Hemodynamic subphenotypes in septic shock and their different responses to fluid balance in relation to ICU mortality

Hemodynamically unstable septic patients often require aggressive fluid resuscitation, but limited evidence exists on which hemodynamic subphenotypes benefit most.

The retrospective cohort study conducted in a tertiary hospital of China. Patients with septic shock who underwent pulse index continuous cardiac output (PiCCO) monitoring within 24 h were included from November 2013 to January 2024. We applied latent profile modelling to identify subphenotypes using all hemodynamic parameters monitored via PiCCO. We then tested the association of 48-h fluid balance with ICU mortality in different subphenotypes using logistic regression.

A total of 691 patients were included. Latent profile models indicated that a four-profile model was the best fit. Hyperdynamic subphenotype (phenotype1) was characterized by highest cardiac output and lowest systemic vascular resistance index (SVRI); high preload subphenotype (phenotype 2) was characterized by highest preload; hypodynamic subphenotype (phenotype 3) was characterised by lowest cardiac output, highest SVRI, lung function, as well as inotropic score; preserved subphenotype (phenotype 4) was presented with relative normal hemodynamic parameters. No significant difference was observed in 24- and 48-hour fluid balance among subphenotypes, and overall, no significant correlation was found between 48-hour fluid balance and ICU mortality. However, a significant interaction existed between 48-hour fluid balance and phenotype 4; in this group, higher fluid balance at 48 h was associated with increased ICU mortality (OR 1.24, 95% CI 1.05 to 1.46; p = 0.011).

Four hemodynamic subphenotypes in septic shock was identified. The impact of 48-hour fluid balance on ICU mortality varied by subphenotype, with increased mortality observed only in the preserved hemodynamic group.