Understanding Acid-Base Physiology in Anesthesia
Ahmed Sharef
teacherWhat is an acid in terms of hydrogen ions?
A hydrogen ion donor.
How is a base defined in relation to hydrogen ions?
A hydrogen ion acceptor.
What does the strength of acids or bases refer to?
Their ability to donate and accept H+ ions, respectively.
What happens to hydrochloric acid (HCl) when dissolved in water?
Almost all of the H in the acid is released as H+.
Why is lactic acid considered a weaker acid than hydrochloric acid?
A considerable quantity of lactic acid remains as lactic acid molecules when dissolved in water.
What is a buffer solution?
A solution where pH changes less when an acid or base is added compared to a non-buffer solution.
What is the normal arterial blood pH range?
7.35 - 7.45.
What pH level indicates acidosis?
pH < 7.35.
What pH level indicates alkalosis?
pH > 7.45.
What are the three major buffering systems?
Bicarbonate, phosphate, and protein buffering systems.
What is the primary buffering system in extracellular fluid?
The bicarbonate system.
What is the chemical equation for carbonic acid dissociation?
H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3-.
How do the kidneys regulate pH?
By either acidification or alkalinization of the urine.
What does an increased anion gap (AG) imply?
Accumulation of organic acids in the body.
What is the formula for calculating the anion gap (AG)?
AG = ([Na+] + [K+]) – ([Cl-] + [HCO3-]).
What is the primary disturbance in respiratory acidosis?
Increased PCO2.
What compensatory mechanism occurs in metabolic acidosis?
Decreased PCO2 (hyperventilation).
What characterizes metabolic alkalosis?
Primary increase in bicarbonate (HCO3-) with or without compensatory increase in carbon dioxide partial pressure (PCO2).
What is a common cause of metabolic alkalosis related to stomach acids?
Loss of stomach acids (vomiting).
How is chloride-responsive metabolic alkalosis typically treated?
With an IV saline solution (sodium chloride).
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Description
Explore the fundamentals of acid-base physiology, including the roles of acids, bases, and buffer systems in maintaining pH balance. Learn about the importance of pH regulation and its impact on enzyme activity and overall health.
Questions
Download Questions1. What is the primary function of a buffer solution in acid-base physiology?
2. Which system is the fastest to respond to pH imbalance in the body?
3. What happens to alveolar ventilation in response to increased CO2 levels?
4. What is the normal range for arterial blood pH?
5. What does an increase in the anion gap typically indicate?
6. What is the most common cause of metabolic alkalosis?
7. Which diagnostic method is used to confirm metabolic alkalosis?
8. What is a symptom of severe metabolic alkalosis?
9. What is the primary treatment for chloride-responsive metabolic alkalosis?
10. What is a common cause of lactic acidosis?
Study Notes
Acid-Base Physiology and Anesthesia
Understanding acid-base physiology is crucial in anesthesia and patient care, as it encompasses the balance of hydrogen ions (H+) in the body, influencing various physiological functions.
Definitions and Strengths of Acids and Bases
- Acids and Bases: Acids donate H+ ions, increasing their concentration, while bases accept H+ ions.
- Strength Hierarchy: Strong acids like hydrochloric acid (HCl) fully dissociate in water, whereas weak acids like lactic acid do not. The strength hierarchy is: HCl > Lactic Acid > Carbonic Acid (H2CO3).
Importance of Acid-Base Balance
- Physiological Significance: Maintaining a stable pH range (7.35 - 7.45 for arterial blood) is essential for enzyme activity and overall metabolic processes.
- Health Implications: Imbalances can lead to acidosis or alkalosis, affecting central nervous system function.
Buffer Systems and Regulation
- Buffer Solutions: Critical for stabilizing pH in biological systems; key buffers include bicarbonate, phosphate, and proteins.
- Regulatory Mechanisms:
- Respiratory Responses: Quick adjustments through changes in breathing rate based on CO2 levels.
- Renal Responses: Longer-term regulation by adjusting urine composition to manage acidity or alkalinity.
Anion Gap and Disorders
- Anion Gap (AG): A diagnostic tool to assess metabolic acidosis; calculated using electrolytes ([Na+] + [K+] – [Cl-] + [HCO3-]). Normal values range from 12 to 16 mEq/L.
- Common Disorders:
- Respiratory Acidosis/Alkalosis involve changes in CO2 levels.
- Metabolic Acidosis/Alkalosis involve alterations in bicarbonate levels.
Types of Alkalosis
- Chloride-responsive Alkalosis: Often due to loss of gastric acid (e.g., vomiting); treated with saline solutions.
- Chloride-resistant Alkalosis: Associated with electrolyte imbalances; potassium chloride may be administered.
Key Takeaways
- Understanding acid-base balance is vital for effective patient management during anesthesia.
- Various buffer systems work together to maintain pH stability quickly or over longer periods.
- Recognizing the signs of acidosis or alkalosis can guide appropriate interventions based on underlying causes.
This synthesis provides an overview of essential concepts related to acid-base physiology relevant to anesthesia practice.
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