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Significance of Mini Bronchoalveolar Lavage Fluid Amylase Level in Ventilator-Associated Pneumonia

A Prospective Observational Study*

Samanta, Sukhen, MD, PDCC, EDIC; Poddar, Banani, MD; Azim, Afzal, MD, PDCC; Singh, Ratender K., MD, PDCC; Gurjar, Mohan, MD, PDCC; Baronia, Arvind K., MD

doi: 10.1097/CCM.0000000000002774
Clinical Investigations

Objectives: Aspiration of oropharyngeal or gastric contents in intubated patients can lead to ventilator-associated pneumonia. Amylase in respiratory secretion has been reported as a possible marker of aspiration. We studied whether elevated α-amylase in mini bronchoalveolar lavage specimens can be suggestive of ventilator-associated pneumonia in intubated patients with high clinical suspicion.

Design: Prospective single-center observational study.

Setting: Department of Critical Care Medicine, tertiary care academic institute.

Patients: Adult patients on mechanical ventilation for more than 48 hours with with clinically suspected ventilator-associated pneumonia as per defined criteria, admitted between December 2014 and May 2016.

Methods: Mini bronchoalveolar lavage samples were collected within 72 hours of endotracheal intubation. Samples were sent for α-amylase level assay and quantitative culture. Ventilator-associated pneumonia was confirmed from mini bronchoalveolar lavage microbial culture of greater than or equal to 104 cfu/mL, and patients were divided into ventilator-associated pneumonia and no ventilator-associated pneumonia groups. Pre- and postintubation risk factors for aspiration were also noted.

Results: The prevalence of ventilator-associated pneumonia was 64.9% among 151 patients in whom it was clinically suspected. Median (interquartile range) mini bronchoalveolar lavage α-amylase levels in ventilator-associated pneumonia and no ventilator-associated pneumonia groups on the day of study inclusion were 287 U/L (164–860 U/L) and 94 U/L (59–236 U/L), respectively (p < 0.001). Median (interquartile range) α-amylase levels in patients with 0, 1, 2, and 3 preintubation risk factors were 65 U/L (35–106 U/L), 200 U/L (113–349 U/L), 867 U/L (353–1,425 U/L), and 3,453 U/L (1,865–4,304 U/L), respectively (p < 0.001) and 472 U/L (164–1,452 U/L) and 731 U/L (203–1,403 U/L) in patients with 1 and 2 postintubation risk factors, respectively (p < 0.001). A mini bronchoalveolar lavage α-amylase of 163 U/L or more yielded sensitivity and specificity of 73% and 68.6%, respectively, with area under the receiver operating characteristic curve of 0.746 (95% CI, 0.66–0.83).

Conclusions: Patients with ventilator-associated pneumonia within 72 hours from intubation have significantly elevated α-amylase concentrations in mini bronchoalveolar lavage fluid. Mini bronchoalveolar lavage α-amylase concentrations increase with increasing number of aspiration risk factors.

All authors: Department of Critical Care Medicine, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.

*See also p. 165.

Dr. Gurjar received funding from Intramural Grant for ongoing research (unrelated to submitted work), Jaypee Medical Publishers, New Delhi, India (royalties for “Manual of ICU Procedures”), and received financial support from the institute to attend 46th Society of Critical Care Medicine Congress. The remaining authors have disclosed that they do not have any potential conflicts of interest.

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