Arterial Blood Gases Flashcards
What is ph?
- pH: 7.35 - 7.45
- Balance of H+
What is PaC02?
- PaCO2: 35 – 45 mmHg
- Respiratory parameter
- Carbonic acid ‘dissolves’ into CO2 and H2O
What is HC03?
- 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
What is an Acid/Base Primary EVENT?
- The PROBLEM that initiates the acid-base imbalance
- Hypoventilation, hyperventilation, vomiting, diarrhea, etc
What is an Acid/Base Primary DISORDER?
- What RESULTS from the primary event
- Respiratory acidosis, metabolic alkalosis, etc
What are the Acid/Base Compensation mechanisms ?
- 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
If the General Cause is METABOLIC what is the acid/base imbalance?
- HCO3 (bicarbonate) level changes secondary to METABOLIC alterations (kidneys)
- The PROBLEM is metabolic in nature
If the General Cause is REPSIRATORY what is the acid/base imbalance?
- H²CO³(carbonic acid) level changes secondary to RESPIRATORY alterations (lungs)
- The PROBLEM is respiratory nature
What happens in Respiratory acidosis and Respiratory alkalosis?
Increase or decrease in CO2
Changes in ventilation
What happens in Metabolic ACIDOSIS and ALKALOSIS?
Changes in [H+] or bicarbonate ions
Acid/Base Mnemonic - ROME
What happens in Metabolic Alkalosis?
- too much Bicarb “OR” not enough CARBONIC ACID
- ABGs:
- pH > 7.48 ↑B
- PaCO2 – 35-45 ↔
- HCO3 > 26 ↑B
What are causes of Metabolic Alkalosis?
- 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
Clinical manifestations of metabolic alkalosis
- CNS over-excitability
- Confusion
- Tremors
- Muscle cramps
- Paresthesias - tingling of fingers and toes, perioral
- Coma
- N/V/D
- Resp depression
What is Respiratory Alkalosis?
- 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 ↔
What causes Respiratory Alkalosis?
- Hyperventilation
- Increased metabolic demands - Fever, sepsis
- Medications
- Acute anxiety
- Hypoxia
- PE or lung disease
- CNS lesions
- Ventilator settings
Clinical manifestations of Respiratory Alkalosis
- CNS over-excitability
- Tachypnea
- Light headedness
- Confusion, blurred vison
- Paresthsia -Numbness of hands and feet, perioral
- Hyperactive reflexes, seizures
- Coma
Respiratory Acidosis - Acute and Chronic
- 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)
Why would HCO3 be within normal limits in Respiratory Acidosis?
No time for kidneys to compensate (takes hours to days)
Respiratory Acidosis Clinical signs and symptoms
CNS depression causing
- hypoventilation
- dyspnea
- respiratory distress
- shallow respirations
- H/A, restlessness, confusion
- tachycardia, arrhythmias
- LOC, stupor, coma
What are common causes of Respiratory Acidosis?
- 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
What happens in Metabolic Acidosis ?
- HCO³ (BICARBONATE) DEFICIT in ECF
- excess acids are added OR bicarb is lost
What are the ABG’s in Metabolic Acidosis?
- pH < 7.35 ↓A
- PaCO2 - 35-45 ↔
- HCO3- < 22 ↓Acid (less base)
What are clincal signs and symptoms of Metabolic Acidosis?
- CNS
- Lethargy, drowsiness
- Confusion
- Tremors, muscle cramps
- Paresthesias Tingling of fingers or toes, perioral
- Hypotension
- Hyperkalemia
- Deep breathing - Kussmaul respirations (DKA)
Respiratory Acidosis/Alkalosis:
COMPENSATION
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
Metabolic Acidosis/Alkalosis:
COMPENSATION
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
