hypocalcaemia Flashcards
albumin in alkalosis
tends to be negatively charged
calcium is more likely to latch onto calcium
more bound calcium and less free ionised calcium
total calcium is the same
may lead to symptoms of hypocalcaemia
hypoalbuminaemia
free ionised calcium stays the same due to hormonaal regulation
less total calcium due to less. bound calcium
false/psuedo hypocalcaemia
less calcium entering the blood
hypoparathyroidism - caused by surgical removal or autoimmune destruction, congenital problems or deficiency in magnesium
low vitamin D
things causing low vit D
deficient diet
malabsorption
cirhhosis
lack of sunlight
chronic renal fialure
things causing hypoparathyroidsim
magnesium deifiency (need this to make parathyroid hormone)
congenital problems eg. di george syndrome
autoimmune destruction
surgical removal
to much calcium leaving the blood
too much ionised calcium gets excreted
eg. in kidney failure because the nephron doesnt effectively reabsorb calcium
tissue injury - burns, rhabdomyalysis, tumour lysis syndrome
inflammatory. processes - acute pancreatitis
why does tissue injury cause hypocalcaemia
cells die and release. intracceullar phosphate into the blood
phosphate binds calcium and makes it insoluble in the blood
effectively decreasing calcium in blood
why does inflammation cause hypocalcaemia
eg. acute pancreatitis
free fatty acids binds ionised calcium which precipitates out
blood transfusions
blood transfusions can cause chelation
bind with calcium
forms complex calcium which is an inactive molecule
tetany
involuntary muscle contraction
happens in hypocalcaemia
chvostek’s sign
facial muscles twitch
troussaes sign
blood pressure cuff cause a relfex
other symptoms of hypocalcaemia
muscle cramps
abdominal pain
perioral tingling
seizures
diagnosis of calcaemia
ECG may show prolonged QT
hypocalcaemia in blood
parathyroid hormone labs
vit D, albumin, phosphorus, magnesium
factitious hypocalcaemia
asymptomatic. decrease in total calcium with a normal ionised calcium level
typically occurs due to low serum albumin
causes of hypoptroteinaemia
nephrotic syndrome, liver cirrhosis, severe malnutrition. malabsorbtion
function of parathyroid hormone
kidneys: incraesed calcium resorbtion, decreases phosphate resorbtion, increases vit D production
GI: increases calcitriol (vit D) synthesis which increases calcium absorbtion
bone: releases calcium and phosphate brom the bones
what does parathyroid hormone do in bone
increases expression of RANKL on osteoblasts
RANKL binds osteoclastic RNK receptor, which increases osteoclast activity, and results in increase bone resorption and calcium release
caalcitriol
A form of vitamin D that becomes hormonally active in the kidneys. Increases calcium absorption in the small bowel and renal tubules and increases calcium release from bones.
PTH secretion is stimulated by
decrease in serum Ca
hyperphosphataemia
mild hyppomagnesaemia
low calcitriol levels
PTH secretion is inhibited by
increase in serum Ca
marked hypomagnesaemia
action of calcitriol
GI: increases calcium and phosphate absorption
kidneys: increases calcium and phosphate resorption
bone: enhances bone mineralisation
calcitonin action
opposes the effects of PTH
inhibits bone resorption, decreasing serum calcium
what triggers calcitonin scretion
increase in serum Ca
what is calcitonin
A hormone produced by parafollicular cells (C cells) in the thyroid gland that inhibits osteoclast activity and renal reabsorption of calcium and phosphate to reduce serum calcium; it may be used therapeutically, e.g., in osteoporosis, or diagnostically, as it is often elevated in medullary thyroid cancer.
neurological manifestations of hypocalcaemia
tetany
parasthesis
spasms
chvostek sign: twitching of the facial muscles ellicited by tapping the facial nerve below and iin fron to fhte ear
trousaeu sign: spasm occuring after iinflation of te pressure cuff
seizure
cardiovascular manifestaations
congestiva heart failure (hypocalcaemia may lead to myocardial dysfunction)
hypotension
cardiac arrythmias (prolonged QT)
manifestations of chronic hypocalcaemia
physiatric manifestations
opthalmological manifestations
dental changes: altered morphology, dental enamel hypoplasia
growth plate abnomrlaities
diagnsotics
diagnostics should not delay treatment - acute symptomatic hypocalcaemia may be fatal
confimr hypocalcaemia - measure total and ionised calcium, check serum albumin
electrolyte abnormalities - BMP, serum phosphate and magnesium
serum intact PTH
serum intact PTH
low or normal: suggests hypoparathyroidism
high: suggests parathyroid function is preserved
why is a normal level of PTH in hypocalcaemia considered low
When serum calcium is low, the physiological response for the parathyroid gland is to secrete more PTH; therefore, a PTH value within normal laboratory range is considered inadequately low in hypocalcemia.
aetiologies of hypocalcaemia when PTH is high
hyperphosphataemia (high phosphate)
chronic kidney disease (high phosphate and high creatinine)
malaborbtion (low magnesium)
vit D deficeincy
findings on fundoscopy
papilloedema
mainstay of hypocalcaemia therapy
calcium supplimentation and treatment of underlying caause
for severe or symptomatic hypocaalcaemia
eg. with tetany, seizures, prologed QT interval
IV calcium supplimentation
continuous telemetry - IV calcium can trigger life threatening arrythmias in patients simultaneously receieving cardiac glycosides (digoxin or digitoxin)
loop diuretics
loop duiretics lose caclium
lose them in hypocalcaemia
CKI effect on calcium
hypocalcaemia
decreased renal hydroxylation of Vit D, reduced calcium absorbtion in the gut, decreased renal excretion of phosphate, hyperphosphhataemia, caclium phosphate precipitation in tissues
milk-alkali syndrome
A syndrome caused by excessive consumption of calcium and absorbable alkali (most commonly calcium carbonate). Presents with hypercalcemia, metabolic alkalosis, and acute kidney injury.
bisphosphonates
Bisphosphonates such as zoledronic acid reduce serum calcium levels by reducing osteoclast-mediated bone resorption and are considered first-line in malignancy-associated hypercalcemia.
