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Chem & Physics of Anesthesia > Diffusion, mixtures and solutions > Flashcards

Diffusion, mixtures and solutions Flashcards

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1
Q

Diffusion

A

The process of net movement of one type of molecule through space as a result of random motion (entropy)

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2
Q

Diffusion through a permeable membrane

A

Two divisions of a container separated by a permeable membrane of thickness
Higher [O2]- alveolar side (west) drives net movement to capillary side (east)
Continuous capillary blood flow causes O2 to be removed maintaining gradient movement west to east

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3
Q

Diffusion through a semi-permeable membrane

A

Dividing membrane semi-permeable, our example not permeable to proteins
Water is freely permeable and attempts to (distribute equally) dilute the concentration gradient equally Osmosis.

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4
Q

Osmotic Pressure

A

is related to the number of non-permeable molecules (solute)

Osmotic pressure is the pressure required to stop osmosis.

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5
Q

Oncotic Pressure

A

In capillaries osmotic pressure when caused by plasma proteins is called Oncotic pressure
Oncotic pressure =24-27mmHg

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6
Q

OSMOLE

A

a gram molecular weight of undissociated solute
ie. 1 mole (gram molecular weight) NaCl= 58.5 Gms (23+35.5=58.5)=2 osmoles
1 osmole Na+ and 1 osmole Cl-
ie. 1 mole KCL=74.55 gm (39.10 + 35.45)=2 osmoles 1 osmole K+ and 1 osmole Cl-

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7
Q

OSMOLALITY

A

Concentration of solute in terms of osmoles per kilogram water
Reflects the total number of ions or molecules in a solution regardless of size or weight

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8
Q

Normal Serum Osmolality

A

285-295 mOsm/kg

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9
Q

Serum Osmolality formula

A

(2 x (Na + K)) + (BUN / 2.8) + (glucose / 18)

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10
Q

OSMOLARITY

A

Concentration of solute in terms of osmoles per liter water

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11
Q

A mole of any solute in 22.4 liters of solution at 0C will exert an osmotic pressure of?

A

1 atm

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12
Q

in a mixed solution the osmotic pressure is the sum of ?

A

the individual molarities

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13
Q

over X% of plasma osmolarity is due to X?

A

99%

electrolytes

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14
Q

plasma proteins account for approx ?

A

1 milliosmole/liter

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15
Q

in dilute solutions such as X, differences between osmolality and osmolarity are ?

A

less than 1%

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16
Q

RBCs lyse at omolarities below?

A

200 mOsm/L

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17
Q

(blank) are impermeable to plasma proteins and this causes (blank blank blank) between plasma and interstitial fluid?

A

Capillaries

osmotic pressure difference

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18
Q

Oncotic pressure is X mmHg?

or X mOsm/kg?

A

24-27 mmhg

285-295 mOsm/kg

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19
Q

NaCl osmolarity

A

308 mOsmol/Liter

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20
Q

LR osmolarity

A

273 mOsmal/liter

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21
Q

requirment for Osmosis across cell membrane

A
  • Must have membrane that is impermeable to one or more solutes.
  • Must have a difference in the concentration of solutes.
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22
Q

requirement for Osmosis across capillary walls

A

Most capillary walls are permeable to small solutes (sodium, chloride, etc).
Albumin doesn’t permeate the capillary wall.

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23
Q

Fick’s Law of Gas diffusion across a fluid membrane formula

A

J = solubility constant for oxygen x diffusivity / membrane thickness x (PAO2- PcapO2)

24
Q

PcapO2

A

pulmonary capillary oxygen partial pressure

25
Q

PAO2

A

alveolar partial pressure

26
Q

Ficks Law of Gas diffusion accross a fluid membrane

A

1) Diffusion rate of gas is directly proportional to:
- Partial pressure gradient
- Membrane area
- Solubility of gas in membrane

2) Diffusion rate of gas is inversely proportional to:
- Membrane thickness
- Square root of the molecular weight

27
Q

Ficks Law explains

A

Concentration effect
Second gas effect
Diffusion hypoxia
Why turning on N2O leads to an increase of volume in gas spaces of the patient’s body

28
Q

Factors determining diffusion rate across membranes for non-gases:

A

Concentration gradient for un-ionized substances
Electrochemical gradient for ions
Lipid solubility
Size

29
Q

Ion Diffusion through a semi-permeable membrane

A

When a semi-permeable membrane is permeable to one ion but not the other oppositely charged ion, a charge imbalance is produced.
This transmembrane potential can be calculated by the Nernst Equation

30
Q

Graham’s Law

A

The diffusion rate of a gas (or liquid) is inversely proportional to the square root of it’s molecular weight

In short, Big molecules diffuse slower than Small molecules
Release a liter each of helium and xenon at the same time in a closed room- helium will achieve greater randomness faster

31
Q

Grahams Law

A

Diffusion is inversely related to the square root of it’s molecular weight

r = 1/ square root of MW

r= rate of diffusion
mw=molecular weight

32
Q

Laws that apply to Diffusion Through a Tissue Sheet

A

Graham’s law, Henry’s law and Fick’s law all apply to tissue diffusion

33
Q

N20 is x times more soluble than x thus we do not use when X

A

N2O is 36 times more diffusible than N, thus do not use when an air filled cavity’s expansion would be undesirable

34
Q

CO2 and N2O are approx X times more diffusible than O2

A

20

35
Q

Main determinant of gasses diffusion when all other factors are equal is

A

Concentration gradient

36
Q

Heterozygous mixtures

A

Uneven distribution of substances (example=earth soil)

37
Q

Homogenous mixtures

A

Even distribution of substances, known as solutions (example=saline, 5% albumin)

38
Q

Solute

A

the dissolved substance

39
Q

Solvent

A

that which the solute dissolves into

40
Q

Molality formula

A

moles of solute / kg solvent

41
Q

molarity formula

A

number of moles solute/ 1 liter solution

42
Q

Mole

A

Molar weight: a gram molecular weight of a substance

43
Q

Milimole

A

miligram molecular weight (1/1000 mole)

44
Q

Equivalent weight

A

gram wt. of a substance which will combine or replace one gram (one mole) of hydrogen; an equivalent wt. can be determined by dividing the molar wt. of a substance by its ionic valence.

45
Q

Milli equivalents

A

1/1000 equivalent

46
Q

Ionic solutions are

A

solutions of atoms or molecules in the ionized form
Ie. NaCl is table salt, a white crystalline substance Na+ Cl- is dissociated or ionized table salt

  • Adding table salt to water allows the weak polar H2O molecules to pull Na away from Cl
  • The salt molecule is thus dissociated (ionized) leaving Na+ wanting an electron and Cl- having an electron alone in its outer shell (orbit)
47
Q

Are Ionized drugs lipid soluble?

A

NO they DO NOT cross lipd membrane layers

48
Q

Are unionized drugs lipd soluble?

A

YES, they do cross lipid membranes

49
Q

if blood/gas coefficient is >1 where is the greater affinity?

A

the blood

50
Q

Partition coefficient

A

the ratio of the amount of substance present in equal volumes of two phases at a stated equilibrium temperature
If one of the phases is gaseous the partition coefficient and the Ostwald coefficient are the same
Partition coefficients frequently used when phases are both solid & liquid ie. tissue-blood coefficient

51
Q

Osmotic pressure

A

all about electrolytes, the pulling power of electrolytes. (the pressure required to stop osmosis).

52
Q

anytime you hear diffusion

A

THINK FICK

53
Q

Diffusion rate of gas is directly proportional to:

A

Partial pressure gradient
Membrane area
Solubility of gas in membrane

54
Q

Diffusion rate of gas is inversely proportional to:

A

Membrane thickness

Square root of the molecular weight (Grahms law)

55
Q

Factors determining diffusion rate across membranes for non-gases

A

Concentration gradient for un-ionized substances
Electrochemical gradient for ions
Lipid solubility
Size

Chem & Physics of Anesthesia (1 decks)

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