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Diagnostic Studies, Unit III > Arterial Blood Gases > Flashcards

Arterial Blood Gases Flashcards

1
Q

Overall Fct, ABG

A

Determine respiratory vs metabolic disorder

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2
Q

Define ABG

A

“Evaluation of lungs’ ability to move oxygen into blood and remove carbon dioxide from blood”

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3
Q

ABG Aquisition

A

Anatomic: ABG is a blood test taken from the radial artery

Logistic: Usually, a respiratory therapist will take collect the blood. The procedure is painful and difficult (deep artery c proximity to radial vn and nerves) and they are better practiced than most other clinicians

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4
Q

Indications, ABG

(4)

A
  1. Assess oxygenation capacity of lungs
  2. Assess respiratory adequacy
  3. Assess acid-base balance
  4. Evaluate pt primary state, compensatory mechanisms, and efficacy of tx
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5
Q

Respiratory Microphysiology

A

See picture.

Note that alveolar elasticity allows for 100% or near 100% concentration gradients and efficient gas exchange. COPD pts lack this, thus decreasing affinity for gas exchange

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6
Q

ABG Measurements and Normal Ranges

(6 values)

A
  1. PaO2 (partial pressure of oxygen) = 80-100 mmHg
  2. PaCO2 (partial pressure of carbon dioxide) = 35-45 mmHg
  3. pH = 7.35-7.45
  4. HCO3 = 24-28 meq/L
  5. SO2 = 95-100% (critical <90% due to change in dissociation curve)
  6. Base Excess = -2 - +2 mmol/L
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7
Q

Base Excess

(define, use, value interpretation)

A

Def: Amt of acid necessary to achieve optimal pH

Use: measure bicarb and overall metabolic acid-base state of pt

Interpretation: units = “equivalents”

  • <0 = acidosis (you must take away acid to reach balance)
  • >0 = alkalosis (you must add acid to reach balance)
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8
Q

ABG Analysis Algorhythm

A

Evaluate ABG results in this order

  • Acid - base balance
    1. pH - normal or abnormal?
    2. PaCO2 - normal or abnormal?
    3. HCO3 - normal or abnormal?
    4. PaCO2 and HCO3 - correlate c pH?
  • Ventilatory/Respiratory adequacy
    1. PaO2, SO2 - normal or abnormal?
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9
Q

ABG Signs, Primary Respiratory Distrubance

A

pH - high

PaCO2 - low

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10
Q

ABG Signs, Metabolic Acidosis

A

Abnormal Values:

  • pH
  • HCO3
  • B.E.
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11
Q

Primary ABG Distrubances

(4)

A
  1. Respiratory Acidosis
  2. Respiratory Alkalosis
  3. Metabolic Acidosis
  4. Metabolic Alkalosis

*Note, these will all couple c compensatory mechanisms, making laboratory interpretation more difficult *

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12
Q

Compensatory Mechanisms

(4 categories, 2/2/3/3 specifics)

A
  1. Respiratory Acidosis (high CO2)
    • ​Renal H+ excretion
    • Renal HCO3 reabsorption
  2. Respiratory Alkalosis (low CO2)
    • ​Renal HCO3 excretion
    • Renal H+ excretion decrease
  3. Metabolic Acidosis
    • ​Initial RR increase
    • Renal H+ excretion
    • Renal HCO3 reabsorption
  4. Metabolic Alkalosis
    • ​Initial RR decrease
    • Renal HCO3 excretion
    • Renal H+ retention
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13
Q

Respiratory Acidosis

(Uncompensated and Compensated)

A

Uncompensated:

  • pH < 7.35
  • PaCO2 >45 mmHg
  • HCO3 - normal

Compensated:

  • pH - normal
  • PaCO2 >45 mmHg
  • HCO3 > 28 meq/L

*General Tx - add bicarb *

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14
Q

Respiratory Alkalosis

(Cause, Uncompensated, Compensated, Tx)

A

Cause: due to decrease in acid concentration, very rarely due to increase in bases

Uncompensated:

  • pH > 7.45
  • PaCO2 <35 mmHg
  • HCO3 - normal

Compensated:

  • pH - normal
  • PaCO2 <35 mmHg
  • HCO3 <24 meq/L

Tx: Ctrl diarrhea to keep bases in

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15
Q

Metabolic Acidosis

(Associated Condition, Pathophys, Uncompensated, Compensated)

A

Asst Condition: DKA

Pathyphys: Bicarb is primary distrubance due to metabolic nature (lack of bicarb makes you more acidic)

Uncompensated:

  • pH < 7.35
  • PaCO2 - normal
  • HCO3 - <24 meq/L
  • BE < -2

Compensated: (via ventilation changes)

  • pH normal
  • PaCO2 <35 mmHg
  • HCO3 < 24 meq/L
  • BE > +2
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16
Q

Metabolic Alkalosis

(pathophys, uncompensated, compensated)

A

Pathphys: usually due to a change in bicarb concentration; amount of acid will stay the same

Uncompensated:

  • pH > 7.45
  • PaCO2 - normal
  • HCO3 > 28 meq/L
  • B.E. > +2

Compensated: (via ventilation changes)

  • pH - normal
  • PaCO2 > 45 mmHg
  • HCO3 > 28 meq/L
  • B.E. < -2
17
Q

Clinical Respiratory Acidosis

(4 disease states, 4 s/sx, 4 dx tests, 8 tx)

A

Disease States: All reflective of change in ventilation status

  1. Lung disease
  2. Airway obstruction
  3. Respiratory center depression
  4. Neuromuscular problems

Signs and Symptoms:

  1. Dyspnea
  2. **Shallow, rapid ventilations **(in attempt to blow off more CO2, but not usually very helpful)
  3. Diaphoresis
  4. Warm, flushed skin

Laboratory Tests:

  1. ABG
  2. CXR
  3. Electrolyte levels, esp K+>5 meq/L
  4. Other blood tests - tox screen (TCA’s are most common cause)

Treatment:

  • Maintain airway
  • Bronchodilators
  • Supplimental oxygen
  • Treat hyperkalemia
  • Antibiotics for infection
  • Tracheal suctioning
  • Monitor cardiac rhtythm
  • Observe for neuro changes
18
Q

Purpose of Compensation

A

Regulate the body pH. Therefore, other ABG values may change from normal to abnormal when a patient is compensating in order to maintain a safe pH

19
Q

Potassium Change c Acidosis

A

K+ is one of the primary intracellular electrolytes. If H+ ions enter the cell, a K+ leaves to maintain intracellular charge.

If done in high amounts hyperkalemia is a risk

20
Q

Clinical Respiratory Alkalosis

(5 disease states, 8 s/sx, 4 dx studies, 6 tx)

A

Disease States:

  1. Hyperventilation
  2. Acute hypoxia c altitude change
  3. Severe anemia
  4. Pulmonary embolus
  5. Drugs - nicotine, salicylates

S/Sx:

  • Tachycardia
  • Syncope
  • Dyspnea
  • Tachypnea
  • Diaphoresis
  • Anxiety
  • Confusion
  • Parethesias

Dx Tests:

  1. ABG
  2. EKG
  3. Electrolye analysis (esp K+ for hypokalemia)
  4. Drug screen (for compensation from ASA overdose)

Treatment:

  1. Treat underlying cause
  2. Supplimental oxygen
  3. Sedative for causative anxiety
  4. Rebreathe CO2 via paper bag
  5. VS monitoring
  6. Observe for neuro changes
21
Q

Clinical Metabolic Acidosis

(4 disease states, 8 s/sx, 4 dx tests, 6 tx)

A

Disease States:

  1. Ketone overproduction - diabetes, alcoholism, hyperthyroidism
  2. Lactic acidosis - shock, CHF, seizures, liver disease
  3. Kidney disease
  4. Drugs - ASA, methanol, ethanol

S/Sx:

  • Diarrhea, vomiting
  • Muscle weakness
  • Hypotension
  • Warm, dry, flushed skin
  • Lethargy
  • Anorexia
  • Blindness (c methanol overdose)
  • Confusion
  • **Kussmal’s respirations **

Dx Studies:

  1. ABG
  2. EKG
    • ​Tall T waves
    • Wide QRS
    • Prolonged PR
  3. Electrolytes - hyperkalemia
  4. Glucose and keytones

Treatment:

  • Mechanical ventilation, if necessary
  • Monitor K+
  • Admin rapid acting insulin (get glucose into cells - change pH)
  • Dialysis (renal failure only)
  • Antidiarrheal med
  • Monitor neurologic status
22
Q

Clinical Metabolic Acidosis

(3 disease states, 6 s/sx, 3 dx studies, 5 tx)

A

Disease States:

  1. ​Diuretics (losing NaCl, reabsorbing more bicarb)
  2. Excessive acid loss from GI tract (vomiting, NG suctioning)
  3. Drugs (antacids, diuretics)

S/Sx:

  • Hypotension
  • Cyanosis
  • N/V/anorexia
  • Weakness
  • Paresthesias
  • Confusion

Lab Tests:

  1. ABG
  2. EKG (low T waves)
  3. Electrolytes
    • hyperkalemia
    • hypercalcemia

Treatment:

  • D/C diuretics/NG suctioning
  • Antiemetic
  • Supplimental O2
  • Seizure precautions
  • Monitor for muscle weakness, tetany
23
Q

Name the Condition:

pH - 7.55

PaCO2 - 37 mmHg

PaO2 - 99 mmHg

SO2 - 98%

HCO3 - 31 meq/L

A

Metabolic Alkalosis, uncompensated

24
Q

Name the Condition:

pH - 7.36

PaCO2 - 32 mmHg

PaO2 - 44 mmHg

SO2 - 78%

HCO3 - 17 meq/L

A

Compensated Metabolic Acidosis

25
Q

Name the Condition:

pH - 7.23

PaCO2- 84 mmHg

PaO2 - 84 mmHg

SO2 - 80%

HCO3 - 26 meq/L

A

Respiratory Acidosis

Diagnostic Studies, Unit III (6 decks)

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