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Y3 Medicine > Electrolyte Abnormalities > Flashcards

Electrolyte Abnormalities Flashcards

(48 cards)

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1
Q

what is hyponatraemia?

A

sodium < 135 mmol/L

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2
Q

what is the presentation of hyponatraemia?

A
  • anorexia
  • nausea
  • malaise
  • headache and irritability
  • decreased GCS and confusion
  • weakness
  • seizures
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3
Q

what are the main causes of hyponatraemia?

A

SIADH
diuretics - esp thiazide
heart failure

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4
Q

how is hyponatraemia sub-categorised?

A
  • hypotonic (inc hypovolaemic, euvolaemic and hypervolaemic)
  • isotonic
  • hypertonic
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5
Q

what is hypotonic hyponatraemia caused by, generally?

A

an increase in intravascular volume (but the subcategories are based on total body water differences)

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6
Q

describe hypovolaemic hyponatraemia

A

there is a deficiency in both total body water and sodium

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7
Q

describe the pathophysiology of hypovolaemic hyponatraemia

A

low fluid volume due to decreased total body water causes ADH release. ADH causes water retention which increases intravascular volume (even though total body water is decreased), diluting the Na.

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8
Q

what are the causes og hypovolaemic hyponatraemia?

A
  • diuretics (thiazide)
  • intrinsic renal disease
  • mineralocorticoid deficiency (Addison’s disease)
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9
Q

describe euvolaemic hyponatraemia

A

total body water remains the same but water moves into the intravascular space, diluting the sodium

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10
Q

what are the causes of euvolaemic hyponatraemia?

A

SIADH - causes increased resorption of water by the kidney (can be euvolaemic or hypervolaemic)
iatrogenic (surgery causes impaired water excretion, certain types of surgical procedures)

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11
Q

describe hyervolaemic hyponatraemia

A

excess total body water means that there is also excess intravascular fluid, causing dilution of sodium

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12
Q

what are the causes of hypervolaemic hyponatraemia?

A
  • chronic renal failure
  • congestive heart failure
  • liver cirrhosis
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13
Q

what is redistributive hyponatraemia?

A

hypertonic hyponatraemia
- hypertonic blood with excess osmolytes causes water to shift from the intracellular to the extracellular compartment (into blood), diluting the extracellular sodium.

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14
Q

what can cause redistributive hyponatraemia?

A

hyperglycaemia

or administration of hypertonic fluids

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15
Q

what is pseudohyponatraemia?

A

isotonic hyponatraemia

= artefact produced by high serum lipid or protein levels

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16
Q

what investigations are carried out in a patient with hyponatraemia?

A
  • serum sodium concentration
  • U&E
  • creatinine
  • glucose
  • serum osmolality
  • urine sodium concentration - SIADH
  • CT brain, chest, abdomen/pelvis (malignancy)
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17
Q

what is the management of hyponatraemia?

A 
acute (<48 hours):
- hypertonic (3%) saline (give in 100 ml increments - up to 300 ml initially over 10 mins)
- treat underlying cause 
chronic:
hypovolaemic:
- give isotonic fluid (250 - 1000 ml boluses to maintain BP)
- treat underlying cause 
hypervolaemic:
- fluid restriction - 1 L/day 
- treat underlying cause
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18
Q

what rate of correction of sodium is aimed for in hyponatraemia and why?

A

up to 8 mmol/L/day correction over 24 hours

- to avoid central pontine myelinolysis

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19
Q

what is SIADH?

A

body produces too much ADH, which causes excess retention of water by the kidneys

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20
Q

what is the normal action of ADH?

Study These Flashcards
A
  • produced by the hypothalamus and released from the posterior pituitary
  • acts on aquaporin 2 receptors in the distal convoluted tubule, increasing the number of aquaporin receptors on the apical surface of cells and increasing water reabsorption
21
Q

what are the causes of SIADH?

Study These Flashcards
A
  • brain injury (meningitis, subarachnoid haemorrhage)
  • malignancy - small cell lung adenocarcinoma can produce ADH
  • drugs - carbamazepine/SSRIs/amitriptylline
  • infectious - lung/cerebral abscess/ atypical pneumonia
  • hypothyroidism
22
Q

what are the symptoms/signs of SIASH?

Study These Flashcards
A

symptoms and signs of hyponatraemia

  • anorexia
  • nausea
  • malaise/weakness
  • irritability / headache
  • low GCS
  • confusion
  • seizures
23
Q

what investigations are carried out when suspecting SIADH?

Study These Flashcards
A
  • fluid status
  • serum sodium (hyponatraemia <135)
  • serum potassium and cortisol (considering Addison’s disease as alternative cause of hyponatraemia)
  • plasma osmolality (reduced)
  • urine osmolality (high due to water reabsorption)
  • urine sodium concentration (high due to water reabsorption (>40 mmol/L - normal is 20))
  • TFTs - hypothyroidism is a cause of SIADH
  • imaging (e.g. CXR for cancer - can be a cause of SIADH)
24
Q

how would you manage SIADH?

Study These Flashcards
A
  • treat underlying cause
  • fluid restriction
  • replace Na - IV or orally (careful not to correct Na too rapidly)
25
what is hypernatraemia?
serum sodium >145 mmol/L
26
what are the causes of hypernatraemia?
- iatrogenic (most common) -giving hypertonic fluids (patient will be hypervolaemic) - dehydration ( burns, diarrhoea vomiting, burns) (patient will be hypovolaemic) - diabetes insipidus
27
what are the symptoms of hypernatraemia?
- thirst - irritable - seizures - muscle spasms - nausea and vomiting
28
what investigations are carried out when suspecting hypernatraemia?
- full history - U&Es - FBC - haemoatocrit, to look for dehydration - blood osmolarity - urine osmolarity - urine output - imaging (CT head - hypopituitarism which can be causing cranial DI)
29
what is the management of hypernatraemia?
- give 0.45% NaCl if euvolaemic or 0.9% NaCl if hypovolaemic - aiming for a 12 mol/L/day decrease in sodium
30
what is hypocalcaemia?
serum calcium <2.2 mmol/L
31
what is the presentation of hypocalcaemia?
- mild - asymptomatic - paraesthesia - carpopedal spasm - muscle cramps - tetany - ckvostek's sign (tapping the facial nerve in front of the ear below the zygomatic arch causes a muscular spasm) - trousseau's sign (inflating a pressure cuff above systolic BP and keeping it there induces a carpopedal spasm) - prolonged QT interval (can lead to heart block or VF) - laryngospasm - bronchospasm - dementia, confusion and papilloedema when prolonged
32
what are the causes of hypocalcaemia?
- hypoparathyroidism (causing decreased Ca absorption) - 2ry hyperparathyroidism (caused by low vitamin D levels which causes low Ca levels which leads to hyperparathyroidism) - chronic kidney disease (reduced active vitamin D and increase in serum phosphorous levels which binds Ca) - acute pancreatitis
33
what investigations need to be carried out when suspecting hypocalcaemia?
- U&E - creatinine (renal function) - amylase (for pancreatitis) - serum phosphate - serum PTH levels - vitamin D levels - ECG to rule out long QT (can occur in hypocalcaemia)
34
how would you manage hypocalcaemia?
- IV calcium gluconate - Oral Ca preparations alongside IV - Oral vitamin D
35
what are the symptoms of hypercalcaemia?
- Moans (tired, depressed, confused) - Groans (constipation, pancreatitis, peptic ulcers) - Stones (kidney stones, polyuria) - Bones (Muscle and bone aches) - polyuria and polydipsia - ectopic calcification (deposition of calcium in tissues)
36
what are the causes of hypercalcaemia?
- malignancy most commonly (ectopic production of parathyroid-related peptide or ectopic calcitriol or osteolysis from bone tumours) - granulomatous conditions such as sarcoidosis and TB - Drugs - thiazide diuretics and vitamin D supplements - primary hyperparathyroidism (parathyroid gland adenoma) - dehydration (urea raised)
37
what investigations are carried out when suspecting hypercalcaemia?
- serum calcium - U&Es - PTH levels - Vitamin D levels - Alkaline phosphatase (bony mets or liver involvement in sarcoidosis) - albumin levels - low in malignancy - phosphate levels - affected in hyperparathyroidism - phosphate levels - X-rays - bone abnormalities
38
what is the management of hypercalcaemia?
- treat underlying cause - 0.9% saline to flush out the Ca - Bisphosphonates IV (to reduce bone turnover) - denosumab - used when resistant to bisphosphonates
39
what is the presentation of hypokalaemia?
- asymptomatic when mild - weakness (beginning in lower extremities and extending upwards) - muscle pain - constipation - respiratory failure - ileus (due to involvement of GI muscles) - paraesthesia - tetany
40
what are the causes of hypokalaemia?
- renal tubular acidosis - hypomagnasaemia - K-losing diuretics (bendroflumethiazide, furosemide) - high aldosterone levels - hyperaldosteronism (inc Conn's syndrome), Cushing's disease, Renal artery stenosis - diarrhoea, vomiting (causes alkalosis and therefore hypokalaemia) - inadequate K replacement in IV fluids whilst nil by mouth
41
what investigations are carried out when suspecting hypokalaemia?
- U&E - Serum bicarbonate - Serum glucose - Serum magnesium (low Mg) - ECG
42
what is seen on an ECG when a patient has hypokalaemia?
- Flat T waves - ST depression - Prominent U waves
43
how would you manage hypokalaemia?
- mild - potassium replacement (potassium chloride supplements). review after 3 days. if needed, consider repeating replacement. if taking thiazide diuretic consider adding a k sparing diuretic - if severe, give Iv K cautiously and slowly (NEVER give IV K as a stat bolus)
44
what is the presentation of hyperkalaemia?
- weakness and fatigue - muscle paralysis - shortness of breath - palpitations/chest pain - bradycardia
45
what are the causes of hyperkalaemia?
- ischaemia/necrosis - infection - trauma - crush injuries - autoimmune - SLE - acidosis (e.g. in DKA) - Addison's disease (aldosterone low- less K excreted) - CKD/AKI - K-sparing diuretics (spironolactone, amiloride) - ACEi/ARBs - neoplasia (tumour lysis syndrome, malignancies) - haemolytic anaemia, causing K release from RBCs
46
what investigations are carried out when suspecting hyperkalaemia?
- FBC (normochromic, normocytic anaemia suggests acute haemolysis) - U&E - capillary blood glucose and plasma glucose - ABG (acidosis) - Creatinine (renal cause) - 24 hr urine output - for renal causes - ECG
47
what is seen on an ECG in hyperkalaemia?
- tall tented T waves - no P waves - wide QRS - bradycardia
48
how would you manage hyperkalaemia that is causing ECG changes or K>7 mmol/L?
- Stop medications that can be causing the hyperkalaemia (spironolactone, amiloride, ACEi/ARBs) - IV calcium gluconate to protect the heart - Insulin and dextrose (causes K to move into cells) - sodium bicarbonate if acidotic - salbutamol (IV or nebulised) (drives K into cells) - calcium resonium + lactulose (binds K in intestines and removes it via faeces) - Dialysis - gold standard for removing K from body

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