Acid-Base Balance and ABGs Quiz

Acid-Base Balance

• Acid-base balance is crucial for maintaining homeostasis.
• The body regulates hydrogen ion concentration (measured as pH).
• Normal pH range: 7.35-7.45.
• pH < 6.8 or > 7.8 is life-threatening.
• Acidosis: pH decreases below normal range.
• Alkalosis: pH increases above the normal range.
• Kidneys and lungs are the main organs controlling acid-base balance.
• The kidneys reabsorb/excrete acids/bases and produce bicarbonate.
• The lungs regulate CO2 levels.

Learning Outcomes

• Describe normal acid-base balance.
• Determine signs, symptoms, and management of imbalances.
• Apply concepts to patient scenarios.

Acid-Base Basics

• Acid-base balance depends on regulating free hydrogen ions (pH).
• Hydrogen ion concentration is measured as pH.
• Arterial blood gases (ABGs) are crucial for diagnosis.

Normal pH Values

• Normal range: 7.35-7.45.
• Acidemia: pH < 7.35.
• Alkalemia: pH > 7.45.

Other Normal ABG Values

• pO2 (80-100 mmHg): measures oxygenation.
• pCO2 (35-45 mmHg): reflects lung function.
• HCO3- (22-26 mEq/L): bicarbonate concentration.
• Anion Gap (8-12): helps categorize metabolic acidosis.

Anion Gap Calculation

• Anion Gap = Na+ - (Cl- + HCO3-).

ABG Overview

• pH (7.35-7.45).
• PaCO2 (35-45 mmHg).
• HCO3- (22-26 mEq/L).

Acidosis/Alkalosis

• Acidosis: pH < 7.35, caused by acid buildup or base loss.
• Alkalosis: pH > 7.45, caused by base buildup or acid loss.

In-Class Activity

• What are the main organs that control acid-base balance?

Acid-Base Control

• Kidneys and lungs are the main organs controlling acid-base balance.

Regulatory Systems

• Chemical Buffers: Act immediately to neutralize changes.
• Respiratory System: Regulates CO2 levels.
• Kidneys: Reabsorb or excrete acids/bases.

Chemical Buffers

• Bicarbonate: Buffers blood and interstitial fluid.
• Phosphate: Effective in renal tubules.
• Protein: Most plentiful, includes hemoglobin.

Respiratory System

• High CO2: Slower breathing, lower pH.
• Low CO2: Faster breathing, higher pH.

Kidneys

• Reabsorb/excrete acids/bases.
• Produce bicarbonate.
• Adjustments take hours to days, bicarbonate and pH change together.

Metabolic vs. Respiratory

• Primary abnormality is often accompanied by compensation, trying to return bicarbonate/CO2 ratio and pH to normal.
• Metabolic alters pH by changing bicarbonate.
• Respiratory alters pH by changing pCO2.

Compensation

• Body never overcompensates, except chronic respiratory alkalosis.
• pH rarely returns to normal.

Arterial Blood Gases (ABG)

• Normal ABG values can still be harmful depending on patient's condition.

Interpreting ABGs

• Step 1: Check pH (acidosis or alkalosis).
• Step 2: Analyze pCO2 (resp).
• Step 3: Evaluate bicarbonate (metabolic).
• Step 4: Assess Compensation.
• Step 5: Review PaO2 and SaO2.

Step 1: Check pH

• Acidosis: pH < 7.35.
• Alkalosis: pH > 7.45.

Step 2: Analyze CO2

• PaCO2 gives information about respiratory component of acid-base balance.
• If abnormal, does the change correspond with a change in pH?

CO2 and pH Relationship

• High pH expects low PaCO2 (hypocapnia).
• Low pH expects high PaCO2 (hypercapnia).

Step 3: Evaluate Bicarbonate

• Bicarbonate reflects the metabolic component.
• High pH, high bicarbonate; low pH, low bicarbonate.

Step 4 - Look for Compensation

• If a change is seen in both PaCO2 and bicarbonate, the body is trying to compensate.
• Compensation occurs as opposites (e.g., metabolic acidosis -> respiratory alkalosis).

Step 5 - What is the PaO2 and SaO2?

• PaO2 reflects the ability to pick up O2 from the lungs.
• SaO2 less than 95% is inadequate oxygenation.
• Low PaO2 indicates hypoxemia.

In Class Sample Problems

• pH, pCO2, and HCO3 values are provided with corresponding Acid-Base Disorders.

Figure 3

• Shows the primary and compensatory changes in metabolic acidosis and alkalosis, respiratory acidosis and alkalosis (involving pCO2 and HCO3).

Acid-Base Imbalances

• Types of acid-base imbalances include Respiratory Acidosis/Alkalosis and Metabolic Acidosis/Alkalosis.

Respiratory Acidosis

• Cause: Compromised breathing leads to hypoventilation and CO2 buildup.
• Origins: Neuromuscular issues, respiratory center depression, lung disease, or airway obstruction.
• At-Risk Clients: Post-op abdominal surgery patients, patients on mechanical ventilation, and patients taking certain medications.
• Symptoms: Mental state (apprehension, restlessness, confusion, tremors) and physical signs (decreased DTRs, diaphoresis, dyspnea, tachycardia).
• ABGs: Uncompensated (pH <7.35, pCO2 > 45, and HCO3 normal) or compensated (pH close to normal, pCO2 > 45, and HCO3 > 26).
• Treatment: Address the underlying cause, respiratory support (bronchodilators and supplemental oxygen), other treatments (treat hyperkalemia, infections, and remove obstructions).

Respiratory Alkalosis

• Cause: Hyperventilation, often caused by pain, salicylate poisoning, nicotine, aminophylline, hypermetabolic states, or acute hypoxia.
• Symptoms: Mental state (anxiety, restlessness, paresthesias) and physical signs (tachycardia, EKG changes). Other symptoms may include diaphoresis, dyspnea (increased rate and depth), and tetany.
• ABGs: Uncompensated (pH > 7.45, pCO2 < 35, and HCO3 normal or compensated (pH close to normal, pCO2 < 35, and HCO3 <22).
• Treatment: Treat the underlying disorder, oxygen and medications (oxygen therapy for hypoxemia, sedatives, or antianxiety agents), treat hyperventilation (paper bag breathing).

Metabolic Acidosis

• Characterized by acid gain or bicarbonate loss, associated with ketone bodies in conditions like diabetes, alcoholism, and starvation.
• Lactic Acidosis: Secondary to shock, heart failure, pulmonary disease, hepatic disease, seizures, or strenuous exercise.
• MUD PILES: Methanol, Uremia, Diabetic ketoacidosis, Propylene glycol, Isoniazid, Lactic acidosis, Ethanol/Ethylene glycol, Salicylates.
• Other Causes: Gastrointestinal bicarbonate loss and renal bicarbonate loss.
• Symptoms: neurological (confusion, dull headache, decreased DTRs, lethargy), gastrointestinal/muscular (abdominal cramps, diarrhea, muscle weakness), other (hypotension, Kussmaul's respirations, warm and dry skin, EKG changes).
• ABGs: Uncompensated (pH <7.35, pCO2 normal, and HCO3 < 22) or compensated (pH close to normal, pCO2 low in response to acidosis, and HCO3 lowered).
• Treatment: DKA (regular insulin), Acidosis (IV bicarbonate), other (fluid replacement, dialysis for drug toxicity, and antidiarrheals).

Metabolic Alkalosis

• Often associated with hypokalemia, hypochloremia, and hypocalcemia; caused by vomiting, NG suction, Cushing's disease, or baking soda.
• Symptoms: General (anorexia, apathy, confusion, cyanosis, hypotension), Neuro/Muscular (muscle twitching, paresthesia, loss of reflexes, weakness), other (nausea, polyuria, vomiting).
• ABGs: Uncompensated (pH >7.45, pCO2 normal, and HCO3 >26) or compensated (pH close to normal, pCO2 elevated in response to alkalosis, and HCO3 elevated).
• Treatment: Medication (IV ammonium chloride), Diuretics/Suction (discontinue diuretics and NG suctioning), antiemetics (control vomiting).

Case Study

• Summarized information about a patient (age 35, female, AIDS, with fever, three months of copious diarrhea, blood pressure is 100/60, pulse is 100, respiratory rate is 18 , afebrile).
• Lab results are provided (Sodium, Potassium, Chloride, BUN, Creatinine, Glucose).
• Arterial blood gas results are provided (pH, pCO2, pO2, HCO3, and total CO2).

This quiz tests your understanding of acid-base balance, particularly in the context of respiratory acidosis and metabolic compensation. You'll explore the relationships between pH, PaCO2, bicarbonate levels, and clinical implications in arterial blood gases (ABGs). Challenge your knowledge and see how well you grasp these critical concepts!