Arterial Blood Gases

Question 1

What is ph?

Answer 1

• pH: 7.35 - 7.45
• Balance of H+

Question 2

What is PaC02?

Answer 2

• PaCO2: 35 – 45 mmHg
• Respiratory parameter
• Carbonic acid ‘dissolves’ into CO2 and H2O

Question 3

What is HC03?

Answer 3

• HCO3-: 22 – 26 mEq/L
• Metabolic parameter
• THIS IS CALCULATED ON THE ABG
• Measured HCO3- is reported as CO2 on a chemistry panel
• Serum CO2

Question 4

What is an Acid/Base Primary EVENT?

Answer 4

• The PROBLEM that initiates the acid-base imbalance
• Hypoventilation, hyperventilation, vomiting, diarrhea, etc

Question 5

What is an Acid/Base Primary DISORDER?

Answer 5

• What RESULTS from the primary event
• Respiratory acidosis, metabolic alkalosis, etc

Question 6

What are the Acid/Base Compensation mechanisms ?

Answer 6

• Physiologic processes that adjust the pH back to the normal range
• If the lungs are the problem – the kidneys will compensate
• If the kidneys are the problem – the lungs will compensate

Question 7

If the General Cause is METABOLIC what is the acid/base imbalance?

Answer 7

• HCO3 (bicarbonate) level changes secondary to METABOLIC alterations (kidneys)
• The PROBLEM is metabolic in nature

Question 8

If the General Cause is REPSIRATORY what is the acid/base imbalance?

Answer 8

• H²CO³(carbonic acid) level changes secondary to RESPIRATORY alterations (lungs)
• The PROBLEM is respiratory nature

Question 9

What happens in Respiratory acidosis and Respiratory alkalosis?

Answer 9

Increase or decrease in CO2

Changes in ventilation

Question 10

What happens in Metabolic ACIDOSIS and ALKALOSIS?

Answer 10

Changes in [H+] or bicarbonate ions

Question 11

Acid/Base Mnemonic - ROME

Answer 11

Question 12

What happens in Metabolic Alkalosis?

Answer 12

• too much Bicarb “OR” not enough CARBONIC ACID
• ABGs:
• pH > 7.48 ↑B
• PaCO2 – 35-45 ↔
• HCO3 > 26 ↑B

Question 13

What are causes of Metabolic Alkalosis?

Answer 13

• Taking excess baking soda, alka-seltzer = too much base
• RESULTS IN - hypokalemia causing hydrogen to shift out the intracellular

space and potassium goes into the cell

• Prolonged vomiting
• NG tube
• Diuretics

Question 14

Clinical manifestations of metabolic alkalosis

Answer 14

• CNS over-excitability
• Confusion
• Tremors
• Muscle cramps
• Paresthesias - tingling of fingers and toes, perioral
• Coma
• N/V/D
• Resp depression

Question 15

What is Respiratory Alkalosis?

Answer 15

• H²CO³ (CARBONIC ACID) DEFICIT in ECF
• Cause - Hyperventilation ¬ primary event gCO2 blown off
• ABGs
• pH > 7.45 ↑ B
• PaCO2 < 35 ↓ B (less H+) blowing off CO2 and H2O
• HCO3- 22-26 ↔

Question 16

What causes Respiratory Alkalosis?

Answer 16

• Hyperventilation
• Increased metabolic demands - Fever, sepsis
• Medications
• Acute anxiety
• Hypoxia
• PE or lung disease
• CNS lesions
• Ventilator settings

Question 17

Clinical manifestations of Respiratory Alkalosis

Answer 17

• CNS over-excitability
• Tachypnea
• Light headedness
• Confusion, blurred vison
• Paresthsia -Numbness of hands and feet, perioral
• Hyperactive reflexes, seizures
• Coma

Question 18

Respiratory Acidosis - Acute and Chronic

Answer 18

• H²CO³ excess in ECF (too much acid/H+)
• pH < 7.35 ↑A
• PaCO2 > 45 ↓A (more H+) retaining CO2 and H2O
• HCO3- 22-26 *↔
• Cause:
• Hypoventilation “primary event” g CO2 retained (H+)
• Acute vs chronic causes (resp arrest vs COPD or oversedation)

Question 19

Why would HCO3 be within normal limits in Respiratory Acidosis?

Answer 19

No time for kidneys to compensate (takes hours to days)

Question 20

Respiratory Acidosis Clinical signs and symptoms

Answer 20

CNS depression causing

• hypoventilation
• dyspnea
• respiratory distress
• shallow respirations
• H/A, restlessness, confusion
• tachycardia, arrhythmias
• LOC, stupor, coma

Question 21

What are common causes of Respiratory Acidosis?

Answer 21

• cardiopulmonary arrest
• head injury
• narcotics/sedatives
• anesthesia
• pulmonary disorders (acute asthma,COPD exacerbation, pneumonia, resp failure)
• pain
• abdominal distension
• airway obstruction
• chest wall deformities
• neuruomuscular problems

Question 22

What happens in Metabolic Acidosis ?

Answer 22

• HCO³ (BICARBONATE) DEFICIT in ECF
• excess acids are added OR bicarb is lost

Question 23

What are the ABG’s in Metabolic Acidosis?

Answer 23

• pH < 7.35 ↓A
• PaCO2 - 35-45 ↔
• HCO3- < 22 ↓Acid (less base)

Question 24

What are clincal signs and symptoms of Metabolic Acidosis?

Answer 24

• CNS
• Lethargy, drowsiness
• Confusion
• Tremors, muscle cramps
• Paresthesias Tingling of fingers or toes, perioral
• Hypotension
• Hyperkalemia
• Deep breathing - Kussmaul respirations (DKA)

Question 25

Respiratory Acidosis/Alkalosis:
COMPENSATION

Answer 25

Are the results of respiratory alterations and the KIDNEY compensates by either:

• conserving (reabsorbing) HCO3 -(bicarbonate) ions (acidosis correction)
• excreting HCO3- (bicarbonate)ions (alkalosis correction)
• Hours to days

Question 26

Metabolic Acidosis/Alkalosis:
COMPENSATION

Answer 26

Are the results of metabolic alterations and the LUNGS compensates by either:

• conserving CO2 ions ( hypoventilation/alkalosis correction)
• excreting CO2 ions (hyperventilation/acidosis correction)
• The kidney also attempts to “correct” imbalance by retaining/excreting HCO³-
• Minutes to hours