Acid/Base Disturbance Flashcards
What does low PaO2 indicate?
Hypoxia and respiratory failure
What does normal pCO2 with low PaO2 indicate?
Type 1 respiratory failure
What does raised pCO2 with low PaO2
Type 2 respiratory failure
A pH below 7.35 signifies…
Acidosis
A pH between 7.35-7.45 signifies…
Normal
A pH above 7.45 signifies…
Alkalosis
What is respiratory acidosis?
Respiratory acidosis is a condition where the body can’t effectively get rid of carbon dioxide (CO2), leading to an excess of CO2 in the blood. This excess CO2 combines with water in the blood to form carbonic acid, which lowers the blood’s pH, making it more acidic. In simple terms, respiratory acidosis happens when your lungs can’t remove enough CO2, causing your blood to become too acidic.
What is the significance of bicarbonate?
Bicarbonate is a substance produced by the kidneys that helps neutralize acid in the blood, keeping the pH level normal. In chronic conditions like COPD, where CO2 is often high, the kidneys produce extra bicarbonate to balance out the acidity. However, in sudden episodes where CO2 rises quickly (like an acute exacerbation of COPD), the kidneys can’t produce bicarbonate fast enough, leading to acidosis even though bicarbonate levels are higher than usual.
What is respiratory alkalosis?
Respiratory alkalosis occurs when someone breathes too rapidly or deeply, leading to the excessive exhalation of carbon dioxide (CO2) from the body. This reduction in CO2 lowers the acid levels in the blood, causing the pH to rise and become more alkaline.
Common conditions that cause this is:
- Hyperventilation Syndrome: Often triggered by anxiety, leading to fast breathing and high oxygen levels in the blood.
- Pulmonary Embolism (PE): A blockage in the lungs that can cause rapid breathing. Unlike hyperventilation syndrome, PE typically results in low oxygen levels in the blood.
How does metabolic acidosis affect pH and bicarbonate?
Low pH
Low bicarbonate
What can cause metabolic acidosis?
- Raised lactate – lactate is released during anaerobic respiration (indicating tissue hypoxia)
- Raised ketones – typically in diabetic ketoacidosis
Increased hydrogen ions – due to renal failure, type 1 renal tubular acidosis or rhabdomyolysis - Reduced bicarbonate – due to diarrhoea (stools contain bicarbonate), renal failure or type 2 renal tubular acidosis
How does metabolic alkalosis affect pH and bicarbonate?
Raised pH
Raised bicarbonate
What are two primary causes of metabolic alkalosis, and how do they lead to a loss of hydrogen (H+) ions in the body?
Gastrointestinal tract: Loss of hydrogen ions can occur due to vomiting, as the stomach produces hydrochloric acid (HCl), and vomiting expels this acid from the body.
Kidneys: Increased activity of aldosterone can lead to the excretion of hydrogen ions through the kidneys, contributing to metabolic alkalosis.
