Fluids/electrolytes - Amir Sam 250821 Flashcards

1
Q

what are the two main stimuli for ADH secretions?

A

serum osmolality (osmoreceptors) and reduced blood volume/pressure (mediated by baroreceptors in carotids, atria, aorta)

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2
Q

what is the first step in the clinical assessment of a patient with hyponatremia?

A

clinical assessment of volume status

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3
Q

what are the clinical signs of hypovolaemia?

A
LOW URINE SODIUM <20
tachycardia
postural hypotension 
dry mucous membranes
reduced skin turgor
confusion/drowsiness 
reduced urine output
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4
Q

what is the most important clinical sign (after assessing volume status) of hypovolaemia

A

low urine sodium

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5
Q

clinic what are the causes of hyponatremia in hypovolaemic patients

A

renal causes - diuretics

extra-renal diarrhoea vomiting

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6
Q

what are the causes of hyponatraemia in a euvolaemic patient

A

hypothyroidism
adrenal insufficiency
syndrome of inappropriate ADH (cns pathology, lung pathology, drugs, tumours, surgery)

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7
Q

clinical assessment of hyponatraemic euvolaemic

A

thyroid function tests, short synacthen test, low plasma and high urine osmolality

diagnosis of siadh made if no hypovolaemia, no hypothyroidism, no adrenal insufficiency, reduced plasma osmolality AND increased urine osmolality (>100)

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8
Q

how would you manage a hypovolaemic hyponatraemic patient

A

volume replacement with 0.9% saline

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9
Q

how would you manage a hypervolaemic patient with hyponatraemia

A

fluid restriction treat the underlying cause

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10
Q

what is the most important point to remember while correcting hyponatraemia

A

serum NA must not be corrected ?8-10 mmol/L in the first 24 hours, due to risk of central pontine myelionlysis
- quadriplegia, dysarthria, dysphagia, seizures, coma, death

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11
Q

Drugs used to treat SIADH

if water restriction is insufficient

A

demeclocycline
- reduces responsiveness of collecting tubule cells to ADH (monitor
tolvaptan - V2 receptor antagonist

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12
Q

hyponatraemia is mostly due to?

A

increased extracellular water

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13
Q

MAIN CAUSES OF HYPERNATRAEMIA

A

unreplaced water loss

patient cannot control water intake

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14
Q

what investigations would you order in suspected diabetes insupidus

A

serum glucose, potassiu,. calcium, plasma and urine osmolality, water deprivation test

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15
Q

how would you treat hypernatraemia

A

fluid replacement 5% dextrose, treat the underlying cause

if they are also hypovolaemic then need 0.9% saline as while

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16
Q

effects of diabetes mellitus on serum sodium

A

variable
hyperglycaemia draws water out of cells leading to hyponatraemia
osmotic diuresis in uncontrolled diabetes leads to loss of water and hypernatraemia

17
Q

how do lower Na if you’ve made it too high

A

dextrose and desmopressin call ITU to advise