Hypocalcaemia Flashcards
pseudohypocalcaemia
describes the situation where total calcium is reduced due to hypoalbuminaemia (calcium binds to albumin) but ionized calcium remains withinthe normal range
= pseudohypocalcaemia
clinical features
- muscles
- neuropsychiatric
- skin
- Spasms
- Perioral paraesthesia
- Tingling around mouth
- Seizures
- Muscle tone increased in smooth muscle – cough, wheeze, dysphagia
- Muscle weakness and cramps
- Bronchospasm or laryngospasm
- Tetany
- choreoathetosis, cataract, rarely cardiomyopathy
Neuropsychiatric:
- Anxious, irritable, irrational
- Orientation impaired (time, place etc.) and confusion
Skin:
- Dermatitis
- Hyperpigmentation
- Brittle nails with characteristic transverse grooves
- Impetigo herpetiformis (decreased calcium and pustules in pregnancy) – a severe form of pustular psoriasis that occurs during pregnancy
what effect does hypocalcaemia have on nerve cells
- Low plasma calcium ion increases the permeability of neuronal membranes to Sodium ions, depolarizing the cell more easily and making the neuron more excitable (increased neuromuscular excitability)
- This can trigger tetany.
what are the main clinical manifestations of increased smooth muscle tone
- Spasms
- Perioral paraesthesia
- Tingling around mouth and in extremities
- Seizures
- Muscle tone increased in smooth muscle – cough, wheeze, dysphagia
- Muscle weakness and cramps
- Bronchospasm or laryngospasm
- Cough, wheeze, pain, stridor
- Tetany
Chovstek and Trosseau’s sign
choreathetosis
Choreathetosis is the occurrence of involuntary movements in a combination of chorea (irregular migrating contractions) and athetosis (twisting and writhing).
impetigo herpetiformis
decreased calcium and pustules in pregnancy
severe form of pustular psoriasis that occurs during pregnancy
ECG changes
- prolonged QT interval due to prolongation of plateau phase
- can cause ventricular arrhythmias
what ventricular arrhythmia in particular does hypocalcaemia cause
- Torsades de Pointes
- get more commonly with hypomagnesemia and hypokalaemia
- magnesium sulphate
Chvostek’s sign
the corner of the mouth twitches when the facial nerve is tapped over the parotid
Trousseau’s sign
on inflating blood pressure cuff to occlude brachial artery, elicits nerve firing, the wrist and fingers flex and draw together - carpopedal spasm
causes of hypocalcaemia with increased phosphate
chronic kidney disease
hypoparathyroidism and pseudohypoarathyroidism
vitamin D deficiency
hypomagnesaemia
tissue injury
how does chronic kidney disease cause hypocalcaemia
- calcium is not reabsorbed in the kidney
- failure of conversion of 25OH vitamin D to active form - 1-25 OH vitaminD
- increased phosphate levels bind calcium
causes of vitamin D deficiency
lack of sunlight
malabsorption
cirrhosis
chronic renal failure
deficient diet
coeliac
how does tissue injury cause hypocalcaemia
eg acute rhabdomyolysis and burns
cells die and release phosphate into the blood which binds to ionized calcium and forms calcium phosphate - decreasing total amount of calcium in the blood
causes of hypocalcaemia with normal/decreased phosphate
osteomalacia (increased ALP)
acute pancreatitis
overhydration
respiratory alkalosis
