F/E & A/B LECTURE 3

Introduction to Acid-Base Balance

• Acid-base balance is essential to the homeostasis of the body and relates closely to the concentration of hydrogen ions in the blood.

• This balance is measured using pH, which is a logarithmic scale that reflects hydrogen ion concentration in the blood and other fluids, providing insight into the body's acid-base status.

• Normal arterial blood pH range is tightly regulated between 7.35 and 7.45; deviations from this range can have significant physiological effects.

• Acidosis is defined as a blood pH less than 7.35, indicating an increase in acidity, while alkalosis is characterized by a pH greater than 7.45, indicating an increase in alkalinity.

Definitions

• Acid: A chemical substance that dissociates and releases hydrogen ions when dissolved in a solution, contributing to the acidity of that solution. Common examples include hydrochloric acid and sulfuric acid.

• Base: A chemical substance that can accept hydrogen ions, effectively neutralizing acids. Bases can also generate hydroxide ions in solution. Examples include sodium hydroxide and bicarbonate.

• Bicarbonate (HCO3): The main alkaline anion in extracellular fluid and a key component of the bicarbonate buffer system, playing a crucial role in maintaining acid-base balance by neutralizing acids in the body.

pH and Hydrogen Ions

• The relationship between hydrogen ions and pH is inversely proportional; more hydrogen ions result in a lower pH and a more acidic environment, while fewer hydrogen ions produce a higher pH and a more alkaline environment.

• This inverse relationship is fundamental in understanding how the body regulates pH. It emphasizes the importance of various physiological processes to maintain homeostasis by either generating or eliminating hydrogen ions.

Body Mechanisms for pH Regulation

1. Blood Buffers:

   • Blood buffers act as the first line of defense against pH changes, providing immediate response (within seconds).

   • Buffer systems absorb excessive hydrogen ions (mitigating acidity) or release them (mitigating alkalinity) to stabilize pH levels.

   • Four primary buffering systems exist: bicarbonate-carbonic acid system, phosphate buffer system, protein buffers (e.g., albumin and globulins), and hemoglobin. Each system functions in a specific context, contributing to rapid pH regulation.

2. Respiratory System:

   • The respiratory system contributes to pH regulation by controlling the levels of carbon dioxide (CO2) and oxygen in the blood through respiration, providing a response that takes minutes to adjust.

   • Increased respiration (hyperventilation) reduces CO2 levels, thus raising pH and decreasing acidity. Conversely, decreased respiration (hypoventilation) leads to CO2 retention, which lowers pH and increases acidity.

   • This regulation is critical, especially during metabolic acidosis or respiratory disorders.

3. Kidneys:

   • The renal system provides the slowest mechanism of pH regulation, taking hours to days to effect significant changes.

   • Kidneys can excrete hydrogen ions into the urine or retain bicarbonate, adjusting pH accordingly. If the body needs to decrease pH due to acidosis, it will eliminate more acid or reabsorb bicarbonate. For alkalosis situations, the kidneys can excrete bicarbonate to lower pH levels.

Acid-Base Imbalances

• Types of Imbalances: The body can experience acidosis or alkalosis, both of which can be either acute or chronic. These imbalances can impair organ function and lead to potentially life-threatening situations if not addressed.

Acidosis

• Acidosis results from too much acid production or too little base. There are two main categories: Respiratory Acidosis and Metabolic Acidosis.

1. Metabolic Acidosis:

   • This condition is characterized by either decreased bicarbonate levels or the excessive production of acid. Common causes include starvation, diabetic ketoacidosis, renal failure, and severe diarrhea.

   • Symptoms of metabolic acidosis may include weakness, drowsiness, and Kussmaul's respirations, which are deep, rapid breathing patterns as the body attempts to eliminate CO2 excess and correct the pH imbalance.

2. Respiratory Acidosis:

   • Respiratory acidosis occurs when the lungs cannot remove enough CO2, leading to a rise in acidity in the blood. Common causes are chronic obstructive pulmonary disease (COPD), over-sedation, and pneumonia.

   • Symptoms may include hypoventilation, lethargy, confusion, headache, decreased blood pH (less than 7.35), and increased CO2 levels (greater than 45 mmHg).

Alkalosis

• Alkalosis arises from too little acid or too much base. It is also classified into two primary categories: Respiratory Alkalosis and Metabolic Alkalosis.

1. Metabolic Alkalosis:

   • This condition results from increased bicarbonate or decreased levels of acid often due to excessive vomiting or antacid intake. Symptoms include irritability, muscle rigidity, possible seizures, and decreases in potassium levels.

2. Respiratory Alkalosis:

   • Respiratory alkalosis is marked by excessive loss of CO2 typically due to hyperventilation. Common symptoms include rapid breaths, feelings of anxiety, dizziness, and notably reduced CO2 levels in the blood. Causes can be attributed to anxiety, fever, pain, and over-ventilation during medical procedures.

Nursing Diagnoses Related to Acidosis and Alkalosis

• Acidosis:

  • Relevant nursing diagnoses may include: decreased cardiac output, risk for injury due to altered mental status, impaired gas exchange, and ineffective breathing pattern.

  • Key nursing interventions may involve monitoring vital signs, fluid replacement therapy, sodium bicarbonate administration when indicated, and providing oxygen therapy to enhance oxygenation.

• Alkalosis:

  • Nursing diagnoses could include ineffective breathing pattern, risk for impaired gas exchange, and deficient fluid volume.

  • Interventions might involve monitoring patient vitals, implementing slow breathing techniques to help calm the patient, exploring possible sedation if anxiety is a contributing factor, and administering IV fluids if the patient is found to be hypovolemic (low fluid volume).

Conclusion

• Acid-base balance is crucial for maintaining various physiological functions within the body, impacting metabolic activity, enzyme function, and oxygen delivery.

• A thorough understanding of the causes, symptoms, and nursing interventions associated with acidosis and alkalosis is essential for effective patient care and optimal health outcomes.