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MBBS IV - Supplementary Courses > Chemical Pathology I - Sodium and Water > Flashcards

Chemical Pathology I - Sodium and Water Flashcards

1
Q

Define Normal, Mild, Moderate, Severe, Dangerous Hyponatremia

A 
Plasma Na level (mmol/L)
Normal: 135-145 
Mild: 130-135 
Moderate: 125-130
Severe: 115-125
Dangerous <115
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2
Q

Symptoms of Hyponatremia at Moderate, Severe and Dangerous levels

A

Moderate: Anorexia, Nausea, Vomiting, Abdominal pain

Severe: Agitation, Confusion, Hallucination, Mental impairment, Incontinence

Dangerous: Seizure, Coma, life-threatening

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3
Q

2 classifications of hyponatremia

A

1) By Hydration
- Hyper-, Eu-, Hypovolemia

2) By serum Osmolality
- Hypotonic in true hyponatremia
- Normotonic in pseudohyponatremia
- Hypertonic - hyperglycemia, IV mannitol

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4
Q

Explain hypovalemic, euvolemic and hypervolemic true hyponatremia

A

Hypovalemic: Low water, Very low Na

Euvolemic: Normal Na, High water (dilutional)

Hypervolemic: Very high water, high Na

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5
Q

3 steps in assessment of Hyponatremia

A

1) Serum osmolality
2) Paired spot urine Na before Na replacement
3) Extracellular fluid volume

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6
Q

3 outcomes after the 1st step in assessment of hyponatremia

A

Assess serum osmolality
1) Normal = Hyponatremia due to Hyperlipidemia or Hyperproteinemia

2) Increased osmolality: Hypertonic Hyponatremia due to Hyperglycemia
3) Decreased osmolality&raquo_space; Do paired spot urine Na before Na replacement

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7
Q

How to use Paired spot urine Na to differentiate causes of Hyponatremia with decreased serum osmolality

A

1) >20 mmol/L:
a) Hypovolemia: Renal sodium loss
b) Euvolemia: Chronic water overload

2) <20 mmol/L
a) Edema: Renal sodium retention
b) Hypovolemia: Extrarenal Na loss
c) Euvolemia: Acute water overload

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8
Q

Serum osmolality normal + Hyponatremia. Dx?

A

Psuedohyponatremia due to Hyperlipidemia (Triglyceride >50mmol/L)
or
Hyperproteinemia (Total protein >150 g/L)

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9
Q

Serum osmolality Increased + Hyponatremia. Dx?

A

Hypertonic hyponatremia

Due to Hyperglycemia

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10
Q

Hyponatremia + Serum osmolality decreased + Spot urine Na >20 mmol/L

Extracellular volume: Hypovolemia.

Dx?

A

Renal sodium loss

  • Diuretics
  • Addison’s disease
  • Salt losing nephritis
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11
Q

Hyponatremia + Serum osmolality decreased + Spot urine Na >20 mmol/L

Extracellular volume: Euvolemia.

Dx?

A

Chronic** water overload

SIADH 
Drugs 
Chronic renal failure 
Hypothyroidism 
Cortisol deficiency
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12
Q

Hyponatremia + Serum osmolality decreased + Spot urine Na < 20 mmol/L

Extracellular volume: Euvolemia.

Dx?

A

Acute** water overload

  • Increased water intake
  • Drugs
  • Hypothyroidism
  • Cortisol deficiency
  • Renal failure
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13
Q

Hyponatremia + Serum osmolality decreased + Spot urine Na < 20 mmol/L

Extracellular volume: Hypovolemia

Dx?

A

Extrarenal Na Loss

  • Vomiting
  • Diarrhea
  • Skin loss
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14
Q

Hyponatremia + Serum osmolality decreased + Spot urine Na < 20 mmol/L

Extracellular volume: Edema
Dx?

A

Renal sodium retention

  • Cirrhosis
  • Cardiac failure
  • Nephrotic syndrome
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15
Q

Most common form of hyponatremia in hospitalized patients?

A

Euvolemic Hyponatremia

  • SIADH
  • Post-operation: Pain and stress/ iatrogenic (excess fluid replacement)
  • Endocrine: Hypothyroidism, Hypopituitism, Cortisol deficiency
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16
Q

8 medications that can cause SIADH

CCOOVAF

A

Carbamazepine

Cyclophosphamide

Oral hypoglycemics

Oxytocin

Vincristine

Amitriptyline

Fluphenazine

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17
Q

Ectopic production of ADH causing SIADH? (4)

A

Duodenal cancer
Pancreatic cancer
Small cell lung cancer
Thymic cancer

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18
Q

Pulmonary diseases that can cause SIADH?

A

Acute asthma
Atelectasis
Infections
Pneumothorax

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19
Q

CNS diseases that can cause SIADH?

A

Autoimmune: MS, Guillain-Barre syndrome
Infection
Vascular accidents

20
Q

One immunosuppressive infection + 3 stress-related factors that can cause SIADH

A

HIV infection

Stress:

  • Emotions
  • Nausea
  • Acute pain and injury
21
Q

Inappropriate release of ADH occurs in which osmolality states?

22
Q

4 physical signs needed to decide ECF status?

A
  • BP
  • Pulse
  • Postural hypotension
  • Signs of dehydration: skin turgor, mucous membranes, tearing
23
Q

Plasma Na at 119 mmol/L
Severity of electrolyte distubrance?
Expected symptoms?

Pulse 140/80
Pulse 68
No dehydration signs
No postural hypotension

Hydration status?
Type of electrolyte disturbance?

Serum osmolality low
Result?

A

Severe HypoNa
Agitation, Confusion, Hallucination, Mental impairment, Incontinence

Hydration normal
Euvolemic hypoNa

Hypo-osmolality means Decrease water and much decreased Na = TRUE HYPONATREMIA

24
Q

Define SIADH and CSWS

A

SIADH = Syndrome of inappropriate secretion of Antidiuretic hormone

CSWS = Cerebral salt wasting syndrome

25
Q

Causes of CSWS?

Electrolyte and fluid imbalance?

A

Cerebral trauma, tumour, cerebral palsy
Pathology in head affecting ADH release
HypoNa and Hypovolemia (Diuresis and natriuresis)

26
Q

Compare CSWS and SIADH

  • Blood urea
  • Blood pressure
  • Central venous pressure
A
  • Blood urea
    CSWS: Increase
    SIADH: Low or normal
  • Blood pressure
    CSWS: Low
    SIADH: Normal
  • Central venous pressure
    CSWS: Decrease
    SIADH: Normal
27
Q

Compare CSWS and SIADH

  • Plasma sodium
  • Urinary sodium
  • Urinary volume
  • Thirst
A
  • Plasma sodium
    CSWS and SIADH: decrease
  • Urinary sodium
    CSWS and SIADH: Increase
  • Urinary volume
    CSWS: Increase
    SIADH: Decrease
  • Thirst
    CSWS: Increase
    SIADH: Normal
28
Q

Treatment of HypoNa and Euvolemia (e.g. SIADH)

A

Fluid restriction

Treat underlying cause

29
Q

Treatment of HypoNa and Hypervolemia

A

Diuretics

Treat underlying cause

30
Q

Treatment of HypoNa and Hypovolemia

A

Fluid replacement

Treat underlying cause

31
Q

Define hypernatremia.

A

Plasma sodium conc. >145 mmol/L

Hypertonic hyperosmolality and cellular dehydration

32
Q

2 processes that generate hypernatremia

A

1) Gain sodium

2) Loss water

33
Q

Outline 3 main causes of gaining sodium causing hypernatremia

A

Iatrogenic:
- Hypertonic saline, dialysis, tube feeding …etc

Excessive sodium ingestion:
- Salt tablet, infant formula…

Excess mineralocorticoid activity

  • Primary hyperaldosteronism
  • Cushing’s syndrome
  • Hyper-Renin-ism
  • Congenital adrenal hyperplasia
34
Q

Outline 2 main causes of water loss causing HyperNatremia

A

Extra-renal loss:

  • Skin: sweat, burns, evaporate
  • Lungs: hyperventilate
  • GI: osmotic diarrhea

Renal loss:

  • Diabetes insipidus (central or nephrogenic)
  • Osmotic diuresis: hyperglycemia, Mannitol, drugs
35
Q

2 main steps in the diagnostic pathway of hypernatremia

A

1) Urine: serum osmolality ratio - paired plasma and urine osmolality tests
2) Extracellular volume

36
Q

Urine: serum osmolality ratio.

How to use this metric to D/dx Hypernatremia

A

Urine: Serum osmolality ratio

i) Around 1 - Osmotic diuresis, glucose, urea
ii) <1 = Central diabetes insipidus or Nephrogenic diabetes insipidus
iii) >1 = Assess extracellular volume for further D/dx

37
Q

Urine:serum osmolality ratio >1

How to use Extracellular volume to D/dx Hypernatremia

A

Urine:serum osmolality ratio >1

Extracellular volume

a) Hypervolemia = salt gain
b) Euvolemic = Extrarenal pure water depletion
c) Hypovolemia = Hypotonic fluid depletion

38
Q

Causes of central Diabetes insipidus?

A

Brain cannot release ADH

Neurogenic 
Congenital 
Trauma
Neoplasia 
Infection 
Granuloma
39
Q

Causes of Nephrogenic diabetes insipidus?

A

Kidney cannot respond to ADH

Congenital 
Renal disease
Hypercalcemia 
Hypokalemia 
Lithium 
Demeclocycline
40
Q

Urine:serum osmolality ratio for patients with severe diabetes insipidus? (exception to normal)

A

Normally, DI U:S ration is <1

Severe DI = U:S ration between 1 and 1.9

41
Q

U:S osmolality ratio >1

Extracellular volume = Hypervolemia

Causes?

A

Salt gain

  • Salt ingestion
  • Mineralcorticoid excess
  • IV bicarbonate/ hypertonic saline
42
Q

U:S osmolality ratio >1

Extracellular volume = Euvolemia

Causes?

A

Extrarenal pure water depletion

  • Inadequate intake, No access to water
  • Too old, too young
  • Thirst center lesion
  • Esophageal obstruction
43
Q

U:S osmolality ratio >1

Extracellular volume = Hypovolemia

Causes?

A

Hypotonic fluid depletion
Extrarenal causes
- GI: vomiting, diarrhea
- Skin: excess sweating

44
Q

Define serum osmolality
Normal Range?
Calculation?

A

Number of osmotic active solutes

Plasma normal: 285 - 295mmol/kg
Calculation: Na x2 + glucose + urea

45
Q

What is Osmolar Gap?
What does high osmolar gap mean?
Normal osmolar gap?

A

Osmolar gap = Measured plasma osmolality - Calculated plasma osmolality (Na x 2 + glucose + urea)

High osmolar gap = more active solutes than anticipated/ unaccounted solutes, usually indicate intoxication or other substances present in blood e.g. hyperglobulinemia

Normal gap <10 mmol/kg

46
Q

How to use osmolar gap to d/dx hyponatremia

A

True hyponatremia: serum osmolality is low

Pseudohyponatremia (hyperlipiddemia or hyperproteinemia): serum osmolality is normal + Osmolar gap is INCREASED ***

47
Q

Pseudohyponatremia > hyperlipidemia and hyperproteinaemia > the lipids and proteins in blood are barely soluble and precipitates > these lipids and proteins in high amount can occupy space in the plasma

If 10mL of plasma is extracted and high lipid and protein occupies space (e.g. 2mL of space), then the remaining 8mL contains a lower mass of Na than anticipated in 10mL, even though the concentration of Na is the same

Hyperproteinaemia e.g. multiple myeloma&raquo_space; lots of protein in antibodies

Hyperlipidemia e.g. excess chylomicrons

A

Pseudohyponatremia > hyperlipidemia and hyperproteinaemia > the lipids and proteins in blood are barely soluble and precipitates > these lipids and proteins in high amount can occupy space in the plasma

If 10mL of plasma is extracted and high lipid and protein occupies space (e.g. 2mL of space), then the remaining 8mL contains a lower mass of Na than anticipated in 10mL, even though the concentration of Na is the same

Hyperproteinaemia e.g. multiple myeloma&raquo_space; lots of protein in antibodies

Hyperlipidemia e.g. excess chylomicrons

MBBS IV - Supplementary Courses (54 decks)

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