Normal pH range for extracellular fluid: 7.35 to 7.45
Mechanisms of pH balance:
Generate, buffer, and eliminate acids and bases.
Definition: Molecule that releases hydrogen (H+).
Example: Hydrochloric acid (HCl) dissociates in water to form H+ and Cl-.
Definition: Ion or molecule that accepts or combines with hydrogen.
Example: Bicarbonate (HCO3-) combines with H+ to form carbonic acid (H2CO3), a weak acid.
Chemical Buffer System
Combines with excessive acids or bases to prevent large changes in pH.
Lungs
Control elimination of CO2.
Kidneys
Eliminate H+ (acidic) and reabsorb/generate new HCO3- (bicarbonate).
ROAM:
Respiratory: Opposite
Metabolic: Equal
pH Standards:
Acidosis: pH < 7.35
Alkalosis: pH > 7.45
Opposite Relation: High pH → Low CO2 (Alkalosis)
Indicators of Acidosis: Low pH → High CO2 (Hypoventilation)
Normal Respiratory Rate: 12 to 20 breaths per minute.
Equal Relation:
High pH → High HCO3- (Alkalosis)
Low pH → Low HCO3- (Acidosis)
Bicarbonate Normal Range: 22 to 26 mEq/L
Collected from radial artery using a needle at a 90-degree angle.
Differentiation: Arterial blood is bright red; venous blood is dark/purple.
Causes: Drug overdose, lung diseases, impaired ventilation.
Presentation:
Low pH, high CO2, normal HCO3- (uncompensated) or high HCO3- (compensated).
Symptoms: Headaches, confusion, drowsiness.
Causes: Panic attacks, hypoxia, drug reactions.
Presentation:
High pH, low CO2, normal HCO3-.
Symptoms: Dizziness, lightheadedness, seizures.
Causes: Excessive production of lactic acid, renal failure, diabetic ketoacidosis.
Presentation:
Low pH, low HCO3-, normal/high CO2.
Symptoms: Nausea, confusion, lethargy.
Causes: Ingestion of antacids, GI loss of acid (vomiting), diuretics.
Presentation:
High pH, high HCO3-, normal CO2.
Symptoms: Confusion, hypokalemia, seizures.
Respiratory System: Rapid response (within 30 minutes) for pH adjustment; effective but only 50-75% as a buffer.
Kidneys: Slower response (5-10 minutes to begin; 3-5 days to complete).
Compensation Levels:
Uncompensated: One parameter normal, one abnormal.
Partially Compensated: Both parameters abnormal, pH still abnormal.
Fully Compensated: Normal pH, both parameters abnormal.
Determining Compensation:
pH normal = fully compensated.
pH abnormal = partially compensated.
One normal parameter indicates uncompensated.
Normal CO2: 35 to 45 mmHg
Normal HCO3-: 22 to 26 mEq/L
Strong emphasis on memorizing the acid-base ranges, mnemonics, and clinical presentations associated with different disorders.
Students encouraged to practice identifying and interpreting ABG values and understanding the primary disorder and compensation status.
Importance of understanding these concepts for nursing practice and exam preparation.