The differences in mortality between vasopressin-treated vs. non-vasopressin-treated patients in SPH1 vs. SPH2 could be related to the differences in vasopressin benefits (lowering norepinephrine dose, decreasing organ dysfunction) vs. side effects (cardiac, gut, digital and renal ischemia [23, 30], and arrhythmias) related to mechanisms such as effects of vasopressin on vascular tone, immune effects (such as cytokines) [32, 33], vascular permeability, renal blood flow and function [9, 34], and von Willebrand factor release. Here, VWF is linked to cardiac arrhythmia.