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General Medicine > Electrolytes > Flashcards

Electrolytes Flashcards

1
Q

What are some of the causes of hyperkalaemia caused by reduced excretion of potassium?

A

AKI —> reduced eGFR

Drugs:

  • K+ sparing diuretics e.g. amiloride, spironolactone
  • ACE inhibitors
  • NSAIDs
  • ciclosporin
  • heparin

Reduced aldosterone

Renal tubular acidosis

Addison’s disease

Metabolic acidosis

Pseudohypoaldosteronism

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2
Q

What are some of the causes of hyperkalaemia caused by increased extraneous load of potassium?

A

KCl

Diet: salt substitutes

Blood transfusion

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3
Q

What are some of the causes of hyperkalaemia caused by increased release of potassium?

A

Metabolic acidosis

Diabetic ketoacidosis

Rhabdomyolysis

Drugs:

  • succinylcholine
  • digoxin
  • beta-blockers
  • insulin

Vigorous exercise

Haemolysis

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4
Q

What are some of the causes of hyperkalaemia caused by artefacts?

A

Increased in vitro release from abnormal cells:

  • leukaemia
  • infectious mononucleosis
  • thrombocytosis

Haemolysis in blood bottle

Vigorous fist clenching during phlebotomy

Increased release from muscles

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5
Q

What are some of the causes of renal retention of potassium?

A

Renal failure:

  • acute
  • chronic

Tubular secretory failure

  • low aldosterone: Addison’s disease, adrenal enzyme defect, hyporeninaemic hypoaldosteronism, NSAIDs, ACE inhibitors, beta-blockers, ciclosporin, heparin
  • normal/high aldosterone: pseudohypoaldosteronism, tubulointerstitial disease, amiloride, spironolactone
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6
Q

What are the signs and symptoms of hyperkalaemia?

A

Muscle weakness

Metabolic acidosis —> Kussmual respiration

Reduced cardiac excitability —> hypotension —> bradycardia —> asystole

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7
Q

What is the ECG appearance in hyperkalaemia?

A

Tall tented T waves (at least 1/3 of height of preceding R wave)

Reduced P wave and widened QRS complex (>3 squares)

Sine wave pattern (pre-cardiac arrest)

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8
Q

What is the management of severe hyperkalaemia?

A

ACUTE

  • continuous ECG monitoring
  • IV access
  • protect myocardium: 10ml of 10% calcium gluconate IV over 5min (rpt after 5min)
  • drive K+ into cells: 10 units of insulin + 50ml of 50% glucose IV over 10-15min (insulin dextrose)
  • +/- correction of severe acidosis by NaHCO3 1.26% infusion
  • +/- IV or nebulised salbutamol 0.5mg in 100ml of 5% glucose over 15min

LATER:

  • IV furosemide + normal saline (if renal function OK)
  • deplete body K+: polystyrene sulfonate resins OR haemodialysis/peritoneal dialysis
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9
Q

What are some of the causes of hypokalaemia caused by increased aldosterone?

A 
Liver failure 
Heart failure 
Nephrotic syndrome 
Cushing's syndrome 
Conn's syndrome 
ACTH-producing tumour
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10
Q

What are some of the causes of hypokalaemia caused by redistribution into cells?

A 
Beta-adrenergic stimulation 
Acute MI 
Insulin
Correction of megaloblastic anaemia 
Alkalosis 
Hypokalaemic periodic paralysis (autosomal dominant)
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11
Q

What are some of the causes of hypokalaemia caused by GI losses?

A 
Vomiting 
Severe diarrhoea 
Purgative abuse 
Villous adenoma 
Ileostomy 
Uterosigmoidoscopy 
Fistulae 
Ileus/intestinal obstruction
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12
Q

What are some of the causes of hypokalaemia caused by renal disease?

A 
Renal tubular acidosis 
Renal tubular damage 
Acute leukaemia 
Nephrotoxicity e.g. amphotericin, aminoglycosides, cytotoxic drugs 
Release of urinary tract obstruction 
Bartter's syndrome 
Liddle's syndrome 
Gitelman's syndrome
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13
Q

What are some of the causes of hypokalaemia caused by exogenous mineralocorticoid?

A

Corticosteroids

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14
Q

What are some of the causes of hypokalaemia caused by reduced potassium intake?

A

IV fluids without K+

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15
Q

What are some of the causes of hypokalaemia caused by increased renal excretion of potassium?

A

Diuretics:

  • thiazides
  • loop diuretics
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16
Q

What are the signs and symptoms of hypokalaemia?

A

Muscle weakness

Symptomatic hyponatraemia

Increased risk of digoxin toxcitiy

17
Q

What is the management of hypokalaemia?

A

Depends on the cause:

  • increased aldosterone: give spironolactone or other potassium sparing diuretic
  • IV fluid replacement: give 20mmol of K+/l
  • diuretics/purgatives: withdraw and give PO K+ supplements
18
Q

What are the causes of hyponatraemia with hypovolaemia?

A

EXTRA-RENAL

  • vomiting
  • diarrhoea
  • haemorrhage
  • burns
  • pancreatitis

RENAL

  • osmotic diuresis
  • severe uraemia
  • diuretics
  • adrenocortical insufficiency
  • tubulo-interstitial renal disease
  • unilateral renal artery stenosis
  • recovery phase of acute tubular necrosis
19
Q

What are the causes of hyponatraemia with euvolaemia?

A

Abnormal ADH release

  • vagal neuropathy
  • Addison’s
  • hypothyroidism
  • severe potassium depletion
  • SIADH (surgery, intracranial, alveolar, drugs, hormones)
20
Q

What is the management of hyponatraemia?

A

Healthy:

  • PO electrolyte-glucose mixture
  • increase sodium intake with slow sodium 60-80mmol/l/day

Vomiting/sever volume depletion:

  • IV fluids + potassium supplements over 24hrs
  • correction of acid-base abnormalities
21
Q

What is the presentation of SIADH?

A
  • confusion
  • nausea
  • irritability
  • fits
  • coma
22
Q

What are the investigations indicated for SIADH?

A

Diagnosis of exclusion - rule out dilutional hyponatraemia and Addison’s

  • ?dilutional hyponatraemia
  • euvolaemia
  • low plasma osmolality with excessive urine osmolality
  • continued urinary sodium excretion above 30mmol/l
  • absence of hypokalaemia and hypotension
  • normal renal, adrenal, and thyroid function
  • no oedema
23
Q

What is the management of SIADH?

A
  • correct underlying cause
  • restrict fluid intake to 500-1l/day
  • measure plasma osmolality, serum sodium, and body weight dailt
  • can give demeclocycline to inhibit ADH
24
Q

What is sick cell syndrome?

A

Leakage of intracellular ions due to reduced Na+/K+ pump action –> hyponatraemia and hypokalaemia

Causes:

  • hypoxia
  • sepsis
  • hypovolaemia
  • malnourishment
25
Q

What are the causes of dilutional hyponatraemia?

A

Intake of water in excess if kidney’s ability to excrete it with no change in body sodium content

  • marathon runners
  • excess glucose infusion
  • drugs
  • psychosis
26
Q

What is the presentation of hyponatraemic encephalopathy?

A
  • headache, confusion, restlessness, drowsiness, myoclonic jerks, generalised convulsions, coma
  • MRI head shows cerebral oedema
  • risks = children under 16, premenopausal women, hypoxaemia
27
Q

What are the investigations in dilutional hyponatraemia?

A

Plasma urine electrolytes and osmolalities

  • plasma sodium, chloride, and urea are LOW –> low serum osmolality
  • urine sodium HIGH
  • exclude Addison’s (short synacthen), hypothyroidism (TSH, T4), SIADH, drug-induced
28
Q

What is the management of dilutional hyponatraemia?

A
  • correct underlying cause
  • fluid intake restriction to 500-1l per day
  • review diuretics
  • correct potassium and magnesium deficiencies
  • anticipate and prevent overcorrection
29
Q

What is osmotic demyelination syndrome?

A

Acute demyelination in the setting of osmotic changes; particularly with rapid increase in extracellular osmolality

Risk factors:

  • chronic alcohol use
  • cirrhosis
  • malnutrition
  • hypokalaemia
  • pre-existing hypoxaemia
  • CNS radiation
  • transplant recipients
30
Q

What are the causes of hyponatraemia with hypervolaemia?

A

Fluid overload

  • heart failure
  • liver failure
  • oliguric kidney injury
  • hypoalbuminaemia
31
Q

What are pseudo hyponatraemia and artefactual hyponatraemia?

A

Pseudohyponatraemia = sodium confined to aqueous phase, but concentration expressed in terms of total volume of plasma –> hyponatraemia but plasma osmolality is normal

Artefactual hyponatraemia = blood test taken from limb receiving sodium infusion

32
Q

What are the causes of hypernatraemia?

A

Water deficit

  • ADH deficiency (pituitary diabetes insipidus)
  • iatrogenic: excessive saline, drugs,
  • insensitivity to ADH (nephrogenic diabetes insipidus, lithium, ATN)
  • insufficient water intake
  • excessive water loss
33
Q

What investigations are indicated in hypernatraemia?

A

Simultaneous urine and plasma osmolality

  • plasma osmolality is HIGH
  • urine osmolality < plasma osmolality
  • high urine osmolality indicates osmotic diuresis due to unmeasured solute or excessive extrarenal loss of water

Administer desmopressin:

  • pituitary diabetes insipidus = increase in urine osmolality
  • nephrogenic diabetes insipidus = no change in urine osmolality
34
Q

What is the management of hypernatraemia?

A

ADH deficiency –> replace with desmopressin

Withdraw nephrotoxic drugs where possible

Replace water orally or IV

  • > 150mmol/l –> 5% glucose/0.45% NaCl
  • > 170mmol/l –> 0.9% NaCl over 48hrs

General Medicine (12 decks)

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