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DiBart 2021 > Chapter 1: Physiology of Body Fluids > Flashcards

Chapter 1: Physiology of Body Fluids Flashcards

1
Q

What is the equation to convert mEq/L to mmol/L?

A

mEq/L = mmol/L x valence

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2
Q

Intracellular homeostasis is maintained by what?

A

Shifts in water, solutes and other substances across the cell membrane.

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3
Q 
Fill in the blanks in mEq/L: 
ECF/ICF
Na+: 
K+:
Ca2+: 
Mg2+:
Cl-: 
HCO3-: 
HPO4 2-, H2PO4-:
Protein -:
A 
Na+: 145/12
K+: 4/140
Ca2+: 2.5/4
Mg2+: 1/34
Cl-: 110/4
HCO3-: 24/12
HPO4 2-, H2PO4-: 2/40
Protein -: 15 (interstitial)/50
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4
Q

In most disease states, loss of fluids occurs initially where?

A

ECF

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5
Q

What is the 60:40:20 rule?

A

An easy way of remembering distribution of body fluids - 60% is water, 40% is ICF and 20% is ECF.

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6
Q

What makes up the transcellular fluid compartment? What percentage of total body fluid does this compartment make up?

A

Fluids produced by specialized cells, such as CSF, GI fluid, respiratory secretion, glandular secretions and synovial fluid. This fluid is estimated to be 1% of body weight, or 2% of total body water.

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7
Q

Dense connective tissue, bone and cartilage contain approximately ____% of total body water.

A

15%

These tissues exchange fluid very slowly and this is usually not taken into account when considering fluid therapy.

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8
Q

The vascular endothelium is freely permeable to ________?

A

Ionic solutes. Therefore, the concentration of these ions is almost the same in ISF as in plasma.

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9
Q

Describe the Gibbs-Donnan equilibrium.

A

Negatively charged, non-diffusible proteins affect the distribution of other small charged solutes and create a small difference in anions and cations across the vascular endothelium.

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10
Q

Describe the two ways that sodium can move into or out of cells.

A

Sodium commonly will diffuse intracellularly due to the high concentration gradient. The Na, K, ATPase pump will also remove sodium from cells to maintain the steep gradient (3 sodium out, 2 potassium in).

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11
Q

What are the most abundant anions in the ECF?

A

Chloride and bicarbonate

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12
Q

What enzyme creates bicarbonate from water and CO2?

A

Carbonic anhydrase

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13
Q

What are the primary cations in the ICF?

A

Potassium and magnesium

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14
Q

Which ion is primarily responsible for generating the cell membrane at approximately -70 mV?

A

Potassium. Almost 100% of potassium is exchangeable.

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15
Q

What are the predominant anions in the ICF?

A

organic phosphates and proteins

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16
Q

Definition of molality:

A

Number of moles of solute per kilogram of solvent

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17
Q

Definition of molarity:

A

Number of moles of solute per liter of solution

18
Q

If at the normal pH of ECF, 80% of phosphate is in HPO4^2- and 20% is in H2PO4^-, what would the phosphate concentration be in mEq/L if the normal phosphate concentration is 4 mg/dL?

A

[0.8 x (-2)] + [0.2 x (-1)] = -1.8
[4 x 10]/31 x 1.8 = 2.3 mEq/L

Tip:
First calculate average valence
Then convert 4 mg/dL to mg/L
Then to convert to mEq-->divide by molecular weight and multiply by average valence
P molecular weight = 31
19
Q

In clinical medicine, why is osmolality measured in serum and not plasma?

A

Because the addition of anticoagulants for plasma would increase the solute in the sample.

20
Q

What is the average measured serum osmolality in the dog? In the cat?

A

Dog: 300 mOsm/L
Cat: 310 mOsm/L

21
Q

True or false: glucose is a permeable solute.

A

False. Glucose is an impermeable solute and therefore an effective osmole.

22
Q

What is tonicity?

A

Effective osmolality

23
Q

True or false: Freezing point depression osmometer measures both effective and ineffective osmoles.

A

True

24
Q

Fill in the blank with either , or =

Oftentimes, the tonicity of a solution is ___ than the measured osmolality.

A

tonicity is often < measured osmolality

25
Q

Colloid osmotic pressure is only about ___% of the total osmotic pressure.

A

0.5%. The remainder is made up of impermeable ions, glucose and BUN (if concentration is increased)

26
Q

What is the formula for calculated osmolality?

A

2([Na] + [K] + Glucose/18 + BUN/2.8

27
Q

In the formula for calculated osmolality, why is Na + K multipled by 2?

A

To account for the contribution of Cl- and HCO3-

28
Q

In the formula for calculated osmolality, why is glucose divided by 18 and BUN by 2.8?

A

To convert mg/dL to mmol/L. The molecular of glucose is 180 and that of BUN is 28

29
Q

What are the types of fluid and solute loss that can occur?

A

Solute in excess of water (hypertonic fluid), isotonic loss, or water in excess of solute (hypotonic fluid)

30
Q

What would the effect of hypotonic fluid loss have on the ECF?

A

The ECF would be hypertonic (and then water would shift from the intracellular space to extracellular to equilibrate)

31
Q

What would the effect of isotonic fluid loss have on the ECF?

A

The ECF would be isotonic. No shift of water

32
Q

What would the effect of hypertonic fluid loss have on the ECF?

A

Hypotonic ECF. And then fluid would shift from ECF to intracellular to equilibrate.

33
Q

What is the definition of effective blood volume?

A

The component of blood volume to which the volume-regulatory system responds by causing renal sodium adn water retention in the setting of cardiac and hepatic failure even though measured total blood and plasma volume may be increased.

34
Q

Exchange of solutes and fluid between plasma and interstitial spaces occurs where?

A

Capillaries

35
Q

What is Starling’s Law (the OG)?

A

Net filtration = Kf [(Pcap - Pif) - (π p-π if)]

Kf = net permeability of the capillary wall
P = hydrostatic pressure generated by heart (cap) or tissues (if)
π = oncotic pressure generated by plasma proteins (p) or filtered proteins and mucopolysaccharides in interstitium (if)
36
Q

What is the net filtration pressure in healthy capillaries?

A

0.3-0.5 mm Hg, at the proximal (arteriolar) end of capillary.

37
Q

What is the normal anion gap in dogs and cats?

A

Dogs: 12-24 mEq/L
Cats: 13-27 mEq/L

38
Q

What is the difference between obligatory water loss and free water loss?

A

Obligatory water loss is the water needed to excrete the daily renal solute load.
Free water loss is the water excreted unaccompanied by solute under the control of ADH.

39
Q

What makes up the majority of urinary solute (two-thirds) in the dog?

A

Urea

40
Q

Secretion of ADH is inhibited by a ____% decrease in serum osmolality?

A

1-2%

41
Q

If a patient has limited food intake, does their water intake needs increase or decrease?

A

Decrease.

DiBart 2021 (9 decks)

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