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.

Hint: Just look at what is out of order, if it is the CO2 then it is respiratory if it is Bicarbonate then it is metabolic. Then look at the pH, if it is low it is acidosis and if it is high it is 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 are the 2 types of Metabolic Acidosis Normal Anion Gap Acidosis

Answer 8

1. Normal Anion Gap Metabolic Acidocis or (Non-anion) Also known as hyperchloremic or non-anion gap acidosis (NAGMA)
2. High Anion Gap Metabolic 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 (HAGMA)
   * Causes of normal anion gap acidosis include:
   * gastrointestinal losses (e.g., diarrhea)
   * Renal tubular acidosis
   * Administration of certain drugs (e.g., acetazolamide usually things that effect Na because Chloride follows sodium).

HAGMA* 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 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

Question 11

What is Right Curve Oxygen dissociation

Answer 11

It is when you increase the relase of Oxygen from the Hemoglobin to the tissue

Question 12

What Is the Oxygen Dissociation Curve

Answer 12

Question 13

What is Left Curve Oxygen Dissociation

Answer 13

It is when you decrease the relase of Oxygen from the Hemoglobin to the tissue. Hence with Left shift, the tissue is Left Behind

Question 14

In the Oxygen Dissociation Curve what shifts the curve to the Right and what shifts it to the Left

Answer 14

The shifters are PCO₂, H⁺, decrease Temperature, Altitude, 2-3 BPG

The left shifters are a decrease in The shifters are PCO₂, H⁺, decrease Temperature, decrease in Altitude, and a decrease in 2-3 BPG

The right shifters are an increase in PCO₂, H⁺, Temperature, Altitude, and 2-3 BPG