How to Read ABGs

Question 1

Rule of 4s
Mnemonic to remember for Acid Base Disorders

Answer 1

Here’s how the “rule of 4s” works:
* pH: Remember that the normal pH is close to 7.40, which rounds off to 7.4 in the “rule of 4s.”
* pCO2: The normal pCO2 is approximately 40 mmHg, which also ends with a “4” in the “rule of 4s.”
* HCO3-: The normal bicarbonate level is around 24 mEq/L, which again has a “4” in the “rule of 4s.”
pO2: The normal pO2 is 80-100 mmHg, which is close to 80 and can be associated with the “rule of 4s.”

Question 2

What is the normal range for pH, PaCO2, HCO3-. What is metabolic acidosis/alkalosis and respiratory acidosis/alkalosis?

Answer 2

• Acidemia (pH < 7.35) indicates acidosis.
• Alkalemia (pH > 7.45) indicates alkalosis.
• High PaCO2 (> 45 mmHg) indicates respiratory acidosis.
• Low PaCO2 (< 35 mmHg) indicates respiratory alkalosis.
• High HCO3- (> 26 mEq/L) indicates metabolic alkalosis.
• Low HCO3- (< 22 mEq/L) indicates metabolic acidosis.

    · While many acid-base disorders involve complex pathology, they manifest themselves as deviations in levels of either arterial PCO2, bicarbonate, or both.
  
    · Four categories:
        · (1) high pCO2 is a respiratory acidosis
        · (2) low pCO2 is a respiratory alkalosis
        · (3) low bicarbonate is a metabolic acidosis (4) high bicarbonate is a metabolic alkalosis.

Question 3

Do you know directional changes in arterial blood values how the body tries to compensate under acid or alkalotic conditions?

Answer 3

You should now

Question 4

Do you know how the body tries to compensate under acid or alkalotic conditions in terms of lab values?

Answer 4

Now you know

Question 5

Sample Problem #1
A patient’s arterial blood gas (ABG) results are as follows:
* pH: 7.30
* PaCO2: 50 mmHg
* HCO3-: 26 mEq/L
Interpret these results.

Answer 5

• pH is below the normal range (7.35-7.45), indicating an acidic pH
• PaCO2 is elevated (normal range: 35-45 mmHg), indicating respiratory acidosis
• HCO3- is within the HIGH normal range (22-26 mEq/L)
• the patient has respiratory acidosis with compensatory metabolic alkalosis (elevated
  HCO3- within normal range)
• The primary acid-base disorder is respiratory acidosis due to high PaCO2, and the metabolic alkalosis is the compensatory response to this acidosis

Question 6

Sample Problem #2
A patient’s arterial blood gas (ABG) results are as follows:
* pH: 7.49
* PaCO2: 30 mmHg
* HCO3-: 25 mEq/L

Interpret these results

Answer 6

• pH is above the normal range (7.35-7.45), indicating basic pH
• PaCO2 is decreased (normal range: 35-45 mmHg), indicating respiratory alkalosis
• HCO3- is within the normal range (22-26 mEq/L)
• Based on these results, the patient has respiratory alkalosis.
• There is no compensatory metabolic disorder present because the HCO3- level is within the normal range.
• Therefore, the primary acid-base disorder is respiratory alkalosis due to low PaCO2.

Question 7

What is the anion gap used to calculate?

Anion Gap = (Sodium) - (Chloride + Bicarbonate)

Answer 7

1. It evaluates and assess acid-base disorders
   • It represents the difference between the measured cations (positively charged ions) and the measured anions (negatively charged ions) in the blood
   • The anion gap is calculated using the following formula:
     Anion Gap = (Sodium) - (Chloride + Bicarbonate)

Question 8

What is Normal Anion Gap Acidosis

Answer 8

• Also known as hyperchloremic or non-anion gap acidosis
  * This type of acidosis occurs when there is an increase in the levels of chloride ions in proportion to the decrease in bicarbonate ions
  * Causes of normal anion gap acidosis include:
  * gastrointestinal losses (e.g., diarrhea)
  * Renal tubular acidosis
  * Administration of certain drugs (e.g., acetazolamide).

Question 9

What High Anion Gap Acidosis

Answer 9

• Also known as anion gap metabolic acidosis
  * This type of acidosis occurs when there is an increase in unmeasured anions (such as lactate,
  ketones, and sulfates) in relation to the decrease in bicarbonate ions
  * Causes of high anion gap acidosis include:
  * Diabetic ketoacidosis
  * Lactic acidosis
  * Renal failure
  * Ingestion of toxins (e.g., methanol, ethylene glycol).

Question 10

How do the different anion gap issues present themselves

Answer 10