Few days seem to go by without our critical care unit admitting at least one patient who's suffered an out of hospital cardiac arrest (OOHCA). Often these patients have been unconscious for several minutes and have what’s described as an “unprotected airway”. This can lead to blood, mucus and stomach contents entering the lungs. The result? Life threatening complications such as mechanical obstruction, chemical pneumonitis and aspiration pneumonia.
Aspiration Pneumonia - right middle and lower lobes are most commonly affected since the right bronchus is wider and more vertical than the left bronchus.
Opinions have been divided over the use of prophylactic antibiotics in the prevention of aspiration pneumonia in these patients. However a recent study in the NEJM now points towards a benefit in their use. Researchers across 16 intensive care units in France analysed 194 patients who suffered an OOHCA. Only those who had a shockable rhythm were included. All were mechanically ventilated and cooled to between 32 and 34 degrees C before being given either amoxicillin-clavulonic acid (augmentin) 1.2g 3 times a day or placebo for 2 days. This was all started within 6 hours of cardiac arrest.
In total, 51 cases of pneumonia were identified within the first 7 days of critical care admission. The difference between the 2 groups was statistically significant - 32 (placebo) and 19 (treatment) (P<0.05). This is perhaps not surprising since the bacteria found in the sputum samples of these patients was mostly gram negative organisms sensitive to augmentin. But before getting carried away with these results it’s worth saying that this difference did not lead to a shorter stay in critical care or a reduction in 28 day mortality amongst those given antibiotics. However this is perhaps not surprising as much larger sample sizes are often needed to show significant differences in these outcomes.
Historically, it was widely believed that aspiration pneumonia was triggered by anaerobic bacteria such as bacteroides and prevotella, however more recent research has shown that infection is often due to aerobic bacteria, in particular gram negative cocci such as haemophilus influenzae and escherichia coli. In the majority of infections more than one bacteria can be identified.
From this study we now have the first evidence to support the use of a short course of augmentin in reducing the incidence of pneumonia in patients who’ve suffered an OOHCA. Large scale studies are now needed to see if this translates into a meaningful difference in survival. Last year, STDZ reported on the PARAMEDIC2 trial that revealed poor neurological outcomes in many of those who suffered an OOHCA. Future interventions need to not only improve survival, but should also enhance neurological outcomes too.
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