This systematic review and meta-analysis of five studies including 788 patients evaluated the impact of early start of vasopressin support on clinical outcomes in septic shock patients within 6 hours after the diagnosis. We found that the overall short-term mortality was about 38.3%, there were no statistically significant difference in the short-term mortality, new onset arrhythmias, ICU length of stay and length of hospitalization between the experimental group and control group, the use of RRT was lower in the experimental group.
Vasopressin is a neurohypophyseal hormone with diverse actions mediated by tissue-specific receptors. The rationale for using vasopressin is the development of relative vasopressin deficiency in patients with septic shock and the observation that low dose vasopressin infusion improves blood pressure, decreases requirements for catecholamines and improves renal function[19]. From a retrospective cohort study [20],it revealed that 17.2% of patients with septic shock in United States hospitals received vasopressin. In the ADRENAL trial[21], which included patients from Australia, the United Kingdom, New Zealand, Saudi Arabia, and Denmark, usage was similar with 16.8% of patients receiving vasopressin at baseline.
Vasopressin levels vary during the different stages of septic shock[22], therefore, timing of vasopressin initiation could play a critical role in septic shock management.
In the VASST trial[3], vasopressin was not associated with improved mortality as compared with norepinephrine but when mortality rates were stratified into patients who received early vasopressin (≤12 h), rates were higher in the norepinephrine group (40.5% vs. 33.2%, P =0.12), initiation of vasopressin within 12 hours could
have been delayed because plasma vasopressin levels were extremely low as early as 6 hours[22].In this meta-analysis, we do not find improved short-term mortality when vasopressin initiated within 6 hours of septic shock onset. Though early initiation of vasopressin in patients with septic shock may achieve and maintain goal MAP sooner[16, 18],surrogate end points evaluated, such as time to goal MAP, failed to translate to a mortality benefit.
Acute kidney injury (AKI) is a common complication of sepsis and septic shock. a post hoc analysis of VASST [23] demonstrated that patients at risk for AKI development according to the Risk, Injury,Failure, Loss of kidney function, and End-stage kidney disease (RIFLE) criteria, who received vasopressin within 12 hours of shock onset had a lower rate of progression to renal failure or loss categories (21% vs 40%, respectively; P =0.03) and a lower need for RRT (17% vs 38%, P = 0.02). In the VANISH trial[9], the early use of vasopressin compared with norepinephrine did not improve the number of kidney failure–free days, Patients in the vasopressin group were less likely to receive RRT compared with the norepinephrine group (25% vs 35%, P =0.03) . In our meta-analysis we found the use of RRT was less in the experimental group than that of the control group. A recent meta-analysis [24]focused on renal outcomes in distributive shock patients who received vasopressin or terlipressin, demonstrated patients who received vasopressin or terlipressin had reduced need for RRT and lower incidence of AKI. However, significant heterogeneity in the studies existed, and the lower incidence of AKI and use of RRT with vasopressin analogues was lost in the septic shock patients.
Catecholamine use has been linked to both an increased incidence of arrhythmias and increased cardiac ischemia[25]. In our meta-analysis we found no reduced new onset arrhythmias when vasopressin initiated within 6 hours of septic shock onset. However, the definition of arrhythmias of the included studies was different, which might render an unsolvable bias. In addition, our meta-analysis showed that there was no statistically significant difference in the ICU length of stay and length of hospitalization between the two groups.
Several limitations should be taken into consideration when interpreting our findings. Firstly, by the nature of meta-analysis in general, the results of this paper were dependent on the quality of available studies. There are only one RCT study included, other four included studies were small-scale single center cohort studies. The results and conclusions should therefore be interpreted with caution. Second, we did not perform a subgroup analysis of RCT and cohort studies, very heterogeneous populations were included in both randomized and observational studies. Third, mean arterial pressure and organ dysfunction is also a very important clinical outcome. However, few included studies had shown this data. In addition, inclusion/exclusion criteria and vasopressin dosage were widely different among included studies which supposed a limitation to interpret results. Therefore, our findings should be interpreted with caution.