Chapter 24: Plasma Calcium, hypercalcemia, and hypocalcemia

Question 1

Plasma Calcium

Answer 1

• present in three forms (1. bound to plasma proteins such as albumin 2. bound to small organic ions such as citrate 3. unbound)
• only free ionized calcium is physiologically active

Question 2

Total Serum Calcium

Answer 2

• measures all of the calcium (bound + unbound)
• Normal range in adults = 9 to 11 mg/dl or 4.5-5.5 mEq/L
• unless a calcium value specifies ionized calcium, it is total calcium

Question 3

Ionized Calcium

Answer 3

• measures only the unbound ionized form of calcium
• the normal range in adults = 4 to 5 mg/dl
• clinically significant calcium imbalances are caused by alteration in the plasma concentration of unbound calcium

Question 4

Hypocalcemia

Answer 4

• serum calcium concentration drops below the lower limit of normal
• fraction of unbound ionized calcium in the blood lowers by more calcium binding to plasma proteins or other organic ions
• the total serum calcium may be normal
• ionized hypocalcemia is present and may cause signs and symptoms

Question 5

Etiology of Hypocalcemia

Answer 5

• Decreased calcium intake or absorption (poor diet, lack of vitamin D, excessive phytates or oxalates)
• decreased physiologic availability of calcium (excessive phosphate, hypoparathyroidism)
• increased calcium excretion (steatorrhea and pacreatitis)

Question 6

Clinical Manifestations of Hypocalcemia

Answer 6

• Decreases the threshold potential causing hyperexcitability of neuromuscular cells resutling in:
• positive trousseau sign (patient’s hand looks wide and rigid)
• Positive Chvostek sign (tap on facial nerve and face starts to spasm, not reliable on infants)
• Parasthesias
• muscle twitching and cramping
• hyperactive reflexes
• carpal spasm
• pedal spasm
• tetany
• laryngospasm
• seizures
• cardiac dysrhythmias

Question 7

Treatment of Hypocalcemia

Answer 7

• give replacement IV or oraly

- vitamin D

Question 8

Hypercalcemia

Answer 8

• occurs when the serum calcium concentration rises above the upper limit of normal
• indicates an elevation of the calcium concentration of extracellular fluid

Question 9

Etiology of Hypercalcemia

Answer 9

• Increased calcium intake or absorption (milk alkali syndrome, vitamin D overdose)
• Shift of calcium from bone to extracellular fluid (hyperparathyroidism, immobilization, bone tumors)
• Decreased calcium excretion (thiazide diuretics)

Question 10

Clinical manifestations of Hypercalcemia

Answer 10

• causes decreased neuromuscular excitability caused by the elevation of the threshold potential of ecitabel cells which causes
• muscle weakenss
• diminished reflexes
• cardiac dysrhythmias
• anorexia, nausea, emesis
• fatigue
• polyuria
• constipation
• Headache, confusion, lethargy, personality change
• Renal calculi
• Pathological fractures