Postoperative pneumonia in elderly patients receiving acid suppressants: a retrospective cohort analysis.

Objective: To test whether gastric acid suppressants are associated with an increased risk of postoperative pneumonia in patients undergoing elective surgery.

Design: Population-wide retrospective cohort analysis.

Setting: Canadian acute care hospitals between 1 April 1992 and 31 March 2008. Patients Consecutive patients aged >65 years admitted for an elective operation.

Outcome Measure: Postoperative pneumonia recorded in inpatient postoperative notes.

Results: A total of 593 265 patients were included, of whom about 21% were taking an acid suppressant (most commonly omeprazole or ranitidine). Overall, 6389 patients developed postoperative pneumonia, with a rate significantly higher for those taking acid suppressants (13 per 1000) than controls (10 per 1000), equivalent to a 30% increase in frequency (odds ratio 1.30 (95% confidence interval 1.23 to 1.38), P<0.001). However, no increase in risk was observed after adjustment for duration of surgery, site of surgery, and other confounders (odds ratio 1.02 (0.96 to 1.09), P=0.48). The general safety of acid suppressants extended to those patients prescribed proton pump inhibitors, experiencing long term treatment, receiving high doses, and undergoing high risk procedures.

Conclusion: After adjustment for patient and surgical characteristics, acid suppressants are not associated with an increased risk of postoperative pneumonia among elderly patients admitted for elective surgery.