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BCPS Exam > Critical Care: Acid-base Disorders > Flashcards

Critical Care: Acid-base Disorders Flashcards

1
Q

Changes in what molecule drive metabolic acid-base disturbances?

A

Bicarbonate (HCO3-)

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2
Q

Changes in what molecule drive respiratory acid-base disturbances?

A

Partial pressure of carbon dioxide (PCO2)

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3
Q

A metabolic acidosis is a ______ HCO3-

A

Decreased

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4
Q

A respiratory acidosis is a _______ PCO2

A

Increased

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5
Q

A metabolic alkalosis is a ________ HCO3-

A

Increased

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6
Q

A respiratory alkalosis is a ________ PCO2

A

Decreased

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7
Q

List two kinds of acid-base compensation

A
  1. Respiratory compensation

2. Metabolic compensation

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8
Q

What is a mixed acid-base disorder?

A

When patients have more than one primary disorder

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9
Q

On what time frame does respiratory compensationn develop? How?

A

Immediately with changes in respiratory rate

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10
Q

On what time frame (in general) does metabolic compensation develop? How?

A

Slowly by regulating the excretion and reasbroption of HCO3- and H+

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11
Q

What is the compensation for metabolic acidosis? How?

A
  1. The compensation for metabolic acidosis is respiratory alkalosis (i.e. decrease in PCO2).
  2. This is achieved by increasing the respiratory rate to eliminate more CO2, thus making pH more basic (i.e. higher pH).
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12
Q

What is the compensation for metabolic alkalosis?

A
  1. The compensation for a metabolic alkalosis is a respiratory acidosis (i.e. increase in PCO2).
  2. This is achieved by slowing the respiratory rate to retain more CO2, thus making the pH more acidic (i.e. lower pH).
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13
Q

What is the compensation for respiratory acidosis?

A

The compensation for a respiratory acidosis is a metabolic alkalosis (i.e. an increase in HCO3-)

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14
Q

What is the compensation for respiratory alkalosis?

A

The compensation for respiratory alkalosis is metabolica cidosis (i.e. a decrease in HCO3-)

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15
Q

Normal value for pH, and range?

A

7.40 (range: 7.35-7.45)

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16
Q

Normal range for PCO2?

A

Normal: 40, range 35-45 mmHg

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17
Q

Normal range for PO2?

A

80-100 mm Hg

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18
Q

Normal range for HCO3-

A

Normal: 24, range 22-26 mEq/L (or mmol/L)

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19
Q

Normal range for SaO2?

A

95%-100%

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20
Q

In metabolic acidosis, a primary disturbance of HCO3 _____ by 1 mmol/L can be compensated by a decrease in PCO2 by ____ mmHg

A
  1. A primary disturbance of HCO3- decrease by 1 mmol/L

2. can be compensated by a decrease in PCO2 by 1.2 mmHg

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21
Q

In metabolic alkalosis, a primary disturbance of HCO3 _____ by 1 mmol/L can be compensated by a increase in PCO2 by ____ mmHg

A
  1. A primary disturbance of HCO3- increase by 1 mmol/L

2. Can be compensated by an increase in PCO2 by 0.7 mmHg

22
Q

Respiratory acidosis compensation: An increase in PCO2 by 10 mm Hg can be acutely compensated by a degree of _____ mmol/L. Chronic compensation can achieve _____ mmol/L

A
  1. A respiratory acidosis caused by an increase in PCO2 by 10 mm Hg
  2. can be acutely compensated by increased HCO3- by 1 mmol/L
  3. And chronically compensated by an increased HCO3- by 3.5 mmol/L
23
Q

Respiratory alkalosis compensation: An decrease in PCO2 by 10 mm Hg can be acutely compensated by a degree of _____ mmol/L. Chronic compensation can achieve _____ mmol/L

A
  1. A respiratory alkalosis caused by a decrease in PCO2 by 10 mm Hg
  2. can be acutely compensated by a decreased HCO3 of 2 mmol/L
  3. And chronically compensated by a decreased HCO3 of 4 mmol/L.
24
Q

If ____ is more than 12, there is a primary metabolic acidosis regardless of pH or HCO3.

A

Anion Gap

25
Q

How to calculate anion gap? What does it represent?

A
  1. (Sodium and Potassium) minus (Chloride + Bicarbonate)

2. It represents unmeasured anions (i.e. organic acids)

26
Q

What is an excess anion gap?

A
  1. Also known as a delta gap.
  2. In non-anion gap acidosis, bicarbonate is lost, and chloride is increased to compensate. This is a hyperchloremic acidosis.
  3. In anion gap acidosis, there is an increase in organic acids which consume bicarbonate.
  4. There should be an equimolar increase in chloride and bicarbonate.
  5. Excess anion gap represents whether this equimolar increase is occuring. It can help determine whether chloride is being lost through a primary alkalosis.
27
Q

How to calculate excess anion gap? How to interpret?

A
  1. Excess AG = Total aG - Normal AG. Add excess AG to HCO3-
  2. If this sum is greater than 30 mEq/L, there is also a primary AG metabolic alkalosis (e.g. chloride is also being lost.)
  3. If the sum is less than a normal serum bicarbonate (e.g. there is a proportional increase in Cl- relative to HCO3- decrease) there is an underlying non-AG metabolic acidosis (e.g. hyperchloremic acidosis).
28
Q

When should an anion gap be calculated?

A

Any time you are evaluating an acid-base disturbance

29
Q

When should an excess anion gap be calculated?

A

When evaluating AG Metabolic acidosis

30
Q

What is the first step in evaluating an acid base disorder?

A
  1. Assess pH, PCO2 and HCO3-.
  2. pH helps you determine if there is an alkemia or a acidemia.
  3. PCO2 derangement determines if it’s respiratory.
  4. HCO3- derangement determines if it’s metabolic.
31
Q

What is the second step in evaluating an acid-base disorder?

A
  1. Calculate an Anion Gap.

2. If the AG is more than 12, there is a primary metabolic acidosis regardless of pH or HCO3-.

32
Q

What is the third step in evaluating an acid-base disorder?

A
  1. Calculate and interpet an EAG.

2. The purpose is help determine mixed acid-base disorders.

33
Q

List three principal causes of respiratory acidosis

A
  1. Pulmonary
  2. Cardiovascular
  3. Neurological
34
Q

List four causes of “pulmonary” respiratory acidosis

A
  1. Pulmonary edema
  2. Pulmonary embolus
  3. Pneumonia
  4. Bronchospasm
35
Q

List two causes of “cardiovascular” respiratory acidosis

A
  1. Cardiac arrest

2. Stroke

36
Q

List three causes of “neurological” respiratory acidosis

A
  1. CNS depression
  2. Spinal cord injury
  3. Sedatives
37
Q

How to treat a respiratory acidosis?

A
  1. Invasive-noninvasive ventilation

2. Correct cause

38
Q

List three broad classes of respiratory alkalosis

A
  1. psychiatric/neurological
  2. traumatic/neurological
  3. respiratory/mechanical
39
Q

List four “psychiatric/neurologic” causes of respiratory alkalosis

A
  1. Anxiety
  2. Pain
  3. Stimulant drugs
  4. Respiratory rate stimulation
40
Q

List three “traumatic/neurologic” causes of respiratory alkalosis

A
  1. CNS tumor
  2. Head injury
  3. Stroke
41
Q

List four “respiratory/mechanical” causes of respiratory alkalosis

A
  1. Hypoxia
  2. reduced oxygen-carrying capacity
  3. Reduced alveolar oxygen extraction
  4. Extracorporeal CO2 removal
42
Q

How to treat respiratory alkalosis?

A
  1. Correct cause
  2. Oxygen supplementation/Noninvvasive ventilation (in decreased oxygen states)
  3. Hypoventilation/sedation (in excessive CO2 removal states)
43
Q

List 8 causes of AG metabolic acidosis

A
  1. MUDPILES
  2. Methanol
  3. Uremia
  4. DKA
  5. Propylene glycol
  6. Intoxication or infection
  7. Lactic acidosis
  8. Ethylene glycol
  9. Salicylate
44
Q

List 9 causes of non-AG metabolic acidosis

A
  1. F-USED CARS
  2. Fistula (pancreatic)
  3. Uteroenteric conduits
  4. Saline excess
  5. Endocrine (hyperparathyroid)
  6. Diarrhea
  7. Carbonic anhydrate inhibitors
  8. Arginine, lysine, Cl-
  9. Renal tubular acidosis
  10. Spironolactone
45
Q

How to treat AG metabolic acidosis

A
  1. Correct cause
  2. Use of bases may be considered (sodium bicarbonate or THAM) in non-AG metabolic acidosis
  3. Base use in AG metabolic acidosis is controversial.
46
Q

What are the two types of metabolic alkalosis?

A
  1. Chloride resistant - increased aldosterone action causing excess secretion.
  2. Chloride responsive - increased loss.
47
Q

List two causes of chloride resistant metabolic alkalosis

A
  1. Hyperaldosteronism

2. Increased mineralocorticoid

48
Q

List three causes of chloride responsive metabolic alkalosis

A
  1. Vomiting
  2. NG suction
  3. Diuretic
49
Q

How to evaluate a metabolic alkalosis?

A
  1. Look at urine chloride.
  2. Urine Cl- > 25 indicates chloride resistant (e.g. excess excretion).
  3. Urine Cl- < 25 indicates chloride resistant (e.g. non-renal loss of chloride.)
50
Q

What is the relationship between albumin and anion gap?

A
  1. Low albumin can cause a normal anion gap despite clinically significant AG metabolic acidosis.
  2. Hypoalbuminemia decreases the AG by 2.5-3 mEq/L for every 1 g/dL decrease in serum albumin less than 4 g/dL.
  3. Measured albumin - 4 g/dl (normal albumin) * 2.5 is the correction amount.

BCPS Exam (34 decks)

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