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Principles of Anesthesia > Acid-Base Disorders & ABG's (Exam II) > Flashcards

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

1
Q

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

A

Acidemia (Acidosis)

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2
Q

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

A

Alkalemia (alkalosis)

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3
Q

What ion is used to measure pH?

A

H⁺

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4
Q

Where does HCO₃⁻ enter and leave the body?

A

Proximal tubule of the kidneys

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5
Q

Where are H⁺ reabsorbed in the kidney?

A

Distal tubule and collecting duct

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6
Q

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

A

Henderson-Hasselbalch Equation

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7
Q

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

A

Primary disorder with secondary compensation.

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8
Q

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

A

A mixed acid/base disorder

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9
Q

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

A

PaO₂ ≈ 240 mmHg at an FiO₂ of 80%

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10
Q

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?

A

PaO₂ ≈ 40 mmHg on room air

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11
Q

What are the cardiovascular consequences of acidosis?

A
  • ↓ contractility
  • ↓ arterial BP
  • Re-entry dysrhythmias
  • Lower threshold for v-fib
  • Less responsive to catecholamines.
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12
Q

What cardiovascular consequence occurs at a pH of 7.2?

A

Impaired contractility

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13
Q

What cardiovascular consequence occurs at a pH of 7.2?

A

Impaired contractility

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14
Q

What cardiovascular consequence occurs at a pH of 7.1?

A

Decreased responsiveness to catecholamines

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15
Q

What are the consequences of acidosis on the nervous system?

A

Obtundation & Coma

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16
Q

What are the consequences of acidosis on the pulmonary system?

A
  • Hyperventilation
  • Dyspnea
  • Respiratory muscle fatigue
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17
Q

What are the consequences of acidosis on body metabolism?

A
  • Hyperkalemia
  • Insulin resistance
  • Anaerobic glycolysis inhibition
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18
Q

How is respiratory acidosis defined?

A
  • An acute decrease in alveolar ventilation results in increased PaCO₂.
  • pH < 7.35
  • Essentially respiratory failure
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19
Q

What are the three umbrella causes of respiratory acidosis?

A
  • Central ventilation control
  • Peripheral ventilation control
  • VQ mismatch
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20
Q

What are the more granular causes of respiratory acidosis?

A
  • 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
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21
Q

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

A

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

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22
Q

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

A

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

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23
Q

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

A

3 mEq/L for every 10 mmHg in the PaCO₂

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24
Q

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

A

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

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25
Q

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

A

Mechanical Ventilation

If hypercarbia is excessive and CO₂ narcosis is present.

26
Q

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

A

Seizures

Excessive HCO₃⁻ in chronically hypercarbic patients causes CNS irritability.

27
Q

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

A

Hyperventilation (blow off CO₂ and thus acid)

28
Q

Can metabolic acidosis be corrected through mechanical ventilation?

A

Nope

29
Q

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

A

Right shift

30
Q

What cellular alterations occur with metabolic acidosis?

A
  • ↑ ionized Ca⁺⁺
  • Dysfunctional transcellular ion pumps
31
Q

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

A

PaCO₂ ≈ (1.5 x HCO₃⁻ ) + 8

32
Q

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

A

PaCO₂ ≈ (1.5 x 14) + 8

PaCO₂ ≈ 29 mmHg

If PaCO₂ is greater than 29 then compensation is inadequate.

33
Q

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

A

1.2 mmHg

34
Q

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

A

38 mmHg

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

35
Q

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

A

11 x 1.2 = 13.2

PaCO₂ ≈ 26.8

If higher then compensation is inadequate.

36
Q

What are the causes of hyperchloremic metabolic acidosis?

A
  • Saline
  • Diarrhea
  • Early Renal Failure
37
Q

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

A

Normal Anion Gap

HCO₃⁻ loss is countered by net gain of Cl⁻

38
Q

What are some causes of a high anion gap?

A
  • Lactic acidosis
  • Ketoacidosis
  • Renal failure
  • Poisonings
39
Q

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

A

False.

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

40
Q

How is a simple anion gap calculated?

A

Na⁺ - ( Cl⁻ + HCO₃⁻ )

41
Q

What should a normal anion gap be?

A

Na⁺ - ( Cl⁻ + HCO₃⁻ )

140 - (102 - 24)

≈ 12 - 14 mEq/L

42
Q

How is a conventional anion gap calculated?

A

(Na⁺ + K⁺) - (Cl⁻ + HCO₃⁻)

43
Q

What should a conventional anion gap be?

A

(Na⁺ + K⁺) - (Cl⁻ + HCO₃⁻)

140 + 4 - (106 - 24)

≈ 14 - 18 mEq/L

44
Q

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

A
  • Hypoalbuminemia
  • Hypophosphatemia
45
Q

What is the treatment for a discordant anion gap?

A

Treat the underlying cause!

  • Ketoacidosis = insulin & fluids
  • Lactic acidosis = improve tissue perfusion
  • Renal failure = dialysis
46
Q

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

A
  • pH < 7.1
  • HCO₃⁻ < 10 mEq/L
47
Q

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

A
  • HCO₃⁻ + H⁺ → CO₂ = more acidosis
  • With chronic acidosis, acute pH changes negates curve shift to the right and results in tissue hypoxia
48
Q

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

A

Dose (mmol) = 0.3 x base deficit x kg

49
Q

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?

A

Dose = 0.3 (-4) x 82kg

Dose = 98.4 mmol of Na⁺HCO₃⁻

50
Q

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

A

½ the correction dose.

51
Q

What is respiratory alkalosis?

A
  • Acute increase in alveolar ventilation
  • ↓ PaCO₂
  • pH > 7.45
52
Q

What are four common causes of respiratory alkalosis?

A
  • Pregnancy
  • High altitude
  • Iatrogenic Hyperventilation
  • Salicylate overdose
53
Q

What are common symptoms of respiratory alkalosis?

A
  • Lightheadedness
  • Visual disturbances
  • Dizziness

all of these from vasoconstriction.

54
Q

What occurs with calcium levels during respiratory alkalosis?

A

Ca⁺⁺ binds to albumin more easily → hypocalcemia

55
Q

What are the signs/symptoms of hypocalcemia?

A
  • Paresthesias
  • Muscle spasms
  • Cramps
  • Tetany
  • Mouth numbness
  • Seizures
  • Trousseau’s Sign
  • Chvostek’s Sign
56
Q

What is Trousseau’s sign?

A

Wrist flexion that occurs with BP cuff inflated.

57
Q

What is Chvostek’s sign?

A

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

58
Q

What are the branches of the facial nerve?

A

To Zanzibar By Motor Car.

  • Temporal
  • Zygomatic
  • Buccal
  • Marginal mandibular
  • Cervical
59
Q

How is metabolic alkalosis defined?

A
  • Marked increase in HCO₃⁻ usually with compensatory increase in CO₂
  • Loss of H⁺ or gain of HCO₃⁻
  • Renal or extrarenal
60
Q

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

A

Can be either!

61
Q

What are common causes of metabolic alkalosis?

A
  • Hypovolemia
  • Vomiting
  • NG suction
  • Diuretic therapy
  • HCO₃⁻ administration
  • Hyperaldosteronism
62
Q

What are the treatments for metabolic alkalosis?

A

Treat underlying cause

  • Volume depletion? saline resuscitation
  • Gastric H⁺ loss? PPI’s
  • Loop diuretics? add K⁺ sparing diuretics

Principles of Anesthesia (24 decks)

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