Fluid and Electrolyte balance Flashcards
1
Q
IV glucose (5%) is mostly distributed where in the body?
A
Mostly intracellularly
2
Q
Colloid fluid will be distributed where in the body?
A
Plasma (will not pass through semi-permeable membrane)
3
Q
Saline will mostly be distributed where in the body?
A
Extracellularly (mostly interstium)
4
Q
What percentage of body weight is water?
A
60%
5
Q
How is body water distributed in an average 70kg male (42L)?
A
Intracellular 28L
Extracellular 14L
- Interstitium 11L
- Plasma 3L
6
Q
What is the barrier between plasma and interstitium?
A
Capillary wall
7
Q
What is the barrier between extracellular fluid and intracellular fluid?
A
Plasma membrane
8
Q
Where is K+ mostly located?
A
Intracellularly
9
Q
Where is Na+ mostly located?
A
Extracellularly
10
Q
Where is Mg2+ mostly located?
A
Intracellularly
11
Q
Where is Cl- mostly located?
A
Extracellularly
12
Q
Where do negative charges come from pricipally inside the cell?
A
Proteins and phosphate
13
Q
Where does the body lose fluid?
A
- Urine - 1500ml
- Faeces - 100ml
- Sweat ~ 50ml
- Insensible losses - 900ml
Total = 2550ml
14
Q
How much urine ouptut is expected per hour?
A
0.5 ml / kg / hour
15
Q
How much more fluid is lost per degree rise in a fever?
A
500ml per 24 hours per degree rise
16
Q
Where can insensible water loss be from?
A
- Transdermal diffusion
- Evaporative loss from respiratory tract
They are solute free
17
Q
What is insensible water loss replaced with?
A
High percent dextrose
18
Q
What are the sensors of body fluid?
A
- Osmoreceptors in hypothalamus
- Low pressure baroreceptors in Right Atria and great veins
- High pressure sensors (carotid sinus / aorta)
19
Q
What do osmoreceptors in the hypothalamus stimulate?
A
- Thirst
- ADH (decreases output)
20
Q
What does an increase in osmolarity lead to?
A
- Increase in thirst
- Increase in release of ADH
- Increase in water intake/retention
- Increase in volume
Opposites for a decrease in osmolarity
21
Q
What disease is an increase in blood volume associated with?
A
Heart Failure
22
Q
What does an increase in blood volume lead to?
A
- Baroreceptors sense
- Decreased renin release
- Decreased aldosterone release
- Increased release of ANP (cardiac myocytes)
- Decreased Na+ and water retention
23
Q
What does a decrease in blood volume lead to?
A
- Baroreceptors sense
- Pressure fall causes ADH release and thirst
- Increased renin release
- Increased levels of Angiotensin II
- Increased aldosterone release
- Decreased release of ANP
- Increased Na+ and water retention
24
Q
What receptors are associated with day to day changes in blood volume?
A
Osmoreceptors in hypothalamus
25
If Na+ drops and osmolarity (tightly regulated) stays the same what happens to total volume?
Total volume (including plasma volume) decreases
26
Where is the area for controlling Na+ balance?
DCT in the nephron
27
What are Na+ levels controlled indirectly by?
Volume receptors
28
What is net Na+ excretion determined via?
Na+ filtered - Na+ reabsorbed
29
How do humans gain K+?
Through food / drink
30
Where is K+ lost?
- Urine (mostly)
| - Sweat and faeces
31
Where is K+ reabsorbed in the nephron?
PCT
32
WHere is K+ secreted?
DCT (controlled secretion)
33
What pump is secretion of K+ linked to?
Na/K+ ATPase (so Na+ is reabsorbed)
34
What hormone changes the apical ion channels and the Na+/K+ exchanger basolaterally?
Aldosterone
35
What percentag of K+ is contained inside cells?
98%
36
What are the effects of increased K+ in plasma?
- Increases activity of basolateral Na+ pump
- More K+ enters cell
- Increased secretion across simple diffusion channels on apical membrane
- Increased secretion of aldosterone
- NOT driven by all, but by direct detection of raised K+ levels by the aldosterone-secreting cells of the adrenal cortex
37
What are the effects of aldosterone on the DCT?
- Increases activity of sodium pump (basolateral)
- Increaes the number of sodium pumps (basolateral)
- Increases the number of sodium and potassium channels in apical membrane
- Result: increased reabsorption of sodium and increased secretion of potassium
38
What is Conn's syndrome?
Hyperaldosteronism leading to hypertension from increased flui volume and hypokalaemia
39
What are risks associated with IV fluids?
- PVC required (peripheral venous catheter)
- Easy to give too much fluid
- Errors in prescribing
- Infection risk
40
What is required in a history before diagnosing IV fluids (what factors should be considered)?
- Limited intake?
- Abnormal losses (how much, what kind of fluid e.g ion rich, ongoing, can you treat the cause)
- Comorbidities?
- Current illness?
- Symptomatic?
- Fluid balance charts
41
What [vital] signs are suggestive of hypovolaemia?
- Systolic BP <100mmHg
- HR > 90
- Capillary refill > 2 secs
- Resp Rate 20 breaths/min
- Urine output < 0.5 mls/kg/hr
- Dry mucous membranes
- Decreased skin turgor
- Responsiveness to passive leg raising (45th)
- Postural hypotension
- Weight
42
What signs are indicative of fluid overload?
- History of cardiac or renal problems
- Raised JVP
- Peripheral oedema
- Inspiratory crackles at lung bases
- Hypertension
43
What investigations are helpful when diagnosing hyper or hypovolemai?
- FBC
- UsandEs
- CXR
- Lactate
- Urine biochemistry
44
What are maintenance fluids?
Regular fluids which are used if an individual has no abnormal losses (0.18% Na/Cl 4% dextrose)
45
What are replacement fluids?
Used to replace abnormal fluid loss used in addition to maintenance fluids
46
What are resuscitation fluids?
Patient is hypovolaemic and requires urgent correction of intravascualr depletion (bolus)
47
what does the colour of a peripheral venous catheter indicate?
The size (smallest yellow largest orange) (most used pink and green)
48
What is the most common infection associated with peripheral venous catheterisation
Staph aureus (should be inspected everyday)
49
How often should a peripheral venous catheter be changed? (unless good reason not to)
72 hours
50
What is 5% dextrose similar to?
Adding water
51
What is the composition of maintenance fluid?
- 0.18% NaCl
| - 4% dextrose
52
What is the composition of isotonic saline? (used when someone is losing ion rich fluid)
0. 9% NaCl (isotonic saline)
| - Also fluids of choice in ressucitation
53
What are different examples of colloid fluids?
- 4.5% albumin (with 0.9% NaC)
- Hydrolysed gelatin (with 0.9% NaC)
- Blood
54
What is the main risk factor of IV colloids?
Anaphylaxis
55
Where is caution required when administering IV fluids?
- Obese patients
- Elderly or frail
- Renal impairment
- Cardiac failure
- Malnourished or at risk of refeeding syndrome
56
What does a Central Venous Pressure line measure?
Right Atrial Pressure
57
What is the target Right atrial pressure (CVP line)?
8 - 12 mmHg
58
What are the principles involved in managing DKA pateints?
ACT RAPID
- Airway, breathing, circulation
- Commence fluid resuscitation
- Treat K+
- Replace insulin
- Acidosis management
- Prevent complications (vulnerable to cerebral oedema)
- Information for patients
- Discharge
59
What are the features of Diabetic Ketoacidosis (DKA)?
```
Hyperglycaemia
- Dehydration
- Tachycardia
- Hypotension
- Clouding of consciousness
Acidosis
- Air hunger (kussmaul's respiration)
- Acetone on breath
- Abdominal pain
- Vomitting
```
SEPSIS features
60
What fluids are given to treat DKA?
- 1L of 0.9% saline in first hour
- Insulin 6 UNITS / hour
- K+ may be low or high - needs K+ IV slowly
61
At what levels of K+ is insulin and/or K+ prescribed?
K+ < 3.3 mmol/L
- 20-30 mmol K+/hour
- Hold insulin
K+ 3.3-5.3 mmol/L
- 20-30 mmol K+/hour per L of IV fluid to keep Serum K+ between 4-5 mmol/L
- Insulin
K+ > 5.3 mmol/L
- K+ not given but checked every 2 hours
- Insulin
62
What are K+ levels expected to be in the region of?
4 - 5 mmol/L when treating DKA
63
Why is an ECG required when treating DKA?
High K+ as a result of DKA can cause cardiac arrhythmias
