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After the MSA > Fluid and electrolyte balance > Flashcards

Fluid and electrolyte balance Flashcards

1
Q

What are the major divisions of the fluid compartments?

A
  • intracellular

* Extracellular: plasma, interstitial, synovial, intraocular, CSF etc.

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2
Q

What are the barriers between the fluid compartments?

A
  • Capillary wall between the plasma and interstitial fluid

* Plasma membrane between the extracellular fluid and intracellular fluid

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3
Q

Describe the exchange of fluid across the capillary membrane

A
  • Hydrostatic pressure pushes fluid out of the capillary

* Osmotic pressure draws fluid into the capillary

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4
Q

How do we gain fluid?

A

Food and water intake

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5
Q

How do we lose fluid?

A
  • Urine
  • Feces
  • Sweat
  • Insensible loses
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6
Q

What are the insensible loses?

A
  • Transepidermal diffusion - water that passes through the skin and is lost by evaporation
  • Evaporative loss from the respiratory tract
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7
Q

What are the differences between sweat and insensible fluid

A
  • Sweat is from specialised skin appendages - sweat glands
  • There is solute loss in sweat but not in insensible loss
  • Sweat is for body temperature regulation, insensible loss cannot be prevented and It is not under regulatory control
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8
Q

What is the central controller of body fluid?

A

The hypothalamus producing ADH secreted by the posterior pituitary

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9
Q

What happens if total sodium falls and osmolality stays the same?

A

Total volume falls

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10
Q

What happens if sodium rises and osmolality stays the same

A

Total volume rises

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11
Q

How do we gain sodium?

A

Food and drink

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12
Q

How do we lose sodium?

A
  • Sweat
  • Feces
  • Urine
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13
Q

Describe the control of plasma Na+

A
  • Hormones controlling sodium balance act on the kidney
  • Aldosterone - retention of sodium
  • Distal collecting tubule is the area of control in the nephron
  • There are no detectors of Na+ conc, it is controlled indirectly via volume sensors
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14
Q

What happens if osmolality rises?

A
  • Increase in thirst
  • Increase in release of ADH
  • Increase in water intake/retention
  • Increase in volume
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15
Q

What happens if osmolality falls?

A
  • Decrease in thirst
  • Decrease in the release of ADH
  • Decrease in water intake/retention
  • Decrease in volume
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16
Q

What happens if there is an increase in volume?

A
  • Increased stretch of the vascular system
  • Baroreceptors detect
  • Decreased renin
  • Decrease in aldosterone
  • Increased release of ANP
  • Decreased sodium and water retention
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17
Q

What happens if there is a decrease in volume?

A
  • Decrease in stretch of the vascular system
  • Baroreceptors
  • If pressure falls, also influences ADH and thirst centres
  • Increase in renin release
  • Increased levels of angiotensin II
  • Increased aldosterone release
  • Decreased release of ANP
  • Increased sodium and water retention
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18
Q

How do we gain K+?

A

• Food/drink

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19
Q

How do we lose K+?

A
  • Predominantly the urine

* Little in sweat or faeces

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20
Q

Describe the control of K+ secretion/absorption

A
  • K+ is freely filtered and predominantly reabsorbed again in the PCT with controlled secretion at the DCT
  • Secretion is linked to Na+ reabsorption
  • Aldosterone changes the apical ion channels and changes the sodium potassium exchanger basolaterally
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21
Q

Describe what happens if the K+ in the plasma is increased

A
  • Increased activity of the basolateral sodium pump
  • More K+ enters the cell, increased simple diffusion across the apical membrane
  • Increased secretion of aldosterone
22
Q

What are the effects of aldosterone on the DCT?

A
  • Increases the activity of the sodium pumps
  • Increases the number or sodium pumps
  • Increases the number of sodium and potassium channels in the apical membrane
23
Q

What are the risks with intravenous fluids?

A
  • Peripheral vascular catheter is required -> chance of infection
  • Easy to give too much fluid
  • Errors in prescribing
24
Q

Vital signs: hypovolaemia

A
  • Systolic BP <100mmHg
  • Heart rate >90bpm
  • Capillary refill >2 seconds
  • Respiratory rate 20 breaths/min
  • Urine output <0.5ml/kg/hour
25
Q

When should you suspect fluid overload?

A
  • history or cardiac/renal problems
  • Raised JVP
  • Peripheral oedema
  • If pulmonary oedema: inspiratory crackles at the lung bases
  • Hypertension
26
Q

Which investigations may be useful for assessing volume status?

A
  • Full blood count
  • Urea and electrolytes
  • Chest X ray
  • Lactate
  • Urine biochemistry
27
Q

What are the sodium requirements?

A

1mmol/kg/24 hours

28
Q

What are the potassium requirements?

A

1 mmol/kg/24 hours

29
Q

What is the calorie requirement?

A

minimum of 400kcal per 24 hours

30
Q

When do you give maintenance fluid?

A

When the patient doesn’t have excess losses

31
Q

When do you give replacement fluid?

A

Replaces previous and/or current abnormal losses, this is in addition to maintenance fluid

32
Q

When do you give resuscitation fluid?

A

When the patent is hypovolaemic and requires urgent correction of intravascular depletion

33
Q

How often should an intravenous catheter be changed?

A

Every 72 hours

34
Q

What are the crystalloid IV fluids?

A
  • 5% dextrose
  • 0.18% NaCl 4% dextrose
  • 0.9% NaCl
  • Plasmalyte
35
Q

What are the colloid IV fluids?

A
  • Albumin
  • Blood
  • hydrolysed gelatin
36
Q

What are the risks of colloid IV fluids?

A

They are proteins so there is a risk of anaphylaxis, stays in the intravascular space

37
Q

Describe the distribution of dextrose

A
  • Effectively water
  • Initially distributes through ISF and plasma, glucose is metabolised so essentially is just water
  • Further distributes into cells as well as ISF and plasma
38
Q

Describe the distribution of plasmalyte

A

Distributes through ISF and plasma, doesn’t enter the cells

39
Q

Describe the distribution of 4.5% albumin

A
  • Tends to stay in the plasma, doesn’t enter the cells

* Blood product

40
Q

Describe the distribution of hydrolysed gelatin

A
  • Initially stays in the plasma, doesn’t enter the cells

* Protein metabolised over time so then is equivalent to 0.9% NaCl

41
Q

What is maintenance fluid?

A

• 0.18% saline 4% dextrose

42
Q

Describe fluid challenge

A
  • Consider if there is oliguria or hypotension and no signs of overload
  • Therapeutic and diagnostic
  • 500mls balanced salt solution given quickly then re assess
  • Can repeat up to 2000mls
43
Q

Cautions for fluid challenge

A
  • Obese patients
  • Elderly or frail
  • Cardiac failure
  • Malnourised or at risk of referring syndrome
  • Chronic kidney disease
44
Q

What do you do when a patient deteriorates

A
  • CVP line to measure right atrial pressure - target of 8-12mmHg
  • POC ultrasound or ECHO - look at the infer vena cava or at the ejection fraction of the heart
45
Q

Diabetic ketoacidosis

A
  • Patient presents shocked, near death and fluid depleted, ACTRAPID:
  • Airway breathing circulation
  • Commence fluid resuscitation
  • Treat potassium
  • Replace insulin
  • Acidosis management
  • Prevent complications
  • Information for patients
  • Discharge
46
Q

What are the clinical features of diabetic ketoacidosis?

A 
Hyperglycaemia: 
• Dehydration 
• Tachycardia
• Hypotension 
• Clouding of consciousness 
Acidosis 
• Air hunger 
• Acetone on breath 
• Abdominal pain 
• Vomiting
47
Q

Why may someone with DKA be dehydrated?

A
  • Hyperglycaemia
  • Vomiting
  • Kaussmaul respiration
  • Altered consciousness (reduced intake) - may be at risk of aspiration if vomiting
48
Q

Describe the clinical signs of dehydration

A
  • Low BP
  • Tachycardia
  • Dry mucous membrane
  • Low/insignificant urine output
49
Q

Levels of what are increased in dehydration

A 
Stress response hormones: 
• Cortisol 
• Glucagon 
• Growth hormone 
• Adrenaline
50
Q

How do you treat a dehydrated patient?

A

• In adults start by giving 1000mls 0.9% saline over first hour
• ACTRAPID: infusion 6 units per hour
• Think about potassium
- if insulin is low, hold insulin and give K+
- if high, give K+ but check serum k+ every 2 hours

After the MSA (22 decks)

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