Phenotypic Patterns of Vasopressor Initiation in Septic Shock: A Retrospective Study of MIMIC-IV

Introduction: Vasopressor initiation in septic shock patients depends on a combination of clinical factors, patient characteristics, institutional protocols, and clinical judgment. In this study, we examined the different factors affecting both the mean arterial pressure (MAP) threshold and the timing of norepinephrine (NE) initiation.


Methods: This retrospective study used the Medical Information Mart for Intensive Care (MIMIC-IV) database to analyze adult patients meeting Sepsis-3 criteria who received NE. Variables collected were demographics, Charlson Comorbidity Index (CCI), first care unit, time between MAP was first recorded below 65 mmHg to NE initiation, and MAP at the time of NE initiation. Pearson’s correlation and multivariable linear regression were used to assess the relationship between the timing of NE initiation and patient demographics and characteristics. Mann-Whitney and Kruskal-Wallis were done to assess the relationship between MAP at the start of NE infusion and patients' demographics and characteristics.


Results: A total of 5109 septic patients who received NE were identified. The median time to NE initiation was 17 minutes (IQR: 5–45). The time till initiation was shorter for patients with higher SOFA score (r= 0.0001, p < 0.001), older age (r= 0.0418, p=0.042), and those with higher CCI (r= -0.066, p=0.1182), whereas no differences were observed for language and race. Trauma and surgical patients were started on NE faster than medical patients (73 minutes ± SD 230.7 versus 115.6 ± SD 605 minutes).
The median MAP at the start of NE was 55.1 mmHg (IQR 51–61 mmHg). At the beginning of NE, males had greater MAPs than females (+1.23 mmHg, p= < 0.0001). Race and first care unit showed no significant correlations. Age, SOFA score, and CCI exhibited significant but weak correlation with MAP at the start, with correlation coefficients of (-0.058, -0.025, -0.073, respectively).


Conclusions: Vasopressor initiation in septic shock patients is a complex, patient-specific decision affected by patients' demographics, illness severity, and institutional guidelines. While early initiation of NE improves outcomes, modest delays may be tolerated in selected patients. Standardized yet individualized approaches may enhance NE use and outcomes in critically ill patients.