Hypocalcemia Flashcards
What is the definition of hypocalcemia?
Serum ionized calcium < normal range (total calcium <8.5 mg/dL or 2.1 mmol/L)
Hypocalcemia is characterized by low levels of calcium in the blood.
What percentage of total calcium is bound to albumin?
50% bound to albumin (40%) and anions (10%)
The remaining 50% is ionized (free calcium).
How do you correct for low albumin in total calcium measurement?
Corrected Ca = Measured Ca + [0.8 × (4.0 – Albumin)]
This formula adjusts calcium levels based on albumin concentration.
What is a common cause of low total calcium?
Hypoalbuminemia
Common in chronic illness, malnutrition, and cirrhosis.
What effect does alkalosis have on ionized calcium levels?
↓ ionized calcium
Alkalosis can occur due to conditions like hyperventilation.
What hormone increases renal calcium reabsorption?
PTH (Parathyroid Hormone)
It also increases bone resorption and calcitriol production.
What are the steps in vitamin D metabolism?
Diet/skin → Vitamin D → Liver (25-OH vitamin D) → Kidney (1,25(OH)2 vitamin D)
This process is crucial for calcium absorption.
Name a major cause of true hypocalcemia.
Postsurgical hypoparathyroidism
Other causes include vitamin D deficiency and autoimmune hypoparathyroidism.
What are some neuromuscular symptoms of hypocalcemia?
Tetany, Chvostek’s sign, Trousseau’s sign
Tetany can present as perioral numbness or carpopedal spasms.
What diagnostic tests are key for assessing hypocalcemia?
Corrected calcium, ionized calcium, PTH, phosphate, magnesium, vitamin D metabolites
Other tests may include creatinine, alkaline phosphatase, and urinary calcium/magnesium.
What radiographic finding may indicate hypocalcemia?
Basal ganglia calcifications
These may result in extrapyramidal signs.
True or False: Hypocalcemia can cause prolonged QT interval.
True
This can lead to arrhythmias and reduced cardiac contractility.
What syndrome is associated with autoimmune hypoparathyroidism?
Autoimmune Polyendocrinopathy Syndrome
It includes adrenal, thyroid, and gonadal failure.
What causes hypocalcemia in critical illness?
Hypoalbuminemia, hypomagnesemia, hyperphosphatemia
Other factors include citrate from transfusions and sepsis.
What is a common cause of hypocalcemia in cancer patients?
Tumor lysis syndrome (hyperphosphatemia)
Chemotherapy-induced hypomagnesemia is also a factor.
Name a drug that can induce hypocalcemia.
Anticonvulsants (e.g., phenytoin, phenobarbital)
Other drugs include aminoglycosides and bisphosphonates.
What does 25-OH vitamin D reflect?
Best reflects total body stores
1,25(OH)2 vitamin D is tightly regulated and less reflective of total stores.
What is the treatment for asymptomatic hypocalcemia?
Oral calcium + vitamin D
Symptomatic hypocalcemia requires IV calcium gluconate.
What is the hallmark of acute hypocalcemia?
Tetany
It signifies the severity of the condition.
What influences calcium levels in the body?
Multiple factors including organ systems, minerals, drugs
These can affect calcium absorption and metabolism.
What is the role of calcitriol in treatment?
Indicated in hypoparathyroidism and renal failure
It enhances calcium absorption in the intestines.
