Calcium Flashcards
Calcium
Ingested and absorbed in the blood and excess secreted in faeces. Extra cellular excreted in kidneys. 99% of calcium in body is bound to phosphorus to form minerals in bone/teeth, the other 1% is in extra cellular fluid and about half is free and half bound to proteins or other ions
Ionised calcium is responsible for stabilising cell membrane, regulating muscle contraction/relaxation, maintaining cardiac function and blood clotting
Calcium regulated by parathyroid, calcitonin, calcitriol (Vit D)
If calcium levels fall PTH mobilises calcium stores, increases GI/kidney reabsorption of calcium. Vit D released from kidneys helps stimulate calcium release from bone, absorption in intestines and reabsorption in kidneys.
Calcitonin (released by thyroid in response to low calcium) has opposite effect of PTH
If hydrogen ions concentration falls and PH rises (alkalosis), more calcium is bound to protein (levels don’t change but less ionised calcium available)
Acidosis- calcium is released from protein making more available
Calcium levels fluctuate with protein levels. If albumin falls calcium declines
Hypocalcaemia
Decreases stores or low levels of extra cellular calcium with normal amount stored in bone
Risk factors- parathyroidectomy, older adults (less active, less sun, less dairy, drugs), lactose intolerance (decreases intake of calcium), alcoholism (interferes with absorption and regulation), bariatric surgery (decreased intake and malabsorption)
S&S -neuro- tetany (Tonic muscle spasm), parasthesia, positive chvosteks sign (contraction of facial muscles when touching facial nerve), seizures, anxiety, trousseaus sign (carpal spasm on doing BP)
Cardio- decreases CO, hypotension, arrhythmias,
GI- abdo cramping, diarrhoea
Resp- airway obstruction, laryngospasm
Diagnose- serum calcium/magnesium/albumin/phosphate, PTH, ECG
Treat- oral/IV calcium
Hypercalcaemia
Increased reabsorption of calcium from bone hyperparathyroidism and malignancies (from bone destruction or the tumour releasing hormones)
Increase intestinal absorption from excess Vit D, calcium containing antacids, excessive milk, diuretics, renal failure
Decreases neuromuscular excitability (muscle weakness/depressed muscle reflex), strengthens cardiac contraction and reduces HR, effects conduction system-heart block, ability of kidneys to excrete calcium is impaired leading to excess sodium and water loss/thirst
S&S- muscle weakness, fatigue
GI- anorexia, nausea/vomiting, constipation, ulcer (increased gastric secretion)
CNS- confusion, lethargy, personality changes, coma
Cardio- arrhythmias, ECG changes, HT
Renal- polyuria, thirst
Treat- IV fluids (isotonic), and loop diuretics, calcitonin, bisphophonates, sodium phosphate/ potassium phosphate (rapid reversal)
