Aseem Kumar

OBJECTIVE: To determine the prevalence and impact on mortality of delays in initiation of effective antimicrobial therapy from initial onset of recurrent/persistent hypotension of septic shock. DESIGN: A retrospective cohort study performed between July 1989 and June 2004. SETTING: Fourteen intensive care units (four medical, four surgical, six mixed medical/surgical) and ten hospitals (four academic, six community) in Canada and the United States. PATIENTS: Medical records of 2,731 adult patients with septic shock. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The main outcome measure was survival to hospital discharge. Among the 2,154 septic shock patients (78.9% total) who received effective antimicrobial therapy only after the onset of recurrent or persistent hypotension, a strong relationship between the delay in effective antimicrobial initiation and in-hospital mortality was noted (adjusted odds ratio 1.119 [per hour delay], 95% confidence interval 1.103-1.136, p<.0001). Administration of an antimicrobial effective for isolated or suspected pathogens within the first hour of documented hypotension was associated with a survival rate of 79.9%. Each hour of delay in antimicrobial administration over the ensuing 6 hrs was associated with an average decrease in survival of 7.6%. By the second hour after onset of persistent/recurrent hypotension, in-hospital mortality rate was significantly increased relative to receiving therapy within the first hour (odds ratio 1.67; 95% confidence interval, 1.12-2.48). In multivariate analysis (including Acute Physiology and Chronic Health Evaluation II score and therapeutic variables), time to initiation of effective antimicrobial therapy was the single strongest predictor of outcome. Median time to effective antimicrobial therapy was 6 hrs (25-75th percentile, 2.0-15.0 hrs). CONCLUSIONS: Effective antimicrobial administration within the first hour of documented hypotension was associated with increased survival to hospital discharge in adult patients with septic shock. Despite a progressive increase in mortality rate with increasing delays, only 50% of septic shock patients received effective antimicrobial therapy within 6 hrs of documented hypotension.

Previous studies have demonstrated the presence of myocardial depression in clinical and experimental septic shock. This depression is associated with the presence of a circulating myocardial depressant substance with physical characteristics consistent with cytokines. The present study utilized an in vitro myocardial cell assay to examine the role of various human recombinant cytokines, including tumor necrosis factor (TNF)alpha and interleukin (IL)1beta, in depression of cardiac myocyte contractile function induced by serum from humans with septic shock. The extent and velocity of electrically paced rat cardiac myocytes in tissue culture was quantified by a closed loop video tracking system. Individually, TNF-alpha and IL-1beta each caused significant concentration-dependent depression of maximum extent and peak velocity of myocyte shortening in vitro. In combination, TNF-alpha and IL-1beta induced depression of myocardial cell contractility at substantially lower concentrations consistent with a synergistic effect. Using immunoabsorption, removal of both TNF-alpha and IL-1beta (but not either alone) from the serum of five patients with acute septic shock and marked reversible myocardial depression resulted in elimination of serum myocardial depressant activity. IL-2, -4, -6, -8, -10, and interferon gamma failed to cause significant cardiac myocyte depression over a wide range of concentrations. These data demonstrate that TNF-alpha and IL-1beta cause depression of myocardial cell contraction in vitro and suggest that these two cytokines act synergistically to cause sepsis-associated myocardial depression in humans.

Signal transducers and activators of transcription (STATs) enhance transcription of specific genes in response to cytokines and growth factors. STAT1 is also required for efficient constitutive expression of the caspases Ice, Cpp32, and Ich-1 in human fibroblasts. As a consequence, STAT1-null cells are resistant to apoptosis by tumor necrosis factor alpha (TNF-alpha). Reintroduction of STAT1alpha restored both TNF-alpha-induced apoptosis and the expression of Ice, Cpp32, and Ich-1. Variant STAT1 proteins carrying point mutations that inactivate domains required for STAT dimer formation nevertheless restored protease expression and sensitivity to apoptosis, indicating that the functions of STAT1 required for these activities are different from those that mediate induced gene expression.

BACKGROUND: Septic shock represents the major cause of infection-associated mortality in the intensive care unit. The possibility that combination antibiotic therapy of bacterial septic shock improves outcome is controversial. Current guidelines do not recommend combination therapy except for the express purpose of broadening coverage when resistant pathogens are a concern. OBJECTIVE: To evaluate the therapeutic benefit of early combination therapy comprising at least two antibiotics of different mechanisms with in vitro activity for the isolated pathogen in patients with bacterial septic shock. DESIGN: Retrospective, propensity matched, multicenter, cohort study. SETTING: Intensive care units of 28 academic and community hospitals in three countries between 1996 and 2007. SUBJECTS: A total of 4662 eligible cases of culture-positive, bacterial septic shock treated with combination or monotherapy from which 1223 propensity-matched pairs were generated. MEASUREMENTS AND MAIN RESULTS: The primary outcome of study was 28-day mortality. Using a Cox proportional hazards model, combination therapy was associated with decreased 28-day mortality (444 of 1223 [36.3%] vs. 355 of 1223 [29.0%]; hazard ratio, 0.77; 95% confidence interval, 0.67-0.88; p = .0002). The beneficial impact of combination therapy applied to both Gram-positive and Gram-negative infections but was restricted to patients treated with beta-lactams in combination with aminoglycosides, fluoroquinolones, or macrolides/clindamycin. Combination therapy was also associated with significant reductions in intensive care unit (437 of 1223 [35.7%] vs. 352 of 1223 [28.8%]; odds ratio, 0.75; 95% confidence interval, 0.63-0.92; p = .0006) and hospital mortality (584 of 1223 [47.8%] vs. 457 of 1223 [37.4%]; odds ratio, 0.69; 95% confidence interval, 0.59-0.81; p < .0001). The use of combination therapy was associated with increased ventilator (median and [interquartile range], 10 [0-25] vs. 17 [0-26]; p = .008) and pressor/inotrope-free days (median and [interquartile range], 23 [0-28] vs. 25 [0-28]; p = .007) up to 30 days. CONCLUSION: Early combination antibiotic therapy is associated with decreased mortality in septic shock. Prospective randomized trials are needed.