Microvascular Circulation

This pilot study is testing a new ultrasound imaging method called Super-Resolution Ultrasound (SRU) to look at blood flow and tiny blood vessels in transplanted kidneys in very detailed images after kidney transplant surgery. The goal is to see whether changes in the kidney's small blood vessels can help predict how well the transplanted kidney will work early after transplant, including whether delayed graft function may occur. Investigators hope this technique can become a safe, noninvasive way to evaluate transplanted kidneys without needing as many invasive biopsies. It may also help doctors better assess donor kidneys at higher-risk of suboptimal functioning.

During major surgical procedures performed under general anesthesia, changes in blood flow and oxygen delivery to tissues may occur due to blood loss, hemodynamic fluctuations, and anesthesia-related physiological effects. These changes can lead to impaired tissue perfusion, which is commonly reflected by increased arterial lactate levels. However, lactate measurements are intermittent and may not detect early perfusion abnormalities. This prospective observational study aims to investigate the relationship between submental tissue oxygenation measured by near-infrared spectroscopy (NIRS), microvascular reactivity assessed by the vascular occlusion test, and arterial lactate levels during major surgery. Adult patients undergoing major abdominal, neurosurgical, or orthopedic procedures will be monitored intraoperatively using non-invasive NIRS techniques, while arterial blood gas analyses will be performed as part of routine clinical care. The study does not involve any changes to standard anesthesia or surgical management. All treatments and clinical decisions will be made by the responsible care team according to routine practice. By evaluating non-invasive indicators of tissue oxygenation and microvascular function, this study aims to improve the understanding of early intraoperative tissue perfusion changes and their association with metabolic markers.

The goal of this clinical trial is to learn whether beta-blockers can improve coronary blood flow and reduce resistance in patients with angina and no obstructive coronary arteries (ANOCA). The main questions it aims to answer are: * Do beta-blockers improve coronary blood flow in patients with ANOCA? * Do beta-blockers reduce coronary microvascular resistance in these patients? Researchers will compare a beta-blocker to a placebo to see if the medication has measurable effects on coronary circulation. Participants will: * Receive a beta-blocker or a placebo * Undergo specialized heart tests (such as coronary flow and resistance measurements) before and after treatment.