Question: Does prophylactic antibiotic therapy decrease incidence of pneumonia in out of hospital cardiac arrest (OHCA) patients receiving targeted temperature management (TTM)?

The Bottom Line:

Both studies suggest that prophylactic antibiotics are associated with (Gagnon) or resulted in (Cariou) lower incidence of early ventilator-associated pneumonia in post-cardiac arrest patients being treated with TTM. 

Both studies failed to show that prophylactic antibiotic use affects more clinically significant outcomes like mortality at day 28 or good functional outcome. 

Study 1: Gagnon et. al., Resuscitation, 2015

Retrospective cohort study. Data from Northern Hypothermia Network, which includes data from 39 hospitals in US and Europe

Objective: to determine if prophylactic antibiotic administration was associated with decreased incidence of pneumonia in post-cardiac arrest patients receiving TTM compared to no prophylactic antibiotic administration.

Patients: 1240 adults over 18 years old who suffered cardiac arrest, ROSC, receiving TTM. Antibiotics were given as prophylaxis in 33.5% of patients.

Outcome:

• Logistic regression for factors associated with development of pneumonia showed that prophylactic antibiotics were associated with reduced incidence of pneumonia.
• OR = 0.09; 95% CI (0.06 - 0.14); p = <0.001
• Logistic regression for factors associated with good functional outcome: use of prophylactic antibiotics was removed from the model before final run because of lack of influence on the outcome.

Strengths:

Identified factors associated with lower risk of pneumonia. Interesting question generating study.

Limitations:

Data independently recorded at different sites. Differences in practice across sites could have affected data.

No standardized antibiotic regimen.

Backwards stepwise logistic regression allows for some control by investigators over reported results.

Study 2: Cariou, NEJM, 2019

Randomized, blinded, placebo controlled study.

Objective: to determine if a 2 day course of prophylactic antibiotics decreases incidence of pneumonia in out of hospital cardiac arrest patients receiving TTM.

Patients: 194 adults who suffered OHCA, ROSC, receiving TTM

Intervention: Amoxicillin/clavulanate 1g/200mg TID for 2 days

Control: Saline infusion TID for 2 days

Outcome:

• Incidence of early VAP (within 7 days of hospitalization) lower in intervention group.
• HR = 0.53; 95% CI (0.31 - 0.92); p = 0.03
• No difference in number of ventilator free days or mortality at day 28 (secondary outcomes).
• No deaths attributable to VAP or sepsis.

Strengths:

Adequately randomized, blinded, and powered for their specific objective. 

Specific inclusion and exclusion criteria, diagnostic criteria for pneumonia

Only one antibiotic was used, reducing potential confounders and bias.

Limitations:

Early VAP is not a particularly patient-centered outcome, especially considering there were no deaths from VAP or sepsis.

Citations:

• Gagnon, et. al. Prophylactic antibiotics are associated with a lower incidence of pneumonia in cardiac arrest survivors treated with targeted temperature management. Resuscitation. 2015; 92:154-159.
• Cariou, et. al. Prevention of early ventilator-associated pneumonia after cardiac arrest. New England Journal of Medicine. 2019; 381:1831-1842.