P2.5- CALCIUM TO ANION GAP Flashcards
1
Q
A
2
Q
What percentage of calcium is in bones?
A
0.99
3
Q
What percentage of calcium is in blood and extracellular fluid?
A
0.01
4
Q
Where is calcium absorbed in the intestine?
A
Primarily in the duodenum (acidic pH)
5
Q
What factors enhance calcium absorption?
A
Vitamin D, acidic pH, lactose, and PTH
6
Q
What factors inhibit calcium absorption?
A
High phosphate intake, oxalates, phytates, corticosteroids
7
Q
How is calcium distributed in the blood?
A
45% free (ionized), 40% bound to proteins (mostly albumin), 15% bound to anions (bicarbonate, citrate, lactate)
8
Q
What are the major functions of calcium?
A
Blood coagulation, enzyme activation, muscle contraction, nerve function, bone strength
9
Q
Which hormones regulate calcium levels?
A
Parathyroid hormone (PTH), Vitamin D, Calcitonin
10
Q
How does PTH affect calcium homeostasis?
A
Increases serum calcium by promoting bone resorption, renal reabsorption, and Vitamin D activation
11
Q
How does calcitonin regulate calcium?
A
Lowers calcium by inhibiting osteoclasts and increasing renal excretion
12
Q
What is the main cause of hypocalcemia?
A
Primary hypoparathyroidism
13
Q
What are other causes of hypocalcemia?
A
Vitamin D deficiency, chronic kidney disease, pancreatitis, hypomagnesemia
14
Q
What are neuromuscular symptoms of hypocalcemia?
A
Tetany, paresthesia, muscle cramps, seizures
15
Q
What cardiovascular abnormality is seen in hypocalcemia?
A
Prolonged QT interval
16
Q
What is considered severe hypocalcemia?
A
Total Ca2+ < 1.88 mmol/L
17
Q
How is hypocalcemia treated?
A
Oral/IV calcium, Vitamin D supplementation, Magnesium correction if deficient
18
Q
What is the main cause of hypercalcemia?
A
Primary hyperparathyroidism
19
Q
How do malignancies cause hypercalcemia?
A
Tumors release PTH-related peptides (PTHrP), stimulating calcium release from bones
20
Q
What are symptoms of hypercalcemia?
A
Fatigue, kidney stones, constipation, depression, polyuria, muscle weakness
21
Q
What is the treatment for hypercalcemia?
A
Hydration, bisphosphonates, calcitonin, corticosteroids
22
Q
What percentage of phosphate is found in bones and teeth?
A
0.85
23
Q
What percentage of phosphate is in soft tissues?
A
0.15
24
Q
How does phosphate exist in plasma?
A
As inorganic phosphate (HPO4²⁻, H2PO4⁻)
25
What are the functions of phosphate?
Energy metabolism (ATP), bone mineralization, buffer system
26
Which hormones regulate phosphate?
PTH (decreases phosphate), Vitamin D (increases phosphate absorption)
27
What is the main cause of hypophosphatemia?
Vitamin D deficiency, hyperparathyroidism, chronic alcoholism
28
What are symptoms of hypophosphatemia?
Muscle weakness, confusion, bone pain, hemolysis
29
What is the main cause of hyperphosphatemia?
Renal failure, hypoparathyroidism, excessive intake
30
What are symptoms of hyperphosphatemia?
Calcification in soft tissues, muscle cramps, tetany
31
What percentage of magnesium is found in bones?
0.53
32
What percentage of magnesium is in soft tissues?
0.46
33
What percentage of magnesium is in serum?
<1%
34
How is magnesium absorbed?
In the small intestine, regulated by dietary intake
35
What hormones regulate magnesium?
PTH increases magnesium absorption
36
What are the primary functions of magnesium?
Cofactor for 300+ enzymes, neuromuscular function, ATP metabolism
37
What is the primary cause of hypomagnesemia?
Chronic alcoholism, malabsorption, prolonged diarrhea
38
What are symptoms of hypomagnesemia?
Neuromuscular hyperexcitability, tetany, seizures, arrhythmias
39
What cardiovascular abnormality is associated with hypomagnesemia?
Prolonged QT interval, torsades de pointes
40
What is the primary cause of hypermagnesemia?
Renal failure, excessive intake (antacids, laxatives)
41
What are symptoms of hypermagnesemia?
Lethargy, hypotension, respiratory depression
42
What is the anion gap (AG) used for?
Evaluating metabolic acidosis and unmeasured anions in the blood
43
What is the formula for anion gap using sodium, chloride, and bicarbonate?
AG = Na⁺ - (Cl⁻ + HCO₃⁻)
44
What is the normal range for anion gap?
8-16 mmol/L (without potassium), 10-20 mmol/L (with potassium)
45
What conditions cause an increased anion gap?
Lactic acidosis, ketoacidosis, renal failure, methanol or ethylene glycol poisoning
46
What conditions cause a decreased anion gap?
Hypoalbuminemia, multiple myeloma, lithium toxicity, bromide intoxication
47
What is the primary laboratory method for measuring electrolytes?
Ion-Selective Electrode (ISE)
48
What sample is required for accurate anion gap calculation?
Serum or heparinized plasma
49
Why is the anion gap important in metabolic acidosis?
Helps differentiate between high-anion gap and normal-anion gap acidosis
50
What are causes of normal-anion gap metabolic acidosis?
Diarrhea, renal tubular acidosis, Addison’s disease
51
What are causes of high-anion gap metabolic acidosis?
Lactic acidosis, ketoacidosis, renal failure, toxins (methanol, ethylene glycol)
52
How does albumin affect anion gap?
Low albumin decreases anion gap
53
How do toxins like methanol and ethylene glycol affect anion gap?
Increase anion gap due to unmeasured organic acids
54
What condition causes both high anion gap and high osmolal gap?
Toxic alcohol poisoning (methanol, ethylene glycol)
55
How does renal failure affect anion gap?
Increases anion gap due to retention of unmeasured anions (sulfates, phosphates)
56
What formula adjusts anion gap for albumin levels?
Adjusted AG = Measured AG + 2.5 × (4.0 - Albumin)
57
What are key laboratory findings in diabetic ketoacidosis (DKA)?
High anion gap, ketonemia, hyperglycemia, metabolic acidosis
58
What are key laboratory findings in lactic acidosis?
High anion gap, low bicarbonate, elevated lactate
59
How does hypoalbuminemia falsely lower anion gap?
Albumin is a negatively charged protein, so lower albumin reduces AG
60
What is the clinical significance of a negative anion gap?
Can indicate lab errors, lithium toxicity, or bromide intoxication
61
What is the major cause of falsely low anion gap?
Hypoalbuminemia
62
How is anion gap useful in diagnosing metabolic disorders?
Helps differentiate between metabolic acidosis causes and identify unmeasured anions
63
What is the primary form of calcium in circulation?
Ionized (free) calcium
64
What is corrected calcium and how is it calculated?
Accounts for albumin levels: Corrected Ca = Measured Ca + 0.8 × (4.0 - Albumin)
65
Why is ionized calcium more clinically relevant than total calcium?
Ionized calcium is the biologically active form
66
What is the reference range for ionized calcium?
1.15-1.35 mmol/L
67
What is the effect of alkalosis on ionized calcium levels?
Decreases ionized calcium
68
What is the effect of acidosis on ionized calcium levels?
Increases ionized calcium
69
How does chronic kidney disease affect calcium?
Leads to hypocalcemia due to phosphate retention and reduced Vitamin D activation
70
What are the effects of hypercalcemia on ECG?
Shortened QT interval, arrhythmias
71
What are the effects of hypocalcemia on ECG?
Prolonged QT interval, risk of arrhythmias
72
How is phosphate regulated in the kidneys?
Reabsorbed in the proximal tubule; regulated by PTH
73
What are dietary sources of phosphate?
Meat, dairy, nuts, grains
74
What is the normal serum phosphate range?
2.5-4.5 mg/dL
75
What condition causes both hypercalcemia and hypophosphatemia?
Primary hyperparathyroidism
76
What is tumor lysis syndrome and how does it affect phosphate?
Massive cell lysis releases phosphate, leading to hyperphosphatemia
77
What role does phosphate play in oxygen delivery?
2,3-BPG (2,3-bisphosphoglycerate) regulates hemoglobin oxygen affinity
78
How does magnesium affect potassium balance?
Hypomagnesemia causes potassium wasting
79
What is the normal serum magnesium range?
0.63-1.0 mmol/L
80
What is the relationship between magnesium and calcium?
Magnesium is required for PTH secretion; low Mg can cause hypocalcemia
81
What are the neuromuscular symptoms of magnesium imbalance?
Hyperreflexia in hypomagnesemia, hyporeflexia in hypermagnesemia
82
What is the effect of hypomagnesemia on the heart?
Increases risk of arrhythmias, torsades de pointes
83
What is the effect of hypermagnesemia on the heart?
Bradycardia, heart block, cardiac arrest
84
What are the primary cations in plasma?
Sodium (Na⁺) and Potassium (K⁺)
85
What are the primary anions in plasma?
Chloride (Cl⁻) and Bicarbonate (HCO₃⁻)
86
What is the primary cause of metabolic acidosis with a normal anion gap?
Diarrhea (loss of bicarbonate)
87
What metabolic disorder is associated with a high anion gap?
Diabetic ketoacidosis (DKA)
88
Why does lactic acidosis cause a high anion gap?
Lactate is an unmeasured anion
89
What effect does renal failure have on anion gap?
Increases anion gap due to retention of sulfate, phosphate, and organic acids
90
What formula adjusts anion gap for albumin levels?
Adjusted AG = Measured AG + 2.5 × (4.0 - Albumin)
91
What is the osmolal gap and how is it calculated?
Difference between measured and calculated osmolality; Osmolal gap = Measured osmolality - (2[Na] + Glucose/18 + BUN/2.8)
92
What conditions cause an elevated osmolal gap?
Methanol poisoning, ethylene glycol poisoning, DKA
93
What electrolyte imbalance is associated with Chvostek's and Trousseau's signs?
Hypocalcemia
94
What electrolyte imbalance is associated with renal osteodystrophy?
Hypocalcemia, hyperphosphatemia
95
How does rhabdomyolysis affect electrolytes?
Hyperkalemia, hyperphosphatemia, hypocalcemia due to muscle breakdown
96
What is the most common cause of hospitalization due to electrolyte imbalance?
Hyponatremia
97
How does Addison’s disease affect electrolytes?
Hyponatremia, hyperkalemia, metabolic acidosis
98
How does Cushing’s syndrome affect electrolytes?
Hypernatremia, hypokalemia, metabolic alkalosis
99
What electrolyte imbalances are common in tumor lysis syndrome?
Hyperkalemia, hyperphosphatemia, hypocalcemia
100
What is the relationship between chloride and bicarbonate in metabolic acidosis?
Inverse relationship; high chloride = normal anion gap acidosis
101
Why is lactate measured in critically ill patients?
Lactate levels indicate tissue hypoxia and sepsis severity
102
What is the preferred specimen for ionized calcium measurement?
Anaerobically collected whole blood
103
What laboratory test confirms metabolic alkalosis?
Elevated bicarbonate (HCO₃⁻)
104
What is the anion gap used to differentiate?
Causes of metabolic acidosis (high vs. normal anion gap)
105
What is the role of aldosterone in electrolyte balance?
Increases sodium retention and potassium excretion
106
What is the effect of hypoaldosteronism on electrolytes?
Hyponatremia, hyperkalemia, metabolic acidosis
107
What condition is characterized by low sodium and high potassium?
Addison’s disease
108
What condition is characterized by high sodium and low potassium?
Cushing’s syndrome
109
What is the effect of loop diuretics on electrolytes?
Hypokalemia, hypocalcemia, hypomagnesemia
110
What is the effect of thiazide diuretics on electrolytes?
Hypokalemia, hypercalcemia, hyponatremia
111
What acid-base disorder is seen in aspirin (salicylate) overdose?
Mixed respiratory alkalosis and metabolic acidosis
112
Why does diabetic ketoacidosis cause high anion gap?
Accumulation of ketone acids (β-hydroxybutyrate, acetoacetate)
113
What condition presents with severe anion gap metabolic acidosis and osmolal gap?
Methanol or ethylene glycol poisoning
114
What are signs of metabolic alkalosis on lab tests?
High bicarbonate, low chloride, high pH
115
What compensatory mechanism occurs in metabolic acidosis?
Hyperventilation (respiratory compensation)
116
What compensatory mechanism occurs in metabolic alkalosis?
Hypoventilation (respiratory compensation)
