The Incidence of Postoperative Pneumonia in Various Surgical Subspecialties: A Dual Database Analysis

Pneumonia is the third most common postoperative complication. However, its epidemiology varies widely and is often difficult to assess. For a better understanding, we utilized two national databases to determine the incidence of postoperative pneumonia after various surgical procedures. Specifically, we used the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) and the Nationwide Inpatient Sample (NIS) to determine the incidence and yearly trends of postoperative pneumonia following orthopaedic, urologic, otorhinolaryngologic, cardiothoracic, neurosurgery, and general surgeries.

The NIS and NSQIP databases from 2009-2013 were utilized. The Clinical Classification Software (CCS) for International Classification of Diseases, 9th edition (ICD-9) codes provided by the NIS database was used to identify all surgical subspecialty procedures. The incidence of postoperative pneumonia was identified as the total number of cases under each identifying CCS code that also had ICD-9 codes for postoperative pneumonia. In the NSQIP database, the surgical subspecialties were selected using the following identifying string variables provided by NSQIP: 1) "Orthopedics", 2) "Otolaryngology (ENT)", 3) "Urology", 4) "Neurosurgery", 5) "General Surgery", and 6) "Cardiac Surgery" and "Thoracic Surgery". Cardiac and thoracic surgery was merged to create the variable "Cardiothoracic Surgery". Postoperative pneumonia cases were extracted utilizing the available NSQIP nominal variables. All variables were used to isolate the incidences of postoperative pneumonia stratified by surgical specialty. A subsequent trend analysis was conducted to assess the associations between operative year and incidence of postoperative pneumonia.

For all NIS surgeries, the incidence of postoperative pneumonia was 0.97% between 2009 and 2013. The incidence was highest among patients who underwent cardiothoracic surgery (3.3%) and urologic surgery (1.73%). Patients who underwent general surgery, neurosurgery, spine surgery, orthopaedic surgery, and ENT surgery had a postoperative pneumonia incidence of 1.1%, 0.6%, 0.5%, 0.5%, and 0.4%, respectively. Overall trend analysis demonstrated a statistically significant decrease in postoperative pneumonia incidence (p <0.001), which paralleled in each specialty as well. In NSQIP, the incidence of postoperative pneumonia for all surgeries that occurred between 2009 and 2013 was 1.3%. The incidences of postoperative pneumonia were highest among patients who underwent cardiothoracic surgery (5.3%), general surgery (1.4%), and neurosurgery (1.4%). The incidences of postoperative pneumonia in patients who underwent ENT surgery, orthopedic surgery, and urologic surgery were 0.7%, respectively. Overall trend analysis demonstrated a statistically significant increase in postoperative pneumonia incidence for patients undergoing cardiothoracic surgery (p <0.001). There were no notable trends for the other surgical subspecialties.

The incidence of postoperative pneumonia differs between the two national databases. Furthermore, the incidences differed among the various surgical subspecialties; however, cardiothoracic surgery had the highest incidence in both databases. Furthermore, cardiothoracic surgery appeared to have an increasing trend in incidence. Standardizing and implementing accurate coding methodologies for this complication are needed for a more accurate assessment of this burdensome complication. Future studies should assess interventions, such as oral cleansing and suctioning, incentive spirometry, as well as designated institution-based pneumonia prevention programs and protocols to help prevent and mitigate the occurrence of this complication.