Abnormal Blood Tests Flashcards
(44 cards)
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
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.
3
Q
What are the causes of hyponatraemia?
Describe the pathophysiology of these causes.
A
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.
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.
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.
7
Q
Describe the pathophysiology of hypernatraemia.
Give examples of causes.
A
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.
9
Q
How is hypernatraemia managed?
A
- Depends on the cause.
- Oral fluids.
- IV fluids with caution.
- Treatment of Diabetes Insipidus.
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
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.
12
Q
Describe the investigation of hyperkalaemia?
A
- Blood tests
- Creatinine / eGFR
- Sodium
- Bicarbonate
- ECG
13
Q
Describe the pathophysiology of hyperkalaemia.
Give examples of causes.
A
14
Q
Describe the management of hyperkalaemia.
A
Emergency Management!
15
Q
Define hypokalaemia.
A
- Normal range for potassium = 3.5-5.5 mmol/L.
- Hypokalaemia = <3.5 mmol/L.
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
17
Q
Describe the pathophysiology of hypokalaemia.
Give examples of causes.
A
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
Define hypocalcaemia.
* 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
What are the clinical features of hypocalcaemia?
* Mild hypocalcaemia is usually asymptomatic.
* Severe hypocalcaemia - muscle spasm and tetany.
* Signs:
* Trousseau's sign ('main d'accoucheur)
* Chvostek's sign
27
Describe the pathophysiology of hypocalcaemia?
Give examples of causes.
28
Describe the management of hypocalcaemia.
* Depends on the cause.
* **Emergency management of severe hypocalcaemia = IV calcium gluconate.**
29
Define hypomagnesaemia.
**Serum magnesium \<0.75 mmol/L.**
30
What are the clinical features of hypomagnesaemia?
* Mild - asymptomatic.
* Severe - tetany.
31
Describe the pathophysiology of hypomagnesaemia.
Give examples of causes.
* Inadequate intake - EtOH excess, malnutrition.
* Excessive loss - urinary / GI.
* Other - PPI, pancreatitis.
32
What is the most important investigation in a patient with hypomagnesaemia?
ECG
33
Describe the management of hypomagnesaemia.
* Treat the underlying cause.
* IV magnesium. Oral Mg has limited use.
34
Define hypermagnesaemia.
Serum magnesium \>1.0 mmol/L.
35
What are the clinical features of hypermagnesaemia?
* Bradycardia
* Hypotension
36
What is the main cause of hypermagnesaemia?
Magnesium-containing medications.
37
How do you manage hypermagnesaemia?
Promote renal excretion
38
Define hypophosphataemia.
Serum phosphate \<0.8 mmol/L.
39
What are the causes of hypophosphataemia?
* Redistribution into cells - refeeding syndrome.
* Inadequate intake - malnutrition. phosphate binders.
* Increased excretion - primary hyperparathyroidism.
40
How should hypophosphataemia be managed?
* Oral supplementation.
* IV in critical care.
41
Define hyperphosphataemia.
Serum phosphate \>1.4 mmol/L.
42
What are the clinical features of hyperphosphataemia?
* Pruritis
* Long term calcium phosphate deposition
43
What are the causes of hyperphosphataemia?
* AKI
* CKD
44
Describe the management of hyperphosphataemia.
* Dietary restriction
* Phosphate binding drugs
