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Principles of Anesthesia I (Summer 2024: Cooper) > Exam 2 ABG's (6/17/24) > Flashcards

Exam 2 ABG's (6/17/24) Flashcards

1
Q

How is Acidemia and Alkalemia defined?

A

Acidemia: Excess production of H+ (in relation to hydroxyl ions)

Alkalemia:Excess production of OH- (in relation to hydrogen ions)

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2
Q

How does CO2 and Bicarb enter and leave the body?

A

CO2: Lungs
Bicarb: Kidneys via proximal tubule

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3
Q

How is Hydrogen reabsorbed in the body?

A
  • Distal Tubule
  • Collecting Duct
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4
Q

Who coined the term “Acid-Base”?

A

Henderson and Hasselbach

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5
Q

Henderson-Hasselbach Equation

A

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

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6
Q

What does Amphoteric mean?
Example:

A

Can be both an acid and a base
Ex. Water

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7
Q

How do we define a strong/weak acid?

Examples:

A

Defined according to the degree of dissociation in water, which determines the strength

Strong Acid: Lactic Acid (pKa 3.4)
Weak Acid: Carbonic Acid (pKa 6.4)

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8
Q

3 Rules of acid-base balance for substances in the body:

A
  1. Electrical Neutrality (Cations = Anions)
  2. Dissociatoin Equilibria (The propensity to dissociate)
  3. Mass Conservation (Amount of the substance must remain constant)
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9
Q

Do strong ions dissociate completely or partially?

A

Completely

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10
Q

What are the most abundant strong ions found in the ECF?

What about some other examples?

A

Na+, Cl-

K+, Sulfate 2-, Mg 2+, Ca 2+

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11
Q

What does Strong Ion difference refer to?

A

The amount of total strong cations minus the total strong anions

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12
Q

True or False:
There are always more strong ECF anions than cations making the SID always negative?

A

False:

There are always more ECF cations than anions making the SID always positive.

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13
Q

The ability of the ECF to maintain a little more strong cations than anions is an ____ of pH.

A

Independent predictor

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14
Q

What is the first thing we should look at to determine whether or not there is an acid-base disturbance?

A

Look at the pH

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15
Q

If both PaCO2 levels and HCO3 levels increase, what kind of disorder can be identified?

A

Primary disorder with secondary compensation

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16
Q

In broad terms, If HCO3 increases but PaCO2 decreases, what kind of disorder can be identified?

A

Mixed acid/base disorder

Mixed alkalosis

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17
Q

How would we define this disturbance?

pH 7.28, PCO2 46, HCO3 18

A

Mixed Respiratory and Metabolic Acidosis

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18
Q

What are some consequences on the CV system that may occur if the pH gets down to 7.2 or 7.1?

A

7.2: Impaired Contractility
7.1: Decreased Responsiveness to catecholamines

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19
Q

What are some other consequences of acidosis on the CV system discussed in lecture?

A
  • Decreased arterial blood pressure
  • Sensitivity to re-entry dysrhythmias (V-Tach)
  • Decreased threshold for v-fib
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20
Q

Consequences of acidosis on the nervous system:

A

Obtundation
Coma

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21
Q

Select All that Apply:

Which of the following are consequences of acidosis on the pulmonary system?

A. Hypoventilation
B. Increased Minute Volume
C. Increased ETCO2 readings
D. Hyperventilation
E. Dyspnea
F. Decreased ETCO2 readings

A

B. Increased Minute Volume
D. Hyperventilation
E. Dyspnea
F. Decreased ETCO2 readings

Rationale: Both D and E are directly from the powerpoint slide. B and F were discussed by Dr. Kane during lecture. “When we hyperventilate, we increase our minute volume to try and blow off more CO2 to reduce acidemia.”

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22
Q

Consequences of acidosis on metabolism?

A
  • Hyperkalemia
  • Insulin Resistance
  • Inhibition of anaerobic glycolysis
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23
Q

An acute decrease in alveolar ventilation results in ___.

A

an increase in PaCO2

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24
Q

Our book states that all the many causes of Respiratory Acidosis stem from one of three main issues. What are these 3 issues?

A
  1. Central Ventilation Control
  2. Peripheral Ventilation Control
  3. V/Q Mismatch
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25
Q

Super-long list of all the causes of Respiratory Acidosis:

DR. PIMP’S ON… lol

A

Drug-Induced ventilatory depression
Restriction of ventilation (rib fx)
Pneumonia, pulm edema, effusions
Inadequate NMBD reversal, CO2 insuf.
Malignant Hyperthermia
Permissive Hypercapnia
Status Asthmaticus
Obstruction of upper airway
Neuromuscular disorders

26
Q

Slow, shallow breathing is usually a ___ problem. Specific causes include:

A

Central problem

Opioids
Benzo’s
Propofol

27
Q

Rapid, shallow breathing is usually a ___ problem.

A

Peripheral Problem

28
Q

In acute hypercarbia, an increase of PaCO2 by ____ , corresponds to a subsequent increase in plasma bicarb of ___.

A

10 mmHg of PaCO2 causes a 1 mmol/L increase in plasma bicarb.

29
Q

Baseline ABG values:
PaCO2 of 36 mmHg
Bicarb of 26 mmol/L

After giving too much morphine in the OR, the patient’s new PaCO2 is 56 mmHg, what is a good estimate of his new bicarb level?

A

28 mmol/L

30
Q

How much does bicarb increase in a chronic hypercarbia patient when PaCO2 increases by 10 mmHg?

A

3 mmol/L

31
Q

Unless specifically told otherwise, what pH, PaCO2 and Bicarb level should we use, per Dr. Kane?

A

pH: 7.4
PaCO2: 40 mmHg
HCO3: 24 mmol/L

32
Q

Treatment for Respiratory Acidosis:

A

Mechanical Ventilation
(Specifically increase the patient’s minute ventilation, tidal volume or both!)

33
Q

Do we need to be more careful with chronic or acute hypercarbic patients when reversing the excess CO2?
Why?
What may happen if we reverse too fast?

A

More caution with chronic hypercarbic patients.
Excessive bicarb can be present.
This causes CNS irritability (seizures)

34
Q

Metabolic acidosis is most likely signifying what?

A

Some type of underlying condition.

35
Q

Metabolic acidosis causes alterations in what?

A

Transcellular ion pumps causing an increase in ionized calcium levels.

36
Q

Does metabolic acidosis cause an increased or decreased affinity for oxygen?

A

Decreased affinity for oxygen
(Right-shift)

37
Q

Formulas for determining the respiratory compensation amount in acute metabolic acidosis:

A

1.5 x HCO3 + 8

OR

For every drop in base excess (deficit) by 1 mEq/L, PaCO2 should drop by 1.2 mmHg

38
Q

The following ABG results were drawn after the body should have had a sufficient amount of time to compensate:

HCO3: 10 mmol/L
PaCO2: 27 mmHg

Based on your knowledge of adequate respiratory compensation in acute metabolic acidosis, determine whether or not these results correspond to adequate compensation.

A

NO. There is not adequate compensation by the respiratory system.

Using this formula (1.5 x HCO3 + 8) = we should get a PaCO2 of 23 mmHg. Anything HIGHER than 23 mmHg is considered inadequate.

39
Q

Determine the new PaCO2 after compensation:

Initial ABG results:
* Base Deficit: 0 mEq/L
* PaCO2: 41 mmHg

New Base Deficit: -5 mEq/L
New PaCO2: ??

A

New PaCO2 = 35 mmHg

Base deficit dropped by 5 mEq/L –> multiply 5 by 1.2 mmHg –> 6 mmHg –> subtract 6 mmHg from 41 mmHg = 35 mmHg

40
Q

If the patient has a normal anion gap in metabolic acidosis, the loss of bicarb is being countered by what to maintain electrical neutrality?

A

Net gain of Chloride ions

Hyperchloremic metabolic acidosis

41
Q

What are some likely causes of the metabolic acidosis if there is a normal anion gap?

A

NaCl infusions
Diarrhea
Early renal failure

42
Q

Select the 2 correct statements regarding the Simple and Conventional formulas used to determine anion gap.

A. The simple formula fails to incorporate Chloride
B. The conventional formula estimates a slightly higher anion gap as “normal” compared to the simple formula
C. The simple formula accounts for Calcium levels
D. The Conventional formula incorporates the Potassium level
E. The simple formula adds the patient’s CO2 level into the equation

A

B and D

Rationale: The conventional formula shows a normal anion gap as 14-18 meq/L, whereas the simple formula shows 12-14 meq/L. The conventional formula also incorporates the Potassium level, whereas the simple formula does not.

43
Q

2 Formulas for determining anion gap?

A

Simple: Na - (Cl + HCO3-) = 12-14 mEq/L

Conventional: (Na + K) - (Cl + HCO3-) = 14-18 mEq/L

44
Q

Why do the 2 formulas to determine anion gap often underestimate the extent of the disturbance?

A

Ignores all the other anions and cations that play a role in the disturbance.

Hypoalbuminemia and hypophosphatemia

45
Q

Describe the process as to how additional acid is added to the extracellular space in metabolic acidosis with a HIGH anion gap.

A
  1. Acid dissociates
  2. Hydrogen ion combines with bicarb
  3. Formation of carbonic acid
  4. Decrease in the amount of available bicarb to combat acidity
46
Q

Mnemonic for Anion gap acidosis

A

C: Cyanide and CO
A: Arsenic
T: Toluene
M: Methanol, Metformin
U: Uremia
D: DKA
P: Paraldehyde
I: Iron
L: Lactate
E: Ethylene glycol
S: Salicylates

47
Q

Lactic Acid is a degradation product of glucose metabolism. Describe the process in which it is formed.

A

From Catecholamines (maybe we gave them) –> Lactate –> pyruvate –> gluconeogenesis

48
Q

Treatment for Ketoacidosis:

A

Insulin and fluids

49
Q

Treatment for lactic acidosis:

A

improve tissue perfusion
fluid resuscitate
discontinue metformin

50
Q

Treatment for acidosis related to renal failure:

A

dialysis

51
Q

Due to bicarb administration being very controversial, the parameters for using it are a pH of ___ or bicarb level of ___

A

pH < 7.1
Bicarb < 10 meq/L

52
Q

Why is using bicarb to treat chronic metabolic acidosis considered controversial?

A

The acute pH changes negate the right-shift of the oxy/hgb curve and does not allow oxygen to be released where it is needed = causes tissue hypoxia

Also possiblity of a worsened acidotic state
(Bicarb reacts with Hydrogen = generates more CO2 = diffusion of CO2 intracellularly = Further decrease in pH)

Negation of Right shift prevents the Bohr Effect from happening.

53
Q

What is the “Full-Correction Dose” of bicarb?
How is this administered to the patient?

A

0.3 x base deficit (mmol/L) x wt(kg)

Give half of the dose and then re-assess

54
Q

Anesthesia management for patients undergoing elective or Emergent/urgent cases while in metabolic acidosis?

A

Elective: Postpone
Urgent/Emergent:
* Guide fluid admin
* Monitors cardiac function
* Frequent lab (Bedside labs)

55
Q

Causes of Respiratory Alkalosis

A
  • Pregnancy
  • High altitude
  • Iatrogenic hyperventilation (during perioperative period)
  • Salicylate overdose
56
Q

Symptoms of Respiratory Alkalosis:

Why do these symptoms occur?

A
  1. Lightheaded
  2. Visual disturbance
  3. Dizziness

Occur due to vasoconstriction

57
Q

In Respiratory alkalosis we get a greater binding of ___ to ___ causing ___.

A

Calcium to Albumin
Causing hypocalcemia

58
Q

The causes of metabolic alkalosis are usually ___.

A

Iatrogenic (Renal/Extrarenal)

Ex. Excess Citrate

59
Q

What are two other names in which Metabolic Alkalosis can be referred to as?

A

Volume depletion alkalosis or volume overload alkalosis

60
Q

Causes of Metabolic Alkalosis:

A

Hypovolemia
Vomiting
NG suction
Diuretic therapy
Bicarb administration
Hyperaldosteronism

61
Q

Symptoms of Metabolic Alkalosis:

A

Lightheadedness
Tetany
Paresthesia

62
Q

Metabolic Alkalosis Treatment for each cause:

Volume Depletion:
Gastric Loss:
Loop Diuretics:

A

Volume Depletion: Saline Admin.
Gastric Loss: Give PPI’s
Loop Diuretics: Add K Sparing diuretics

Principles of Anesthesia I (Summer 2024: Cooper) (18 decks)

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