The present study was undertaken to determine the impact of preexisting COPD on outcomes after surgery for an acute abdominal surgical diagnosis. The prevalence of COPD in our entire cohort of emergency patients was 5.7%. This agrees with previous research that found a comparable prevalence of COPD among surgical patients [7].

The results suggest that compared to controls, patients with preexisting COPD had an increased postoperative pulmonary complication rate, ICU admission rate, ventilator dependence rate and in-hospital death rate after emergency abdominal surgery. No statistically significant differences were observed in the overall complication rate or for prolonged LOS in the ICU or hospital. Furthermore, multivariable regression analysis showed that preexisting COPD was associated with an increased risk of PPCs and VD. There was no significant association between COPD and in-hospital mortality.

To our knowledge, the current study is the first to report on the outcomes of a sizable number of patients with preexisting COPD compared with matched controls after emergency abdominal surgery.

Almost 72% of these patients had at least 1 postoperative complication, and 41% died in the hospital. This implies that, as reported by others [6] regarding elective surgery, preexisting COPD affects the outcomes of the abdominal emergency patient population as well.

The observed incidence of a composite outcome of PPCs, the rate of ventilator dependence and in-hospital mortality were higher than previous outcome reports despite high-level hospital services, including ICU care. This is likely due to a combination of different patient characteristics and high-risk emergency surgical procedures. For example, 88% of COPD patients had an ASA class equal to or above 3 with severe systemic disease, and COPD patients had on average 6 coexisting conditions per patient. Patients with severe coexisting conditions on admission are more than seven times more likely to have a complication than those without such conditions [24].

Therefore, in addition to the complexity of disease and surgical treatment in emergencies, where the acute insult is greater, many preexisting factors increase the risk that a patient will have an adverse event following surgery during hospitalization.

To our knowledge, these findings have not been reported with regard to the outcomes of COPD patients after surgery for emergency abdominal diagnosis in a large patient cohort (cases and controls), and relevant data are scarce.

The majority of previous studies concentrated mainly on the outcomes of COPD patients after elective surgery [5, 9, 10, 12, 25, 26]. In those studies, the included number of emergency cases of COPD patients was either unknown or very small without matched controls, making it difficult to draw a conclusion from the analysis. Thus, the overall information generated by those studies regarding the effect of COPD on outcomes after surgery in the emergency setting was inconclusive.

Patient characteristics (patient factors) also increased the risk of an adverse event following surgery. For example, 51% of the studied patients were older than or aged 70 years, and elderly patients had more complicated disease that increased the risk of complications and in-hospital mortality after surgery [27,28,29,30,31].

Interestingly, these outcomes did not vary significantly with the severity of COPD. For example, our analysis of the subgroup of patients with valid spirometric results showed that 65% of the patients with mild to moderate COPD and 76% with severe COPD suffered at least 1 postoperative complication. Similarly, the in-hospital mortality rates were 38.6% and 36.4% among patients with mild to moderate and severe COPD, respectively (data not shown). This is in agreement with the findings of the study by Manganas et al. [12] that reported on outcomes after elective coronary artery bypass grafting. These authors found no association between the severity of airflow obstruction and the mortality rate. In another study among patients after elective abdominal surgery, Kim et al. [5] found no association between mild-to-moderate COPD and the risk of PPCs. However, because of the small sample size for each spirometric stage in our study, as described in detail in the Methods section, comparison of the obtained findings was difficult, and the results must be interpreted with caution.

In the current study, COPD was independently associated with an increased risk of PPCs and VD but not in-hospital mortality. This is in agreement with previous reports that suggested that COPD is an independent risk factor for PPCs and VD but not for in-hospital mortality after controlling for other covariates [8, 12, 25, 32].

Of the complications that we included for analysis, PPCs were the most common after emergency abdominal surgery and had a strong association with in-hospital mortality. Other index complications were less common. Therefore, according to the results of our study, preexisting COPD may predispose patients to mortality indirectly through its impact on PPCs following surgery for abdominal emergencies. The lack of a clear association between COPD and in-hospital mortality following surgery for abdominal emergencies may reflect the dominance of other factors, such as pulmonary complications and acute multiple organ failure, which were all noted in previous studies [15, 33, 34], in determining the clinical course of these patients. In general, it is our impression that the impact of COPD on mortality was offset by the dominance of other factors.

For patients undergoing elective surgery, preexisting comorbid conditions, including COPD, can be modified to reduce the risk of severe complications and improve the outcome. Unfortunately, in unforeseen and life-threatening emergency events, preoperative risk factor modification is almost impossible. On the other hand, surgery is mandatory because almost all of these patients who had emergency operations would have died of the condition for which they were treated if left untreated. Therefore, while treating patients with preexisting COPD for an abdominal emergency where the acute insult is greater, surgeons should be aware of expected severe and multiple complications, including prolonged ventilator dependence. More personal attention and information regarding high-risk procedures, personal experiences and previous outcomes should be integrated into the treatment and communicated with the patient (if possible), the families and health care proxies. Efforts to improve the postoperative outcomes of such patients will necessarily require a focus on the prevention of postoperative morbidity and on the timely diagnosis and management of complications that do occur, as suggested by others [28, 35, 36].

Several limitations of this study merit attention. First, the current study was limited by its retrospective nature. As such, potential bias may have been introduced as a result of systemic coding errors, lack of accurate severity adjustment for comorbid conditions, and absence of adequate information on health-related behaviors, particularly smoking, as a central risk factor for COPD. Our data collection relied on existing documentation that was not specifically collected for this study or its variables. Furthermore, this study involved patients from a single center and was not designed to attribute causality between preexisting COPD and poor surgical outcomes.

Second, the present study was limited by the inability to stratify patients by COPD severity. Not all patients had a valid spirometric finding. For some patients, we were unable to determine whether missing spirometric data were absent because the associated findings were truly absent or whether the findings were present but not recorded in our electronic database. However, the impact of this limitation was likely to be small because, as discussed above, the postoperative mortality and morbidity among those patients with valid spirometric results were similar to those of patients without.

Third, the COPD group was sicker (higher comorbidity burden) than the non-COPD group. However, in the multivariable analysis, we adjusted for all of these comorbid conditions to predict outcomes based on adjusted variables. Therefore, once a multivariable analysis was completed, it would have adjusted for the difference.

Fourth, it is possible that the associations between COPD and the outcomes we described were impacted by other variables that we might not have accounted for.

Despite these limitations, our analysis of a relatively large cohort of matched patients undergoing surgery for an acute abdominal surgical diagnosis demonstrated preexisting COPD to be an important contributor to subsequent postoperative outcomes. This study represents a real-life situation in which surgeons are confronted with COPD patients who need surgery as soon as possible during the same admission in which the diagnosis was made. Because of the relatively large sample size, the results of this study more closely approximate the true impact of COPD on outcomes after emergency abdominal surgery than results from studies with smaller cohorts of patients.