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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
Q

What is the general equation in the renin-angiotensin system?

A

Renin&raquo_space; angiotensin&raquo_space; aldosterone.

26
Q

What is the renin-angiotensin system activated by?

A

Reduced intravascular volume due to;

  • Na depletion
  • Haemorrhage
27
Q

What effect does the renin-angiotensin system have on sodium?

A

Causes renal sodium retention.

28
Q

How does measuring plasma and urine sodium ascertain R/A/A status?

A

If urine Na

29
Q

What are the clinical problems associated with altered Na levels?

A
  • HYPONATRAEMIA (decreased Na and excess water in ECF)
  • HYPERNATRAEMIA (excess Na and decreased water in ECF)
  • DEHYDRATION
30
Q

How is hyponatraemia diagnosed?

A
  • Plasama osmolility
  • Urine Na
  • Oedema
31
Q

What are the clinical features of hyponatraemia?

A
  • Decreased Na in plasma

- Increased water in plasma

32
Q

How do diuretics cause hyponatraemia?

A
  • More renal loss of Na than water
  • Increased water intake (due to increased ADH)

> > decreased plasma [Na]

33
Q

What other electolyte imbalance occurs when diuretics cause hyponatraemia?

A

Increased plasma [creatinine] and [urea].

34
Q

How does syndrome of inappropriate antidiuretic hormone secretion (SIADH) cause hyponatraemia?

A

Increased ADH
» decreased urine volume&raquo_space; increased urine [Na]

AND&raquo_space; increased renal water reabs&raquo_space; IVV&raquo_space; haemodilution

35
Q

What other electolyte imbalance occurs when SIADH causes hyponatraemia?

A

Decreased plasma [urea].

36
Q

How might a patient present when SIADH causes hyponatraemia?

A

Thirsty but well hydrated.

37
Q

What are the main causes of hyponatraemia? (3)

A
  • Diuretics
  • SIADH
  • Increased water intake
38
Q

What are the main causes of hypernatraemia? (3)

A
  • Decreased water intake
  • Osmotic diuresis
  • Aldsterone
39
Q

How does decreased water intake cause hypernatraemia?

A
  • Decreased intravascular volume&raquo_space; decreased urine&raquo_space; ^ plasma [Na]
  • Haemoconcentration&raquo_space; ^ plasma [Na]
40
Q

What is the reference range of potassium?

A

3.6-5.0 mmol/L.

41
Q

What serious problems are associated with disorders of potassium? (2)

A
  • Cardiac conduction defects

- Abnormal neuromuscular excitability

42
Q

Where is most of the potassium in the body stored?

A

Majority of potassium is in cells.

-small proportion in plasma

43
Q

What effect does ICF-ECF exchange of plasma have on plasma K?

A

Significantly changes plasma [K], as only a small proportion of potassium is in the plasma.

44
Q

Name 3 things that have an effect on plasma [K].

A
  • Acidosis
  • Insulin/glucose therapy
  • Adrenaline
45
Q

How much potassium is in plasma and interstitial fluid?

A

5 mmol/L in each.

  • total: 70 mmol
  • 2% of body’s potassium
46
Q

How much potassium is in intracellular fluid?

A

150 mmol/L.

  • total: 3400 mmol
  • 98% of body’s potassium
47
Q

What is the relationship between potassium and hydrogen ions?

A
  • Exchange across cell membrane

- Both bind to negatively charged proteins

48
Q

What effect does acidosis have on potassium?

A

Acidosis causes potassium to move out of cells.
» hyperkalaemia
(H+ moves in)

49
Q

What effect does alkalosis have on potassium?

A

Alkalosis causes potassium to move into cells.
» hypokalaemia
(H+ moves out)

50
Q

What should be given when correcting acidosis?

A

A potassium infusion.

51
Q

What are the main causes of hyperkalaemia?

A
  • Renal failure
  • Acidosis (intracellular exchange)
  • Mineralocorticoid dysfunction
  • Cell death
52
Q

How is hyperkalaemia treated?

A
  • Correct acidosis if present
  • Give glucose and insulin
  • Ion exchange resins
  • Dialysis
53
Q

How do glucose and insulin treat hyperkalaemia?

A

Drive potassium into cells.

54
Q

What are the main causes of hypokalaemia?

A
  • Low intake
  • Increased urine loss (e.g. diuretics)
  • GIT losses (e.g. vomiting)
  • Hypokalaemia without depletion
55
Q

What are the 2 main causes of hypokalaemia without depletion?

A
  • Alkalosis

- Insulin/gluscose therapy

56
Q

What are the main effects of hypokalaemia?

A
  • Acute changes in ICF/ECF ratios

- Chronic losses from ICF

57
Q

What are the effects of acute changes in ICF/ECF ratios due to hypokalaemia?

A

Neuromuscular.

-lethargy, muscle weakness, heart arrhythmias

58
Q

What are the effects of chronic losses from the ICF due to hypokalaemia?

A
  • NEUROMUSCULAR (lethargy, muscle weakness, heart arrhythmias)
  • KIDNEY (polyuria, alkalosis)
  • VASCULAR
59
Q

How is potassium depletion detected?

A 
HISTORY
- diarrhoea, vomiting, lethargy, diuretics
-cardiac arrhythmias
ELECTROLYTE TESTS
-hypokalaemia
-alkalosis
60
Q

How is potassium depletion treated?

A
  • Replace potassium

- Regular monitoring of plasma levels

61
Q

When is it especially important to monitor plasma potassium levels in order to prevent hypokalaemia?

A
  • Diuretic therapy
  • Digoxin use
  • Compromised renal function

Year 2 EMS MoD (20 decks)

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