Chapter 24: Water & Electrolyte Flashcards

1
Q

Newborn baby’s body weight is about

A

75% water

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2
Q

Total body water (TBW)

A

content of average young adults is 60% in men and 50% in women

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3
Q

obese and elderly people body water %

A

as little as 45% by weight

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4
Q

why is women’s totals body water average slightly less?

A

they have more adipose tissue, which displaces water

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5
Q

Fluid compartments

A

areas separated by selectively permeable membranes and differing in chemical composition

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6
Q

ECF is divided into

A
  • 25% tissue (interstitial) fluid
  • 8% blood plasma and lymph
  • 2% transcellular fluid
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7
Q

intracellular fluid (ICF) %

A

65%

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8
Q

extracellular fluid (ECF)

A

35%

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9
Q

Fluid balance

A

when daily water gains and losses are equal (about 2,500 mL/day)

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10
Q

gains come from which two sources?

A

metabolic water and performed water

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11
Q

Metabolic water

A

formed by aerobic metabolism and dehydration synthesis

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12
Q

Preformed water

A

ingested in food and drink

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13
Q

cutaneous transpiration

A

water that diffuses through epidermis and evaporates

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14
Q

Insensible water loss

A

not usually aware of it; breath and cutaneous transpiration

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15
Q

Sensible water loss

A

noticeable output; urine and moderate sweating

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16
Q

Fluid deficiency

A

fluid imbalance that arises when fluid output exceeds intake over long period of time

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17
Q

Volume depletion (hypovolemia)

A
  • proportional amounts of sodium and water are lost without replacement
  • Total body water declines but osmolarity remains normal
  • Caused by hemorrhage, burns, chronic vomiting or diarrhea, aldosterone hyposecretion (Addison disease)
18
Q

Dehydration (negative water balance)

A
  • body eliminates significantly more water than sodium
  • ECF osmolarity rises
  • Caused by lack of water intake, diabetes mellitus, diabetes insipidus (ADH hyposecretion), profuse sweating, overuse of diuretics
19
Q

why is fluid excess is much less common than fluid deficiency?

A

because kidneys are highly effective in compensating for excessive intake by excreting more urine

20
Q

Volume excess

A
  • both sodium and water are retained and ECF remains isotonic
  • Caused by aldosterone hypersecretion or renal failure
21
Q

Hypotonic hydration (water intoxication or positive fluid balance)

A
  • more water than sodium is retained or ingested and ECF becomes hypotonic
  • lose large amounts of water and salt through urine and sweat, but replace it by drinking only plain water
22
Q

Fluid sequestration

A
  • excess accumulation of fluid in a particular location
  • Hemorrhage can cause fluid sequestration as blood pools and clots in the tissues
23
Q

Edema

A

accumulation of fluid in interstitial spaces; most common form of fluid sequestration

24
Q

Pleural effusion

A

fluid accumulation in pleural cavity, caused by some lung infections

25
Q

Functions of sodium

A
  • gradient is a source of potential energy for cotransport of other solutes such as glucose, potassium, and calcium
  • sodium potassium pump
  • important means of generating body heat
26
Q

Sodium imbalances

A

Hypernatremia and Hyponatremia

27
Q

Hypernatremia

A
  • plasma sodium concentration greater than 145 mEq/L
  • From administration of IV saline
  • Complications : Water retention, hypertension
28
Q

Hyponatremia

A
  • plasma sodium concentration less than 130 mEq/L
  • Person loses large volumes of sweat or urine, replacing it with drinking plain water
  • Result of excess body water, quickly corrected by excretion of excess water
29
Q

Functions of potassium

A
  • Electrical signaling in nerve and muscle cells
  • most abundant cation of ICF
  • Greatest determinant of intracellular osmolarity and cell volume
  • Essential cofactor for protein synthesis and other processes
  • sodium potassium pump
30
Q

Potassium imbalance

A
  • Most dangerous types of electrolyte imbalances
  • Hyperkalemia and hypokalemia
31
Q

Hyperkalemia

A

plasma potassium concentration above 5.5 mEq/L&raquo_space; Increased Excitability

32
Q

Hypokalemia

A

plasma potassium concentration less than 3.5 mEq/L&raquo_space; Nerve and muscle cells Decreased excitablilty

33
Q

chemical buffer

A
  • substance that binds + H and removes it from solution as its concentration begins to rise, or releases +H into solution as its concentration fall
  • restores normal pH in fraction of a second
34
Q

buffer systems

A

mixtures composed of weak acids and weak bases

35
Q

Three major chemical buffers

A

bicarbonate, phosphate, and protein systems

36
Q

Bicarbonate buffer system

A

solution of carbonic acid and
bicarbonate ions (Carbonic anhydrase enzyme)

37
Q

Protein buffer system

A
  • proteins act as buffers due to the side groups of their amino acids
  • accounts for about three-quarters of all chemical buffering in the body fluids
  • Proteins are more concentrated than bicarbonate or phosphate systems, especially in the Intracellular ICF
38
Q

acidosis

A

HYPERVENTILATION

39
Q

alkalosis

A

HYPOVENTILATION

40
Q

what can neutralize more acid or base than either the respiratory system or chemical buffers?

A

the kidneys