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Renal IVF > Fluid Administration > Flashcards

Fluid Administration Flashcards

1
Q

Describe the pharmaceutics of hypertonic saline

A

CVC only
Stable in storage
10ml contains 2g of salt, 20g per 100ml
pKa 3.09, good water solubility, osmolality 6840 mosm/kgh

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2
Q

What is the osmolality of hypertonic saline?

A

CVC only
Stable in storage
10ml contains 2g of salt, 20g per 100ml
pKa 3.09, good water solubility, osmolality 6840 mosm/kg

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3
Q

What ist he pKA of hypertonic saline

A

CVC only
Stable in storage
10ml contains 2g of salt, 20g per 100ml
pKa 3.09, good water solubility, osmolality 6840 mosm/kg

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4
Q

What is the osmolality of hypertonic saline

A

CVC only
Stable in storage
10ml contains 2g of salt, 20g per 100ml
pKa 3.09, good water solubility, osmolality 6840 mosm/kg

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5
Q

What additional organ action does hypertonic saline have aside from osmolality, circulating volume icnrease

A

Anti-inflammatory

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6
Q

What are the side effect of hypertonic saline?

A

Metabolic acidosis (NAGMA) – hyperchloraemia
Hypokalaemia
Seizures (sodium fluctuations)
Coagulopathy (apt/INR)
Altered platelet aggregation

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7
Q

What is the duration of action of hypertonic saline?

A

130 minutes of ICP effectO

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8
Q

Onset of hypertonic saline ffect

A

<1 minutes

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9
Q

Vd and distirbution of hypertonic saline?

A

Vd 0.2L/kg, confined to ECF – 25% intravascular 75% ISF

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10
Q

pH of 0.9% saline

A

9g NaCl; IV/SC/orally or as a neb. Clear colourless solution, non pyrogenic heat stable packaging
8.8g of NaCl added to water, pKa 3.1
pH 4.5-7

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11
Q

How many g of salt in 1 L of 0.9% saline?

A

9g NaCl; IV/SC/orally or as a neb. Clear colourless solution, non pyrogenic heat stable packaging
8.8g of NaCl added to water, pKa 3.1
pH 4.5-7

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12
Q

pka of saline

A

9g NaCl; IV/SC/orally or as a neb. Clear colourless solution, non pyrogenic heat stable packaging
8.8g of NaCl added to water, pKa 3.1
pH 4.5-7

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13
Q

What effect does 1L of saline have on volume

A

Volume expansion fo the IV by 25% of the infused volume after 25-30 minutes, below circulatory reflex activation threshold. Effect greater prior to redistribution.

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14
Q

What effect does 1L of saline have on Na

A

0.5-1mmol/L

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15
Q

What effect does 1L of saline have on Cl

A

3mmol/L rise

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16
Q

What effect does 1L of saline have on bciarbonate

A

decrease by 3mmol/L

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17
Q

What effect does 1L of saline have on osmoreceptors

A

0.2mosm/kg change
Therefore <1% and no change

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18
Q

What effect does 1L 0.9% saline have on oncotic pressure? How is this corrected?

A

Osmoreceptors not activated – as change is 0.2mosm/kg (<1% or <2.8mosm/kg), dilution of oncotic pressure  drop from 30mmHg to 28.5mmHg  glomerulotub. Bal

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19
Q

What effect does 1L of hartmans have on Na and Cl

A

Trivial sodium elevation 0.5-1mmol/L, chloride elevation up to 3mmol/L, decreased bicarbonate and base excess up to 3mmol/L. Osmoreceptors not activated – as change is 0.2mosm/kg (<1% or <2.8mosm/kg), dilution of oncotic pressure  drop from 30mmHg to 28.5mmHg  glomerulotub. Bal.
For Hartamns ½ rise in Na and Cl.

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20
Q

What si the pH of hartmains

A

5-7

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21
Q

What is the electrolyte content of NaCl

A

154 Na
154 ClW

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22
Q

What is the osmolality of saline?

A

286 measured (freezing point) (308 calculated)

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23
Q

What is the electrolyte content of Hartmans

A

131mmol Na
5mmol K
2mmol Ca
112mmol Cl
28mmol lactate – metabolised not osmotically active

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24
Q

What is the electrolyte content of Plasmoluyte

A

140 Na
5 K
1.5mmol Mg
23mmol gluconate
27mmol acetate
98mmol Cl

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25
Q

What is the pH of plasmolyte

A

7.4

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26
Q

What is the Osmolality of Hartmans

A

276 (effective osmolality is 248)

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27
Q

What is the osmolality of Plasmalyte?

A

294mosm calc. 244 reality

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28
Q

What it he duration of action of saline

A

20-40 minutes in health euvolaemic longer in shock up to 8hrs (RAAS)

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29
Q

What is the duration of action of 1L of hartmans or plasmolyte?

A

50% of infused volume out of IV space in 30mins, finishes in another 30min

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30
Q

What is the bioavailability and absorption of saline

A

100% bioavailability, well absorbed

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31
Q

What is the Vd of saline?

A

0.2L/kg, in ECF  25% intravascular – 250mls – redistribution delay means during infusion ~400-450mls
75% interstitial – 750mls

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32
Q

1L fo saline results in what response in circulatory reflexes?

A

Below circulatory reflex activation 5%, volume expansion maximal prior to redistribution(during infusion) . See action at other organ system for electrolyte and osmolality effects

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33
Q

What is the redistribution of Hartmans after 1L is given? Baroreceptors affected? Osmolality?

A

900ml extraC, 100ml intraC, 25:75 ratio leaves 225ml IV. Below Baroreceptor.
No lactic acidosis (no H+ ion) – incorporated in ciritc acid cycle consuming H+ion (decreased total body acidity) making CO2
1L = 9 calories. Osmolality change 1mmol/L change <1%.

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34
Q

What is the fate of lactate in hartamns

A

900ml extraC, 100ml intraC, 25:75 ratio leaves 225ml IV. Below Baroreceptor.
No lactic acidosis (no H+ ion) – incorporated in ciritc acid cycle consuming H+ion (decreased total body acidity) making CO2
1L = 9 calories. Osmolality change 1mmol/L change <1%.

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35
Q

What effect does plasmolyte have on IV fluid post 1L total given? What effect does it have on osmolaliuty?

A

Same as Hartmans but 227mls IV. Osmo ~3%
Acetate enter citric acid cycle  CO2 and water (consume H+ ion)
1L 15calories. K+ inside cells, Mg mostly extracell. Gluconate excreted in urine unchanged.

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36
Q

What is the fate of acetate in plasmolyte

A

Same as Hartmans but 227mls IV. Osmo ~3%
Acetate enter citric acid cycle  CO2 and water (consume H+ ion)
1L 15calories. K+ inside cells, Mg mostly extracell. Gluconate excreted in urine unchanged.

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37
Q

What is the fate of gluconate in plasmolyte?

A

Same as Hartmans but 227mls IV. Osmo ~3%
Acetate enter citric acid cycle  CO2 and water (consume H+ ion)
1L 15calories. K+ inside cells, Mg mostly extracell. Gluconate excreted in urine unchanged.

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38
Q

Describe the pharmaceutics of 5% dextrose?

A

Crystalloid fluid – isotonic monosaccharie solution
50g dextrose, IV. From hydrolysis of corn starch, Sterile, no buffers or bacteriostatic agents
pKa 12.9 i.e. non ionised, water solubility
pH 3.5 – 6.5 (regardless of conc of glucose)

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39
Q

pKa of dextrose 5%

A

Crystalloid fluid – isotonic monosaccharie solution
50g dextrose, IV. From hydrolysis of corn starch, Sterile, no buffers or bacteriostatic agents
pKa 12.9 i.e. non ionised, water solubility
pH 3.5 – 6.5 (regardless of conc of glucose)

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40
Q

pH of 5% dextrose

A

Crystalloid fluid – isotonic monosaccharie solution
50g dextrose, IV. From hydrolysis of corn starch, Sterile, no buffers or bacteriostatic agents
pKa 12.9 i.e. non ionised, water solubility
pH 3.5 – 6.5 (regardless of conc of glucose)

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41
Q

Where does dextrose come from for the manufactuer of fluids/

A

Crystalloid fluid – isotonic monosaccharie solution
50g dextrose, IV. From hydrolysis of corn starch, Sterile, no buffers or bacteriostatic agents
pKa 12.9 i.e. non ionised, water solubility
pH 3.5 – 6.5 (regardless of conc of glucose)

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42
Q

Describe the redistribution of 5% dextrose

A

Expands extracellular fluid volume and ICF – 8% of infused volume after 15-20 minutes remains intravascular. 2.5% change in osmolality sensed by OVLT osmosesnor leading to decreased vasopressin release and diuresis.

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43
Q

What is the change in osmolality after 1L fo dextrose is infused?

A

Expands extracellular fluid volume and ICF – 8% of infused volume after 15-20 minutes remains intravascular. 2.5% change in osmolality sensed by OVLT osmosesnor leading to decreased vasopressin release and diuresis.

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44
Q

Side effects of 5% dextrose

A

Hyperglycaemia + Hyponatraemia
Higher concentration dextrose  RBC lysis (hyperosmolar  fluid out of RBC)  thrombosis and phlebitis

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45
Q

Osmolality fo 5% dextrose

A

250 (calculated 278mmol/L  278mosm/L) –
(556 for 10%, 2780 for 50%)

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46
Q

Half life of volume expansion from 5% dextrose

A

15-20 minutes

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47
Q

Vd of 5% dextrose? Redistribution volumes

A

Vd 0.6L/kg – distributed widely after 20 minutes
- 66% intracellular  660mls
- 26% intersitital  260mls
- 8% intravascular  80mls

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48
Q

Metabolic fate of 5% dextrose?

A

Each glucose metabolised by all tissues with aerobic metabolism to 6H20 and 6CO2 but especially the liver – thus from 1L makes extra 30ml of fluid
Eliminated by kidney and lungs

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49
Q

Effect on electrolytes and osmolality of 5% dextrose 1L being given?

A

Below circulatory threshold (80ml^ = 1.5%)
2.5% change in osmolality (6.5mmol) OVLT stimulated and decreased vasopressin (diuresis).
Na drop 4mmol/L  angiotensin 2 + aldosterone ction
Decrease bicarbonate and base excess 3mmol/L
198 calories

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50
Q

What is the OVLT

A

Organum vaculosum laminae terminalis

Circumventricular organs

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51
Q

Where does albumin come from?

A

Concentrated human plasma albumin/ Colloid - From multiple whole blood donor/ plasma apheresis collection.

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52
Q

How is albumin prepared from blood?

A

Ethanol fractionation or chromatographic separation methods. Pasteurised by heat at 60 degrees for 10 hours. Octanoate preservative weakly antimicrobial and antifingual, stops denaturing in pasteurisation

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53
Q

What is the purpose of octanoate in albumin

A

Ethanol fractionation or chromatographic separation methods. Pasteurised by heat at 60 degrees for 10 hours. Octanoate preservative weakly antimicrobial and antifingual, stops denaturing in pasteurisation

54
Q

What is the molecular weight of albumin

A

MW 67000 daltons. Shelf life 36 months. Hypotonic saline carrier fluid, weak acid pKa 6.75 good water solibility

55
Q

What is the shelf life of albumin

A

MW 67000 daltons. Shelf life 36 months. Hypotonic saline carrier fluid, weak acid pKa 6.75 good water solibility

56
Q

What is the pKa of albumin

A

MW 67000 daltons. Shelf life 36 months. Hypotonic saline carrier fluid, weak acid pKa 6.75 good water solibility

57
Q

Is albumin an acid or base?

A

MW 67000 daltons. Shelf life 36 months. Hypotonic saline carrier fluid, weak acid pKa 6.75 good water solibility

58
Q

What is baseline oncotic pressure? What proportion of this is due to albumin?

A

Oncotic mediated expansion of extracellular fluid volume– increasing circulating volume, albumin exerts 75% of the total 20-30mmHg oncotic pressure

59
Q

100ml of 20% albumin draws how much fluid into the vasculature?

A

100ml of 20% albumin draws interstitial fluid and intracellular fluid over 15 minutes, and negative charge attracts sodium adding another 50% to intrinsic osmotic activity

Combined effect
- Interstitial fluid -32mls
- Intracellular fluids -88mls
- IV +220mls (inclusive of the 100mls given)

60
Q

What non fluid and electrolyte factors does giving albumin lead to?

A

Neutralises vasodilating effects of nitric oxide
Buffer in intersitital space (only one)
Immunomodulatory – antioxidant by binding copper and iron which cause production of reactive oxygen species; addit binding bilirubin and homocysteine; and neutralising oxygen radicals/nitrites.
Transport – endogenous + exogenous binding – calcium, fatty acids, bile acids, zinc

61
Q

Side effects and cons to using albumin

A

May worsen TBI mortality, ?efficacy (see notability)
Allergic and anaphylactic reactions possible
Hyperoncotic – risk of fluid overload
More expensive than crystalloid

62
Q

What is the make up of 4% albumin

A

Na 140
Cl 128 (or in normal saline)
Albumin 40g/L – makes it isooncotic with blood (no extra water attracted interstitial)
Electrolyte effect similar to salineW

63
Q

What is the make up of 20% albumin?

A

Na 48-100
Octanoate 32mmolLL
Albumin 200g/L (0.03mmol/L)  20g

64
Q

Osmolality of albumin 20%

A

Hypotonic saline carrier (130mosm/kg electrolytes, total 210-262 mosm/Kg, 20%)

65
Q

Lifespan of albumin

A

27 days

66
Q

Volume benefits of giving albumin lasyt how long

A

6-12 hours

67
Q

Vd of albumin?

A

Vd 0.07L/kg – confined to circulating volume. 4% per hour redistribution of albumin to interstitial fluid – septic can be 10% per hour. 50% lost from vascular compartment per day (interstitial). 100ml of 20% albumin draws an addition 120ml of interstitial fluid over 15 minutes (11ml per g), keeping the 100ml originally given intravascular.

68
Q

Albumin redistribution

A

Vd 0.07L/kg – confined to circulating volume. 4% per hour redistribution of albumin to interstitial fluid – septic can be 10% per hour. 50% lost from vascular compartment per day (interstitial). 100ml of 20% albumin draws an addition 120ml of interstitial fluid over 15 minutes (11ml per g), keeping the 100ml originally given intravascular.

69
Q

How much fluid does 1g of albumin generally attract

A

11ml per g

70
Q

How is albumin digested

A

By fibroblasts and macrophages (reticuloendothelial system) - 50% muscle and skin, 15% liver, 10% kidneys to free amino acids; 10% lost in gut.

Minimal renal excretion, most degraded by macrophages and 10% eliminated through the gut

71
Q

What effect does albumin administration have on osmolality

A

The attraction of free water intravascularly by 20% albumin would seem to risk decreasing osmolality, and triggering osmoreceptors however the Gibbs Doonan effect drags positively chanrged ions preventing significant changes.
4% albumin 500mls may trigger barocreceptor reflex, does not trigger osmoreceptors,

72
Q

What is the distribution of 4% albumin

A

50% intravascu;alr compared to 25% of NaCl

Baroreflex activiated

73
Q

4% albumin osmolality and oncotic pressure

A

Isoosmolar
Isooncotic

74
Q

Define a colloid

A

a fluid with heterogeneity, multiphasic constituents and insoluble particles in solution.

A fluid containing particles unable to pass through physiological semipermeable membranes

75
Q

Colloid characteristics

A
  • Scatter light
  • Susended in solvent without precipitating and separating
  • Subject to Brownian movement
  • All have the same charge keeping them separated by electrostatic propulsion
76
Q

Pharmaceutics of an ideal colloid

A

◦ No special storage requirements
◦ No need for crossmatching, or interference with crossmatching
◦ Long shelf life
◦ Not susceptible to biological contamination (eg. by acting as a substrate for microbial growth, or by allowing donor-recipient viral transmission)
◦ Cheap and readily available
◦ Acceptable to all patients (i.e. no cultural objections)

77
Q

Pharmacokinetics of an ideal colloid

A

◦ No special limitations on volume that can be infused
◦ Low viscosity
◦ Distributed to intravascular compartment only
◦ Cleared completely and without reliance on organ function
◦ No toxic metabolites or accumulation

78
Q

Pharmacodynamics of an ideal colloid

A

◦ High oncotic effect
◦ No interference with organ function (including red cell function)
◦ Non-pyrogenic, non-allergenic & non-antigenic
◦ No interference with haemostasis, coagulation, or acid-base balance

79
Q

Why theoretically are colloids good fluids for resuscitation?

A
  • The mechanisms which drive this distribution include:
    ◦ Oncotic pressure of the colloidal particles
    ◦ Gibbs-Donnan effects of the charge of the colloidal particles (for example, the negatively charged albumin attracts additional osmotically active sodium into the intravascular space)
  • A minor volume expanding effect is also attributable to the volume of the dispersed molecules themselves, which is non-trivial for large molecules. For example, the volume of normal plasma consists of 7-8% colloid.
  • Ergo, if the goal is to increase the circulating volume, fluid solutions containing substances with a large molecular weight should be more efficient, in terms of intravascular volume increase per volume of infused fluid
80
Q

Classify colloids

A
  • Synthetic colloids
    ◦ Polyvinylpyrrolidone
  • Semi-synthetic colloids
    ◦ Gelatins (eg. gelofusine, polygeline, )
    ◦ Dextrans (they are all called “dextran X”, where X is the molecular mass in kDa)
    ◦ Starches (eg. hydroxyethyl starch)
  • Plasma derivatives
    ◦ Purified plasma proteins (eg. albumin)
    ◦ Whole plasma products (eg. fresh frozen plasma)
81
Q

What are gelatin fluid sourced from

A

Succynylated bovin gelatin

82
Q

What is the carrier fluid for geltains

A

0.9% saline

83
Q

What is the viral and bacterial infection risk of gelatins

A

Minimal
CJD not ruled outAntigenic r

84
Q

Risk of gletains

A

Anaphylactogen
Decrease clot integrity

85
Q

Cost of geltains

A

Cheap

86
Q

Packaging of geltains

A

PVC flexible bags with logn shelf life in years

87
Q

Packaging of starch fluds

A

PVC flexible bags with logn shelf life in years

88
Q

Duration of effect of geltains

A

4-6 hours

89
Q

Starch fluids derived from?

A

Maize or corn

90
Q

Carrier fluid for starches

A

0.9% saline

91
Q

Bacterial and viral infection risk of starches

A

Minimal to zero

92
Q

Side effects of starches

A

Anaphylaxis
Renal failure
Pruritis

93
Q

Duration of action of starches as a fluid

A

6 hours

94
Q

Describe the autonomic effects of losing 1000mls of blood

A
  • Arterial hypotension causes baroreflex activation + low pressure volume receptors of the right atrium and great veins + if severe (with reduced cardiac output/fall in pH) may also induce chemoreceptor activation peripherally accentuating the response
  • Both reflexes result in autonomic phenomena:
    ◦ Decreased vagal stimulus; thus increased heart rate
    ◦ Sympathetic activation both directly and indirectly through systemic catecholamine release from adrenal glands, which has multiple effects:
    ‣ Increased peripheral vascular resistance - increased blood pressure
    ‣ Redistribution of blood flow away from the cutaneous, skin and splanchnic circulation - reduced renal and gut blood flow
    ‣ Precapillary constriction and reduced blood flow —> reduced hydrostatic pressure in downstream capillaries as net reabsorption leading to autotransfusion
    ‣ Venoconstriction mobilising venous reservoir - increased venous return
    ‣ Stimulation of vasopressin release via the projections from the nucleus of the solitary tract to the hypothalamus
    ‣ Stimulation of renin release by sympathetic stimulation of the juxtaglomerular cells, and due to lower renal perfusion
  • Net effect
    ◦ Reduced SBP and DBP
    ◦ Reduced pulse pressure
    ◦ Tachycardia
  • Increased inotropy
  • Increased PVR with vasoconstriction
    ◦ Cardiac output will be intitially reduced but with compensation will improve towards normal

Maximal response within 30 seconds

95
Q

Describe the neurohormonal effects of losing 1000mls of blood

A
  • Renin secretion causes:
    ◦ Vasoconstriction (by angiotensin)
    ◦ Increased sodium retention (by aldosterone) leading to increased reabsorption of water
    ◦ Increased thirst
  • Vasopressin release causes:
    ◦ Vasoconstriction (by V1 receptors), augments noradrenaline mediated arteriolar vasoconstriction
    ◦ Increased water retention (by V2 receptors)
  • Venous hypotension decreases atrial natriuretic peptide secretion, which causes:
    ◦ Decreased renal blood flow
    ◦ Decreased urinary water and sodium excretion
  • Catecholamines - see above
  • The net effect is decreased urine output and increased retention of sodium and water
96
Q

What impact does >20% loss of blood have

A

Compensatory mechanisms overwhelmed resulting in reduced BP and tissue perfusion with anaerobic metabolism and lactic acidosis. Decreased catecholamine sensitivity

97
Q

Medium to longer term response to blood loss

A
  • Erythropoerisis is stimulated by EPO release from the kidney stimulated by decreased oxygen delivery leading to increased RBC production - happens within the first 24 hours but takes 4-8 weeks to fully restore circualting RBC voluem
  • Albumin synthesis is stimulated in the liver and restores circulating protein levels to normal within a few days
  • Plasma volume returns to normal within 12-72 hours
98
Q

Describe the classes of hypovolaemic shock

A
99
Q

During the infusion of 1L of NaCl as a bolus what initiailly occurs?

A
  • Volume effect is greater during the infusion (prior to redistribution)
  • During this time, the blood volume may be expanded by 50-70% of the infused volume
  • This increases stroke volume by increasing preload causing an increase in cardiac output (frank Starling relationship) and blood pressure due to initially normal SVR, and therefore stimulates cardiovascular reflexes
100
Q

What reflex action is taken during the bolus of 1L of 0.9% saline

A

◦ Initially, a short-lived increase in heart rate (Bainbridge reflex, atrial stretch)
◦ Followed by a decrease in heart rate (baroreceptors - aortic arch/carotid sinus) - stimulated by increased pressure/stretch –> decreased outflow to vasomotor centres –> reduced SNS outflow
◦ Decrease in SVRI (baroreceptors)
◦ Decreased secretion of renin by renal juxtaglomerualr cells as increased Na delivery to macula densa, with subsequent decreases in angiotensin and aldosterone - reduced vasoconstriction and reduced afterload, dropping BP and aldosterone reducing sodium reabsorption
◦ Tubuloglomerular feedback activation: increased salt delivery to the nephron results in decreased glomerular blood flow, which decreases salt delivery (i.e. this is a negative feedback mechanism)
◦ Natriuretic peptide release increases due to atrial stretch
◦ Brief period of pressure diuresis possible, and a brief drop in circulating ADH while plasma volume expansion >10% before returning to normal with redistribution - affected by RAAS also

101
Q

What is tubuloglomerular feedback and how does it play into administration of saline fluid

A

◦ Tubuloglomerular feedback activation: increased salt delivery to the nephron results in decreased glomerular blood flow, which decreases salt delivery (i.e. this is a negative feedback mechanism)

102
Q

How long does redistribution of a 1L fluid bolus of saline take?

A
  • Redistribution begins immediately, and is complete within 25-30 minutes

Distribution
* VOD=0.2L/kg, basically confined to the extracellular fluid
* (thus: 25% remains intravascular, 75% becomes interstitial)

103
Q

Describe the changes in electrolytes and osmolality after a 1L bolus of saline

A

Changes in electrolytes and osmolality
* Change in osmolality: minimal (<1%) ; unnoticed by osmoreceptors (saline is isotonic)
* Change in plasma oncotic pressure: Dilution of plasma proteins increases the fraction of filtered water at the glomerulus, increasing the urine output (i.e. excretion of both water and sodium)
* Change in biochemistry:
◦ trivial sodium elevation (~0.5-.0 mmol/L)
◦ nontrivial chloride elevation (up to 3 mmol/L)
◦ decrease in bicarbonate and base excess (also up to 3 mmol/L)
◦ Metabolic acidosis (this fluid has SID = 0)

104
Q

Describe how glomerular tubular balance plays into the response to a fluid bolus

A

Increased free water excretion due to
◦ Decreased peritubular capillary oncotic pressure causing
◦ Reduced water reabsorption from proximal tubule
◦ Therefore the degree to which plasma is concentrated by increased filtration or dilution of plasma proteins before reaching the kidney determines reabsorptino

105
Q

What is the osmolality of a 3% saline bag

A
  • 900mosm/kg –> 3x that of plasma
  • Na remains in ECF, water will distribute according to osmolality, Cl remains in ECF
106
Q

What effect does 1L of 3% saline have on body fluid balance

A

70kg person with TBW of 42L. ICF is 23L and ECF 19L with osmolality 290mosm/kg

Before infusion
* Total body solute content = 42L x 290 = 12 180 mosm
* ECF solute content - 19 x 290 = 5510
* ICF solute content = 23 x 290 = 6670 mosm

After infusion
* 43L of total body water
* ECF solute content = 5510 + 900 = 13 080
* ICF solute content = 6670 (unchanged)

Therefore osmolality = 13080/42 = 304 mosm/kg
ECF volume 21.1 L and ICF volume 21.9L
* Decreased ICF volume
* Interstitial volume expansion insufficient to cause oedema, interfere with gas transfer or nutrient or waste transfer

  • ECF increased by 2.1L with 1/4 or so intravascular 500mls.
    ◦ Blood volume increased by 10% –> 7-10% is the trigger for volume receptors –> ANP
    ‣ ANP promotes sodium excretion at the kidney and inhibits renin secretion
    ‣ Decreased renin stimulation (high Na content delivery to DCT)
    * Aldosterone inhibition - reduced Na reabsorption
    * Decreased angiotensin - reduced Na reabsorption, increased GFR
    ◦ This will also lower the sensitivity of the volume receptors and will inhibit ADH secretion
    ◦ Volume receptors more powerful than osmoreceptor response
  • Plasma osmolality increased by 4.8% –> triggers osmoreceptors ++ and ADH secretions increases to retain water and driving thirst
    ◦ This will slow down the rate of excretion of excess water
107
Q

What effect would 1L 3% saline infusion have on ECF

A
  • ECF increased by 2.1L with 1/4 or so intravascular 500mls.
    ◦ Blood volume increased by 10% –> 7-10% is the trigger for volume receptors –> ANP
    ‣ ANP promotes sodium excretion at the kidney and inhibits renin secretion
    ‣ Decreased renin stimulation (high Na content delivery to DCT)
    * Aldosterone inhibition - reduced Na reabsorption
    * Decreased angiotensin - reduced Na reabsorption, increased GFR
    ◦ This will also lower the sensitivity of the volume receptors and will inhibit ADH secretion
    ◦ Volume receptors more powerful than osmoreceptor response
  • Plasma osmolality increased by 4.8% –> triggers osmoreceptors ++ and ADH secretions increases to retain water and driving thirst
    ◦ This will slow down the rate of excretion of excess water
108
Q

What effect would a 1L 3% saline bolus have on osmolality?

A
  • ECF increased by 2.1L with 1/4 or so intravascular 500mls.
    ◦ Blood volume increased by 10% –> 7-10% is the trigger for volume receptors –> ANP
    ‣ ANP promotes sodium excretion at the kidney and inhibits renin secretion
    ‣ Decreased renin stimulation (high Na content delivery to DCT)
    * Aldosterone inhibition - reduced Na reabsorption
    * Decreased angiotensin - reduced Na reabsorption, increased GFR
    ◦ This will also lower the sensitivity of the volume receptors and will inhibit ADH secretion
    ◦ Volume receptors more powerful than osmoreceptor response
  • Plasma osmolality increased by 4.8% –> triggers osmoreceptors ++ and ADH secretions increases to retain water and driving thirst
    ◦ This will slow down the rate of excretion of excess water
109
Q

Describe the ADME of a oral water absorption

A

Absorption is near-complete ~98.5% bioavailability, rapid, and mainly occurs in the proximal small bowel
* As water enters it becomes isotonic by mixing with saliva, stomach juices and intestinal fluids
* Most of the diffusion is transcellular
◦ It is driven by osmotic mechanisms (active absorption of other electrolytes, especially sodium)

Distribution is equal into all body fluid compartments, and proportional to their relative sizes:
* 66% into the intracellular fluid
* 340ml or 33% to extracellular fluid
◦ 25.5% into the interstitial fluid
◦ 8.5% into the circulating blood volume –> 80ml

Elimination is by renal excretion, where the filtered fraction is reabsorbed by a highly regulated mechanism. Hlaf life of a litre of water is about an hour

110
Q

What is the distribution of oral water

A

Absorption is near-complete ~98.5% bioavailability, rapid, and mainly occurs in the proximal small bowel
* As water enters it becomes isotonic by mixing with saliva, stomach juices and intestinal fluids
* Most of the diffusion is transcellular
◦ It is driven by osmotic mechanisms (active absorption of other electrolytes, especially sodium)

Distribution is equal into all body fluid compartments, and proportional to their relative sizes:
* 66% into the intracellular fluid
* 340ml or 33% to extracellular fluid
◦ 25.5% into the interstitial fluid
◦ 8.5% into the circulating blood volume –> 80ml

Elimination is by renal excretion, where the filtered fraction is reabsorbed by a highly regulated mechanism. Hlaf life of a litre of water is about an hour

111
Q

What effect would 1L of oral water ingestion have on osmaolity

A

Osmolality decreases
* For one litre of pure water, this would be a 2.5% decrease in osmolality (40L of fluid diluted by 1L)
◦ Osmolality drop from 280 to 273
* This is sensed by the osmosensitive circumventricular organs (OVLT); even 1% would be enough
◦ Organum vasculosum of lamina terminalis
* Afferent –> fibres from osmoreceptors decrease vasopressin release in posterior pituitary –> reducing V2 receptor stimulation and reduced apical expression of aquaporin in the collecting duct of nephrons reducing water reabsorption and promoting diuresis

112
Q

What si the absorption and bioavailability of oral water? How fast does this occur?

A

Absorption is near-complete ~98.5% bioavailability, rapid, and mainly occurs in the proximal small bowel
* As water enters it becomes isotonic by mixing with saliva, stomach juices and intestinal fluids
* Most of the diffusion is transcellular
◦ It is driven by osmotic mechanisms (active absorption of other electrolytes, especially sodium)

Distribution is equal into all body fluid compartments, and proportional to their relative sizes:
* 66% into the intracellular fluid
* 340ml or 33% to extracellular fluid
◦ 25.5% into the interstitial fluid
◦ 8.5% into the circulating blood volume –> 80ml

Elimination is by renal excretion, where the filtered fraction is reabsorbed by a highly regulated mechanism. Hlaf life of a litre of water is about an hour

113
Q

What is the half life of 1L of water orally ingested

A

Absorption is near-complete ~98.5% bioavailability, rapid, and mainly occurs in the proximal small bowel
* As water enters it becomes isotonic by mixing with saliva, stomach juices and intestinal fluids
* Most of the diffusion is transcellular
◦ It is driven by osmotic mechanisms (active absorption of other electrolytes, especially sodium)

Distribution is equal into all body fluid compartments, and proportional to their relative sizes:
* 66% into the intracellular fluid
* 340ml or 33% to extracellular fluid
◦ 25.5% into the interstitial fluid
◦ 8.5% into the circulating blood volume –> 80ml

Elimination is by renal excretion, where the filtered fraction is reabsorbed by a highly regulated mechanism. Hlaf life of a litre of water is about an hour

114
Q

What effect does 1L of oral fluid ingestion have on sodium

A

Plasma sodium concentration decreases
* This increases the stimulus for angiotensin and aldosterone release
* The net effect of these is to increase the reabsorption of sodium in the nephron

115
Q

What effect does 1L of oral water ingestion have on blood volume

A

Blood volume increases (very slightly)
* For one litre of pure water, this would be a 80ml increase in volume, or about 1.6%
* This change is below the sensitivity threshold of the cardiovascular regulatory reflexes, and should not lead to any change in blood pressure for a normal healthy person

116
Q

Losing 1L of body fluid to dehydration results in what change in fluid compartments? In osmoallity? Volume? Baroreceptor response?

A

Losing 1L is the loss of 1.4% of total body weight for a 70kg patient
* The loss fo water from any one compartment rapidly is corrected by inflow of water from another compartment.
◦ 80mls lost from intravascular space
◦ 250ml lost from interstitial fluid
◦ 670ml from intracellular fluid
* Osmolality change 2.5%, and 1.6% change in volume
◦ Sufficient to trigger the osmoreceptor but not he baroreceptors –> ADH release
* Electrolyte changes
◦ Na rise from 140 –> 143
* No baroreceptor response as 2% change insufficient
* Glomerulotubular balance - Intravascular protein concentration increases reabsorption of fluid from the proximal tubule retaining water

117
Q

At extremes of dehydration what response is seen?

A
  • Dehydration results in haemoconcentration, and haemoconcentration predictably leads to increased blood viscosity, though the relationship is unpredictably non-linear - whole blood viscocity increases markedly more than linearly would be predicted from haemoconcentration and plasma viscocity increases
  • Heart has to work harder due to decreased circulatory volume in exercise + having to perfuse the areas it would shut down (skin/muscle) in haemoarrhage i.e. uncompensate hypovolaemia
118
Q

Describe the physiology of intracellular fluid at baseline? % of body mass? L in a 70kg man? % of total body water?

A
  • Intracellular Fluid = 33% of total body mass ( 23.1 litres) ; this volume is regulated by the movement of free water.
    ◦ 55% of total body water
    ◦ 70% of intracellular contents is water, and viscocity is very near water but diffusion through this compartment takes 4x longer
119
Q

Extracellular compartment at baseline is what % of body mass? % of body water>. L in a 70kg man? Regulated by?

A
  • Extracellular Fluid = 27% (18.9 litres); this volume is regulated by the movement of sodium. and 45% of total body water
120
Q

Extracellular fluid is made up of what subcompartments of fluid?

A

◦ Plasma volume (2.8L) (1/4 of ECF/ 7.5% of total fluid)
‣ Red cells 2.5% of body mass, 4.5% of total fluid (nearly 2L) BUT inside cells
‣ Blood volume is 12% of total fluid or 7% of body mass
◦ Interstitial and lymph fluid
‣ 12% of body mass, 20% of total fluid 8.4L
◦ Dense connective tissue and bone
‣ 15% of total body fluid, 9% of total mass however slow to mobilise and dose not participate in infusion physiology. The rest is functional ECF
◦ Adipose tissue

121
Q

What % fo total fluid is plasma volume?

A

◦ Plasma volume (2.8L) (1/4 of ECF/ 7.5% of total fluid)
‣ Red cells 2.5% of body mass, 4.5% of total fluid (nearly 2L) BUT inside cells
‣ Blood volume is 12% of total fluid or 7% of body mass
◦ Interstitial and lymph fluid
‣ 12% of body mass, 20% of total fluid 8.4L
◦ Dense connective tissue and bone
‣ 15% of total body fluid, 9% of total mass however slow to mobilise and dose not participate in infusion physiology. The rest is functional ECF
◦ Adipose tissue

122
Q

What proportion of total body fluid does intersittial fluid take u

A

◦ Plasma volume (2.8L) (1/4 of ECF/ 7.5% of total fluid)
‣ Red cells 2.5% of body mass, 4.5% of total fluid (nearly 2L) BUT inside cells
‣ Blood volume is 12% of total fluid or 7% of body mass
◦ Interstitial and lymph fluid
‣ 12% of body mass, 20% of total fluid 8.4L
◦ Dense connective tissue and bone
‣ 15% of total body fluid, 9% of total mass however slow to mobilise and dose not participate in infusion physiology. The rest is functional ECF
◦ Adipose tissue

123
Q

What is transcellular fluid and what % of body fluid does it contribute

A
  • Transcellular fluid: ~1.5% of body mass or 2.5% of total body fluid (1050ml); fluid formed by the secretory activity of cells,
124
Q

What 3 factors trigger humeral responses to fluid administration

A
  • to the increase in renal perfusion
    ◦ Renin, angiotensin and aldosterone secretion is depressed
    ◦ As the result, the reabsorption of sodium and water in the distal nephron is decreased
  • to the change in atrial stretch
    ◦ Natriuretic peptide release increases, as atrial stretch stimulates their release, which in turn stimulates natriuresis and diuresis
  • to the change in osmolality
    ◦ The change in osmolality is sensed by the hypothalamus
    ◦ Vasopressin secretion from the posterior pituitary is then altered to produce the desired change in the urine concentrating function of the distal nephron
125
Q

What non humeral reflexes are present that are affected by infusion of fluids

A
  • Atrial stretch receptors sense the increase in venous pressure, and briefly increase the heart rate (Bainbridge reflex) - when the patient is hypovolaemic baroreceptor reflex overrides this, seen more with euvolaemia
  • Baroreceptors sense the increase in arterial pressure generated by the increase in stroke volume, and decrease the heart rate and the systemic vascular resistance, thereby renormalising the blood pressure
126
Q

What is contained within 500ml of 20% mannitol

A

500ml of 20% mannitol –> 100g of mannitol. 1100mmol/L. Mannitol distributed evenly into extracellualr fluid but not mechanism of entry into cells.

127
Q

What effect does mannitol have on osmotic pressure and fluid distributiuon when 500ml is infused?

A

◦ Intracellular dehydration, including brain parenchyma
◦ Rheological effects of mannitol infusion - improved RBC deformability due to shrinkage –. decreased blood viscocity improving microvascular perfusion
◦ Extracellular volume expansion - redistribution completely equally between interstitial and intravascular (same conc) –> 1100mmol in 14L ECF leads to big rise in osmolality 25mmol/L causing redistribution of fluid –>
‣ IV increase by 360mls –> 7% blood volume increase –> minimal baroreceptor response
‣ interstitial 1L, and
‣ drop in intracellular by 930mls –> 10-12% drop in intracranial pressure in mammals, 30% with hypocapnoea within 5-15 minutes and over 2-3 hours returns to baseline (hyeprtonic saline lasts 130 minutes)

128
Q

What electrolyte effects are induced by 500ml fo 20% mannitol being given?

A

◦ Hyperosmolar hyponatremia
‣ Triggers osmoreceptors –> increased ADH but less effective due to mannitol osmotic effect in tubules (effect diuresis). More water is lost than Na
‣ Increase in free water intravascularly drops Na from 140 to 127mmolL –> as mannitol is excreted though this improves
◦ Hyperkalemia - combination fo solute drag with fluid moving out of cells but also intracellular dehydration increasing K concentraiton favouring movement out

129
Q

What are the electrolyte and osmolar contents of 1 unit of pRBC

A

Due to ranging volumes, haematocrit, and duration of storage effects the effect is uncertain. Let us assume 250mls is given of which its haematocrit is 60%. Therefore 150mls of cells, 100mls of fluid. 100ml of water has an osmolality of 340mosm/L so giving 100ml you get 34mmol of electrolytes
* Na 15mmol remaining ECF
* K 2mmol - note this is just the free extracellualr K, the cells containg 150mmol/L (i.e. 15mmol)
* Cl 15mmol ECF
* HCO3 1mmol ECF
* Lactate 1 mmol metabolised by the liver

130
Q

What happens to the fluid of 1 unit of pRBC

A

Redistribution
* Over 15 minutes
* ECF now has a slight bump in osmolality causing some minor redistribution from intracaellular fluid
◦ 26ml of water remains intravascular + 150ml of cells
◦ Interstitum has 79mls extra
◦ Intracellular -6mls
* Haematocrit change - if haematocrit started at 0.3 then this was 1500ml of 5000 –> increased by 150mls so 6% increase (when measured it is more likely 2% increase)
* Hb rises by 10g/L

131
Q

What is the osmolality, baroreceptors ad electrolyte outcome of 1 unit of PRBC

A

Response
* Osmolality reamins constant as essentially isoosomolar
* Baroreceptors - intravascular volume increases by 176mls from 5000 to 5176 a 3.5% change
* Electrolytes
◦ Largely stable
◦ Citrate chelates 1mmol of Ca per pRBC and as 31mmol in ECF

132
Q
A

Renal IVF (7 decks)

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