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Biochemistry and Haemotology > Electrolytes > Flashcards

Electrolytes Flashcards

1
Q

Where is sodium found?

A

55% in plasma and other extracellular fluid
40% in bone as sodium hydroxyapatite
2-5% in organs and cells

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2
Q

Which electrolyte is the most abundant within ECF?

A

Sodium - 90% of the extracellular cations

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3
Q

What is sodiums role within ECF?

A

Maintaining plasma and extracellular fluid volume.

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4
Q

What is the role of ADH in the prevention of water depletion and hyperosmolaority?

A

Renal concentration and water retention - acts to fight water depletion and hyperosmolarity.
Thirst centre in the posterior pituatary release ADH - acts to conserve water and therefore dilutes sodium.

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5
Q

What is tonicity?

A

The ability of a solution to change the shape or tone of a cell by changing the volume of internal water.

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6
Q

Define osmosis

A

The movement of water molecules from an area of high concentration to and area of low concentration through a partially permeable membrane. It is a passive process

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7
Q

What effect does hypertonic solutions have on cells?

A

Water will move from the intracellular space and into the extracellular space as there is a higher water content within the cell, meaning that the cell with shrink/shrivel in size

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8
Q

What effect dow hypotonic solutions have on cells?

A

Water will move from the extracellular space into the intracellular space through osmosis leading to the cell swelling in size and potentially rupturing.

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9
Q

What effect dose dietary sodium have on the kidneys and intestines?

A

When dietary sodium is high, less is absorbed through the GI tract and renal excretion increases, the opposite occurs with low sodium intake.

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10
Q

What causes hypovolemic hyponatremia?

A

Water and sodium levels both decrease in the extracellular fluid - sodium loss is greater.
Non-renal losses - losses of fluid - D&V, fistulas, gastric suctioning, CF, burns and wounds
Renal losses - osmotic diuresis, salt loosing nephritis, adrenal insufficency, diuretic use.

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11
Q

What is hypervolemic hyponatremia?

A

As sodium is a concentration, the concentration of water is greater than that of the sodium - the extracelluar fluid is more dilute.
Heart failure, nephroitic syndrome, excessive administration of hypotonic IV fluids

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12
Q

What is euvolemic hyponatremia?

A

Difficult to diagnose
increase in total body water however the sodium concentration remains constant.
glucocorticoid therapy - impaired renal function
Hypothyroidism - thyroid hormones increase renal blood flow
SIADH

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13
Q

What is the significant risk of severe hyponatremia?

A

Cerebral oedema

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14
Q

What are the signs and symptoms of hyponatremia

A

Many patients are asymptommatic
Need to distingusish between acute vs chronic onset

GI - ?Nausea and vomiting
Neuro - headache, lethargy, reversible ataxia, psychosis, seizures, cerebral oedema, raised ICP

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15
Q

Management options of hypovolemic hyponatremia?

A

Isotonic saline administration

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16
Q

Management of hypervolemic hyponatremia

A

fluid restriction and diuretic use to decrease the water content of the extracelluar space

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17
Q

Management of euvolemic hyponatremia

A

fluid restriction to less than 1l/day

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18
Q

When does Hypovolemic hypernatreamia occur?

A

?Excessive sweating, vomiting, diarrhoea, diuretics or renal disease

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19
Q

When does hypervolemic hypernatremia occur?

A

Both water and sodium levels have increase - relatively rare.
Iatrogenic in nature due excessive administration of hypertonic saline or sodium bicarbonate.
Sometimes hyperaldosteronism

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20
Q

When does euvolemic hypernatremia occur?

A

loss in total body water however the sodium levels remain constant.
Elevated temperature, impaired thirst response, prolonged tachypnoea, diabetes insipidus

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21
Q

What are the signs and symptoms of hypernatremia?

A 
Restlessness, lethargy, irritability
Disorientation, confusion
Stupor, coma, seizures death
Laboured breathing
muscle twitching, spasticity hyperreflexia
nausea vomiting intense thirst
22
Q

Treatment options for euvolemic hypernatremia

A

Where the water loss exceeds sodium losses

5% Dextrose

23
Q

Treatment options for hypovolemic hypernatremia

A

Isotonic saline until hypotension resolves then 0.45% Saline or 5% Dextrose

24
Q

Treatment options for hypervolemic hypernatremia

A

The goal is to remove excess sodium - diuretics with 5% dextrose, if renal impairment is present then dialysis may be required.

25
Q

What is the predominant intracellular cation?

A

Potassium - 98% intracellular
less than 2% is extracellular
the concentration of 3.5 to 5.5

26
Q

What role does potassium play in the ECF/ICF?

A

The ratio between ICF and ECF determines the resting membrane potential of both nerve cells and muscle cells.

27
Q

What causes hypokalemia?

A

Redistribution of K into cells - B2 agonists, phosphodiesterase inhibitors, exogenous insulin
Renal and extrarenal losses

28
Q

What are the symptoms of hypokalemia?

A

Often asymptomatic

Generalised weakness, some ascending paralysis, cardiac arrhythmias may be present

29
Q

Treatment options for hypokalemia

A

Identify the source
Replace potassium, orally - Sando-K
Peripherally as infusion - max 40mmols/,litre
Centrally much more concentrated

30
Q

What could cause a false-positive hyperkalemia?

A

a release of intracellular potassium during phlebotomy or storage of the blood sample

31
Q

Causes of Hyperkalemia

A

Excessive intake - supplements or stored blood
Decreased excretion - renal failure, K sparing diuretics, ACE inhibitors
Translocation from ICF to ECF, acidosis, hyperglycaemia, rhabdomyolysis, adrenal insufficency, b2 blockers

32
Q

Symptoms of hyperkalemia

A

Often asymptommatic

generalised weakness, paralysis and cardiac arrhythmias

33
Q

What are the cardiovascular symptoms of hyperkalaemia

A

Arrhythmias, heart block, delayed conduction, ventricular standstill, Significant ECG

34
Q

Neuromusclar symptoms of hyperkalemia

A

parathesisa, weakness, respiratory insufficiency

35
Q

How does salbutamol reduce K

A

Binds to B2 receptors, stimulates cAMP, stimulates sodium/potassium pumps
increases movement of plasma potassium ecf to icf

36
Q

Describe how insulin and dextrose lowers extracellular potassium

A

As iinsulin acts by movinng glucose from the extracellular space and into cells, the sodium potassium pumps are activated and therefore moves potassium into the cells.
Doesnt reduce the amount of potassium in the body but it does reduce extracellular potassium.
Give 50mls of 50% glucose with 10 units of actrapid.

37
Q

What is the role of calcium in the treatment of hyperkalemia?

A

Calcium does not directly have any effect on potassium levels. Used for myocardial protection
You give calcium chloride or calcium gluconate over 10 to 30 minutes.

38
Q

What treatment option is avaliable for refractory hyperkalemia

A

Haemodialysis and CRRT.
Actively removes potassium from the extracellular compartment.
Can cause a rapid fall within the first hour of treatment.

39
Q

What is the chief anion in ECF

A

Chloride ion

Moves in and out of the cells with sodium and potassium

40
Q

What constitutes the cointrol of chloride ions

A

Intake of chloride
Excretion of chloride
Renal reabsoprtion

41
Q

What relationship does chloride and bicarbonate have?

A

When chloride ions increase, bicarbonate decreases, when chloride ions decease, bicarbonate increases

42
Q

What causes hypochloremia

A

Reduced intake
Excesssive losses - prolonge vomiting, diarrhoea, NG Suctioning
Medications - bicarbonate, corticosteriods, laxatives and diuretics

43
Q

What causes hyperchloremia

A

Increased intake - IV Fluids
Secondary to metabloic acidosis
Some medication - ammonium chloride, acetazolamide

44
Q

What is the role of bicarbonate within homeostasis

A

acts as a buffer to changes in pH, excreted and reabsorbed to maintain a constant pH

45
Q

High levels of Bicarbonate occur in

A

vomiting, dehydration, blood transfusions, overuse of medications that contain bicarb as well as chronic resp acidosis.

46
Q

Low levels of Bicarbonate occur in

A

Hyperventilation, aspirin and alcohol overuse. diarrhoea, severe malnutrition, severe burns, shock, liver and kidney disease, uncontrolled diabetes

47
Q

Where is magnesium found within the body

A

50-60% found in bone
only 1% extracellular
the rest is found intracellular space.

48
Q

What is the main role of Magnesium within the body

A

Enzyme activity, the use of ATP, replication and trasncription of DNA, metabolism of carboghydrates, stabilisation of membrane potentials and nerve conduction

49
Q

What causes imbalances in magnesium within the body?

A

Reduced intake - unbalanced diet, depleted foods, dieting
Impaired absoprtion - GI disturbances,
Increased excretion - alcoholism, laxative use, diuretics

50
Q

What other electrolytes disturbances can occur following hypomagnesia

A

Hypomagnesaemia (due to it leading to hypokalaemia and hypocalcaemia) can cause potentially fatal complications (eg, ventricular arrhythmia, coronary artery vasospasm, cardiac arrest).

51
Q

What are the common early symptoms of hypomagnesia

A

neuromuscular and neuropsychiatric disturbances - tremor, fasciculations, tetany, Chvostek and Trousseau signs, and convulsions.

52
Q

What are some of the symptoms of Hypermagnesemia

A

2 to 3 mmol/L — nausea, flushing, headache, lethargy, drowsiness, and diminished deep tendon reflexes.
3 to 5 mmol/L — somnolence, hypocalcaemia, absent deep tendon reflexes, hypotension, bradycardia, and ECG changes.
Above 5 mmol/L) — muscle paralysis, respiratory paralysis, complete heart block, and cardiac arrest. In most cases, respiratory failure precedes cardiac collapse.

Biochemistry and Haemotology (8 decks)

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