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PSA > Fluids > Flashcards

Fluids Flashcards

1
Q

Replacement fluids

Typical fluid

A

0.9% saline (crystalloid)

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2
Q

Replacement fluids

Exceptions (2)

A

Hypernatraemic or hypoglycaemic:
- 5% dextrose

Has ascites:
- Human-albumin solution (saline would worsen ascites)

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3
Q

Replacement fluids: how fast?

A
  • If tachycardic/hypotensive, give 500 mL bolus immediately (250mL if HF), then reassess HR, BP and urine output
  • If only oliguric (and not due to urinary obstruction), give 1L over 2-4 hrs then reassess HR, BP and urine output
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4
Q

Replacement fluids: how depleted is someone?

A

Use their obs:

  • Reduce urine output (oliguric if < 3mL/hr, anuric if 0ml/hr) indicated 500 mL of fluid depletion
  • Reduced urine output plus tachycardia indiciated 1L of fluid depletion
  • Reduce urine output plus tachy plus shocked indicates 2L+ of fluid depletion
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5
Q

Fluids

% of intracellular fluid?

A

65%

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6
Q

Fluids

% of extracellular fluid?

A

35%

25% in interstitial and 10% in intravascular

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7
Q

Fluids

Intracellular fluid composites

A
  • High potassium concentration
  • Low sodium concentration
  • Intracellular solute concentrations remain more or less constant
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8
Q

Fluids

Extracellular fluid composites

A
  • High sodium concentration

- Low potassium concentration

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9
Q

Fluids

What is Starling’s hypothesis?

A

The fluid movement due to filtration across the wall of a capillary is dependent on the balance between the hydrostatic pressure gradient and the oncotic pressure gradient across the capillary

  • Water moves between intra- and extra-cellular compartments through osmosis
  • Distribution of water is determined largely by extracellular sodium ion concentration
  • Extracellular solute concentration determines intracellular water quantity and consequently cell vol
  • Gradient is maintained by sodium-potassium ATPase pump
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10
Q

Fluids

Urine output of a) healthy person b) fluid replacement aim

A

a) 1 ml/kg/hr

b) Aim for 0.5ml/kg/hr

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11
Q

Fluids

Sources of fluid loss (6)

A
  • Urine
  • GI (approx 100ml/day lost via faeces)
  • Insensible losses (500-800 ml per day on average). Can increase if sweating, febrile, tachypnoeic, open cavity surgery.
  • Surgical (biliary drain, pleural and peritoneal drain output)
  • Bleeding
  • Burns
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12
Q 
Fluids 
What is lost in:
a) Sweat
b) Diarrhoea/increased stoma output
c) Vomiting
d) Insensible los
A

a) Sodium
b) Sodium, potassium, bicarbonate
c) Potassium, chloride and hydrogen ions (hence picture of hypochloraemic metabolic alkalosis, sometimes with mild hypokalaemia)
d) Pure water loss

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13
Q

Fluids

What are crystalloids

A

Essentially mineral salts

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14
Q

Fluids
What are colloids?
Examples
Distribution

A

Contain larger water-insoluble molecules such as complex branched carbohydrates or gelatin

  • Blood
  • Dextrans
  • Gelatin (e.g. gelofusine)
  • Human albumin solution
  • Hydroxyethyl starch (HES)

Distribution: All stays in intravascular compartment

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15
Q

Fluids

Things to consider when choosing type of fluid

A
  • Type of fluid loss
  • Renal function
  • Cardiac function
  • Concomitant electrolyte abnormalities
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16
Q

What should you assess before prescribing fluids?

A
  • BP
  • Cap refill
  • Fluid balance charts
  • Response to straight leg raise
  • Skin turgor
  • Weight
17
Q

Fluids
Isotonic crystalloids
Definition and example

A
  • Stay almost entirely within the extracellular compartment, 25% to intravascular and 75% to interstitial
  • E.g. NaCl 0.9%
18
Q

Fluids
Hypertonic crystalloids
Definition and example

A
  • Increase plasma tonicity and draw fluid out of cells

- E.g. NaCl 3%, mannitol

19
Q

Fluids
Hypotonic crystalloids
Definition and example

A
  • Lower serum osmolarity and are not commonly used

- NaCl 0.45%

20
Q

Fluids

How does 1L of glucose 5% distribute?

A

2/3rds intracellular
1/3rd extracellular
Approx 80mls will stay in the intravascular compartment

21
Q

Define distributive shock?

3 causes

A

Results in a relative hypovolaemia

Causes: sepsis, anaphylaxis, neurogenic shock

22
Q

Hypovolaemia shock

3 causes

A

Most common form of shock encountered

Causes: hemorrhage, burns or any cause of substantial fluid loss

23
Q

Grading of shock

A

15%/750ml

  • Grade 1
  • Mild resting tachycardia, slight delayed CPT 3 secs

15-30%/750-1500mL

  • Grade 2
  • Cool peripheries, tachycardic, decreased pulse pressure, delayed CRT 5 seconds

30-40%/1500-2000mL

  • Grade 3
  • Marked tachycardia and tachypnoea, low systolic BP, narrow pulse pressure, oliguria, low vol pulse, a postural drop of 20-30, confusion/agitation

50-50%/2000-2500mL

  • Grade 4
  • Low GCS/unconscious, minimal or no urine output, thready pulse, very tachycardic, very low immeasurable BP, cold skin
24
Q

Cardiogenic shock

Causes (4)

A
  • Relative or absolute reduction in cardiac output due to primary cardiac disorder
  • Circulatory collapse occurs as a result of pump failure
  • May also have raised JVP or cardiac arrhythmias
    Causes: ischaemia, heart failure, arrhythmias, cardiomyopathy
25
Q

Obstructive shock

Causes (2)

A
  • Physical impedance to blood flow

Causes: PE, cardiac tamponade

26
Q

Fluids

What is the passive leg raise

A
  • Mimics fluid bolus by tipping pt. to redirect fluid to heart
  • One minute after measure HR, BP and stroke vol
  • Return patient to original position and check again - should return to baseline
27
Q

Fluid resus

A

500 ml of Sodium Chloride 0.9% over less than 15mins

  • Review MAP, urine output, CRT
  • These are in addition to calculated maintenance fluids
28
Q

Maintenance fluids

A
  • Matched the patient’s ideal body weight
  • Total vol divided by 24 to give hrly rate
  • Prescribe less for older adults, frail, renal/cardiac failure, malnourished, risk of refeeding syndrome
29
Q

Replacement fluids

A
  • Adjust to account for existing fluid and/or electrolyte deficits or excesses, ongoing losses (e.g. diarrhea, fever) or abnormal distribution
30
Q

Tx of fluid overload

A
  • Stop IV fluids
  • Furosemide
  • Sublingual nitrate
  • IV nitrate
  • CPAP
31
Q

Maintenance fluids: which fluids and how much?

A
  • General rule = adults 3L IV per 24 hrs
  • Elderly 2L
  • Adequate electrolytes are provided by 1L of 0.9% saline and 2L of 5% dextrose (1 salty, 2 sweet)
32
Q

How can you provide potassium?

A

KCl in:
- 5% dextrose (not replacement)
or
- 0.9% saline

33
Q

How much potassium?

A
  • Guided by U&Es

- Normal K+ - give roughly 40 mmol KCl per day (20 mmol in 2 bags)

34
Q

Max rate of potassium

A
  • Max is 10mmol/hr
35
Q

Max concentration of potassium

A
  • Max is 40mmol/litre
36
Q

Maintenance fluids: how fast?

a) 3L
b) 2L

A

a) 3L per day = 8-hourly bags

b) 2L per day = 12-hrly bags

37
Q

NICE guidelines for maintenance fluids?

A

25-30 ml/kg of water

  • 1 mmol/kg/day of potassium, sodium and chloride
  • 50-100 g/day of glucose to limit starvation ketosis
38
Q

When should you NOT give dextrose/

A
  • In a stroke due to risk of cerebral oedema

- With KCl in replacement of K+

PSA (8 decks)

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