Which item is NOT listed as one of the five ASA standard monitors?

• A. EtCO2 monitor
• B. Temperature monitor
• C. Pulse Oximeter
• D. Invasive arterial line monitor

Answer: (D)

The main idea is that ASA’s standard intraoperative monitors are five noninvasive tools used to ensure safety in any anesthesia case: rhythm and timing are tracked with ECG, oxygenation with pulse oximetry, ventilation with capnography (EtCO2), circulation with noninvasive blood pressure, and body temperature with a temperature monitor. An invasive arterial line, while extremely useful for continuous arterial blood pressure measurement and arterial blood gas sampling in certain patients or procedures, is not part of those standard monitors. It’s an invasive, additional monitoring method added for specific indications rather than a routine component for all cases. So the item that isn’t listed among the standard monitors is the invasive arterial line monitor, with the others—EtCO2, temperature, and pulse oximetry—being part of the standard set.