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1Principles 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

Concentration of what ion is used to measure pH?

A

H⁺

“the power of hydrogen”

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4
Q

Where does HCO₃⁻ enter/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? What is the equation?

A

Henderson-Hasselbalch Equation

pH = 6.1 + log(serum bicarb/0.03 x PaCO₂)

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7
Q

Water is amphoteric. What does this mean?

A

Water can act as a base and receive protons or act as an acid and donate protons

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8
Q

What determines the strength of an acid/base?

A

the degree of dissociation

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9
Q

Lactic acid has a pKa of 3.4 and completely dissociates making it a ____?

A

strong acid

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10
Q

Carbonic acid has a pKa of 6.4 and incompletely dissociates making it a ____?

A

weak acid

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11
Q

If both PaCO₂ and HCO₃⁻ increase or decrease in the same direction, then you have what?

A

Primary disorder with secondary compensation.

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12
Q

What does balance of the negative and positively charged ions entail?

A

electrical neutrality

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13
Q

What is the dissociation equilibria?

A

the propensity (tendency) to dissociate

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14
Q

What are the most abundant ECF strong ions?

A

Na⁺ and Cl⁻

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15
Q

What is the strong ion difference (SID)?

A

an independent predictor of pH

[total strong cations - strong anions]

Always positive in ECF (have more cations in ECF)

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16
Q

If both PaCO₂ and HCO₃⁻ increase or decrease in different directions, then you have what?

A

A mixed acid/base disorder

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17
Q

What are normal ranges for:
pH?
PCO₂?
HCO₃?

A

pH: 7.34-7.45
PCO₂: 35-45
HCO₃: 22-26

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18
Q

What are the cardiovascular consequences of acidosis? (5)

A
  • ↓ contractility
  • ↓ arterial BP
  • Re-entry dysrhythmias
  • Lower threshold for v-fib
  • Less responsive to catecholamines.
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19
Q

What cardiovascular consequence occurs at a pH of 7.2?

A

Impaired contractility

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20
Q

What cardiovascular consequence occurs at a pH of 7.1?

A

Decreased responsiveness to catecholamines

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21
Q

What are the consequences of acidosis on the nervous system?

A

Obtundation ⇒ Coma

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22
Q

What are the consequences of acidosis on the pulmonary system? (3)

A
  • Hyperventilation
  • Dyspnea
  • Respiratory muscle fatigue
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23
Q

What are the consequences of acidosis on body metabolism? (3)

A
  • Hyperkalemia
  • Insulin resistance
  • Anaerobic glycolysis inhibition
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24
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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25
Q

What are the three umbrella causes of respiratory acidosis?

A
  • Central ventilation control
  • Peripheral ventilation control
  • VQ mismatch
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26
Q

What are the more granular causes of respiratory acidosis?

A
  • Drug-induced ventilatory 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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27
Q

If someone has slow shallow breathing, what kind of problem could this entail?

A

central problem

Could be somnolence from residual opioids, benzos, or propofol

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28
Q

If someone has rapid shallow breathing, what kind of problem could this entail?

A

peripheral problem

Could be issue with neuromuscular, thoracic, or VQ mismatch

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29
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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30
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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31
Q

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

A

3 mEq/L for every 10 mmHg in the PaCO₂

32
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)

33
Q

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

A

Mechanical Ventilation (increase minute ventilation)

If hypercarbia is excessive and CO₂ narcosis is present.

34
Q

What can occur if chronic hypercarbia is corrected?

A

Seizures

Excessive HCO₃⁻ in chronically hypercarbic patients causes CNS irritability.

35
Q

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

A

Hyperventilation (blow off CO₂ and thus acid)

36
Q

Can metabolic acidosis be corrected through respiratory compensation?

A

Not fully

37
Q

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

A

Right shift (↑H⁺)

38
Q

What cellular alterations occur with metabolic acidosis?

A
  • ↑ ionized Ca⁺⁺
  • Dysfunctional transcellular ion pumps
39
Q

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

A

PaCO₂ ≈ (1.5 x HCO₃⁻ ) + 8

Ex: HCO₃ = 12
[1.5 x 12 + 8 = 26 mmHg]
If greater than 26 then compensation is inadequate.

40
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.

41
Q

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

A

1.2 mmHg

If doesn’t drop by this much then compensation inadequate.

42
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.

43
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.

44
Q

What are the causes of hyperchloremic metabolic acidosis?

A
  • Saline
  • Diarrhea
  • Early Renal Failure
45
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⁻

46
Q

What are some causes of a high anion gap?

A
  • Lactic acidosis
  • Ketoacidosis
  • Renal failure
  • Poisonings
47
Q

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

A

False.

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

48
Q

How is a simple anion gap calculated?

A

Na⁺ - ( Cl⁻ + HCO₃⁻ )

49
Q

What should a normal simple anion gap be?

A

Na⁺ - ( Cl⁻ + HCO₃⁻ )

140 - (102 - 24)

≈ 12 - 14 mEq/L

50
Q

How is a conventional anion gap calculated?

A

(Na⁺ + K⁺) - (Cl⁻ + HCO₃⁻)

51
Q

What should a conventional anion gap be?

A

(Na⁺ + K⁺) - (Cl⁻ + HCO₃⁻)

140 + 4 - (106 - 24)

≈ 14 - 18 mEq/L

52
Q

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

A
  • Hypoalbuminemia
  • Hypophosphatemia
53
Q

What are causes for Anion Gap Acidosis?

A

Cyanide and CO
Arsenic
Toluene
Methanol, Metformin
Uremia
DKA
Paraldehyde
Iron
Lactace
Ethylene glycol
Salicylates

54
Q

What is a degradation product of glucose metabolism?

A

Lactic acidosis

55
Q

How effect can catecholamines have in terms of acid and metabolism?

A

catecholamines lead to lactate production ⇒ pyruvate ⇒ gluconeogenesis

56
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
57
Q

When is NaHCO₃ (Sodium Bicarbonate injection) indicated?

A
  • pH < 7.1
  • HCO₃⁻ < 10 mEq/L
58
Q

What are the two reasons for NaHCO₃ treatment controversiality?

A
  • HCO₃⁻ + H⁺ → CO₂ ⇒ more acidosis
  • With chronic acidosis, acute pH changes negates Right curve shift (Bohr effect) and results in tissue hypoxia
59
Q

How is a correction dose of NaHCO₃ calculated?

A

Full Dose (mmol) = 0.3 x base deficit x kg

60
Q

The CRNA wishes to calculate a Full correction dose of NaHCO₃ for an 82 kg patient with a base deficit of -4. What would the dose of NaHCO₃ be?

A

Dose = 0.3 (-4) x 82kg

Full Dose = 98.4 mmol of NaHCO₃

61
Q

When giving a correction dose of NaHCO₃, how much should be given initially?

A

½ the correction dose and reassess

62
Q

If a patient has metabolic acidosis and needs urgent/emergent surgery, what should be considered?

A

Hemodynamic monitoring
and frequent labs

63
Q

If a patient has metabolic acidosis and needs elective surgery, what should be considered?

A

Postpone surgery

64
Q

What is respiratory alkalosis?

A
  • Acute increase in alveolar ventilation (hyperventilation) ⇒↓PaCO₂
  • pH > 7.45
65
Q

What are four common causes of respiratory alkalosis?

A
  • Pregnancy
  • High altitude
  • Iatrogenic Hyperventilation (related to medical tx)
  • Salicylate overdose
66
Q

What are common symptoms of respiratory alkalosis? (3)

A
  • Lightheaded
  • Visual disturbances
  • Dizziness

all of these from vasoconstriction.

67
Q

What occurs with calcium levels during respiratory alkalosis?

A

Ca⁺⁺ binds to albumin more easily → hypocalcemia

68
Q

What are the signs/symptoms of hypocalcemia? (8)

A
  • Paresthesias
  • Muscle spasms
  • Cramps
  • Tetany
  • Circumoral numbness
  • Seizures
  • Trousseau’s Sign
  • Chvostek’s Sign
69
Q

What is Trousseau’s sign?

A

Wrist flexion that occurs with BP cuff inflated.

70
Q

What is Chvostek’s sign?

A

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

71
Q

What are the branches of the facial nerve?

A

To Zanzibar By Motor Car.

  • Temporal
  • Zygomatic
  • Buccal
  • Marginal mandibular
  • Cervical
72
Q

How is metabolic alkalosis defined?

A
  • Marked increase in HCO₃⁻ usually compensated by increase in CO₂
  • Loss of H⁺ or gain of HCO₃⁻
  • Renal or extrarenal
73
Q

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

A

Can be either

74
Q

What are common causes of metabolic alkalosis? (6)

A
  • Hypovolemia
  • Vomiting
  • NG suction
  • Diuretic therapy
  • HCO₃⁻ administration
  • Hyperaldosteronism
75
Q

What are common symptoms correlated with metabolic alkalosis?

A

attributed to Calcium imbalances ⇒ lightheaded, tetany, paresthesia

76
Q

What are the treatments for metabolic alkalosis?

A

Treat underlying cause

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

1Principles of Anesthesia (26 decks)

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