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Year 2 EMS MoD > Disorders of Sodium, Water and Potassium > Flashcards

Disorders of Sodium, Water and Potassium Flashcards

1
Q

What is measured in U + Es? (6)

A
  • Sodium
  • Potassium
  • Urea
  • Creatinine
  • (chloride)
  • (bicarbonate)
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2
Q

What is estimated from U + Es?

A

Water.

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3
Q

What are electrolytes important for? (4)

A
  • Maintain cellular homeostasis
  • Cardiovascular physiology (BP)
  • Renal physiology (GFR)
  • Electrophysiology
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4
Q

What are the 5 important concepts?

A
  • Concentrations
  • Compartments
  • Contents
  • Volumes
  • Rates of gain/loss
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5
Q

Which of these concepts is mainly measured by the lab?

A

Concentrations.

-the other factors are deduced

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6
Q

What is ECF composed of?

A

Plasma + interstitial fluid.

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7
Q

What is the normal volume of water in ECF and ICF?

A 
ECF = ~19L
ICF = ~ 23L
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8
Q

What is the approximate sodium concentration of ICF and ECF?

A

ICF - 10mmol/L

ECF - 140mmol/L

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9
Q

What is the approximate potassium concentration of ICF and ECF?

A

ICF - 150 mmol/L

ECF - 5 mmol/L

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10
Q

What effect does decreasing the volume of water in the body have (e.g. excess sweating)?

A
  • Increased plasma concentration of electrolyte (e.g. Na)

- ICF loses more fluid than ECF

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11
Q

What is the total volume of water in the body?

A

~42 L.

19+23

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12
Q

Give an example of loss of isotonic fluid from the body.

A

Haemorrhage (bleeding).

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13
Q

What is the effect of 2L blood loss (isotonic)? (3)

A
  • Loss from ECF
  • No change in [Na]
  • No fluid redistribution
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14
Q

What is the effect of 3L loss of hypotonic fluid (e.g. dehydrated)? (3)

A

-Greater loss from ICF than ECF
-Small increase in [Na]
-Fluid redistribution between ECF and ICF
» CELLS SHRINK

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15
Q

What is the effect of 2L gain of isotonic fluid (e.g. saline drip)? (3)

A
  • Gain to ECF
  • No change in [Na]
  • No fluid redistribution
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16
Q

Does gain/loss of isotonic fluid lead to fluid redistribution?

A

NO.

-no change in ICF volume

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17
Q

What is the effect of 2L gain of hypotonic fluid (e.g. water)? (3)

A

-Greater gain in ICF than ECF
-Small decrease in [Na]
-Fluid redistribution between ECF and ICF
» CELLS EXPAND

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18
Q

What are the body’s main compensatory mechanisms?

A
  • PHYSIOLOGICAL - thirst, ADH, RAAS

* THERAPEUTIC - IV, diuretics, dialysis

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19
Q

What is ADH?

A

Anti-diuretic hormone.

-AKA vasopressin

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20
Q

What is ADH produced by?

A

Median eminence.

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21
Q

What causes an increase in ADH release?

A

Rise in osmolality.

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22
Q

What are the main effects of ADH? (3)

A
  • Decreases renal water loss (» water retention)
  • Increases thirst
  • Constricts blood vessels
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23
Q

How does measuring plasma and urine osmolality ascertain ADH status?

A

Urine > plasma suggests ADH is active.

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24
Q

How does measuring plasma and urine urea ascertain ADH status?

A

Urine urea > plasma urea suggests water retention.

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25
What is the general equation in the renin-angiotensin system?
Renin >> angiotensin >> aldosterone.
26
What is the renin-angiotensin system activated by?
Reduced intravascular volume due to; - Na depletion - Haemorrhage
27
What effect does the renin-angiotensin system have on sodium?
Causes renal sodium retention.
28
How does measuring plasma and urine sodium ascertain R/A/A status?
If urine Na
29
What are the clinical problems associated with altered Na levels?
- HYPONATRAEMIA (decreased Na and excess water in ECF) - HYPERNATRAEMIA (excess Na and decreased water in ECF) - DEHYDRATION
30
How is hyponatraemia diagnosed?
- Plasama osmolility - Urine Na - Oedema
31
What are the clinical features of hyponatraemia?
- Decreased Na in plasma | - Increased water in plasma
32
How do diuretics cause hyponatraemia?
- More renal loss of Na than water - Increased water intake (due to increased ADH) >> decreased plasma [Na]
33
What other electolyte imbalance occurs when diuretics cause hyponatraemia?
Increased plasma [creatinine] and [urea].
34
How does syndrome of inappropriate antidiuretic hormone secretion (SIADH) cause hyponatraemia?
Increased ADH >> decreased urine volume >> increased urine [Na] AND >> increased renal water reabs >> IVV >> haemodilution
35
What other electolyte imbalance occurs when SIADH causes hyponatraemia?
Decreased plasma [urea].
36
How might a patient present when SIADH causes hyponatraemia?
Thirsty but well hydrated.
37
What are the main causes of hyponatraemia? (3)
- Diuretics - SIADH - Increased water intake
38
What are the main causes of hypernatraemia? (3)
- Decreased water intake - Osmotic diuresis - Aldsterone
39
How does decreased water intake cause hypernatraemia?
- Decreased intravascular volume >> decreased urine >> ^ plasma [Na] - Haemoconcentration >> ^ plasma [Na]
40
What is the reference range of potassium?
3.6-5.0 mmol/L.
41
What serious problems are associated with disorders of potassium? (2)
- Cardiac conduction defects | - Abnormal neuromuscular excitability
42
Where is most of the potassium in the body stored?
Majority of potassium is in cells. | -small proportion in plasma
43
What effect does ICF-ECF exchange of plasma have on plasma K?
Significantly changes plasma [K], as only a small proportion of potassium is in the plasma.
44
Name 3 things that have an effect on plasma [K].
- Acidosis - Insulin/glucose therapy - Adrenaline
45
How much potassium is in plasma and interstitial fluid?
5 mmol/L in each. - total: 70 mmol - 2% of body's potassium
46
How much potassium is in intracellular fluid?
150 mmol/L. - total: 3400 mmol - 98% of body's potassium
47
What is the relationship between potassium and hydrogen ions?
- Exchange across cell membrane | - Both bind to negatively charged proteins
48
What effect does acidosis have on potassium?
Acidosis causes potassium to move out of cells. >> hyperkalaemia (H+ moves in)
49
What effect does alkalosis have on potassium?
Alkalosis causes potassium to move into cells. >> hypokalaemia (H+ moves out)
50
What should be given when correcting acidosis?
A potassium infusion.
51
What are the main causes of hyperkalaemia?
- Renal failure - Acidosis (intracellular exchange) - Mineralocorticoid dysfunction - Cell death
52
How is hyperkalaemia treated?
- Correct acidosis if present - Give glucose and insulin - Ion exchange resins - Dialysis
53
How do glucose and insulin treat hyperkalaemia?
Drive potassium into cells.
54
What are the main causes of hypokalaemia?
- Low intake - Increased urine loss (e.g. diuretics) - GIT losses (e.g. vomiting) - Hypokalaemia without depletion
55
What are the 2 main causes of hypokalaemia without depletion?
- Alkalosis | - Insulin/gluscose therapy
56
What are the main effects of hypokalaemia?
- Acute changes in ICF/ECF ratios | - Chronic losses from ICF
57
What are the effects of acute changes in ICF/ECF ratios due to hypokalaemia?
Neuromuscular. | -lethargy, muscle weakness, heart arrhythmias
58
What are the effects of chronic losses from the ICF due to hypokalaemia?
- NEUROMUSCULAR (lethargy, muscle weakness, heart arrhythmias) - KIDNEY (polyuria, alkalosis) - VASCULAR
59
How is potassium depletion detected?
``` HISTORY - diarrhoea, vomiting, lethargy, diuretics -cardiac arrhythmias ELECTROLYTE TESTS -hypokalaemia -alkalosis ```
60
How is potassium depletion treated?
- Replace potassium | - Regular monitoring of plasma levels
61
When is it especially important to monitor plasma potassium levels in order to prevent hypokalaemia?
- Diuretic therapy - Digoxin use - Compromised renal function

Year 2 EMS MoD (20 decks)

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