Life-threatening low blood pressure due to a serious infection is called "septic shock." Septic shock is treated with vasopressors, medications that raise blood pressure. Sometimes first-line vasopressors are inadequate, prompting addition of a second-line vasopressor called vasopressin. However, the threshold at which to start vasopressin remains unclear. This pragmatic, cluster-randomized, cluster-crossover trial will evaluate two different strategies for septic shock treatment commonly used in current practice, comparing a lower versus a higher threshold for adding vasopressin to first-line vasopressors.