Acid-Base Disorders & ABG's (Exam II)

Question 1

What is the excessive production of H⁺ in relation to hydroxyl ions?

Answer 1

Acidemia (Acidosis)

Question 2

Excessive production of OH- in relation to H⁺ is known as ________.

Answer 2

Alkalemia (alkalosis)

Question 3

What ion is used to measure pH?

Answer 3

H⁺

Question 4

Where does HCO₃⁻ enter and leave the body?

Answer 4

Proximal tubule of the kidneys

Question 5

Where are H⁺ reabsorbed in the kidney?

Answer 5

Distal tubule and collecting duct

Question 6

What is the name of the acid-base balance equation?

Answer 6

Henderson-Hasselbalch Equation

Question 7

If both PaCO₂ and HCO₃⁻ increase at the same time, then you have what?

Answer 7

Primary disorder with secondary compensation.

Question 8

If PaCO₂ decreases and HCO₃⁻ increases at the same time, then you have what?

Answer 8

A mixed acid/base disorder

Question 9

If the PaO₂ is is 60 at room air, what would the PaO₂ be with an FiO₂ of 80%?

Answer 9

PaO₂ ≈ 240 mmHg at an FiO₂ of 80%

Question 10

A patients ABG is drawn and shows the PaO₂ to be 120 mmHg on an FiO₂ of 60%. What would the CRNA anticipate the patient’s PaO₂ to be on room air?

Answer 10

PaO₂ ≈ 40 mmHg on room air

Question 11

What are the cardiovascular consequences of acidosis?

Answer 11

• ↓ contractility
• ↓ arterial BP
• Re-entry dysrhythmias
• Lower threshold for v-fib
• Less responsive to catecholamines.

Question 12

What cardiovascular consequence occurs at a pH of 7.2?

Answer 12

Impaired contractility

Question 13

What cardiovascular consequence occurs at a pH of 7.2?

Answer 13

Impaired contractility

Question 14

What cardiovascular consequence occurs at a pH of 7.1?

Answer 14

Decreased responsiveness to catecholamines

Question 15

What are the consequences of acidosis on the nervous system?

Answer 15

Obtundation & Coma

Question 16

What are the consequences of acidosis on the pulmonary system?

Answer 16

• Hyperventilation
• Dyspnea
• Respiratory muscle fatigue

Question 17

What are the consequences of acidosis on body metabolism?

Answer 17

• Hyperkalemia
• Insulin resistance
• Anaerobic glycolysis inhibition

Question 18

How is respiratory acidosis defined?

Answer 18

• An acute decrease in alveolar ventilation results in increased PaCO₂.
• pH < 7.35
• Essentially respiratory failure

Question 19

What are the three umbrella causes of respiratory acidosis?

Answer 19

• Central ventilation control
• Peripheral ventilation control
• VQ mismatch

Question 20

What are the more granular causes of respiratory acidosis?

Answer 20

• Drug-induced resp depression
• Permissive hypercapnia
• Upper airway obstruction
• Status asthmaticus
• Restriction of ventilation (flail chest, rib fracture)
• Neuromuscular dysfunction
• MH
• Pneumonia/ edema / pleural effusion

Question 21

In acute hypercarbia, how much will plasma HCO₃⁻ increase for every 10 mmHg increase in PaCO₂ ?

Answer 21

↑ HCO₃⁻ by 1 mmol/L (1mEq/L) for every 10 mmHg of PaCO₂

Question 22

An acutely hypercarbic patients PaCO₂ is noted to be 70 mmHg. What would the CRNA anticipate the HCO₃⁻ to be?

Answer 22

3 mmol/L ( or 3 mEq/L) higher than normal

Question 23

How much will plasma HCO₃⁻ compensate in the chronically hypercarbic patient?

Answer 23

3 mEq/L for every 10 mmHg in the PaCO₂

Question 24

A chronically hypercarbic patient has a PaCO₂ of 60mmHg. What would the CRNA anticipate the HCO₃⁻ to be?

Answer 24

6 mEq/L higher than normal ( normal range is 22 - 26 so 28 - 32 expected)

Question 25

What is the treatment for a hypercarbic, respiratory acidotic patient?

Answer 25

Mechanical Ventilation **If hypercarbia is excessive and CO₂ narcosis is present.**

Question 26

What can occur if a COPD patient's chronic hypercarbia is corrected?

Answer 26

**Seizures** *Excessive HCO₃⁻ in chronically hypercarbic patients causes CNS irritability.*

Question 27

What is the response of the ventilatory center to metabolic acidosis?

Answer 27

Hyperventilation (blow off CO₂ and thus acid)

Question 28

Can metabolic acidosis be corrected through mechanical ventilation?

Answer 28

Nope

Question 29

What shift in the oxyhemoglobin dissociation curve occurs with metabolic acidosis?

Answer 29

Right shift

Question 30

What cellular alterations occur with metabolic acidosis?

Answer 30

- ↑ ionized Ca⁺⁺ - Dysfunctional transcellular ion pumps

Question 31

How can expected PaCO₂ be calculated in an acute metabolic acidosis patient?

Answer 31

PaCO₂ ≈ (1.5 x HCO₃⁻ ) + 8

Question 32

What would the expected PaCO₂ be an acute metabolic acidosis patient with an HCO₃⁻ of 14?

Answer 32

PaCO₂ ≈ (1.5 x 14) + 8 PaCO₂ ≈ 29 mmHg *If PaCO₂ is greater than 29 then compensation is inadequate*.

Question 33

For every 1 mEq/L drop in Base Excess, PaCO₂ should fall by _______.

Answer 33

1.2 mmHg

Question 34

If Base Deficit is -2 then the PaCO₂ should be....

Answer 34

38 mmHg *If the PaCO₂ is higher than this, then compensation is inadequate.*

Question 35

A patient's base deficit is -11, what would on expect the compensatory PaCO₂ to be?

Answer 35

11 x 1.2 = 13.2 PaCO₂ ≈ 26.8 If higher then compensation is inadequate.

Question 36

What are the causes of hyperchloremic metabolic acidosis?

Answer 36

- Saline - Diarrhea - Early Renal Failure

Question 37

What type of anion gap is produced in hyperchloremic metabolic acidosis?

Answer 37

Normal Anion Gap HCO₃⁻ loss is countered by net gain of Cl⁻

Question 38

What are some causes of a high anion gap?

Answer 38

- Lactic acidosis - Ketoacidosis - Renal failure - Poisonings

Question 39

More HCO₃⁻ is available with high anion gap disorders. T/F?

Answer 39

False. Excessive acid combines with HCO₃⁻ → carbonic acid → less available HCO₃⁻

Question 40

How is a simple anion gap calculated?

Answer 40

Na⁺ - ( Cl⁻ + HCO₃⁻ )

Question 41

What should a normal anion gap be?

Answer 41

Na⁺ - ( Cl⁻ + HCO₃⁻ ) 140 - (102 - 24) ≈ **12 - 14 mEq/L**

Question 42

How is a conventional anion gap calculated?

Answer 42

(Na⁺ + K⁺) - (Cl⁻ + HCO₃⁻)

Question 43

What should a conventional anion gap be?

Answer 43

(Na⁺ + K⁺) - (Cl⁻ + HCO₃⁻) 140 + 4 - (106 - 24) ≈ 14 - 18 mEq/L

Question 44

What two conditions will cause an underestimation of the extent of the anion gap?

Answer 44

- Hypoalbuminemia - Hypophosphatemia

Question 45

What is the treatment for a discordant anion gap?

Answer 45

Treat the underlying cause! - Ketoacidosis = insulin & fluids - Lactic acidosis = improve tissue perfusion - Renal failure = dialysis

Question 46

When is Na⁺HCO₃⁻ (Sodium Bicarbonate injection) indicated?

Answer 46

- pH < 7.1 - HCO₃⁻ < 10 mEq/L

Question 47

What are the two reasons for Na⁺HCO₃⁻ treatment controversiality?

Answer 47

- HCO₃⁻ + H⁺ → CO₂ = more acidosis - With chronic acidosis, acute pH changes negates curve shift to the right and results in tissue hypoxia

Question 48

How is a correction dose of Na⁺HCO₃⁻ calculated?

Answer 48

Dose (mmol) = 0.3 x base deficit x kg

Question 49

The CRNA wishes to calculate a correction dose of Na⁺HCO₃⁻ for an 82 kg patient with a base deficit of -4. What would the dose of Na⁺HCO₃⁻ be?

Answer 49

Dose = 0.3 (-4) x 82kg Dose = 98.4 mmol of Na⁺HCO₃⁻

Question 50

When giving a correction dose of Na⁺HCO₃⁻, how much should be given initially?

Answer 50

½ the correction dose.

Question 51

What is respiratory alkalosis?

Answer 51

- Acute increase in alveolar ventilation - ↓ PaCO₂ - pH > 7.45

Question 52

What are four common causes of respiratory alkalosis?

Answer 52

- Pregnancy - High altitude - Iatrogenic Hyperventilation - Salicylate overdose

Question 53

What are common symptoms of respiratory alkalosis?

Answer 53

- Lightheadedness - Visual disturbances - Dizziness *all of these from vasoconstriction*.

Question 54

What occurs with calcium levels during respiratory alkalosis?

Answer 54

Ca⁺⁺ binds to albumin more easily → **hypocalcemia**

Question 55

What are the signs/symptoms of hypocalcemia?

Answer 55

- Paresthesias - Muscle spasms - Cramps - Tetany - Mouth numbness - Seizures - **Trousseau's Sign** - **Chvostek's Sign**

Question 56

What is Trousseau's sign?

Answer 56

Wrist flexion that occurs with BP cuff inflated.

Question 57

What is Chvostek's sign?

Answer 57

Tapping of Facial Nerve (CN VII) resulting in involuntary facial contraction.

Question 58

What are the branches of the facial nerve?

Answer 58

**To Zanzibar By Motor Car**. - **T**emporal - **Z**ygomatic - **B**uccal - **M**arginal mandibular - **C**ervical

Question 59

How is metabolic alkalosis defined?

Answer 59

- Marked increase in HCO₃⁻ usually with compensatory increase in CO₂ - Loss of H⁺ or gain of HCO₃⁻ - Renal or extrarenal

Question 60

Is metabolic alkalosis a disorder of volume overload or volume depletion?

Answer 60

Can be either!

Question 61

What are common causes of metabolic alkalosis?

Answer 61

- Hypovolemia - Vomiting - NG suction - Diuretic therapy - HCO₃⁻ administration - Hyperaldosteronism

Question 62

What are the treatments for metabolic alkalosis?

Answer 62

Treat underlying cause - Volume depletion? saline resuscitation - Gastric H⁺ loss? PPI's - Loop diuretics? add K⁺ sparing diuretics