Strategy to reduce antibiotic prescription in cases of airway aspiration

Introduction

Airway aspiration (AWA) of gastric content is a very frequent complication in patients presenting to emergency rooms after incidents linked to a depressed level of consciousness. The routine use of antibiotics in this situation determines a high-pressure selection for multiresistant microorganisms. However, how often AWA is the causative situation for early ventilator-associated pneumonia is not known. Also a gold standard for a diagnostic workup is needed. Our aim was to know how frequent AWA determines infectious aspiration pneumonia confirmed by evolution and microbiological samples, and to propose a methodological approach to rule out antibiotic usage.

Methods

Over a 2-year period, in 82 patients admitted to our ICU, AWA was confirmed by the direct observation of gastric content when orotracheal intubation was performed by a trained physician due to a Glasgow coma scale below 12. Usual diagnosis: acute brain injury, 52 patients (73%); Simplified Acute Physiology Score II 37 ± 11; age, 44 ± 15 years; all were mechanically ventilated, average 6 ± 2 days; ICU stay ± 10 days; mortality 21%. Rectal fever, leukocytosis, thoracic radiology and PaO₂/FiO₂ were recorded on a daily basis. The Clinical Pulmonary Infection Score (CPIS) and semiquantitative tracheal aspirates (SQTA) were performed twice: in the first 48 hours and between the third and fifth days.

Results

Out of 82 patients, 23 (28%) developed clinically and microbiologically confirmed pneumonia. Fever and leukocytosis showed no significant differences in patients with or without pneumonia during the first 5 days. Also the PaO₂/FiO₂ index was not different. As for radiology, when unilateral focal condensation was present, pneumonia was confirmed later (relative risk = 3.3, 95% CI = 1.7 to 6.4). CPIS in the first 48 hours showed a negative predictive value for pneumonia of 89%, and SQTA with no microorganism growth a negative predictive value of 96%. In our patient group, 42 (51%) had CPIS <6 and SQTA growth; in them no antibiotic usage is recommended. On the contrary, out of 20 patients who had CPIS ≥6 and positive SQTA, 16 (75%) developed pneumonia within the first 5 days of the ICU stay; this group deserves antibiotics. CPIS ≥6 without pneumonia, probably due to lung inflammation, was observed in 10 out of 28 patients (36%).

Conclusion

(1) In our ICU population, pneumonia develops in only 28% of those presenting with AWA. (2) Through CPIS <6 and negative SQTA performed in the first 48 hours we could identify that in more than one-half of AWA patients antibiotics are not needed. (3) CPIS is not a reliable early indicator of pneumonia in patients with AWA.