Disorders of Sodium, Water and Potassium Flashcards Preview

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

Flashcards in Disorders of Sodium, Water and Potassium Deck (61):
1

What is measured in U + Es? (6)

-Sodium
-Potassium
-Urea
-Creatinine
-(chloride)
-(bicarbonate)

2

What is estimated from U + Es?

Water.

3

What are electrolytes important for? (4)

-Maintain cellular homeostasis
-Cardiovascular physiology (BP)
-Renal physiology (GFR)
-Electrophysiology

4

What are the 5 important concepts?

-Concentrations
-Compartments
-Contents
-Volumes
-Rates of gain/loss

5

Which of these concepts is mainly measured by the lab?

Concentrations.
-the other factors are deduced

6

What is ECF composed of?

Plasma + interstitial fluid.

7

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

ECF = ~19L
ICF = ~ 23L

8

What is the approximate sodium concentration of ICF and ECF?

ICF - 10mmol/L
ECF - 140mmol/L

9

What is the approximate potassium concentration of ICF and ECF?

ICF - 150 mmol/L
ECF - 5 mmol/L

10

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

-Increased plasma concentration of electrolyte (e.g. Na)
-ICF loses more fluid than ECF

11

What is the total volume of water in the body?

~42 L.
(19+23)

12

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

Haemorrhage (bleeding).

13

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

-Loss from ECF
-No change in [Na]
-No fluid redistribution

14

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

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

15

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

-Gain to ECF
-No change in [Na]
-No fluid redistribution

16

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

NO.
-no change in ICF volume

17

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

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

18

What are the body's main compensatory mechanisms?

*PHYSIOLOGICAL - thirst, ADH, RAAS
*THERAPEUTIC - IV, diuretics, dialysis

19

What is ADH?

Anti-diuretic hormone.
-AKA vasopressin

20

What is ADH produced by?

Median eminence.

21

What causes an increase in ADH release?

Rise in osmolality.

22

What are the main effects of ADH? (3)

-Decreases renal water loss (>> water retention)
-Increases thirst
-Constricts blood vessels

23

How does measuring plasma and urine osmolality ascertain ADH status?

Urine > plasma suggests ADH is active.

24

How does measuring plasma and urine urea ascertain ADH status?

Urine urea > plasma urea suggests water retention.

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