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Yr 2 - EMS > Electrolyte Disorders > Flashcards

Electrolyte Disorders Flashcards

1
Q

What is a U&E test?

A

Blood test for urea and electrolytes when assessing renal function.

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2
Q

What is measured in U&E test?

A
  • Sodium - Potassium - (Chloride) - (Bicarbonate) - Urea - Creatinine Water is estimated
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3
Q

What are common causes of electrolyte imbalance?

A
  • Kidney disease - Illnesses with symptoms that cause fluid loss/dehydration (e.g. vomiting, diarrhoea, sweating) - Intestinal/digestive issues - Hormone imbalance - Medications like antibiotics, diuretics and those used to treat cancer and heart disease - Haemorrhage
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4
Q

In terms of body functioning, what 6 electrolytes are the most important?

A
  • Sodium - Potassium - Chloride - Bicarbonate - Calcium - Phosphate
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5
Q

How does excretion of ions usually occur?

A
  • Excretion of ions occurs mainly through the kidneys, with lesser amounts lost in sweat and in faeces. - Excessive sweating may cause a significant loss, especially of sodium and chloride. - Severe vomiting or diarrhoea will cause a loss of chloride and bicarbonate ions.
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6
Q

What 2 components make up the ECF?

A

Plasma + Interstitial Fluid

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7
Q

What is the typical volume of sodium inside and outside cell?

A

ECF: 140 mmol/L

ICF: 10 mmol/L

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8
Q

What is the typical ECF volume? ICF volume?

A

The major division is into Intracellular Fluid (ICF: about 23 litres) and Extracellular Fluid (ECF: about 19 litres) based on which side of the cell membrane the fluid lies.

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9
Q

What is the major cation of ECF?

A

Sodium - is responsible for one-half of the osmotic pressure gradient that exists between the interior of cells and their surrounding environment

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10
Q

How is sodium excreted?

A

Mainly by the kidneys:

  • Sodium is freely filtered through the glomerular capillaries of the kidneys
  • Much of the filtered sodium is reabsorbed in the proximal convoluted tubule
  • Some remains in the filtrate and urine, and is normally excreted
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11
Q

How does decreasing blood volume affect the conc of any solute?

A

This will raise the conc of any solute

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12
Q

After a huge water loss (e.g. dehydration), how does this affect ECF and ICF?

A

Water lost first from ECF (this is where most of the water is) and there is a redistribution

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13
Q

Sodium and potassium body distribution:

A
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14
Q

What is an isotonic solution?

A

In an isotonic solution—iso means the same—the extracellular fluid has the same osmolarity as the cell, and there will be no net movement of water into or out of the cell.

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15
Q

How does a loss of isotonic fluid from the body affect sodium?

A
  • Loss is from ECF
  • No change in [Na]
  • No fluid redistribution
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16
Q

What is a hypotonic solution?

A

If the extracellular fluid has lower osmolarity than the fluid inside the cell, it’s said to be hypotonic—hypo means less than—to the cell, and the net flow of water will be into the cell.

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17
Q

What is the effect of a loss of hypotonic fluid?

A
  • Greater loss from ICF than ECF
  • Small increase in [Na]
  • Fluid redistribution between ECF and ICF
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18
Q

What is the effect of a gain of isotonic fluid e.g. saline drip

A
  • Gain is to ECF
  • No change in [Na]
  • No fluid redistribution
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19
Q

How does a gain of isotonic fluid (e.g. saline drip) affect blood pressure?

A

Increases blood pressure

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20
Q

What is the effect of a gain of hypotonic fluid e.g. water, dextrose?

A
  • Greater gain to ICF than ECF
  • Small decrease in [Na]
  • Fluid redistribution between ECF and ICF
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21
Q

What is hyponatraemia? What is it usually associated with?

A
  • A lower-than-normal concentration of sodium
  • Usually associated with excess water accumulation in the body, which dilutes the sodium
  • Also due to loss of sodium from the body
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22
Q

What can cause a loss of sodium?

A
  • A decreased intake of the ion coupled with its continual excretion in the urine.
  • Several conditions, including excessive sweating, vomiting, or diarrhea; the use of diuretics; excessive production of urine, which can occur in diabetes; and acidosis, either metabolic acidosis or diabetic ketoacidosis.
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23
Q

What can cause a relative decrease in blood sodium?

A

An imbalance of sodium in one of the body’s other fluid compartments, like IF, or from a dilution of sodium due to water retention related to edema or congestive heart failure.

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24
Q

At the cellular level, what is the effect of hyponatraemia?

A
  • Increased entry of water into cells by osmosis, because the concentration of solutes within the cell exceeds the concentration of solutes in the now-diluted ECF
  • The excess water causes swelling of the cells; the swelling of red blood cells—decreasing their oxygen-carrying efficiency and making them potentially too large to fit through capillaries—along with the swelling of neurons in the brain can result in brain damage or even death.
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25
Q

What is hypernatraemia? What can it result from?

A
  • Hypernatremia is an abnormal increase of blood sodium.
  • It can result from water loss from the blood, resulting in the hemoconcentration of all blood constituents.
  • Hormonal imbalances involving ADH and aldosterone may also result in higher-than-normal sodium values.
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26
Q

What is the effect of ADH?

A

Stimulates water reabsorption:

  • Released when osmolarity rises
  • Increases thirst
  • Decreases renal water loss
27
Q

What tests can be done to ascertain ADH status?

A
  • Measure plasma and urine osmolality
  • Urine > plasma suggests ADH is active
    • Urine is very conc as water has been reabsorbed

OR

  • Measure plasma and urine urea
  • Urine >> plasma suggests water retention
28
Q

What does a lower osmolality mean?

A

The particles are more diluted

29
Q

What activates RAAS?

A

Reduction in intravascular volume (drop in blood pressure) :

  • Na depletion
  • Haemorrhage
30
Q

What is the effect of RAAS?

A
  • Renal Na retention
  • Water retention
31
Q

What test can be done to ascertain R/A/A status?

A
  • Measure plasma and urine Na
  • If urine < 10 mmol/L suggests R/A/A active
    • More Na has been retained as less lost in urine
32
Q

If there has been a loss of 2L of isotonic fluid, what happens when there is a 2L replacement with isotonic fluid?

A

This is ideal - no change in [Na] and no fluid redistribution

33
Q

If there has been a 2L loss of isotonic solution, what happens if there is a 2L replacement with hypotonic fluid?

A

This is wrong: fall in [Na] and fluid redistribution

  • Oedema
  • Na hasn’t been replaced
34
Q

What fluid do you need to use as a replacement if there has been a loss of hypotonic fluid?

A

Replacement with hypotonic fluid:

  • [Na] restored
  • Fluid redistribution
35
Q

What happens if you replace a loss of hypotonic fluid with isotonic fluid?

A

This is wrong especially if patient has renal failure

  • [Na] increased
  • Fluid redistribution
36
Q

Describe the water and Na in ECF in hyponatraemia and hypernatraemia

A

Hyponatraemia:

  • Too little Na in ECF
  • Excess water in ECF

Hypernatraemia

  • Too little water in ECF
  • Too much Na in ECF
37
Q

Describe Na and water levels in dehydration

A
  • Water deficiency
  • Fluid (Na and water) depletion
38
Q

Clinical case 1: Patient is dry and has been treated for CCF.

  • Plasma
    • Na 120 (135-145 mmol/L)
    • Urea 15 (3.0-8.0 mmol/L)
  • Urine
    • Na 50 mmol/L
    • Urea 150 mmol/L
A
  • Plasma: Low sodium and high urea
  • Patient has been overtreated with diuretic
    • Treated for CCF
    • Hence why patient is dry
39
Q

How can diuretics lead to hyponatraemia?

A
  • Diuretics decrease Na reabsorption
  • This increases renal loss: Na > water
  • This increases urine [Na] and decreases plasma [Na]
40
Q

How does an increase in renal loss affect IVV?

A
  • Decreases IVV
    • This decreases GFR
      • This increases plasma [creat] and [urea]
    • This increases ADH
41
Q

What is SIADH?

A

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a condition in which the body makes too much antidiuretic hormone (ADH).

42
Q

How can SIADH lead to hyponatraemia?

A
43
Q

How can a decreased water intake lead to hypernatraemia?

A
44
Q

How can osmotic diuresis lead to hypernatraemia?

A

Osmotic diuresis is the increase of urination rate caused by the presence of certain substances in the small tubes of the kidneys.

45
Q

What is the potassium reference range?

A

3.6 to 5.0 mmol/L

46
Q

What is the major intracellular cation?

A

Potassium

47
Q

Where is the majority of potassium found?

A

Inside the cell not in the plasma

48
Q

What can the pump moving K+ in and out of cell be affected by?

A
  • Acidosis
  • Insulin/glucose therapy
  • Adrenaline
  • Rapid cellular incorporation - TPN, leukamia
49
Q

What is the effect of K+ being shifted into the plasma?

A

Plasma conc is affected hugely as is originally so low

50
Q

What is the relationship of Potassium to Hydrogen ions?

A

K+ and H+ exchange across the cell membrane –> both bind to negatively charged proteins (e.g. Hb)

51
Q

How does acidosis affect potassium?

A

Excess H+ ions causes K+ to move out of the cell –> hyperkalaemia

Conversely, K+ depletion and excess can affect acid-base status

52
Q

How does alkalosis affect potassium levels?

A

Causes potassium to move into cells –> hypokalaemia

53
Q

Causes of hyperkalaemia?

A
  • Artefactual
    • Delay in sample analysis
    • Haemolysis
    • Drug therapy - Excess intake
  • Renal
    • Acute Renal Failure
    • Chronic Renal Failure
  • Acidosis (intracellular exchange)
  • Mineralocorticoid Dysfunction
    • Adrenocortical failure
    • Mineralocorticoid resistance - eg spironolactone
  • Cell Death
    • Cytoxic therapy
54
Q

What is the treatment of hyperkalaemia?

A
  • Correct acidosis if this is cause
  • Stop unnecessary supplements / intake
  • Give Glucose & insulin
    • Drives potassium into cells
  • Ion exchange resins
    • GIT potassium binding
  • Dialysis
    • short and long-term
55
Q

What are the causes of excess potassium depletion?

A
  • Low intake
  • Increased urine loss
    • diuretics / osmotic diuresis
    • tubular dysfunction
    • mineralocorticoid excess
  • GIT losses
    • vomiting
    • diarrhoea / laxatives
    • fistulae
  • Hypokalaemia without depletion
    • alkalosis
    • insulin / glucose therapy.
56
Q

What can acute changes in ICF/ECF ratios of K+ cause?

A

Neuromuscular –> lethargy, muscle weakness, heart arrhythmias

57
Q

What can chronic losses of K+ from ICF lead to?

A
  • Neuromuscular:
    • lethargy, muscle weakness, heart arrhythmias
  • Kidney:
    • polyuria
    • alkalosis - increase renal HCO3 production
  • Vascular
  • Gut
58
Q

What history would indicate K+ depletion?

A
  • Diarrhoea, vomiting, drugs (diuretics, digoxin)
  • Cardiac arythmias
  • Symptoms of lethargy/weakness
59
Q

What electrolytes investigations can indicate potassium depletion?

A
  • Hypokalaemia
  • Alkalosis - raised HCO3
60
Q

How can K+ depletion be treated?

A
  1. Replacement of deficit
    1. Oral
    2. IV
  2. Monitor plasma K+ regularly
61
Q

Hypernatraemia due to alsosterone

A
62
Q

If a cell is placed in a hypotonic solution, what happens?

A

there will be a net flow of water into the cell, and the cell will gain volume

63
Q

What is the effect of blood volume (IVV) on GFR?

A

For example, increased blood volume increases arterial pressure, renal perfusion, and glomerular filtration rate.

Decreased IVV –> decreased GFR –> increased [creat] and [urea]

64
Q

Effect of aldosterone on Na and K?

A

Na –> reabsorption

K (and H+) –> excretion

Yr 2 - EMS (60 decks)

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