Hypocalcemia Flashcards
where is most calcium located in the body
bones (99%) blood 1%
there is a continous exchange of ca2+ between blood and bone tissue
which hormones regulate amount of calcium in circulation
Parathyroid- PTH (made in Parathyroid gland
Calcitriol- active vit D (made in kidney)
What happens if serum calcium level is low? (normal physiology)
PTH upregulated
promotes calcium release from bones whilst reducing calcium loss from urine
At the same time, it stimulates production of calcitriol, promoting calcium absorption in SI and increases reabsorption in kidneys
TOGETHER, they bring up ca2+ levels back to normal
What happens if serum calcium level in high? (normal physiology)
the reverse of what happens if calcium is low.
What is hypocalcaemia? (levels)
abnormally low levels, serum levels of <2.1mmol/L
Causes of hypocalcemia
-PTH deficiency (when the parathyroid glands aren’t functioning properly.
clinical manifestations of hypocalcemia (signs and symptoms)
Because hypocalcemia leads to enhanced excitation of the nervous system and muscle cells, the symptoms and signs primarily involve the neuromuscular and cardiovascular systems.
SYMPTOMS:
- paresthesias of the lips and extremities
- muscle cramps, and in
- severe cases, tetany, laryngospasm with wheezing, or life-threatening stridor.
SIGNSS:
- hypotension, Chvostek’s sign (tapping the facial nerve at the angle of the jaw [over the masseter muscle] leads to contraction of the facial muscles),
- Trousseau’s sign (occlusion of the brachial artery with a blood pressure cuff leads to carpal spasm).
- Cataracts and calcifications of the basal ganglia can occur if hypocalcemia is long-standing.
- The electrocardiogram (EKG) may show a prolonged QT interval or atrioventricular (AV) block.
Causes of Hypocalcemia. There are many causes of hypocalcemia; the mnemonic “HIPOCAL” will help you remember the most important ones.
MNEMONIC: Causes of Hypocalcemia (“HIPOCAL”)
Hypoparathyroidism/Hungry bones
Infection
Pancreatitis/Packed red blood cells
Overload states
Chronic renal failure
Absorption abnormalities
Loop diuretics
HOW DOES Hypoparathyroidism/Hungry bones cause hypocalcaemia?
The two major causes of hypoparathyroidism are neck surgeries such as thyroidectomy with damage to the parathyroid glands and autoimmune parathyroid destruction. Rare causes include DiGeorge’s syndrome and parathyroid injury as a result of infection or irradiation. Functional hypoparathyroidism (i.e., decreased secretion of parathyroid hormone [PTH]) may result from magnesium deficiency.
With hypoparathyroidism, low production of PTH causes an imbalance: the calcium levels in your blood decrease (hypocalcemia) and serum phosphorus increases (hyperphosphatatemia). Simply put, low levels of PTH disrupt the calcium/phosphorus balance.
how does infection cause hypocalcaemia?
Infection. Up to 20% of patients with gram-negative sepsis can be hypocalcemic due to abnormalities in the parathyroid–vitamin D axis. This hypocalcemia may cause hypotension, which (if due to hypocalcemia) is often responsive to calcium replacement
how does Pancreatitis cause hypocalcaemia?
serum calcium less than 8 mg/dL is one of Ranson’s criteria for severe pancreatitis. Calcium levels thus correlate with the severity of acute pancreatitis.
how does Packed red blood cells cause hypocalcaemia?
how does Massive blood transfusions can lead to metabolic alkalosis due to breakdown of citrate in the stored blood to bicarbonate. In addition, serum calcium may form complexes with citrate to induce hypocalcemia.e
how does Chronic renal failure cause hypocalcaemia?
. Chronic renal failure. Vitamin D is metabolized in the normal kidney to 1,25-dihydroxyvitamin D, which promotes intestinal calcium absorption. In patients with renal failure, intestinal calcium absorption decreases and patients become hypocalcemic.
how does Absorption abnormalities cause hypocalcaemia?
Patients with malabsorption of calcium, magnesium, or vitamin D will often have hypocalcemia.
how does loop diuretics cause hypocalcaemia?
Loop diuretics. Unlike thiazide diuretics (which can cause hypercalcemia), furosemide and other loop diuretics lead to enhanced renal excretion of calcium and can cause hypocalcemia.
