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Adult Years > Abnormal Blood Tests > Flashcards

Abnormal Blood Tests Flashcards

1
Q

Define hyponatraemia.

A
  • Normal range of sodium in serum 135-145 mmol/L
  • Hyponatraemia = Na < 135 mmol/L
    • Mild = 130-135 mmol/L
    • Moderate = 125-129 mmol/L
    • Severe <124 mmol/L
  • Acute < 48 hours
  • Chronic > 48 hours
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2
Q

What are the clinical features of hyponatraemia?

A
  • Can be an incidental finding with no symptoms.
  • Symptoms correlate with severity of hyponatraemia but also due to the speed at which hyponatraemia develops.
    • When plasma osmolality falls quickly, water rapidly flows into cerebral cells causing swelling.
    • Gradual development allows cerebral cells to reduce intracellular osmolality, so the osmotic gradient forcing is reduced.
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3
Q

What are the causes of hyponatraemia?

Describe the pathophysiology of these causes.

A
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4
Q

What is SIADH?

A
  • ADH works to promote water retention in the distal tubule.
    • Released in response to increasing plasma osmolality.
  • In SIADH, ADH causes excessive water retention without a physiological cause, resulting in hyponatraemia.
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5
Q

Describe the management of hyponatraemia.

A
  • Treatment depends on severity, acuity and underlying cause.
  • Acute onset with signs of cerebral oedema - prompt correction with hypertonic saline.
  • In chronic hyponatraemia, rapid overcorrection can be very dangerous, so slow correction is key (< 10mmol/L/24h).
  • Correct hypovolaemia.
  • Euvolaemic / hypervolaemic - fluid restriction.
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6
Q

Define hypernatraemia.

A
  • Normal range of sodium in serum 135-145 mmol/L.
  • Na >145 mmol/L = hypernatraemia.
    • Severe hypernatraemia > 160mmol/L.
  • Hypernatraemia represents a defecit of water relative to sodium.
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7
Q

Describe the pathophysiology of hypernatraemia.

Give examples of causes.

A
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8
Q

What are the appropriate investigations of a patient with hypernatraemia?

A
  • Electrolyte, glucose, renal biochemistry.
  • Urine osmolality / serum osmolality.
  • Urine electrolytes.
  • Desmopressin challenge tests.
  • MRI or CT brain.
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9
Q

How is hypernatraemia managed?

A
  • Depends on the cause.
  • Oral fluids.
  • IV fluids with caution.
  • Treatment of Diabetes Insipidus.
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10
Q

Define hyperkalaemia.

A
  • Potassium is the major intracellular cation.
  • Crucial to normal functioning of nerves, muscles and the heart.
  • Normal range of potassium in serum = 3.5-5.5 mmol/L.
  • Hyperkalaemia = >5.5mmol/L.
    • Mild = 5.5-5.9 mmol/L
    • Moderate = 6.0-6.4 mmol/L
    • Severe = >6.5 mmol/L
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11
Q

What are the clinical features of hyperkalaemia?

A
  • Mild - moderate high K is asymptomatic.
  • Severe high K can cause muscle weakness, but sometimes even severe hyperkalaemia can be relatively asymptomatic untill collapse / arrest.
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12
Q

Describe the investigation of hyperkalaemia?

A
  • Blood tests
    • Creatinine / eGFR
    • Sodium
    • Bicarbonate
  • ECG
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13
Q

Describe the pathophysiology of hyperkalaemia.

Give examples of causes.

A
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14
Q

Describe the management of hyperkalaemia.

A

Emergency Management!

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15
Q

Define hypokalaemia.

A
  • Normal range for potassium = 3.5-5.5 mmol/L.
  • Hypokalaemia = <3.5 mmol/L.
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16
Q

What are the clinical features of hypokalaemia?

A
  • Asymptomatic 3.0-3.3 mmol/L.
  • Severe hypokalaemia causes:
    • Muscle weakness
    • Tiredness
    • Paralytic ileus
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17
Q

Describe the pathophysiology of hypokalaemia.

Give examples of causes.

A
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18
Q

What are the investigations for hypokalaemia?

A
  • Blood tests
    • Bicarbonate
    • Magnesium
    • Calcium
  • ?Renin
  • Urinary potassium
19
Q

Describe the management of hypokalaemia.

A
  • Treat the underlying cause.
  • Replacement
    • KCl orally
    • IV - higher concentrations should be given centrally
20
Q

Define hypercalcaemia.

A
  • Normal calcium level 2.1-2.6 mmol/L.
  • Hypercalcaemia = > 2.6 mmol/L.
  • Bound to albumin, so level needs to be corrected for hypoalbuminaemia.
    • Adjusted calcium = Total calcium - 0.02 (40 - Albumin)
  • Common biochemical abnormality.
21
Q

What are the clinical features of hypercalcaemia?

A
  • Can present acutely with severe hypercalcaemia and dehydration.
22
Q

What are the causes of hypercalcaemia?

A

* Commonest cause of primary hyperparathyroidism is single adenoma.

23
Q

Describe the appropriate investigation of hypercalcaemia.

A
  • PTH is the key test
  • Phosphate also helpful
  • Renal function (tertiary hyperparatyroidism)
  • Screen for malignancy - CXR, myeloma screen, CT imaging
24
Q

Describe the management of hypercalcaemia.

A
  • Treat the underlying cause.
  • Urgent management.
25
Q

Define hypocalcaemia.

A
  • Normal range for calcium = 2.1-2.6 mmol/L.
    • Hypocalcaemia = <2.1 mmol/L.
  • Bound to albumin, so level needs to be corrected for hypoalbuminaemia.
  • Less common than hypercalcaemia.
26
Q

What are the clinical features of hypocalcaemia?

A
  • Mild hypocalcaemia is usually asymptomatic.
  • Severe hypocalcaemia - muscle spasm and tetany.
  • Signs:
    • Trousseau’s sign (‘main d’accoucheur)
    • Chvostek’s sign
27
Q

Describe the pathophysiology of hypocalcaemia?

Give examples of causes.

A
28
Q

Describe the management of hypocalcaemia.

A
  • Depends on the cause.
  • Emergency management of severe hypocalcaemia = IV calcium gluconate.
29
Q

Define hypomagnesaemia.

A

Serum magnesium <0.75 mmol/L.

30
Q

What are the clinical features of hypomagnesaemia?

A
  • Mild - asymptomatic.
  • Severe - tetany.
31
Q

Describe the pathophysiology of hypomagnesaemia.

Give examples of causes.

A
  • Inadequate intake - EtOH excess, malnutrition.
  • Excessive loss - urinary / GI.
  • Other - PPI, pancreatitis.
32
Q

What is the most important investigation in a patient with hypomagnesaemia?

A

ECG

33
Q

Describe the management of hypomagnesaemia.

A
  • Treat the underlying cause.
  • IV magnesium. Oral Mg has limited use.
34
Q

Define hypermagnesaemia.

A

Serum magnesium >1.0 mmol/L.

35
Q

What are the clinical features of hypermagnesaemia?

A
  • Bradycardia
  • Hypotension
36
Q

What is the main cause of hypermagnesaemia?

A

Magnesium-containing medications.

37
Q

How do you manage hypermagnesaemia?

A

Promote renal excretion

38
Q

Define hypophosphataemia.

A

Serum phosphate <0.8 mmol/L.

39
Q

What are the causes of hypophosphataemia?

A
  • Redistribution into cells - refeeding syndrome.
  • Inadequate intake - malnutrition. phosphate binders.
  • Increased excretion - primary hyperparathyroidism.
40
Q

How should hypophosphataemia be managed?

A
  • Oral supplementation.
  • IV in critical care.
41
Q

Define hyperphosphataemia.

A

Serum phosphate ​>1.4 mmol/L.

42
Q

What are the clinical features of hyperphosphataemia?

A
  • Pruritis
  • Long term calcium phosphate deposition
43
Q

What are the causes of hyperphosphataemia?

A
  • AKI
  • CKD
44
Q

Describe the management of hyperphosphataemia.

A
  • Dietary restriction
  • Phosphate binding drugs

Adult Years (27 decks)

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