Electrolytes

Question 1

Where is sodium found?

Answer 1

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

Question 2

Which electrolyte is the most abundant within ECF?

Answer 2

Sodium - 90% of the extracellular cations

Question 3

What is sodiums role within ECF?

Answer 3

Maintaining plasma and extracellular fluid volume.

Question 4

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

Answer 4

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.

Question 5

What is tonicity?

Answer 5

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

Question 6

Define osmosis

Answer 6

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

Question 7

What effect does hypertonic solutions have on cells?

Answer 7

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

Question 8

What effect dow hypotonic solutions have on cells?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

What causes hypovolemic hyponatremia?

Answer 10

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.

Question 11

What is hypervolemic hyponatremia?

Answer 11

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

Question 12

What is euvolemic hyponatremia?

Answer 12

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

Question 13

What is the significant risk of severe hyponatremia?

Answer 13

Cerebral oedema

Question 14

What are the signs and symptoms of hyponatremia

Answer 14

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

Question 15

Management options of hypovolemic hyponatremia?

Answer 15

Isotonic saline administration

Question 16

Management of hypervolemic hyponatremia

Answer 16

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

Question 17

Management of euvolemic hyponatremia

Answer 17

fluid restriction to less than 1l/day

Question 18

When does Hypovolemic hypernatreamia occur?

Answer 18

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

Question 19

When does hypervolemic hypernatremia occur?

Answer 19

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

Question 20

When does euvolemic hypernatremia occur?

Answer 20

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

Question 21

What are the signs and symptoms of hypernatremia?

Answer 21

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

Question 22

Treatment options for euvolemic hypernatremia

Answer 22

Where the water loss exceeds sodium losses

5% Dextrose

Question 23

Treatment options for hypovolemic hypernatremia

Answer 23

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

Question 24

Treatment options for hypervolemic hypernatremia

Answer 24

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

Question 25

What is the predominant intracellular cation?

Answer 25

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

Question 26

What role does potassium play in the ECF/ICF?

Answer 26

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

Question 27

What causes hypokalemia?

Answer 27

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

Question 28

What are the symptoms of hypokalemia?

Answer 28

Often asymptomatic | Generalised weakness, some ascending paralysis, cardiac arrhythmias may be present

Question 29

Treatment options for hypokalemia

Answer 29

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

Question 30

What could cause a false-positive hyperkalemia?

Answer 30

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

Question 31

Causes of Hyperkalemia

Answer 31

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

Question 32

Symptoms of hyperkalemia

Answer 32

Often asymptommatic | generalised weakness, paralysis and cardiac arrhythmias

Question 33

What are the cardiovascular symptoms of hyperkalaemia

Answer 33

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

Question 34

Neuromusclar symptoms of hyperkalemia

Answer 34

parathesisa, weakness, respiratory insufficiency

Question 35

How does salbutamol reduce K

Answer 35

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

Question 36

Describe how insulin and dextrose lowers extracellular potassium

Answer 36

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.

Question 37

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

Answer 37

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.

Question 38

What treatment option is avaliable for refractory hyperkalemia

Answer 38

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

Question 39

What is the chief anion in ECF

Answer 39

Chloride ion | Moves in and out of the cells with sodium and potassium

Question 40

What constitutes the cointrol of chloride ions

Answer 40

Intake of chloride Excretion of chloride Renal reabsoprtion

Question 41

What relationship does chloride and bicarbonate have?

Answer 41

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

Question 42

What causes hypochloremia

Answer 42

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

Question 43

What causes hyperchloremia

Answer 43

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

Question 44

What is the role of bicarbonate within homeostasis

Answer 44

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

Question 45

High levels of Bicarbonate occur in

Answer 45

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

Question 46

Low levels of Bicarbonate occur in

Answer 46

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

Question 47

Where is magnesium found within the body

Answer 47

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

Question 48

What is the main role of Magnesium within the body

Answer 48

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

Question 49

What causes imbalances in magnesium within the body?

Answer 49

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

Question 50

What other electrolytes disturbances can occur following hypomagnesia

Answer 50

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

Question 51

What are the common early symptoms of hypomagnesia

Answer 51

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

Question 52

What are some of the symptoms of Hypermagnesemia

Answer 52

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.