Early Vasopressor Initiation Before Complete Fluid Resuscitation in Adults With Septic Shock: A Systematic Review

Guidelines suggest at least 30 mL/kg of crystalloid within three hours in septic shock but do not specify when vasopressors should begin in relation to that bolus. Hence, we systematically reviewed contemporary evidence on initiating vasopressors before fluid resuscitation is complete. For this review, early initiation was defined as commencement of a first-line vasopressor before the treating team or study protocol judged initial volume expansion complete, and every included study's own time-zero anchor, threshold, and definition of completeness were extracted. PubMed, Scopus, Web of Science, and ClinicalTrials.gov were searched from 1 January 2021 to 18 August 2026, supplemented by citation searching. Reporting followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines, and synthesis followed Synthesis Without Meta-analysis. Eligible studies were randomised controlled trials (RCTs) and comparative observational studies in adults with septic shock or sepsis-induced hypotension, contrasting earlier with later vasopressor initiation relative to fluid loading. Risk of bias was assessed with Risk of Bias 2 and Risk of Bias in Non-randomized Studies - of Interventions, and certainty of evidence with the Grading of Recommendations Assessment, Development, and Evaluation. Heterogeneity in exposure definition precluded meta-analysis. In total, 11 studies (two multicentre RCTs and nine comparative observational studies; 18,362 adults; eight countries) were included. Thresholds for "early" spanned 25 minutes to three hours and were anchored variably to triage, shock recognition, or the first fluid bolus; completeness of fluid resuscitation was protocolised in only the two RCTs and left to clinician judgement in seven cohorts, with the pre-vasopressor fluid volume unmeasured in two. Both RCTs were neutral for their primary patient-centred endpoints (moderate certainty) despite achieving 1.1 to 2.1 L separation in 24-hour fluid volume (high certainty). Observational findings were discordant (very low certainty): four cohorts reported lower mortality with earlier initiation, one propensity-matched registry analysis reported higher 28-day mortality, and three found no association. Benefit was concentrated in patients meeting Sepsis-3 criteria, with high predicted vasopressor requirement, and with marked diastolic hypotension and a wide pulse pressure. No safety penalty was identified (moderate certainty). Initiating vasopressors before fluid resuscitation is complete is safe and reduces early fluid exposure and time to haemodynamic target, but does not improve survival when applied indiscriminately. The evidence supports the 2026 Surviving Sepsis Campaign position that concurrent vasopressor administration be reserved for case-by-case use in unstable shock, and future trials should enrol by vasoplegic phenotype rather than by time alone.