In 2018 a paper was published in Ultrasound in Medicine and Biology showing absence of the second systolic peak in patients with severe sepsis.

These findings illustrate how important it is to discriminate a first and second systolic phase in pulsatile signals such as arterial blood pressure or intra arterial blood flow velocity.


The graph above shows (age corrected) Z-scores for a group of 16 patients before (red) and after (yellow) fluid resuscitation. All patients had high Z-scores for all parameters before as well as after fluid resuscitation. Fluid resuscitation increased the Sys1 and Sys2 components, allowing a slight decrease in HR.

These high Z-scores for Sys1, Sys2 and Dias@560 may implicate a diffuse loss of cerebral arteriolar resistance, either due to low blood pressure or because of circulating endotoxins.