Acid/Base and Electrolytes

Question 1

Causes of respiratory alkalosis

Answer 1

1. Systemic (sepsis, ASA, liver failure, endocrine, CHF)
2. Central (respiratory center, ischemia, CNS tumor, hyperventilation)
3. Lungs (PNA, asthma, PE)

Question 2

Causes of respiratory acidosis

Answer 2

1. Chest cavity (flail chest, PTX, effusion)
2. Central (sedation, CVA, narcotics)
3. Lungs (PNA, asthma, FB, COPD)

Question 3

Steps in acid-base diagnosis

Answer 3

1. Obtain ABG and electrolytes
2. Compare HCO3 on ABG and electrolytes to verify accuracy
3. Calculate anion gap
4. Know 4 major causes of high AG acidosis
5. Know 2 causes of hyperchloremic or nongap acidosis

Question 4

4 major causes of high AG acidosis

Answer 4

1. ketoacidosis
2. lactic acid acidosis
3. renal failure
4. toxins

Question 5

2 causes of hyperchloremic or nongap acidosis

Answer 5

1. bicarb loss from GI tract

2. renal tubular acidosis

Question 6

Conditions with increased serum osmolality

Answer 6

• Marked hyperglycemia
• DI
• Hypernatremia (iatrogenic)

Question 7

Conditions with decreased serum osmolality

Answer 7

• Hyponatremia w/euvolemia

- Hyponatremia w/hypervolemia

Question 8

Nephrotic syndrome is characterized by:

Answer 8

Proteinuria with low serum albumin

Question 9

How to calculate anion gap

Answer 9

AG = Na - (Cl + HCO3)

Question 10

What is considered severe hyponatremia and how does it present?

Answer 10

• Na less than 120 mEq/L

- Mental status changes, seizure, coma

Question 11

How is sodium corrected with hyperglycemia?

Answer 11

Sodium correction factor of 2.4 per 100 glucose

Question 12

Treatment of hypernatremia that developed over hours?

Answer 12

Rapid correction (1 mEq/L/h)

Question 13

Treatment of hypernatremia that developed at an unknown rate?

Answer 13

No greater than 0.5 mEq/L/h to avoid cerebral edema

Question 14

What is hypokalemia usually associated with?

Answer 14

Diuretic therapy

Question 15

How should hypokalemia be treated?

Answer 15

Replace potassium ORALLY whenever possible

Question 16

Describe hyperkalemia

Answer 16

• True emergency

- Suspect in patients with renal failure, DM, or those taking K supplements

Question 17

Describe hypocalcemia

Answer 17

• Occurs in critically ill pts
• Rarely life threatening on its own
• Usually asymp until severe
• Often a/w disorders of Mg and P

Question 18

How to treat hypocalcemia

Answer 18

• Check serum P before replacing Ca IV

- Use caution in giving IV Ca to digoxin pts

Question 19

What causes hypercalcemia?

Answer 19

Usually caused by malignancy or hyperPTH

Question 20

How to treat hypercalcemia?

Answer 20

• Volume replacement/expansion

- Promotes Ca excretion, inhibits osteoclasts, decreases Ca absorption

Question 21

Describe hypophosphatemia

Answer 21

• Often asymp unless severe

- Commonly occurs along w/disorders of Ca, Mg, K

Question 22

Treatment of hypophosphatemia

Answer 22

ORAL replacement preferred and should be initiated even in asymp pts

Question 23

Describe hyperphosphatemia

Answer 23

• Often a/w renal dz and hypoPTH

- May be a manifestation of tumor lysis or rhabdo

Question 24

Treatment of hyperphosphatemia

Answer 24

Volume expansion and using insulin/glucose to shift phosphate into cells

Question 25

Describe hypomagnesemia

Answer 25

• A/w disorders of Ca, K, P
• Common in malnourished pts and those with renal dz
• Oral replacement preferred

Question 26

Describe hypermagnesemia

Answer 26

• Symptoms rare until Mg levels severely high

- Usually 2/2 renal failure or excess Mg intake

Question 27

Treatment of hypermagnesemia

Answer 27

Ca gluconate to reverse respiratory paralysis until forced diuresis or dialysis lowers serum Mg