Acid-Base Balance and pH

Acid-Base Balance and pH

• Maintaining a steady balance between acids and bases is crucial for homeostasis.
• Health issues like diabetes mellitus, COPD, and kidney disease can disrupt this balance.
• An acid gives up a hydrogen ion, while a base accepts one.
• pH measures hydrogen ion concentration.
• The pH scale ranges from 1-14.
• Blood is normally slightly alkaline, with a pH of 7.35 to 7.45. 7.35 indicates acidosis.

Acid-Base Regulation

• Metabolic processes produce acids that the body must neutralize and excrete.
• There are three regulatory mechanisms: buffers, the respiratory system, and the renal system.
• The respiratory center in the medulla controls breathing to retain or eliminate carbon dioxide, influencing the body's acid levels.
• Acidosis triggers hyperventilation to breathe off CO2.
• Alkalosis triggers hypoventilation to retain CO2.

Respiratory System

• The body uses a reversible equation, CO₂ + H₂O = H₂CO₃ = H++ HCO₃⁻.
• Decreased respirations lead to CO2 retention.
• The balance is maintained by a 20:1 ratio between bicarbonate and carbonic acid, which maintains pH

Renal System

• The renal system helps by reabsorbing and conserving bicarbonate.
• The renal system excretes H+ and weak acids, regulating acid-base balance in the long term.
• During acidosis, the kidneys excrete H+ and retain bicarbonate.
• During alkalosis, the kidneys retain H+ and excrete bicarbonate.

Alterations and Imbalances

• Imbalances occur when compensatory mechanisms of the body, like buffer, renal and respiratory systems fail.
• Imbalances are classified as respiratory (CO₂) or metabolic (HCO₃), and as acidosis or alkalosis, or acute or chronic.
• Clinical manifestations depend on pH rather than the source of imbalance.
• Acidosis causes CNS depression and Kussmaul respirations.
• Alkalosis causes CNS irritability and hypocalcemia.

Blood Gas Values

• Arterial blood gas (ABG) values provide information about acid-base status, underlying causes of imbalance, and the body’s ability to regulate pH.
• PaCO2 indicates respiratory function.

Arterial Blood Gas Analysis

• Normal PaO2 is 80-100.
• Normal PaCO2 is 35-45.
• Normal pH is 7.35-7.45.
• Normal SaO2 is 94-100.
• Normal HCO3– is 22-26.

Respiratory Acidosis

• Blood gas values are pH less than 7.35 and PaCO2 greater than 45 mm Hg.
• Renal compensation when HCO3 is greater than 26 mEq/L.
• If HCO3 is 22-26 mEq/L, it is uncompensated.
• Respiratory acidosis can be caused by airway obstruction, pneumonia, asthma, chest injuries, pulmonary edema, emphysema, or opiate use.

Signs and Symptoms of Respiratory Acidosis

• People may experience slow, shallow respirations, dyspnea, weakness, dizziness, restlessness, sleepiness, and changes in mental alertness.

Managing Respiratory Acidosis

• Management includes postural drainage, deep-breathing exercises, bronchodilators, and antibiotics, if indicated.
• Caution should be exercised when administering narcotics, hypnotics, and tranquilizers.
• Focus on establishing or maintaining an open airway and oxygen administration.
  • Establishment or maintenance of an airway can include methods like tracheostomy and endotracheal tube
• If things are very serious Mechanical ventilation may be used.

Metabolic Acidosis

• Blood gas values are pH less than 7.35 and HCO3 less than 22 mEq/L.
• If PaCO2 is less than 35 mm Hg it is compensated.
• If PaCO2 is 35-45 mm Hg it is uncompensated.
• Renal failure, diabetic ketoacidosis, shock, severe diarrhea, lactic acidosis, and starvation can cause metabolic acidosis.

Metabolic Alkalosis

• Blood gas values are pH greater than 7.45 and HCO3 greater than 26 mEq/L.
• Respiratory compensation when PaCO2 is greater than 45 mm Hg.
• If PaCO2 is 35-45 mm Hg it is uncompensated.
• Vomiting, extensive gastrointestinal suction, hypokalemia, excessive consumption of antacids with bicarbonate, and diuretic therapy can cause metabolic alkalosis.

Signs and Symptoms of Metabolic Alkalosis

• Potential neurologic signs include dizziness, confusion, lightheadedness, headache, muscle cramping, tingling, numbness of the fingers, and seizures.
• Slow, shallow respirations, decreased chest movements, and cyanosis may be signs of respiratory issues.
• There maybe signs and symptoms of potassium and calcium depletion (hypokalemia/hypocalcemia)

Management of Metabolic Alkalosis

• Carbon dioxide retention can be aided by having the patient to hold their breath.
• You can also have the patient breathe into a paper sack and re-breathe the carbon dioxide just exhaled.
• Recycling exhaled carbon dioxide can eventually restore normal carbonic acid levels in the blood.

Respiratory Alkalosis

• Blood gas values are pH greater than 7.45 and PaCO2 less than 35 mm Hg.
• Renal compensation occurs when HCO3 is less than 22 mEq/L.
• If HCO3 is 22-26 mEq/L, it is uncompensated.
• Hypoxemia from acute pulmonary disorders, pulmonary embolism, hyperventilation, fever, anxiety, overdose of aspirin, and head injuries can cause respiratory alkalosis.

Signs and Symptoms of Respiratory Alkalosis

• Potential signs and symptoms include hyperventilation, tingling of the fingers, N/V, epigastric pain, dizziness, lightheadedness, confusion, headache, seizures, hyperreflexia, tachycardia, and dysrhythmias.

Management of Respiratory Alkalosis

• Primarily managing the underlying cause.
• Prevent further hyperventilation by helping the patient re-establish a proper carbon dioxide blood level.
  • To do this you can have the patient breathe into a paper bag.
• Sedatives can be administered to calm the patient slowing breathing.