Electrolyte abnormalities Flashcards
What defines hyponatraemia?
serum sodium concentration of <135 mmol/L
most common electrolyte abnormality
disorder of water balance reflected by an excess of total body water relative to electrolytes
Low plasma osmolality
What is a medical emergency associated with hyponatraemia?
Cerebral oedema
What factors are at play in hyponatraemia?
Loss of sodium
Increase in fluid - most important
BUT hyponatraemia can happen in eu or hypovolaemic states too
What are RFs for hyponatraemia?
Older age Hospitalisation Long term conditions e.g. DM, CHF Medications e.g. SSRIs, Thiazide diuretics, PPIs High fluid intake
What are some presenting features of hyponatraemia?
N+V - cerebral oedema Mild cog symptos Orthostatic hypotension Abnormal JVP Reduced urine output Oedema Lung crackles Abnormal JVP
What is the management for acute onset <48 hours hyponatraemia?
Hypertonic 3% saline infusion
Supportive care
Treat underlying cause
What is the management for chronic onset >48 hours hyponatraemia? hypovolaemic
Isotonic fluid infusion
What is the management for chronic onset >48 hours hyponatraemia? hypervolaemic
Fluid restricct
Treat underlying cause
+/- loop diuretic or spironolactone
2nd line
Vasopressin receptor antagonist
Define hypernatraemia
serum sodium concentration of >145 mmol/L
What is the most common presentation of hypernatraemia?
patient in the intensive care unit who is unable to drink water, has a large urine or stool output, and is unable to concentrate urine normally
the older nursing home resident, usually with dementia
What are causes of hypernatraemia?
dehydration
osmotic diuresis e.g. hyperosmolar non-ketotic diabetic coma
diabetes insipidus
excess IV saline
What are they types of hypokalaemia?
With alkalosis
With acidosis - more associated because K+ levels rise and fewer H+ can enter cells
With/out HTN
What causes hypokalaemia with alkalosis?
vomiting
thiazide and loop diuretics
Cushing’s syndrome
Conn’s syndrome (primary hyperaldosteronism)
What causes hypokalaemia with acidosis?
diarrhoea
renal tubular acidosis
acetazolamide
partially treated diabetic ketoacidosis
What are presenting features of hypokalaemia?
Muscle weakness
Hypotonia
Digoxin toxicity
What are the ECG features of hypokalaemia?
U waves
small or absent T waves
prolonged PR interval
ST depression
What causes hypokalaemia with hypertension?
Cushing’s syndrome
Conn’s syndrome (primary hyperaldosteronism)
Liddle’s syndrome
11-beta hydroxylase deficiency*
What causes hypokalaemia without hypertension?
diuretics GI loss (e.g. Diarrhoea, vomiting) renal tubular acidosis
What are causes of hyperkalaemia?
AKI Drugs Metabolic acidosis Addison's Rhabdomylosis Massive blood transfusion
What drugs can cause hyperkalaemia?
ACE inhibitors angiotensin 2 receptor blockers spironolactone ciclosporin heparin
How can stages of hyperkalaemia be classified?
mild: 5.5 - 5.9 mmol/L
moderate: 6.0 - 6.4 mmol/L
severe: ≥ 6.5 mmol/L
What ECG changes are seen in hyperkalaemia?
peaked or ‘tall-tented’ T waves
loss of P waves
broad QRS complexes
sinusoidal wave pattern
What are the management principles for hyperkalaemia?
Stabilise the cardiac membrane - IV calcium gluconate
Shift K+ intracellularly - Insulin/dextrose infusion
Nebulised salbutamol
Remove K+ from body = Calcium resonium (oral or enema), Loop diuretics, dialysis
What practically is the emergency treatment for hyperkalaemia?
If >6.5 mmol/L or ECG changes
IV calcium gluconate
Insulin/dextrose infusion
What are common differentials for hypercalcaemia?
Primary hyperparathyroidism
Malignancy
Multiple myeloma
What are the features of hypercalcaemia?
‘bones, stones, groans and psychic moans’
corneal calcification
shortened QT interval on ECG
hypertension
What is the initial management fro hypercalcaemia?
Rehydration with normal saline
Bisphosphonates
What are the features of hypocalcaemia?
tetany: muscle twitching, cramping and spasm
perioral paraesthesia
if chronic: depression, cataracts
ECG: prolonged QT interval
What signs are seen in hypocalcaemia?
Trousseau’s
Chvostek’s
What is Trousseau’s sign?
carpal spasm if the brachial artery occluded by inflating the blood pressure cuff and maintaining pressure above systolic
wrist flexion and fingers are drawn together
What is Chvostek’s sign?
tapping over parotid causes facial muscles to twitch
What causes hypocalcaemia?
vitamin D deficiency (osteomalacia)
chronic kidney disease
hypoparathyroidism
rhabdomyolysis
magnesium deficiency (due to end organ PTH resistance)
massive blood transfusion
acute pancreatitis
How is severe, acute hypocalcaemia managed?
IV replacement (calcium gluconate) ECG monitoring
