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principles of anesthesia i > Acid-Base Disorders & ABGs (Exam II) > Flashcards

Acid-Base Disorders & ABGs (Exam II) Flashcards

1
Q

What is considered a normal pH range?

A

7.35-7.45

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2
Q

What are the normal values for K+, Cl-, Na+, HCO3-

A

K+ 3.5-5.0
Cl- 100-105
Na+ 135-145
HCO3- 22-26

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3
Q

Change in relative concentrations of F/E change water’s ability to auto-ionize

A

Ensures optimal function of enzymatic function

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4
Q

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

A

Acidemia (Acidosis)

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5
Q

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

A

Alkalemia (alkalosis)

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6
Q

pH is the measure of __.

A

H⁺ ions

The Power of Hydrogen

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7
Q

Where does CO2 enter/leave the body?

A

Via the lungs

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8
Q

Where does HCO₃⁻ enter and leave the body?

A

Via the Proximal Convoluted Tubule

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9
Q

Where in the kidney is H⁺ reabsorbed?

A

Distal Convoluted Tubule
Collecting Duct

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10
Q

What is the name of the “Acid-Base” balance equation?

A

Henderson-Hasselbalch equation

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11
Q

What is the Henderson-Hasselbalch equation?

A

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

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12
Q

Water is described as being amphoteric, what does this mean?

A

It can act as either an Acid or Base
or
Can donate a proton or receive a proton

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13
Q

The degree of dissociation in water determines the __.

A

Strength of an acid or base

pKa<3
is for a strong acid

3<pKa<7
is for a weak acid

7<pKa<11
is for a weak base

pKa>11
is for a strong base

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14
Q

What are the 3 Rules of Equilibrium described in lecture?

A

Electrical Neutrality
Negative and positive ions must cancel out
Dissociation Equilibria
Propensity of a substance to dissociate
Mass Conservation
The amount of a substance remains constant

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15
Q

Strong ions _ _.

A

Dissociate completely

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16
Q

What are the two most abundant ECF strong ions?

A

Na+
Cl-

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17
Q

What are the 4 other strong ions discussed in lecture?

A

K+
SO42-
Mg2+
Ca2+

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18
Q

What is Strong Ion Difference?

A

Total strong cations - strong anions = SID
In the ECF, SID is always positive
An independent indicator of pH

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19
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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20
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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21
Q

What are the normal range values for pH, PCO2, and HCO3 discussed in lecture?

A

pH 7.35-7.45
PCO2 35-45
HCO3 22-26

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22
Q

Identify the disorder
pH 7.33, PCO2 48, HCO3 26

A

Respiratory acidosis

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23
Q

Identify the disorder
pH 7.58, PCO2 35, HCO3 29

A

Metabolic alkalosis

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24
Q

Identify the disorder
pH 7.28, PCO2 46, HCO3 18

A

Mixed metabolic/respiratory acidosis

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25
Q

Identify the disorder
pH 7.48, PCO2 32, HCO3 22

A

Respiratory alkalosis

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26
Q

What are the cardiovascular consequences of acidosis?

A
  1. Impaired contractility (pH 7.2)
  2. Decreased arterial BP
  3. Sensitivity to re-entry dysrhythmias
  4. Decreased threshold for V-fib
  5. Decreased responsiveness to catecholamines (pH 7.1)
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27
Q

What are the neurovascular consequences of acidosis?

A
  1. Obtundation
  2. Coma
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28
Q

What are the respiratory consequences of acidosis?

A
  1. Hyperventilation
  2. Dyspnea
  3. Respiratory muscle fatigue
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29
Q

What are the 3 metabolic consequences of acidosis?

A
  1. Hyperkalemia
  2. Insulin resistance
  3. Inhibition of anaerobic glycolysis
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30
Q

What is the definition of respiratory acidosis?

A
  1. An acute decrease in alveolar ventilation resulting in an increased PaCO₂.
  2. pH < 7.35
  3. Respiratory failure
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31
Q

What are the three main categorical causes of respiratory acidosis

A
  • Central ventilation control
  • Peripheral ventilation control
  • V/Q mismatch
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32
Q

What are the 8 causes of respiratory acidosis?

A
  1. Drug-induced ventilatory depression
  2. Permissive hypercapnia
  3. Upper airway obstruction
  4. Status asthmaticus
  5. Restriction of ventilation (flail chest, rib fx)
  6. Malignant hyperthermia
  7. Pneumonia/pulmonary edema/pleural effusion
  8. Inadequate NMBD reversal, opioid excess, CO2 insufflation
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33
Q

Slow, shallow breathing is a _ problem usually caused by _, _, and _.

A

Central
Residual opioids
Benzodiazepines
Propofol
(Acute Respiratory Acidosis)

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34
Q

Rapid, shallow breathing is a _ problem and can be caused by _, _, or _ .

A

peripheral
Neuromuscular
Thoracic
V/Q mismatch

Acute Respiratory Acidosis

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35
Q

What are some neuromuscular causes of acute respiratory acidosis?

A

Residual NM blockade
High epidural/spinal

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36
Q

What are some thoracic causes of acute respiratory acidosis?

A

Pneumothorax
Hemothorax

37
Q

What are some V/Q mismatch issues that can cause acute respiratory acidosis?

A

Abdominal splinting
Retained secretions
Atelectasis

38
Q

Obstructed breathing is an _ problem and can be caused by _, _, _, or _.

A

Airway
Supraglottic obstruction
Glottic obstruction
Subglottic obstruction
Bronchospasm

39
Q

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

A

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

40
Q

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

A

↑ HCO₃⁻ by 3 mmol/L (3 mEq/L) for every 10 mmHg of PaCO₂

41
Q

On arrival to the ICU following a bowel resection, our patients PaCO2 is 80mm Hg. What is the expected HCO3-?

A

4 mmol/L (4 mEq/L) higher than normal

42
Q

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

A

Mechanical Ventilation

If hypercarbia is excessive and CO₂ narcosis is present.

43
Q

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

A

Seizures

Excessive HCO₃⁻ in chronically hypercarbic patients causes CNS irritability.

44
Q

What is a normal tidal volume range?

A

6-8 mL/kg

45
Q

If a hypercarbic patient’s tidal volume is already within normal range, how else would you correct the acidosis?

A

Adjust the respiratory rate

46
Q

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

A

Hyperventilation (blow off CO₂ and thus acid)

47
Q

Can metabolic acidosis be corrected through mechanical ventilation or tachypnea?

A

No

48
Q

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

A

Rightward shift

49
Q

What cellular alterations occur with metabolic acidosis?

A

↑ ionized Ca⁺⁺
Dysfunctional transcellular ion pumps

50
Q

What can cause metabolic acidosis?

A

Increased acid production
Decreased excretion of acid
Acid ingestion
Renal/GI bicarbonate loss

51
Q

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

A

PaCO₂ ≈ (1.5 x HCO₃⁻ ) + 8

52
Q

What would the expected PaCO₂ be of an acute metabolic acidosis patient with an HCO₃⁻ of 12 mmol/L?

A

PaCO₂ ≈ (1.5 x 12) + 8
PaCO₂ ≈ 26 mmHg

If PaCO₂ is greater than 26 then compensation is inadequate; concomitant problem

53
Q

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

A

1.2 mmHg

Otherwise compensation is inadequate

54
Q

How is Hyperchloremic Metabolic Acidosis defined?

A

Bicarbonate loss countered by a net gain of chloride ions

Electrical neutrality maintained (Na balanced by sum of bicarb and chloride)

55
Q

What are the causes of Hyperchloremic metabolic acidosis?

A

Sodium chloride infusions
Diarrhea
Early Renal Failure

56
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⁻

57
Q

How is a simple anion gap calculated?

A

Na⁺ - ( Cl⁻ + HCO₃⁻ )

58
Q

What should a normal simple anion gap be?

A

Na⁺ - ( Cl⁻ + HCO₃⁻ )

140 - (102 - 24)

≈ 12 - 14 mEq/L

59
Q

How is a conventional anion gap calculated?

A

(Na⁺ + K⁺) - (Cl⁻ + HCO₃⁻)

60
Q

What should a conventional anion gap be?

A

(Na⁺ + K⁺) - (Cl⁻ + HCO₃⁻)

140 + 4 - (106 - 24)

≈ 14 - 18 mEq/L

61
Q

Which is more accurate, normal or conventional anion gap?

A

Conventional

62
Q

What two conditions can cause an underestimation of anion gap?

A

Hypoalbuminemia
Hypophosphatemia

63
Q

What is a high anion gap?

A

Additional acid is added to the extracellular space

H+ ion combines with bicarb = carbonic acid
Less available bicarb

64
Q

What are the causes of a high anion gap?

A

Lactic acidosis
Ketoacidosis
Renal Failure
Poisoning

65
Q

What is the treatment for high anion gap?

A

Treat the underlying cause!

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

66
Q

What is the useful mnemonic for anion gap acidosis?

A

CATMUDPILES

67
Q

What does the CAT in CATMUDPILES stand for?

A

C: Cyanide and CO
A: Arsenic
T: Toluene

68
Q

What does the MUD in CATMUDPILES stand for?

A

M: Methanol, Metformin
U: Uremia
D: DKA

69
Q

What does the PILES in CATMUDPILES stand for?

A

P: Paraldehyde
I: Iron
L: Lactate
E: Ethylene glycol
S: Salicylates

70
Q

When is NaHCO₃ (Sodium Bicarbonate injection) indicated?

A

pH < 7.1
HCO₃⁻ < 10 mEq/L

71
Q

What are the two reasons for NaHCO₃ treatment controversiality?

A

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

72
Q

How is a correction dose of NaHCO₃ calculated?

A

Dose (mmol) = 0.3 x base deficit x kg

73
Q

The CRNA wishes to calculate a correction dose of NaHCO₃ 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 NaHCO₃

74
Q

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

A

1/2 the correction dose

75
Q

With regards to anesthesia management and metabolic acidosis, what are the considerations?

A

Elective surgery: Postpone
Urgent/Emergent: Consider hemodynamic monitoring
(Fluid administration)
(Monitor cardiac function)
(Frequent labs)

76
Q

What is respiratory alkalosis?

A

Acute increase in alveolar ventilation
↓ PaCO₂
pH > 7.45

77
Q

What are four common causes of respiratory alkalosis?

A

Pregnancy
High altitude
Iatrogenic Hyperventilation (Perioperative period)
Salicylate overdose

78
Q

What are common symptoms of respiratory alkalosis?

A

Lightheadedness
Visual disturbances
Dizziness
all of these from vasoconstriction.

79
Q

What occurs with calcium levels during respiratory alkalosis?

A

Ca⁺⁺ binds to albumin more easily → hypocalcemia

80
Q

What are the 8 signs/symptoms of hypocalcemia?

A

Paresthesias
Muscle spasms
Cramps
Tetany
Mouth numbness
Seizures
Trousseau’s Sign
Chvostek’s Sign

81
Q

What is Trousseau’s sign?

A

Wrist flexion that occurs with BP cuff inflation.

82
Q

What is Chvostek’s sign?

A

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

83
Q

With regards to anesthesia management and respiratory alkalosis, what are the considerations?

A

Pain management
Anxiety management
Agitation de-escalation
Assess mechanical ventilation strategy
Therapeutic hyperventilation (rebreathing w/bag)

84
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 (net loss of H+ or net gain of bicarb)

85
Q

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

A

Can be either

Referred to as either volume depletion or volume overload alkalosis

86
Q

What are six common causes of metabolic alkalosis?

A

Hypovolemia
Vomiting
NG suction
Diuretic therapy
HCO₃⁻ administration
Hyperaldosteronism

87
Q

What are the symptoms of metabolic alkalosis?

A

Lightheadedness
tetany
paresthesia

88
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 i (8 decks)

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