Chemical Pathology/ Abnormal Electrolytes Flashcards

1
Q

What is hyperkalemia?

A

Serum potassium concentration >5 mEq/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What factors place chronic kidney disease patients at risk for hyperkalemia?

A

They have reduced potassium excretion by the kidneys, are prone to metabolic acidosis, and are more likely to be on medications (RAS antagonists) that have hyperkalemia as a possible side effect.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What type of renal tubular acidosis causes hyperkalemia?

A

Type IV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

In general, what are the causes of hyperkalemia?

A
  1. Decreased potassium excretion: renal failure, renal hypoperfusion (heart failure, volume depletion), aldosterone deficiency or insensitivity, medications (ACEIs, potassium-sparing diuretics, NSAIDs)
  2. Excessive release of intracellular potassium (acidosis, trauma, tumors, hemolysis, infection)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Hyperkalemia needs to be treated emergently when what factors are present?

A
  • Electrocardiogram changes (peaked T wave, loss of P wave, widened QRS)
  • rapid rise in potassium
  • potassium >6 mEq/L
  • renal failure
  • moderate to severe acidosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What medications are used to meet the following goals when treating emergent hyperkalemia?

–> Myocardial stabilization and prevention of fatal arrhythmia

A

Intravenous (IV) calcium gluconate or calcium chloride (does not lower potassium)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What medications are used to meet the following goals when treating emergent hyperkalemia?

–> Cellular uptake of potassium

A
  • IV insulin (glucose is added to prevent hypoglycemia)
  • IV sodium bicarbonate
  • nebulized beta-adrenergic (such as albuterol)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What medications are used to meet the following goals when treating emergent hyperkalemia?

—>Elimination of potassium

A

Furosemide or dialysis depending on the patient’s renal function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the medical treatment of nonemergent hyperkalemia?

A

Sodium polystyrene sulfonate (PO or PR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is hypokalemia?

A

Serum potassium concentration <3.5 mEq/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

In a stable patient, oral potassium chloride powder (diluted in liquid) may be used to treat most cases of hypokalemia . What is the approximate treatment dose for the following potassium level?

–>Less than 3.0 mEq/L

A

20 mEq PO every 2 hours for four doses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

In a stable patient, oral potassium chloride powder (diluted in liquid) may be used to treat most cases of hypokalemia . What is the approximate treatment dose for the following potassium level?

—> 3.0 to 3.5 mEq/L

A

20 mEq PO every 2 hours for two doses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are some common causes of hypokalemia?

A
  • vomiting (bulimia, infection, hyperemesis gravidarum)
  • diarrhea (infection, excessive laxative use)
  • thiazide and loop diuretics
  • hyperaldosteronism
  • type I and II renal tubular acidosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

In the acute setting of hyperglycemia requiring intense insulin therapy, why is it necessary to administer potassium along with insulin?

A

Insulin promotes potassium uptake into the cells and decreases serum potassium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why does vomiting cause hypokalemia even though gastric fluid has little potassium?

A

Loss of hydrogen ions (acidic gastric fluid) → metabolic alkalosis → alkalosis causes potassium shift into cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the symptoms of hypokalemia?

A
  • weakness
  • fatigue
  • muscle cramps
  • constipation
  • arrhythmias (severe cases)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is hypernatremia?

A

Serum sodium concentration >145 mEq/L. Total sodium may actually be normal or less than normal depending on the patient’s volume status.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the difference between hypovolemia (aka volume depletion) and dehydration?

A
  • Hypovolemia refers to the loss of extracellular fluid volume (water plus sodium and other solutes) with resulting decreased tissue perfusion.
  • Dehydration is a kind of hypovolemia but involves a disproportionately greater loss of free water to sodium, causing hypernatremia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the common causes of hypervolemic hypernatremia?

A
  • Hyperaldosteronism (eg, idiopathic adrenal hyperplasia, Conn syndrome)
  • Excess sodium administration by physicians (eg, hypertonic intravenous fluid, parenteral nutrition, bicarbonate administered as NaHCO 3 ) or caregivers (eg, errors preparing infant formula)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is diabetes insipidus (DI) and how does it cause hypernatremia?

A
  • Normally when the body senses dehydration, ADH (antidiuretic hormone) is released.
  • The kidneys then concentrate the urine in order to retain more water.
  • In DI, there is either no production of ADH (central ADH) or there is ADH insensitivity (nephrogenic DI).
  • Inappropriately dilute urine is produced causing an elevation of serum sodium.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the major complication of treating hypernatremia too rapidly, especially if the patient has chronic hypernatremia?

A

Cerebral edema

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is hyponatremia?

A

Serum sodium concentration <135. Total sodium may actually be normal or higher than normal depending on the patient’s volume status.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the mechanism of hyponatremia in patients with diabetic ketoacidosis (or hyperglycemia nonketotic coma)?

A

Even though glucose is not an electrolyte, it acts as a solute. So in a hyperglycemic state, serum osmolality is high. This draws fluid out of the intracellular compartment into the extracellular fluid. Serum sodium is diluted.

24
Q

Describe the mechanism behind hypervolemic hypoosmolar hyponatremia.

A

In an edematous state (ie, CHF) there is a misperceived volume status. Total body water is increased, but effective circulatory volume is low. In response, the renin-angiotensin-aldosterone system activates (increases sodium and water retention) and ADH is released (increases water retention). Their net effect causes hyponatremia and further exacerbates volume overload.

25
What is the most common iatrogenic cause of hypovolemic hypoosmolar hyponatremia, especially in the elderly?
Thiazide diuretics
26
What is the major complication of treating hyponatremia too rapidly, especially if the patient has chronic hyponatremia?
Central pontine myelinolysis
27
When a patient develops the syndrome of inappropriate antidiuretic hormone (SIADH), do the following increase or decrease? --\> Serum sodium
Decreases
28
When a patient develops the syndrome of inappropriate antidiuretic hormone (SIADH), do the following increase or decrease? --\> Serum osmolality
Decreases
29
When a patient develops the syndrome of inappropriate antidiuretic hormone (SIADH), do the following increase or decrease? --\> Urine osmolality
Increases
30
What is pseudohyponatremia?
Elevated triglycerides or proteins → a decreased proportion of the serum is composed of water (and the sodium in it) → if the lab measures sodium concentration in whole serum (vs. serum water), sodium appears to be too low
31
What is the normal range for serum calcium concentration?
9-10.5 mg/dL
32
Lab values for calcium may be falsely low in patients with hypoalbuminemia (lab measures protein-bound calcium, not ionized [free] calcium). What is the formula for corrected total calcium in the setting of hypoalbuminemia?
Corrected total calcium (mg/dL) = total calcium (mg/dL) + 0.8 × (4-serum albumin [g/dL])
33
Does hypocalcemia occur with low or high magnesium levels?
Low
34
Does hypocalcemia occur with low or high phosphorus levels?
High
35
What is the most common symptom of hypocalcemia?
Neuromuscular instability (nerve and muscle twitching, muscle cramping, tingling)
36
What is Chvostek sign?
It is a sign of tetany seen in hypocalcemia. Tapping the facial nerve where it emerges just anterior to the ear causes spasm of the ipsilateral facial muscles.
37
What is the ECG hallmark of hypocalcemia?
Prolonged QTc interval
38
What are the two most common causes of hypercalcemia ?
1. Hyperparathyroidism 2. Malignancy
39
What are the symptoms of hypercalemia?
Multisystem symptoms including “stones, bones, moans abdominal groans, and psychic overtones”: kidney stones, bone pain and osteoporosis, muscle weakness and fatigue, abdominal discomfort, mental dysfunction
40
In metabolic acidosis/alkalosis and respiratory acidosis/alkalosis, are hydrogen, bicarbonate, and carbon dioxide level high or low?
41
Of the above(shown in the attached table) acid-base disturbances, for which is hyperventilation the compensatory mechanism?
Metabolic acidosis
42
Of the above(in the attached table) acid-base disturbances, for which is hypoventilation the compensatory mechanism?
Metabolic alkalosis
43
How is anion gap calculated? g
Difference between measured cations and measured anions: [Na] − [Cl] − [HCO 3] = anion gap
44
What is the typical acid-base disturbance(s) in Diabetic ketoacidosis?
Increased anion gap metabolic acidosis
45
What is the typical acid-base disturbance(s) in Opiate overdose?
Respiratory acidosis
46
What is the typical acid-base disturbance(s) in Chronic renal failure?
Increased anion gap metabolic acidosis
47
What is the typical acid-base disturbance(s) in Vomiting?
Metabolic alkalosis
48
What is the typical acid-base disturbance(s) in Salicylate intoxication?
Respiratory alkalosis and increased anion gap metabolic acidosis
49
What is the typical acid-base disturbance(s) in Lactic acidosis?
Increased anion gap metabolic acidosis
50
What is the typical acid-base disturbance(s) in Pulmonary embolism?
Respiratory alkalosis
51
What is the typical acid-base disturbance(s) in Chronic renal failure?
Increased anion gap metabolic acidosis
52
What is the typical acid-base disturbance(s) in Neuromuscular disorder (ALS, multiple sclerosis, Guillain-Barré)?
Respiratory acidosis
53
What is the typical acid-base disturbance(s) in Prolonged diarrhea?
Normal anion gap metabolic acidosis
54
What is the typical acid-base disturbance(s) in Methanol, formaldehyde, or ethylene glycol intoxication?
Increased anion gap metabolic acidosis
55
What is the typical acid-base disturbance(s) in Renal tubular acidosis?
Normal anion gap metabolic acidosis