Prompt Administration of Antibiotics and Fluids in the Treatment of Sepsis: A Murine Trial

Abstract

Objectives: Sepsis, the acute organ dysfunction caused by a dysregulated host response to infection, poses a serious public health burden. Current management includes early detection, initiation of antibiotics and fluids, and source control as necessary. Although observational data suggest that delays of even a few hours in the initiation of antibiotics or IV fluids is associated with survival, these findings are controversial. There are no randomized data in humans, and prior animal studies studied time from experimental manipulation, not from the onset of clinical features of sepsis. Using a recently developed murine cecal ligation and puncture model that precisely monitors physiologic deterioration, we hypothesize that incremental hourly delays in the first dose of antibiotics, in the first bolus of fluid resuscitation, or a combination of the two at a clinically relevant point of physiologic deterioration during polymicrobial sepsis will shorten survival.

Design: Randomized laboratory animal experimental trial.

Setting: University basic science laboratory.

Subjects: Male C57BL/6J, female C57BL/6J, aged (40-50 wk old) male C57BL/6J, and BALB/C mice.

Interventions: Mice (n = 200) underwent biotelemetry-enhanced cecal ligation and puncture and were randomized after meeting validated criteria for acute physiologic deterioration. Treatment groups consisted of a single dose of imipenem/cilastatin, a single bolus of 30 mL/kg fluid resuscitation, or a combination of the two. Mice were allocated to receive treatment at the time of meeting deterioration criteria, after a 2-hour delay or after a 4-hour delay.

Measurements and main results: Hourly delays in the initiation of antibiotic therapy led to progressively shortened survival in our model (p < 0.001). The addition of fluid resuscitation was unable to rescue animals, which received treatment 4 hours after meeting enrollment criteria. Systemic inflammation was increased, and host physiology was increasingly deranged with hourly delays to antibiotics.

Conclusions: We conclude that antibiotic therapy is highly time sensitive, and efforts should be made to deliver this critical therapy as early as possible in sepsis, perhaps extending into the first point of medical contact outside the hospital.

Figure 1. Survival curves

Proportion of animals (n=10 in each sub-cohort) surviving, plotted using the Kaplan-Meier method as function of time after meeting criteria for acute physiologic deterioration, which served as the enrollment point for each trial. Plots are divided by treatment: all cohorts (A), fluid resuscitation only (B), antibiotic treatment only (C), or combination therapy with antibiotics and fluid resuscitation (D).

Figure 2. Animal physiology after trial enrollment

Core temperature (Celsius) and heart rate (beats per minute) are plotted as a function of time after meeting criteria for acute physiologic deterioration using fractional polynomial panel analysis to generate a mean curve for each sub-cohort. Plots shown are mean with 95% confidence intervals. Plots are divided by treatment: fluid resuscitation only (A), antibiotic treatment only (B), or combination therapy with antibiotics and fluid resuscitation (C). n=10 animals for each sub-cohort.

Figure 3. Parameters of shock

Mixed venous blood gas analysis was performed 24 hours after trial enrollment. Sub-cohorts are separated by treatment and by treatment timing. Parameters shown include pH (A), bicarbonate concentration (B), base excess (C), and lactate (D). Data is represented as median with individual data points.

Figure 4. Systemic inflammation and organ injury

Biomarkers of inflammation (tumor necrosis factor-alpha, [A]; interleukin-6, [B]; interleukin-10, [C]) and organ dysfunction (Cystatin C, [D]) measured 24 hours after trial enrollment. Sub-cohorts are separated by treatment and by treatment timing as indicated. Data is represented as median with individual data points.

Figure 5. Survival curves and animal physiology in aged, female and BALB/C mice

Plots are divided by treatment: aged mice (A), female mice (B), and BALB/C mice (C). Top panel represents proportion of animals surviving, plotted using the Kaplan-Meier method as function of time after meeting criteria for acute physiologic deterioration. Middle and bottom panels represent core temperature (celsius) and heart rate (beats per minute) plotted as a function of time after meeting criteria for acute physiologic deterioration using fractional polynomial panel analysis to generate a mean curve for each sub-cohort. Plots shown are mean with 95% confidence intervals. (n=10 in each cohort)