How Accurate Is Non-Invasive Blood Pressure Monitoring During Trendelenburg Laparoscopic Surgery?

This study will test how accurate a blood pressure cuff is during certain types of surgery. During some abdominal surgeries done with small tools and a camera (called laparoscopic surgery), doctors place patients in a head-down position called the Trendelenburg position. In this position, it may be harder for the blood pressure cuff on the arm to give correct readings. This study will compare the cuff's readings (non-invasive) with readings from a thin tube placed inside an artery (invasive), which is more accurate but also more risky and uncomfortable. The researchers will use a method called error grid analysis to check how closely the cuff readings match the invasive ones. They hope to learn if the blood pressure cuff is accurate enough to be used safely in this kind of surgery. If it is, doctors may not need to use the invasive method as often. People 18 years or older who are already going to have invasive blood pressure monitoring as part of their planned surgery can join the study. The study will collect blood pressure measurements about every 20 minutes during surgery, as well as basic information like age, weight, and what medicines are given.