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

What are the cardiovascular consequences of acidosis?

Answer 8

• ↓ contractility at pH of 7.2
• ↓ arterial BP
• Re-entry dysrhythmias
• Lower threshold for v-fib
• Less responsive to catecholamines. at pH of 7.1

Question 9

What cardiovascular consequence occurs at a pH of 7.2?

Answer 9

Impaired contractility

Question 10

What cardiovascular consequence occurs at a pH of 7.1?

Answer 10

Decreased responsiveness to catecholamines

Question 11

What are the consequences of acidosis on the nervous system?

Answer 11

Obtundation & Coma

Question 12

What are the consequences of acidosis on the pulmonary system?

Answer 12

• Hyperventilation
• Dyspnea
• Respiratory muscle fatigue

Question 13

What are the consequences of acidosis on body metabolism?

Answer 13

• Hyperkalemia
• Insulin resistance
• Anaerobic glycolysis inhibition

Question 14

How is respiratory acidosis defined?

Answer 14

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

Question 15

What are the three umbrella causes of respiratory acidosis?

Answer 15

• Central ventilation control
• Peripheral ventilation control
• VQ mismatch

Question 16

What are the more granular causes of respiratory acidosis?

Answer 16

• 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
  inadequate NMBD reversal, Opioid excess and CO2 insufflation (CO2 absorbed in vessels and reach lung to be expired

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

3 mEq/L for every 10 mmHg in the PaCO₂

Question 20

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

Answer 20

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

Question 21

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

Answer 21

Mechanical Ventilation

If hypercarbia is excessive and CO₂ narcosis is present.

Question 22

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

Answer 22

Seizures

Excessive HCO₃⁻ in chronically hypercarbic patients causes CNS irritability.

Question 23

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

Answer 23

Hyperventilation (blow off CO₂ and thus acid)

Question 24

Can metabolic acidosis be corrected through mechanical ventilation?

Answer 24

Nope

Question 25

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

Answer 25

Right shift

Question 26

What cellular alterations occur with metabolic acidosis?

Answer 26

- ↑ ionized Ca⁺⁺ - Dysfunctional transcellular ion pumps

Question 27

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

Answer 27

PaCO₂ ≈ (1.5 x HCO₃⁻ ) + 8

Question 28

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

Answer 28

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

Question 29

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

Answer 29

1.2 mmHg

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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

Question 32

What are the causes of hyperchloremic metabolic acidosis?

Answer 32

- Saline - Diarrhea - Early Renal Failure

Question 33

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

Answer 33

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

Question 34

What are some causes of a high anion gap?

Answer 34

- Lactic acidosis - Ketoacidosis - Renal failure - Poisonings

Question 35

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

Answer 35

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

Question 36

How is a simple anion gap calculated?

Answer 36

Na⁺ - ( Cl⁻ + HCO₃⁻ )

Question 37

What should a normal anion gap be?

Answer 37

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

Question 38

How is a conventional anion gap calculated?

Answer 38

(Na⁺ + K⁺) - (Cl⁻ + HCO₃⁻)

Question 39

What should a conventional anion gap be?

Answer 39

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

Question 40

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

Answer 40

- Hypoalbuminemia - Hypophosphatemia

Question 41

What is the treatment for a high anion gap?

Answer 41

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

Question 42

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

Answer 42

- pH < 7.1 - HCO₃⁻ < 10 mEq/L

Question 43

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

Answer 43

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

Question 44

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

Answer 44

Dose (mmol) = 0.3 x base deficit x kg

Question 45

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 45

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

Question 46

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

Answer 46

½ the correction dose.

Question 47

What is respiratory alkalosis?

Answer 47

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

Question 48

What are four common causes of respiratory alkalosis?

Answer 48

- Pregnancy - High altitude - Iatrogenic Hyperventilation - Salicylate overdose

Question 49

What are common symptoms of respiratory alkalosis?

Answer 49

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

Question 50

What occurs with calcium levels during respiratory alkalosis?

Answer 50

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

Question 51

What are the signs/symptoms of hypocalcemia?

Answer 51

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

Question 52

What is Trousseau's sign?

Answer 52

Wrist flexion that occurs with BP cuff inflated.

Question 53

What is Chvostek's sign?

Answer 53

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

Question 54

What are the branches of the facial nerve?

Answer 54

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

Question 55

How is metabolic alkalosis defined?

Answer 55

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

Question 56

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

Answer 56

Can be either!

Question 57

What are common causes of metabolic alkalosis?

Answer 57

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

Question 58

What are the treatments for metabolic alkalosis?

Answer 58

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

Question 59

What is the best mechanism to reverse chronic hypercarbia?

Answer 59

Increase Vm via Vt or RR in order to blow off excess CO2.

Question 60

What must be present prior to HCO3- adminstration

Answer 60

Evidence of metabolic acidosis should be shown prior to giving bicarb. This will help prevent excessive HCO3- in chronic hypercarbia patient which leads to CNS irritability and seizures.