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Biochemistry > Fluid And Electrolyte Balance > Flashcards

Fluid And Electrolyte Balance Flashcards

1
Q

What is the most abundant cation in the ECF?

A

Sodium

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2
Q

How is sodium measured?

A

Sodium is typically measured using an ion-selective electrode (ISE) method, which measures the activity of sodium ions in a patient’s blood sample.
This method is fast, accurate, and reliable, making it a common and widely used test in clinical laboratories.

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3
Q

What does the prefix hypo- mean?

A

Low

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4
Q

What does the prefix hyper- mean?

A

High

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5
Q

What are causes of hyponatraemia? (3)

A

1.Increased sodium loss
⬇️ Aldosterone production, diuretics or nephropathy in renal disorders
Low K+
2.Increased water retention
Dilution of Na+
⬇️ Plasma proteins
3.Water imbalance
SIADH

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6
Q

What are causes of hypernatraemia?

A

1. Excess water loss
Not usually caused by an excess of Na+ but relative deficit of water so often coincides with dehydration.

2. Decreased water intake
Older persons 👵

3.Increased intake or retention
Hyperaldosteronism

Measurement of urine required to evaluate the causes of hyponatraemia.

Severity:
Diabetes insipidus < Osmotic diuresis < loss of thirst

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7
Q

Describe causes of hypokalaemia

A

1. GI loss
Vomiting

2. Renal Loss
Nephritis

3. Cellular shift
Alkalosis

4. Decreased intake

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8
Q

Causes of hyperkalaemia

A

1. Decreased renal excretion
Acute or chronic renal failure

2. Cellular shift
Acidosis

3. Increased intake
Oral orIV replacement therapy

4. Artifactual
Sample haemolysis

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9
Q

Describe the features of pseudohyperkalaemia

A

Pseudohyperkalaemia is a false elevation of potassium levels that can occur due to certain pre-analytical factors, such as prolonged tourniquet application during blood collection or high-speed centrifugation.
Pseudohyperkalaemia is not a true indication of elevated potassium levels in the body and should be confirmed using other tests.

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10
Q

Symptoms of severe hypokalaemia

A

Muscle weakness; paralysis; Heart rhythm abnormalities

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11
Q

Name two pathological processes involving electrolytes

A

Volume and osmotic regulation (Na+, Cl- and K+)
Myocardium rhythm and contractility (K+, Mg2+)

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12
Q

__________ is the number of solute particles in 1 kg of solvent.

A

Osmolality

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13
Q

__________ is the concentration of solutes per litre of solvent - can be inaccurate due to temp and pressure.

A

Osmolarity

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14
Q

__________ is the difference between the measured __________ and the calculated _________. Due to differences in the way blood solutes are measured and their calculation methods in the laboratory.

A

Osmolar gap
Osmolality
Osmolarity

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15
Q

What is the controller of Osmolality?

A

Arginine vasopressin hormone (AVH) (ADH)

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16
Q

Where is ADH released from?

A

Posterior pituitary

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17
Q

Define Polydipsia

A

The feeling of extreme thirstiness.

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18
Q

ADH release is stimulated by (4)

A

⬆️Plasma Osmolality
⬇️Blood volume
⬇️BP
Stress

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19
Q

Where is ADH produced?

A

Hypothalamus

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20
Q

What is the primary function of ADH?

A

Primary function is ↓water loss in the kidneys which reduces the concentration of electrolytes.

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21
Q

High ADH conc means

A

•↑ H2O permeability in distal tubules and collecting ducts of the kidney.
•↑ H2O reabsorption, ↓ H2O excretion.
•Establishes a negative feedback loop.

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22
Q

Define hypovolemia

A

Loss of water & Na+ without replacement.
Total body water declines but osmolarity remains normal.
Haemorrhage, sever burns, vomiting, diarrhoea.

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23
Q

_________ _____ are a major factor in estimating glomerular filtration rate - the gold standard marker of kidney health.

A

Creatinine levels

24
Q

Direct ISE

A

Requires larger undiluted samples

25
Q

Indirect ISE

A

Requires smaller, diluted sample but can be prone to dilution error

26
Q

Dilution error

A

The dilution & calculations to produce ISE results depend on the assumption that the sample contains normal fat levels.

In very lipidaemic samples, this will result in apparent hyponatraemia even when the biologically-active Na+ concentration in the aqueous phase is normal.

27
Q

Pseudo-hyponatraemia

A

When serum sodium concentration is actually normal but erroneously reported as low due to presence of either hyper-lipidemia or hyper-proteinemia.

28
Q

Symptoms of true hyponatraemia

A

Nausea; Confusion; Headache; Impaired consciousness

29
Q

Treatment of hyponatraemia

A

Correction of condition causing H2O or Na+ in excess of H2O, loss
Fluid management
Vasopressin receptor antagonists (conivaptan)

30
Q

Symptoms of hypernatraemia

A

Altered mental status; Lethargy; Irritability

31
Q

Treatment for hypernatraemia

A

IV fluids to reduce Na+ with careful monitoring

32
Q

What happens in rapid reduction of Na+?

A

Cerebral oedema, convulsions and permanent brain injury

33
Q

Sources of Potassium

A

Beans🫘
Green veg 🥦
Bananas🍌

34
Q

Hypokalaemia is linked to ________.

A

Alkalosis

35
Q

Hyperkalaemia is linked to ________.

A

Acidosis

36
Q

What is he hormonal regulator of K+?

A

Aldosterone

37
Q

Where is aldosterone produced?

A

Produced by the cells of the adrenal cortex in the adrenal gland

38
Q

What is the action of aldosterone on K+?

A

Release through the renin-angiotensin mechanisms or though direct release stimulates secretion into the tubular lumen; stimulates Na+ and water reabsorption from the gut, salivary and sweat glands in exchange for K+

39
Q

Plasma volume decreases => ?

A

Increase in plasma angiotensin II

40
Q

Increased plasma angiotensin II => ?

A

Increased aldosterone secretion in adrenal cortex

41
Q

Increased plasma potassium => ?

A

Increased aldosterone secretion in the adrenal cortex

42
Q

Renin-angiotensin system

A

1️⃣ Drop in blood pressure and fluid volume
2️⃣ Renin released form the kidney acts on angiotensin released from the liver
3️⃣ ACE is released from the lungs acts on angiotensin I to form angiotensin II

43
Q

Effects of angiotensin II

A

Acts on adrenal gland to stimulate release of aldosterone
Acts on blood vessels stimulating vasoconstriction

44
Q

Name the two mechanisms for potassium transport

A

1.Electrical potential gradient (Na+K+ pump)
2.Acid base balance (K+H+ pump)

45
Q

What is the effect of excercise on potassium levels?

A

K+ is released during exercise, changes reversed after several minutes of rest

46
Q

What is the effect of hyperosmolality?

A

Causes H2O carrying K+ to diffuse into cells

47
Q

What is the effect of cellular breakdown on potassium?

A

Release K+ into the ECF

48
Q

What membrane is used for potassium ISE?

A

Valinomycin

49
Q

Reasons for artefactual hyperkalaemia (4)

A

Haemolysis
Delayed processing
Exposure to cold
Abnormal cells

50
Q

Symptoms of hyperkalaemia

A

Muscle weakness; Irritability; Decreased BP

51
Q

Treatment of hyperkalaemia

A

Calcium glauconite to stabilise heart muscle
Intravenous insulin and dextrose to promote potassium entry into cells

52
Q

Symptoms of hypokalaemia

A

Muscle weakness; Fatigue; Constipation

53
Q

Treatment of hypokalaemia

A

Oral replacement
IV K replacement
Dietary correction

54
Q

Hyponatraemia medical emergency

A

<120mmol/L for >48hours

55
Q

Hypernatraemia level >160mmol/L has…

A

Mortality rate of 60-75%

56
Q

Phone ward if potassium levels are…

A

<2.5mmol/L
>6.5mmol/L

Biochemistry (19 decks)

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