Lecture 9 - Fluid Replacement Therapy Flashcards

1
Q

What is osmolality?

A

The number of solute particles per kg of solvent

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2
Q

What is osmolarity?

A

The number of particles of solute per litre of solution

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3
Q

What is tonicity?

A

It compares the osmotic pressure gradient of two solutions separated by a semipermeable membrane

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4
Q

What is an isotonic solution?

A

When the osmolality of the solution is the same as the Osmolality within the cell

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5
Q

What is a hypotonic solution?

A

Solution has a lower Osmolality than the cell
(Less solute particles in the solution compared to the cell)

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6
Q

What is a hypertonic solution?

A

High solute in the solution outside of the cell, less solute in the cell

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7
Q

What is the TBW in a man?

A

60%

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8
Q

What is the TBW in a woman?

A

55%

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9
Q

Why do men have a higher percentage of water in their body?

A

They have more muscle than women and muscle is very good at retaining water

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10
Q

Describe how water is distributed throughout the body:

A

2/3 Intracellular fluid
1/3 extracellular fluid:
-25% in plasma
-75% in interstital fluid

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11
Q

What is the TBW percentage of a new baby?

A

75%

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12
Q

Why are babies very vulnerable to fluid loss?

A

They are 75% water so can lose lots of body weight if dehydrated

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13
Q

What is the TBW in the elderly?

A

45%

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14
Q

Why is the elderlys TBW % low at 45%?

A

As we age we lose muscle mass so can store less water

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15
Q

What is the main ions found in the extracellular fluid compartment (plasma + interstitium)?

A

Na+

Cl-

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16
Q

What is the main ion located in the intracellular fluid compartment?

A

K+

(Levels of Na+ are low)

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17
Q

Why is the concentration of Na+ low in the Intracellular fluid compartment?

A

The Na+ is able to freely flow between the leaky capillaries in the extracellular fluid compartment to the plasma and interstitial fluid

But cant freely flow into the intracellular fluid compartment, needs to cross cell membrane via transporters

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18
Q

Why may patients need fluids?

A

Nil by mouth (cant eat)
GI issues
Dehydration
Fluid loss
Abnormal electrolytes

19
Q

What are the 3 main reasons for giving IV fluids?

A

Resuscitation
Replacement
Maintenance

20
Q

What do hospital patients usually release/activate too much that leads to hyponatremia and volume overload?

A

To much ADH
RAAS
Catecholamines

Leads to reduced water excretion
Increased water and salt retention, the inc water retention causes dilutional hyponatraemia

21
Q

What is considered normal saline solution?

A

0.9% NaCl

22
Q

How much glucose is contained in a L bag of 5% glucose?

A

50g

23
Q

What is contained in a Hartmanns fluid bag?

A

Na+
K+
Cl-
Lactate (which provides HCO3- ions)

24
Q

What is the normal range for plasma osmolarity?

A

275-295mOsm/L

25
Q

Describe how 1L 5% Dextrose/glucose IV fluid would distribute through all the body compartments:

Where does the glucose go?
Where does the water go?
How is the osmolarity affected?

A

Glucose rapidly taken up into the cells (Intracellular)

Water proportionally distributes into all 3 compartments: 2/3 intracellular (666ml)
1/3 extracellular (25% intravascular and 75% in the interstitium) 1000- 666 = 334 334 x 0.25 =83.5ml 334 x 0.75 = 250.5 ml
Plasma = 83.5ml
Interstitium = 250.5ml

Osmolality of all the compartments decreases (becomes more dilute)

26
Q

Describe how 1L 0.9% saline NaCl IV fluid would distribute through all the body water compartments:

Where does the Na+ and Cl- go?
Where does the water go?
How does osmolarity change?

A

Na+ and Cl- remain in the ECF compartment freely moving between the plasma and the interstitium
This is also because 0.9% saline is isotonic with blood plasma so theres no oncotic gradient for water to move into ICF
Water proportionally distributes in the extracellular fluid compartment

27
Q

What IV fluid is better for rapidly increasing Intra vascular/circulating volume and why? (Better for resuscitation)
5% dextrose 1L
or
0.9% NaCl saline 1L?

A

0.9% saline

Its osmolarity is similar to blood plasma in the ECF so remains in the ECF compartment wherea 5% dextrose also distributes water into the ICF compartment

28
Q

What other IV fluid acts in a similar way to 0.9% NaCl saline and is therefore good at resuscitation?

A

Hartmanns solution

29
Q

Describe how 1L 4% Dextrose 0.18% saline NaCl IV fluid (4/5 dextrose and 1/5th saline) would distribute through all the body water compartments:

Where does the saline distribute?
Where does the 5% dextrose distribute?
How is osmolarity affected?

A

The saline distributes in the ECF compartment so the Na+, Cl- and its 200ml water distributes in the ECF compartment proportionally

The dextrose moves into the Intracellular compartment immediately of the 5% dextrose, its 800ml fluid proportionally distributes in the ECF and ICF compartments

This reduces the osmolarity of all the compartments

30
Q

When are “resuscitation fluids used?

A

When patients are in a Hypovolaemic state (so intravascular volume is depleted)

31
Q

What are some indicators that a patient needs urgent fluid resuscitation?

A

Low BP
High HR
Cap refill is over 2s
Resp rate > 20
When leg is raised when lying down indicates low BP

32
Q

When does a patient need maintenance fluids?

A

Patient haemodynamically stable but cant meet their daily fluids requirements via oral or enteral routes (e.g going into surgery or nil by mouth)

33
Q

What is the main ion in gastric juice?

A

Cl-

34
Q

What ions are lost in large amounts in diarrhoea?

A

K+
Na+

35
Q

According to the NICE guidelines for Maintenance IV fluids:
How much water should a patient be given per day?
How much K+, Na+ and Cl- per day?
How much glucose per day?

A

MAINTENANCE:

25 - 30 mL/kg/day for water

1mmol/Kg/day for Na+, K+ and Cl-

50 - 100g glucose per Day

36
Q

According to NICE guidelines how is IV fluid given for Resusciation?

A

Cause of fluid deficit identified
Give fluid bolus 500ml of crystalloids (rapid IV fluids)
Normally Saline or Hartmanns
If patients still need fluid resus after given 2000ml need expert help
If patients not had over 2000ml fluid give 250-500ml fluid bolus of crystalloids

37
Q

According to NICE guidelines what is the process of giving IV fluids for REPLACEMENT?

A

Dependant on what is being lost

Normally for losses normal saline or Hartmanns is given

38
Q

How is the osmolarity and fluid volumes going to change in a patients fluid compartments when they are overloaded with Normal Saline?

Explain:

A

Increased fluid volume in the ECF compartment
Osmolarity remains the same since 0.9% NaCl saline is isotonic

39
Q

How is the osmolarity and fluid volumes going to change in a patients fluid compartments when they drink several litres of water without urinating (micturating)?

Explain:

A

Volume in ECF increases
This decreases the ECF osmolarity since no additional ions taken in
This sets up osmotic gradient between the ECF and ICF
Water moves down gradient into ICF increasing the volume of the ICF and decreasing its Osmolarity

40
Q

How is the osmolarity and fluid volumes going to change in a patients fluid compartments when they’ve been stabbed in the leg and is haemorrhaging?

Explain:

A

ECF fluid compartment volume decreases but Osmolality remains the same since a chunk of blood has been lost

41
Q

How is the osmolarity and fluid volumes going to change in a patients fluid compartments when they have had a 5 day history of diarrhoea and vomiting secondary to gastroenteritis and has therefore lost about 1L of water today?

Explain:

A

Lots of water lost from the ECF which increases its Osmolarity
This sets up osmotic gradient between ECF and ICF
Water moves from ICF to ECF decreasing the volume of the ICF and INC the osmolarity of the ICF compartment

42
Q

How is the osmolarity and fluid volumes going to change in a patients fluid compartments when they drink lots of salt water?

Explain:

A

ECF volume increases but also has a higher osmolarity due to the increased amount of Na+ and Cl- in the ECF compartment
This leads to an osmotic gradient being set up between the ECF and ICF causing fluid to move from ICF into ECF compartment decreasing ICFs volume

43
Q

What is normally added to IV fluid bags and why?

A

20 or 40mmol of KCl to meet the patients requirements for K+

44
Q

Look at slide 30, try and formulate an IV solution using the table above to meet this mans requirements:

A

Answer is on slide 30