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Clinical Pathology > Water And Electrolyte Metabolism > Flashcards

Water And Electrolyte Metabolism Flashcards

(65 cards)

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1
Q

What is the total body water?

A

42L

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2
Q

What percentage of body weight is taken up by water in men?

A

About 60%

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3
Q

What percentage of body weight is taken up by water in women?

A

About 55%

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4
Q

What percentage of body weight is taken up by water in children?

A

75-80%

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5
Q

What percentage of water is in the ICF❓

A

66%

28L

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6
Q

What percentage of water is in the ECF❓

A

33%

14L

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7
Q

What percentage of water is in the plasma❓

A

8%

11L in ISF
3.5L in plasma

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8
Q

List the electrolyte composition of cations:

  1. Na
  2. K
  3. Ca
  4. Mg

In plasma

A

Na- 142mmol/L
K- 4mmol/L
Ca- 2.3mmol/L
Mg- 1mmol/L

Total cations- 150mmol/L

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9
Q

List the electrolyte composition of anions:

  1. Cl
  2. HCO3
  3. Phosphates
  4. Sulphates
  5. Proteins

In plasma

A
  1. Cl- 103mmol/L
  2. HCO3-27mmol/L

Measured anions- 130mmol/L

3,4,5- Unmeasured anions

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10
Q
  1. The anion gap in health is measured using which formula?
  2. What range is healthy?
  3. A derangement from this range might signify?
A
  1. Cations-measured anions
  2. 6-20mmol/L
  3. Lactic acidosis
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11
Q

List the electrolyte composition of cations:

  1. Na
  2. K
  3. Ca
  4. Mg

In ICF

A

Na- 12mmol/L

K- 156mmol/L

Ca- 1mmol/L

Mg- 13mmol/L

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12
Q

List the ICF anions

A

Proteins

Phosphates

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13
Q

Total body osmolality?

A

285mmol/kg

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14
Q

Total ECF osmolality?

A

282-295mmol/kg

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15
Q

Arginine vasopressin is secreted in response to❓

What is it’s function❓

A

⬆️osmolality

⬆️water retention by the kidneys
⬇️urine production

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16
Q

What electrolytes maintain ECF osmolality❓

A 
Na
Cl
HCO3 
Glucose
Urea
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17
Q

What electrolytes maintain ICF osmolality❓

A

K

Phosphates

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18
Q

What electrolytes maintain ISF osmolality❓

A

Colliod osmotic pressure/oncotic pressure by plasma proteins

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19
Q

What should you watch out for in assessing a patient for fluid therapy❓

A

History

Cardiac/Renal/Liver disease

Vomiting/Diarrhea

Nausea, headache, confusion

Fever, nasogastric suction, surgical drains, fistulae, artificial ventilation

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20
Q

What would you examine for in assessing a patient for fluid therapy❓

A
  1. Plasma volume:
    BP, pulse, JVP, CVP
  2. ISF volume- edema
  3. ICF volume-look for evidence of cerebral dysfunction
  4. Skin turgor
  5. Urine output
  6. Mucous membranes
  7. Level of consciousness
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21
Q

Describe the Na distribution in the body

A

In a 70kg man

•Total Na- 3700mmol

  • 75% is exchangeable
  • 25% isn’t exchangeable(in bone)
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22
Q

How much Na is taken in❓

How much Na sodium is excreted❓

A

100mmol/day-300mmol/day (in Western diets)

5mmol/L

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23
Q

What regulates Na output❓

A

Aldosterone- ⬇️Na output by ⬆️ Na reabsorption

Atrial Natriuretic peptide- ⬆️Na output

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24
Q

What is hyponatreamia?

A
  1. Fall in plasma Na below the reference range of 135-145mmol/L

⬇️Na
OR
⬆️Water

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25
What are the 2 broad classifications❓
1. Edematous Hyponatraemia: •Congestive Heart Failure CCF •Nephrotic syndrome •Inappropriate IV saline 2. Non-edematous hyponatraemia: •SIAD •Renal failure •⬆️intake
26
How is hyponatreamia treated?
Correction of Na loss Diuretics Fluid restriction
27
How is hyponatreamia diagnosed?
Hypotension | Tachycardia
28
Hyponatraemia due to Na loss from GI can be seen in?
Vomiting Diarrhea Fistula
29
Hyponatraemia due to Na loss from urine can be seen in?
Aldosterone deficiency- addison’s disease (hypocortisolism) Aldosterone antagonists-Spironolactone or triamterine
30
Speak briefly about SIAD
* Normal total body sodium * ⬆️secretion of ADH * ⬆️Water retention * Leads to non edematous hyponatraemia ``` •Can be encountered in: Malignancies Infections Trauma Carcinoma of the lungs Head injury ``` Or Reduction in circulating blood volume Nausea and vomiting Pain •Could be drug induced eg thiazide diuretics
31
What is hypernatreamia❓
Na>135-145mmol/L
32
What are the causes of hypernatreamia❓
1. Water depletion as seen in dehydration 2. Water and sodium depletion in diarrhea, vomiting 3. Excess Na intake or retention seen in Conn’s syndrome or Cushing’s syndrome (hypercortisolism)
33
What is the clinical presentation of hypernatreamia❓
Dehydration in water loss Increased JVP and pulmonary edema as seen in fluid overload
34
How is hypernatreamia treated?
Give oral fluids slowly Give 5% dextrose slowly
35
Describe the K distribution in the body
Total body K- 3600mmol 98% intracellular 5% extracellular
36
How much K is taken in❓ How much K sodium is excreted❓
Variable. 30-100mmol/day Variable, mostly by kidneys
37
What stimulates cellular uptake of K❓
Insulin
38
What is hypokalamia?
K<3mmol/L
39
What are the clinical effects of hypokalamia?
Severe weakness Hyporeflexia Cardiac arrhythmias Increased sensitivity to digoxin
40
What are the ECG changes in hypokalamia?
Flattened T waves | Prominent U waves
41
What are the causes of hypokalamia?
GIT losses: vomiting, diarrhea, fistula Renal losses- renal disease, diuretic therapy, ⬆️aldosterone production Drug induced- thiazide diuretics, corticosteroids, cabenoxolone
42
How is hypokalemia treated?
1. Oral k supplements 2. IV potassium- 🚫>20mmol/h under ECG monitoring
43
What is hyperkalamia?
K>5mmol/L >7mmol/L- risk of cardiac arrest •Commonest and most serious electrolyte emergency
44
What are the clinical features of hyperkalamia?
Muscle weakness
45
What are the ECG changes in hyperkalamia?
Widened QRS complex Peaked T waves
46
What are the causes of hyperkalamia?
Renal failure/⬇️GFR Mineralocorticoid deficiency: Addison’s disease Aldosterone antagonists like spironolactone or triamterene Acidosis Potassium released from damaged cells Artefactual increase in hemolysed serum
47
How would you treat hyperkalamia?
Infusion of insulin and glucose Infusion of sodium gluconate Dialysis In crush injuries- ABC (Airway, Breathing, Circulation) Cation exchange resin like resonium A
48
What fluids are used in IV fluid therapy❓
1. Water- 5% dextrose 2. Isotonic NaCl- 0.9% NaCl 3. Plasma/Whole blood 4. 1.26% sodium bicarbonate 5. Potassium supplements
49
What are the sources of hydrogen ion in the body❓
Metabolism Oxidation of sulphur-containing amino acids of proteins ingested as food As dissolved CO2 in blood
50
What is the reference range of H+ in the body❓
35-45nmol/L •<20 and >120nmol/L is not compatible with life
51
How is H+ managed in terms of excretion❓
1. Through buffers: •a solution of the salt of a weak acid which is able to bind hydrogen ions •Blood buffers- CHO3, Hb, proteins •Urinary buffers- Phosphate, NH4+ 2. Through renal excretion bound to urinary buffers
52
Describe how bicarbonate reabsorption is achieved❓
Refer to photos
53
How is bicarbonate regeneration achieved❓
Refer to photos
54
Describe the transport of carbon dioxide
Refer to photos
55
List the arterial blood gas values for: 1. H+ 2. HCO3 3. PCO2 4. PO2
1. H+ - 35-46nmol/L 2. HCO3- 22-30mmol/L 3. PCO2- 4-6kP (36-46mmHg) 4. PO2- 11-15kP (85-105mmHg)
56
Respiratory disorders directly affect❓
PCO2
57
What happens in metabolic acidosis❓
H is high or normal | HCO3 is always low
58
Metabolic acidosis can occur in what disease states❓
Renal disease Diabetic ketoacidosis Lactic acidosis
59
What happens in respiratory acidosis❓
H is high or normal | PCO2 is always high
60
Acute respiratory acidosis is not a medical emergency True or false❓
False
61
Respiratory acidosis can occur in what disease states❓
Airway obstruction Respiratory centre depression Lung disease Neuromuscular disease eg poliomyelitis Extrapulmonary thoracic dx like flail chest
62
What happens in respiratory alkalosis❓
Occurs in conditions when respiration is stimulated or is no longer subject to feedback control
63
What could cause respiratory alkalosis❓
Mechanical overventilation Hysterical overbreathing ⬆️Intracranial pressure Hypoxia
64
What happens in metabolic alkalosis❓
H is depressed HCO3 is raised PCO3 is raised (respiratory compensation)
65
What could cause metabolic alkalosis❓
Prolonged vomiting Nasogastric suction Conn’s syndrome

Clinical Pathology (6 decks)

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