## **Core Concept**
In a patient with blunt abdominal trauma presenting with hypotension (BP 90/60 mm Hg) and tachycardia (pulse rate 124), the primary concern is to identify the source of bleeding or fluid loss. This clinical scenario suggests hypovolemic shock, likely due to internal bleeding.

## **Why the Correct Answer is Right**
The correct answer, **Focused Assessment with Sonography for Trauma (FAST)**, is a bedside ultrasound examination that is quick, non-invasive, and can be performed in emergency settings to detect free intraperitoneal fluid (which could indicate bleeding) or signs of cardiac tamponade. It's particularly useful in unstable patients where moving to the CT scanner could pose a risk. FAST can help in making a rapid decision for surgical intervention.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While a **Complete Blood Count (CBC)** can provide valuable information about the patient's hematocrit levels and potential blood loss, it does not directly identify the source of bleeding and takes time to perform and report.
- **Option B:** **CT abdomen with contrast** is highly sensitive and specific for detecting injuries but requires a stable patient who can be transported to the CT scanner. This patient is unstable (hypotensive and tachycardic), making CT a less suitable immediate choice.
- **Option D:** **X-ray abdomen** is not useful in acute trauma settings for assessing internal injuries or bleeding.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is the **FAST** examination is particularly valuable in acute trauma settings for quickly identifying free fluid (often blood) in the abdomen, pericardium, or pleural spaces. The mnemonic **FAST** stands for Focused Assessment with Sonography for Trauma, checking for fluid in the **F**our areas: **F**ree fluid in the peritoneum, **A**ortic aneurysm (or more commonly, free fluid around the aorta), **S**plenic view, and **T**ranscardiac (pericardial) view.

## **Correct Answer:** . **Focused Assessment with Sonography for Trauma (FAST)**