A recent study examined whether starting vasopressin earlier in the course of septic shock improves patient outcomes. Septic shock is a severe form of sepsis characterised by profound circulatory failure and high mortality. Norepinephrine is the recommended first-line vasopressor, but escalating doses can cause adverse effects such as arrhythmias and myocardial injury. Vasopressin acts through non-adrenergic pathways and may reduce catecholamine exposure, preserve renal perfusion, and limit adrenergic toxicity. However, the best time to initiate vasopressin remains uncertain despite guideline recommendations to add it when norepinephrine doses reach 0.25–0.5 μg/kg/min.
The investigators used a two-part design. First, they conducted a retrospective multicentre observational study using the Korean Shock Society registry, which prospectively collects data from 20 tertiary hospitals in South Korea. Second, they performed a systematic review and meta-analysis of published randomised controlled trials (RCTs) and observational studies, integrating their own registry findings with existing evidence. The primary outcome for both analyses was mortality, with secondary outcomes including ICU length of stay, need for renal replacement therapy (RRT), and arrhythmias.
The registry analysis included 5,837 adults with septic shock enrolled between 2015 and 2023. Of these, 2,001 patients received vasopressin in addition to norepinephrine. Patients were categorised according to the norepinephrine dose at vasopressin initiation (<0.25, 0.25–<0.5, or ≥0.5 μg/kg/min) and the time elapsed from starting norepinephrine to vasopressin initiation (<2 hours, 2–<6 hours, or 6–<24 hours).
The overall 28-day mortality in the registry cohort was 30.1%. Among patients who received vasopressin, mortality increased as vasopressin was started later and at higher norepinephrine doses. Initiating vasopressin when norepinephrine was ≥0.5 μg/kg/min was independently associated with significantly higher 28-day mortality compared with starting at <0.25 μg/kg/min. Starting vasopressin 6–24 hours after norepinephrine initiation was also associated with increased mortality compared with initiation within 2 hours. Spline analyses suggested mortality risk began to rise when norepinephrine exceeded approximately 0.36 μg/kg/min and when vasopressin was delayed beyond about 8.1 hours. Higher-dose initiation was also associated with longer ICU stays, but no significant association was observed with RRT.
The systematic review identified 15 eligible studies: 5 RCTs and 10 observational studies, including the Korean registry data. These studies collectively included more than 6,000 patients. Definitions of “early” vasopressin varied, but most studies used a time threshold of 3–7 hours after shock onset or a norepinephrine-equivalent dose threshold below 0.25 μg/kg/min.
In the RCTs, early vasopressin was not associated with a statistically significant reduction in mortality. However, it significantly reduced the need for renal replacement therapy. There were no significant differences in ICU length of stay or arrhythmia rates. In contrast, observational studies showed that early vasopressin was associated with lower mortality and shorter ICU stays (mean difference −1.06 days), although there was no significant reduction in RRT or arrhythmias.
Subgroup analyses provided further support for a timing effect. Among observational studies directly comparing early versus late vasopressin initiation, early treatment was associated with significantly lower mortality and a shorter ICU stay (−1.27 days).
The authors discuss several plausible mechanisms for benefit, including correction of relative vasopressin deficiency, restoration of vascular tone via V1a receptors, improved renal perfusion, and catecholamine-sparing effects. They also emphasise potential harms, such as digital or mesenteric ischaemia and myocardial ischaemia. Because septic shock is highly heterogeneous, factors such as shock duration, receptor expression, comorbidities, and corticosteroid use may influence the response to vasopressin.
This study suggests that earlier initiation of vasopressin in septic shock may improve outcomes, particularly by reducing mortality and ICU length of stay in observational studies and decreasing the need for renal replacement therapy in RCTs. The findings support considering vasopressin before norepinephrine doses escalate substantially, broadly aligning with current Surviving Sepsis Campaign recommendations. Nevertheless, definitive evidence of a survival benefit is lacking, and further well-designed randomised trials are needed to determine which patients benefit most and to establish the optimal timing of vasopressin initiation.
Source: European Journal of Internal Medicine
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