretory activities
  • hypocalcemia -> causes muscle tetany
  • hypercalcemia -> increase heart rate and contractility but very high calcium levels may cause heart arrhythmias
  • calcium balance is controlled by parathyroid hormone (PTH) and calcitonin
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16
Q

influence of PTH parathyroid hormone on calcium

A
  • bones are the largest reservoir for Ca and phosphates
  • PTH promotes increase in calcium levels in blood by targeting bones, kidneys, and small intestine (indirectly through vitamin D)
  • calcium reabsorption and phosphate excretion go hand in hand
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17
Q

regulation of anions

A
  • Cl- is the major anion in the ECF
  • helps maintain the osmotic pressure of the blood
  • follows Na ions out of filtrate
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18
Q

an increase in the ECF solute content causes ______

A
  • water to move into the cell
  • solute to move out of the cell
  • water to move out of the cell*
  • both a and b
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19
Q

you would expect blood levels of ANP to increase when _____

A
  • blood pressure is increased
  • there is an increase in preload
  • the walls of the atria are stretched
  • all of the above occur*
  • a and c only
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20
Q

acid-base balance

A
  • pH affects all functional proteins and biochemical reactions
  • normal pH of body fluids:
  • arterial blood- pH 7.4
  • venous blood- pH 7.35
  • alkalosis or alkalemia- arterial blood pH > 7.45
  • acidosis or acidemia- arterial pH < 7.35
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21
Q

most H+ is produced by metabolism

A
  • phosphoric acid from breakdown of phosphorus containing proteins in ECF
  • lactic acid from anaerobic respiration of glucose
  • fatty acids and ketone bodies from fat metabolism
  • H+ liberated when CO2 is converted to HCO3- in blood
22
Q

concentration of hydrogen ions is regulated sequentially by:

A
  • chemical buffer systems- rapid- first line of defense
  • brain stem respiratory centers- act within 1-3 min
  • renal mechanisms- most potent, but require hours to days to effect pH changes
23
Q

strong acids

A
  • dissociate completely in water (liberate their H+)

- can dramatically affect pH

24
Q

weak acids

A
  • dissociate partially in water
  • are efficient at preventing pH changes
  • act as chemical buffers
25
Q

strong bases

A
  • dissociate easily in water

- quickly tie up H+

26
Q

weak bases

A

-accept H+ more slowly

27
Q

acidity of solution reflects the free hydrogen ions

28
Q

chemical buffer

A
  • system of one or more compo9unds that act to resist pH changes when strong acid or base is added
  • binds to H+ when pH drops and releases them when pH rises
    1. bicarbonate buffer system- most effective in ECF
    1. phosphate buffer system most effective in urine and ICF
    1. protein buffer system- in plasma and cells
29
Q

bicarbonate buffer system: if strong acid is added

A
  • if strong acid is added:
  • pH decreases only slightly, unless all available HCO3- (alkaline reserve) is used up then buffer system is ineffective and pH will drop
  • HCO3- concentration is closely regulated by the kidneys
  • HCl + NaHCO3 (sodium bicarb) -> H2CO3 (carbonic acid) + NaCl
  • strong acid + weak base -> to weak acid + salt
30
Q

bicarbonate buffer system is strong base is added

A
  • pH rises only slightly
  • H2CO3 (carbonic acid) supply is almost limitless (from CO2 released by respiration) and is subject to respiratory controls
  • NaoH (sodium hydroxide) + H2CO3 -> NaHCO3 + H2O
  • strong base + weak acid -> to weak base + water
  • weak base replaces strong base to prevent change in pH
31
Q

physiological buffer systems

A
  • respiratory and renal systems
  • act more slowly than chemical buffer systems
  • have greater buffering power than chemical buffer systems
32
Q

respiratory regulation of H+

A
  • respiratory system eliminates CO2
  • a reversible equilibrium exists in the blood
  • CO2 + H2O -> H2CO3 -> H+ HCO3- (bicarbonate ion)
  • during CO2 unloading the reaction shifts to the left (and H+ is incorporated into H2O) LUNGS
  • during CO2 loading the reaction shifts to the right (and H+ is buffered by proteins) TISSUES
33
Q

respiratory regulation of H+ acidosis

A
  • hypercapnia activates medullary chemoreceptors
  • response -> increase RR
  • rising plasma H+ activates peripheral chemoreceptors
  • response -> increase RR
  • more CO2 is removed from the blood
  • H+ concentration is reduced
34
Q

respiratory regulation of H+ alkalosis

A
  • alkalosis depresses the respiratory center
  • respiratory rate and depth decrease
  • CO2 and H+ concentration increases
35
Q

acid-base imbalances

A
  • respiratory system impairment causes acid-base imbalances
  • hypoventilation -> respiratory acidosis
  • hyperventilation -> respiratory alkalosis
36
Q

renal mechanisms of acid-base balance

A
  • most important renal mechanisms
  • conserving (reabsorbing) or generating new HCO3- (bicarbonate ions) will lose H+ and increase pH
  • excreting HCO3- will acidify blood and decrease pH
  • generating or reabsorbing one HCO3- is the same as increasing pH
  • H2CO3 (carbonic acid) -> H+ + HCO3- (bicarbonate ion)
37
Q

abnormalities of acid-base balance

A
  • respiratory acidosis and alkalosis- failure of respiratory system to perform its normal pH balancing role
  • metabolic acidosis and alkalosis- all abnormalities of acid-base imbalances except those caused by too much or too little CO2
38
Q

respiratory acidosis

A
  • the most important indicator of adequacy of respiratory function is PCO2 level (normally 35-45mmHg)
  • PCO2 above 45 -> respiratory acidosis
  • most common cause of acid base imbalances
  • due to decrease in ventilation or gas exchange- hypoventilation
  • characterized by falling blood pH and rising PCO2
  • common causes- pneumonia, emphysema, bronchitis
39
Q

respiratory alkalosis

A
  • PCO2 below 35 mmHg -> respiratory alkalosis
  • a common result of hyperventilation due to stress or pain
  • panic attack
  • not common
40
Q

metabolic acidosis and alkalosis

A
  • any pH imbalance not caused by abnormal blood CO2 levels
  • indicated by abnormal HCO3- levels
  • lowered HCO3- (free H+) - acidosis
  • elevated HCO3- alkalosis
  • normal bicarbonate levels - 22-26 mEg/L
41
Q

causes of metabolic acidosis

A
  • ingestion of too much alcohol ( -> acetic acid)
  • excessive loss of HCO3- (persistent diarrhea)
  • accumulation of lactic acid, shock, ketosis in diabetic crisis, starvation, and kidney failure
42
Q

metabolic alkalosis causes

A
  • much less common
  • indicated by rising blood pH and HCO3-
  • caused by vomiting of the acid contents of the stomach or by intake of excess base (antacids)
43
Q

effects of acidosis and alkalosis

A
  • blood pH below 7 -> depression of CNS -> coma > death
  • blood pH above 7.8 -> excitation of nervous system -> muscle tetany, extreme nervousness, convulsions, respiratory arrest
44
Q

respiratory compensation in metabolic acidosis

A
  • high H+ levels stimulate the respiratory centers
  • rate and depth of breathing are elevated
  • respiratory system tries to correct
  • blood pH is below 7.35 and HCO3- level is low
  • as CO2 is eliminated by the respiratory system, PCO2 falls below normal
45
Q

respiratory compensation for metabolic alkalosis

A
  • revealed by:
  • slow, shallow breathing, allowing CO2 accumulation in the blood
  • high pH (over 7.45) and elevated HCO3- levels
46
Q

renal compensation

A
  • hypoventilation causes elevated PCO2
  • respiratory acidosis- renal compensation is indicated by high HCO3- levels
  • respiratory alkalosis exhibits low PCO2 and high pH
  • renal compensation is indicated by decreasing HCO3- levels
47
Q

holy grail guide

A
  • respiratory acidosis- pH < 7.35; PCO2 > 45; HCO3- > 26 IF compensating
  • respiratory alkalosis- pH > 7.45; PCO2 < 35; HCO3- < 22 IF compensating
  • metabolic acidosis- pH < 7.35; PCO2 < 35 if compensating; HCO3- decreased
  • metabolic alkalosis- pH > 7.45; PCO2 > 45 if compensating ; HCO3- elevated
  • easy way to remember:
  • if the pH and PCO2 are moving in the reverse direction than it is a REspiratory issue
  • if the pH and PCO2 are moving in the same direction than it is a MEetabolic issue
  • decreased pH = acidosis
  • elevated pH = alkalosis
  • RE = reverse
  • ME = same
48
Q

a falling blood pH and a rising partial pressure of carbon dioxide due to pneumonia or emphysema indicates ________

A
  • respiratory acidosis*
  • respiratory alkalosis
  • metabolic acidosis
  • metabolic alkalosis
49
Q

which of the following is the initial H+ regulatory mechanism in the body

A
  • renal excretion
  • chemical buffers*
  • brain stem respiratory centers
  • lactic acid production
50
Q

a patients test results show PCO2 > 45 mmHg, HCO3- level of 24 mEg/L, and pH < 7.35. These indicate ____

A
  • metabolic acidosis
  • metabolic alkalosis
  • respiratory acidosis*
  • respiratory alkalosis
51
Q

test results: pH 7.48; PCO2 is 46 mmHg; HCO3+ 33 m/Eg/L. Patient is breathing slow and shallow

A
  • metabolic acidosis
  • metabolic alkalosis*
  • respiratory acidosis
  • respiratory alkalosis
52
Q

a patient is breathing rapidly, and blood pH analysis indicates an abnormally low value, what is the likely diagnosis

A
  • respiratory acidosis*
  • metabolic acidosis
  • metabolic alkalosis
  • respiratory alkalosis

HAN 202 (16 decks)

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