ABG's Flashcards
Purpose of ABG
To access acid-base status and to determine adequacy of oxygenation and ventilation
Normal Values: pH
- 35-7.45
- balance of H+ ions
Normal Values: pCO2/Co2
35-45 mmHg
- respiratory parameter
- carbonic acid HCO3 dissolves into CO2 + H2O
Normal Values: HCO3-
22-26
- metabolic parameter
- This is CALCULATED on the ABG
- Measured HCO3- is reported as CO2 on a chemistry panel
- Serum CO2
Normal Values: O2
95-100%
Normal Values: pO2
80-100
Primary Event
The PROBLEM that initiates the acid-base imbalance
-Hypoventilation, Hyperventilation, vomiting, diarrhea….
Primary Disorder
What RESULTS from the primary event
-Respiratory acidosis, metabolic alkalosis ect…
Compensation mechanisms
Physiologic process that adjust the pH back to normal range
- If lungs are problem – kidneys will compensate
- If kidneys are problem – lungs will compensate
General CAUSE of imbalance is termed: “METABOLIC”
- HCO3 (Bicarb) level changes secondary to METABOLIC alterations (kidneys)
- The PROBLEM is metabolic in nature
General CAUSE of imbalance is termed: “RESPIRATORY”
- H2CO3 (carbonic acid) levels changes secondary to RESPIRATORY alterations (lungs)
- The PROBLEM is respiratory in nature.
Types of Imbalances: Respiratory acidosis + Respiratory alkalosis
Increase or decrease in CO2 changes in ventilation
Types of Imbalances: Metabolic acidosis
Metabolic alkalosis
Changes in [H+] or bicarbonate ions
PaCO2
Acid (carbon dioxide)
-Respiratory
HCO3
Base (bicarbonate)
-Metabolic (kidney)
Causes of Metabolic Alkalosis
- Too much baking soda (alka-seltzer)
- results in hypokalemia causing hydrogen to shift out of the intracellular space and K+ goes into the cell - Prolonged vomiting
- NG tube
- Diuretics
Metabolic Alkalosis: S/S
-CNS over-excitability causing: (restlessness) -Confusion -Tremors -Muscle cramps -Paresthesia's (tingling of fingers and toes) -Coma -N/V/D -Respiratory depression -Dysrhythmias (Tachycardia) -Hypokalemia -Compensatory Hypoventilation
Metabolic Alkalosis can be caused by
too much Bicarb (HCO3) or not enough Carbonic Acid (H2CO3)
ABG’s
pH: high
PaCO2: 35-45 (same)
HCO3 > 26 (high)
H2CO3 (carbonic acid) = CO2 + H2O
Might see H2CO3 or CO2
Respiratory Alkalosis can be caused by
H2CO3 deficit in ECF
Primary cause: Hyperventilation (CO2 blown off)
ABGs
pH: high
PaCO2: <35 (low)
HCO3: 22-26 (same)
Respiratory Alkalosis: Causes
- Hyperventilation
- Increased metabolic demands (fever, sepsis)
- Medications
- Acute anxiety
- Hypoxia
- PE or lung disease
- CNS lesions
- Ventilator settings
Respiratory Alkalosis: S/S
CNS Over-excitability causing: -tachypnea -Light headedness -Confusion, blurred vision -Paresthesia -Hyperactive reflexes -Coma -Hypokalemia -Tachycardia -N/V (similar to metabolic alkalosis)
Respiratory Acidosis: Acute or Chronic
H2CO3 excess in ECF (too much acid/H+)
Hypoventilation (CO2 remains)
Acute: respiratory arrest
Chronic: COPD or over sedation
pH: Low
PaCO2: >45
HCO3: 22-26 (same)
HCO3 (bicarb) WNL if acute respiratory acidosis, NO time for kidneys to compensate
HCO3 will be high if Chronic (COPD)
Respiratory Acidosis: causes
- Cardiopulmonary arrest
- head injury
- Narcotics/sedatives
- Anesthesia (paralyze lungs)
- Pulmonary disorders (acute asthma, COPD, PNA, resp failure)
- Pain
- Abdominal distension
- Airway obstruction
- Chest wall deformities
- Neuromuscular problems
**All caused by Hypoventilation
Respiratory Acidosis: S/S
CNS Depression causing
- Hypoventilation
- Dyspnea
- Respiratory distress
- Shallow respirations
- H/A, restlessness, confusion
- tachy, arrhythmias
- Dec LOC, Stupor, Coma
- Dec BP
Metabolic Acidosis
HCO3 (Bicarb) Deficit in ECF
-Excess acids are added or bicarb is lost
ABGs
pH: Low
PaCO2: 35-45 (same)
HCO3: <22
Metabolic Acidosis: Causes
- renal failure
- Fistulas (loss of Bicarb)
- Diabetes (type 1 DM-DKA)
- Lactic acidosis
- Prolonged diarrhea (relative increased acid d/t loss of HCO3)
- Starvation (body using fat for energy resulting in ketosis)
- Shock and cardiac arrest
Metabolic Acidosis: S/S
CNS
- lethargy
- Confusion
- tremors, muscle cramps
- paresthesia’s
- 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
- Excreting HCO3
-takes hours to days for kidneys to compensate
Metabolic Acidosis/Alkalosis Compensation
Are the results of metabolic alterations and the LUNGs compensate by either
- Conserving CO2 ions (hypoventilation)
- Excreting CO2 ions (hyperventilation)
-The kidney also attempts to correct imbalance by retaining/excreting HCO3
