The goal of this observational study is to learn about blood pressure response to the vasopressor drug vasopressin in people with septic shock. The main questions it aims to answer are: * Are the levels of molecules showing communication between cells different between people whose blood pressure improves and people whose blood pressure does not improve when given a vasopressor medication? * Are measurements found on echocardiography (heart ultrasound) different between people whose blood pressure improves and people whose blood pressure does not improve when given a vasopressor medication? * Are measurements of blood oxygen in tissues just below the skin different between people whose blood pressure improves and people whose blood pressure does not improve when given a vasopressor medication? Participants will be asked to contribute one or two blood samples. Participants who are ordered the drug vasopressin will contribute two blood samples. Both samples will be about two tablespoons for a total of about four tablespoons. One sample will be drawn before starting vasopressin infusion and the second sample will be drawn between one and six hours after starting the vasopressor drug infusion. At the same time points, advanced echocardiography pictures and measurements of oxygen in tissues from a sensor placed on one of the hands will be taken. Participants who are not ordered the drug vasopressin and only ordered the drug norepinephrine will contribute only one blood sample. At the time the sample is collected, advanced echocardiography pictures and measurements of oxygen in tissues from a sensor placed on one of the hands will be taken. This research also involves analyzing data obtained during the participant's hospital stay.