Questions: Determine the acid-base disorder present: Interpret the following ABG: pH 7.21 PaCO2 33 HCO 12

Transcript text: Determine the acid-base disorder present: Interpret the following ABG: pH 7.21 PaCO2 33 HCO 12

Solution

Solution Steps

Step 1: Determine the Primary Disorder

First, we need to determine if the primary disorder is acidosis or alkalosis by looking at the pH. A normal pH range is 7.35 to 7.45.

Given: \( \text{pH} = 7.21 \)

Since the pH is less than 7.35, this indicates acidosis.

Step 2: Identify the Primary Cause

Next, we need to determine whether the acidosis is metabolic or respiratory by examining the PaCO2 and HCO3 levels.

Given: \( \text{PaCO2} = 33 \, \text{mmHg} \) (normal range: 35-45 mmHg)
Given: \( \text{HCO3} = 12 \, \text{mEq/L} \) (normal range: 22-26 mEq/L)

The HCO3 is significantly lower than normal, indicating a primary metabolic acidosis. The PaCO2 is also lower than normal, which suggests a compensatory respiratory alkalosis.

Step 3: Assess Compensation

In metabolic acidosis, the body compensates by decreasing PaCO2 through hyperventilation. The expected compensatory PaCO2 can be estimated using Winter's formula:

\[ \text{Expected PaCO2} = 1.5 \times \text{HCO3} + 8 \pm 2 \]

Substituting the given HCO3 value:

\[ \text{Expected PaCO2} = 1.5 \times 12 + 8 \pm 2 = 26 \pm 2 \]

The expected range for PaCO2 is 24 to 28 mmHg. The actual PaCO2 is 33 mmHg, which is higher than expected, indicating that there is an additional respiratory acidosis component.