CIDから報告された、Prophylactic Antimicrobial Therapy for Acute Aspiration Pneumonitis
Prophylactic antimicrobial therapy is frequently prescribed for acute aspiration pneumonitis following macro-aspiration with the intent of preventing the development of aspiration pneumonia; however, few clinical studies have examined the benefits and harms of this practice.
A retrospective cohort study design was used to assess outcomes of patients receiving antimicrobial prophylaxis with those receiving supportive care only during the initial two days following an acute aspiration pneumonitis episode. The primary outcome was in-hospital mortality within 30-days. Secondary outcomes included transfer to critical care, and antimicrobial therapy received including escalation of therapy and antibiotic-free days between days 3 to 14 following the acute aspiration event.
Among 1483 patients reviewed, 200 met the case definition for acute aspiration pneumonitis including 76 (38%) who received prophylactic antimicrobial therapy and 124 (62%) receiving supportive management only. Unadjusted in-hospital mortality was similar between both groups (25%; 95% CI, 17-36% vs. 25%; 95% CI, 18-33%; p=1). Patients receiving antimicrobial prophylaxis were no less likely to require transfer to critical care (5% vs. 6%; p=.7) and subsequently received more frequent escalation of antibiotic therapy (8% vs. 1%; p=.002) and fewer antibiotic-free days (7.5 vs. 10.9; p <.0001). After adjusting for patient-level predictors, antimicrobial prophylaxis was not associated with any improvement in mortality (OR 0.9; 95% CI, 0.4-1.7; p=0.7).
Prophylactic antimicrobial therapy for patients with acute aspiration pneumonitis does not offer clinical benefit and may generate antibiotic selective pressures that result in the need for escalation of antibiotic therapy among those who develop aspiration pneumonia.
First, the observational retrospective nature of our study is subject to confounding variables which may have influenced patient outcomes. Confounding by indication was likely present in that patients with more severe aspiration pneumonitis episodes tended to receive prophylactic antimicrobial therapy. However, no difference in outcomes was noted following multivariate analysis adjusting for measurable confounders, nor following a sensitivity analysis excluding patients with the poorest clinical outcome during the acute aspiration pneumonitis episode.
Second, despite the large number of patients reviewed, our study cohort is relatively small and not powered to detect a less than 10% difference in mortality. Third, our study was not designed to evaluate the impact of prophylactic antimicrobial therapy on the development of pneumonia. We instead focused on mortality as a more objective clinical outcome due to the lack of gold standard to assess pneumonia. Based on our observation that prophylactic antimicrobial therapy was associated with a greater need for subsequent antibiotics, it may be inferred that this therapy was ineffective in preventing pneumonia as suggested in other studies.
Finally, our study only included non-mechanically ventilated patients with documented macro-aspiration events with acute aspiration pneumonitis and would not apply to patients with silent aspiration or in whom the diagnosis of aspiration pneumonitis is ambiguous.