Electolytes Flashcards

1
Q

Anion gap

A

(Sodium+potassium)-(chloride+bicarbonate)

Normal range 10-18

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2
Q

Metabolic acidosis - normal anion gap

A

renal tubular acidosis,
GI bicarbonate loss(diarrhoea, fistula, ureterosignoidostomy), drugs,
ammonium chloride injection,
Addison’s disease

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3
Q

Metabolic acidosis -raised anion gap

A
Lactate 
- type A: shock, hypoxia, burns 
- type B: metformin
Ketones - DKA, alcohol
Urate- renal failure 
Acid poisoning - salicylates, methanol
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4
Q

Metabolic alkalosis causes

A

Loss of hydrogen or gain of bicarbonate (Kidney/ GI tract)

  • vomiting/ aspiration
  • diuretics
  • liquorice, carbenlxolone
  • hypokalemia
  • primary alderosteronism
  • congential adrenal hyperplasia
  • cushing’s syndrome
  • bartter’s syndrome
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5
Q

Metabolic alkalosis mechanism

A

Activation of renin-angiotensin II- aldosterone system
Causes reabsorption of sodium in exchange for H+ in distal convoluted tubule

ECF depletion (vomiting, diuretics) -> na and cl loss -> activation RAA system -> Raised aldosterone levees

In hypokalemia, K shift into cells -> ECF. Shift of H into cells to maintain neutrality

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6
Q

Hyponatraemia

A

Due to water excess or sodium depletion
Psuedo hyponatriemia - hyperlipidemia or drip arm sample
Every 100mg/dL increase of blood glucose will lower Na 1.6meq

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7
Q

Hypertonic hyponatriemia

A

Plasma osmolality >290
Hyperglycaemia
Hypertonic mannitol

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8
Q

Isotonic hyponatriemia

A
Plasma osmolality 275-290
Pseudo hyponatriemia 
Sodium free irrigate solutes
- hysterectomy
- TURP
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9
Q

Hypotonic hyponatriemia (hypervolaemic)

A
Plasma osmolality <275
High ECF
Interstitial fluid shift
-congestive HF
- cirrhosis
- nephrotic syndrome
- renal failure
- sepsis
- anaphylaxis 
- pregnancy
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10
Q

Hypotonic hyponatriemia (euvolaemic)

A

SIADH

  • CNS disorders: haemorrhage, surgery, trauma, mass lesions, stroke
  • pulmonary: infection, acute resp failure, positive pressure ventilation
  • drugs
Hypothyroidism 
Malignancy
Primary poly dips is
Decreased Na intake (tea and toast, beer potomania)
Secondary adrenal insufficiency
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11
Q

Hypotonic hyponatriemia (hypovolaemic)

A
  • Cerebral salt wasting: haemorrhage, surgery, trauma
  • Hypokalemia
  • Renal sodium loss: diuretics, osmotic diuretics, primary adrenal insufficiency, salt wasting nephropathy, bicarbonaturia, ketonuria
  • Extra renal sodium loss: diarrhoea, vomiting, blood loss, excess sweating, fluid sequestration (bowel obstruction, peritonitis, pancreatitis, muscle trauma, burns)
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12
Q

Hypernatremia

A

Dehydration
Osmotic diuretics Eg Hyperosmolar non ketotic diabetic coma
Diabetes insipidus
Excess IV saline

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13
Q

Potassium regulation

A

Aldosterone
Acid base balance
Insulin levels

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14
Q

Hyperkalaemia ECG changes

A

Tall tented t waves
Small p waves
Widened QRS
Sinusoidal pattern and asystole

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15
Q

Hyperkalemia

A

Metabolic acidosis (hydrogen and potassium compete for exchange with sodium across cell membrane in distal tubule)

Acute renal failure
Drugs: K sparing diuretic, ace-I, cyclosporin
Addisons
Rhabdomyolosis
Massive blood transfusion

Nb - beta blockers interfere with K transport into cells, potential cause in renal failure

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16
Q

Management hyperkalemia

A

IV calcium gluconate (stabilise cardiac membrane)
Insulin/dextrose, salbutamol men’s (shift extra cellular to intracellular)

Calcium resinous, loop diuretic, dialysis (remove potassium from body)

17
Q

Hypokalemia with alkalosis

A

Vomiting
Diuretics
Cushing’s syndrome
conn’s syndrome (primary hyperaldosteronism)

18
Q

Hypokalemia with acidosis

A

Diarrhoea
Renal tubular acidosis
Partially treated DKA
Acetazolamide

19
Q

ECG features hypokalemia

A
U waves
Small or absent T waves 
Prolong PR interval
ST depression 
LoNg QT
20
Q

Hypomagnesemia causes

A
Diuretics
TPN
Diarrhoea
Alcohol
Low K/Ca
Cisplatin (NSCLC)
21
Q

Hypomagnesemia features

A
Paraesthesja
Tetany
Seizures
Arrhythmia
Low PTH secretion -> low calcium
ECG features similar to hypokalemia 
Exacerbates digoxin toxicity
22
Q

Hypophosphatemia causes

A
Alcohol excess
Acute liver failure
DKA
Refeeding syndrome 
Osteomalacia
Primary hyperparathyroidism
23
Q

Hypophosphatemia consequences

A

Red cell hemolysis
White cell and platelet dysfunction
Muscle weakness and rhabdo
CNS dysfunction

24
Q

Hypocalcemia ecg

A

Prolonged QT

25
Q

Trousseau’s sign

A

Hypocalcemia
Carpal spasm in brachial artery occluded
95% of people with low Ca
1% normal

26
Q

Chvostek’s sign

A

Hypocalcemia
Less sensitive than Trousseau’s - 70%
10% normal Ca
Tapping over parotid causes facial muscles to twitch

27
Q

Treat severe hypocalcemia

A

IV calcium gluconate 10ml of 10% solution over 10mins

ECG monitoring

28
Q

Hypercalcemi

A

Most common malignancy (bone nets, myeloma, PTHrP from squamous lung)
Primary hyperparathyroidism

29
Q

Differentiating MGUS and myeloma

A

Absence of complications -

Immune paresis, hypercalcemia and bone pain

30
Q

Treatment hypercalcemia

A

Fluids
Bisohosphonates if malignancy, take 2-3days to work with maximal effect at 7days
Corticosteroids in sarcoidosis