This year about 20 million patients in the U.S. will undergo a procedure in which a doctor will thread a catheter into a blood vessel to treat a cardiac ailment, say, or provide dialysis or chemotherapy. But in five percent of these “vascular-access procedures,” the catheter accidentally punctures the vessel, causing a slow leak of blood that can be hard to detect—but which can wind up wreaking havoc. Houston medtech startup Saranas says it’s developed a device that can detect the bleeding within a matter of minutes.