UPSC-CMS 2012 — Anesthesiology

Question 1: A pulmonary artery (Swan-Ganz) catheter measures all of the following except

• A. Pulmonary artery wedge pressure (PAWP)
• B. Left ventricular end diastolic volume (LVEDV) (Correct Answer)
• C. Mixed venous oxygen saturation (SvO2)
• D. Cardiac output (CO)

Explanation: ***Left ventricular end diastolic volume (LVEDV)*** - While a Swan-Ganz catheter can measure **pulmonary artery wedge pressure (PAWP)**, which is a surrogate for **left ventricular end-diastolic pressure (LVEDP)**, it cannot directly measure **left ventricular end-diastolic volume (LVEDV)**. - LVEDV requires imaging techniques like **echocardiography** or **cardiac MRI** for direct measurement. *Pulmonary artery wedge pressure (PAWP)* - The Swan-Ganz catheter can measure **PAWP**, which reflects **left atrial pressure** and, in the absence of mitral valve disease, - Is an estimate of **left ventricular end-diastolic pressure (LVEDP)**, therefore assessing left ventricular preload. *Mixed venous oxygen saturation (SvO2)* - The catheter has a fiberoptic sensor that can continuously measure **SvO2** from the pulmonary artery. - **SvO2** provides an assessment of the balance between oxygen supply and demand. *Cardiac output (CO)* - **Cardiac output** is commonly measured using the **thermodilution method** via the Swan-Ganz catheter. - A bolus of saline is injected into the right atrium, and temperature changes are detected in the pulmonary artery to calculate flow.