Pulmonary Risks in Patients Being Treated for Aortic Aneurysms and Occlusive Disease

Thomas Sisson

Pulmonary complications occur commonly following major vascular surgery. The spectrum of such complications has been best studied following abdominal aortic aneurysm (AAA) repair. This high incidence of pulmonary morbidity is perhaps not surprising when one considers that tobacco exposure, a major risk factor for vascular disease, is also the most significant risk factor for the development of chronic obstructive pulmonary disease (COPD). The types of pulmonary complications that have been reported are, in general, severe, and one would anticipate the development of these complications following major vascular surgery to increase the length of hospital stay and the mortality rate. Thus it is important to recognize the factors that contribute to perioperative pulmonary complications and to mitigate these factors whenever possible.

Pulmonary Complications of Open Vascular Surgery

Open repair versus endovascular repair continues to be a common approach for the management of AAAs. With the recognition that an endovascular approach will modify the morbidity and mortality of AAA surgery, Nathan and colleagues set out to better define the morbidity and mortality of open repair in the current era. To accomplish this, they retrospectively analyzed a prospectively maintained database of patients (N = 408) who had undergone open repair of an AAA between June 2003 and June 2009 at the Hospital of the University of Pennsylvania. To put in perspective how commonly the surgeons at the Hospital of the University of Pennsylvania employed an open approach over this time period, another 715 patients underwent endovascular repair of an AAA (or 63.7% of patients undergoing AAA repair).

The primary outcome of this study was 30-day and 5-year survival, but the authors also examined, as a secondary endpoint, the incidence of pulmonary complications, defined as ventilator-dependent respiratory failure, pneumonia, pleural effusion requiring drainage, or reintubation. The authors found that 45 of the 408 patients (11%) met criteria for one of these serious respiratory complications. Although the authors did not comment on whether a pulmonary complication influenced 30-day mortality, patients who experienced this endpoint did have a significantly worse 5-year survival (45.6% of those with pulmonary complications vs. 66.3% survival for those without complications). It is also important to note that 30.1% of the patients who underwent an open AAA repair had underlying COPD, and the preexistence of this diagnosis predicted worse 30-day (91.9% vs. 97.2%) and 5-year (55.8% vs. 67.3%) survivals compared to patients without underlying COPD.

A similar rate of pulmonary complications was reported following open AAA repair at the Mayo Clinic in Rochester, Minnesota. In this retrospective study, the authors were interested in comparing the complication rates including pulmonary morbidity in patients who had undergone an open approach (n = 261) versus endovascular treatment (n = 94) of an infrarenal AAA. The type of surgery performed was left to the discretion of the surgeon, and in general, an endovascular approach was done in patients who were considered at higher risk for complications because of preexisting comorbidities or prior abdominal operations. In the group who underwent open repair, 54 developed pulmonary complications defined as pneumonia (11.5%), respiratory insufficiency (7.7%), and/or pulmonary embolism (1.5%).

A third retrospective analysis of patients undergoing open infrarenal AAA repair also addressed the incidence of pulmonary complications following this procedure. In this study, 162 consecutive Korean patients treated with an open approach between 2000 and 2009 were analyzed for the development of postoperative pulmonary complications, defined by the presence on x-ray of a pleural effusion, pulmonary edema, pneumonia, and atelectasis, within the first 30 days of their operation. The authors detected a postoperative pulmonary complication rate of 14% in their patient population. Whether the development of pulmonary morbidity affected other outcomes such as survival in these patients was not reported.

Impact of Pulmonary Complications Following Open Abdominal Aortic Aneurysm Repair on Patient Outcomes

Pulmonary complications reported in the aforementioned trials are, in general, serious, and one would predict that these sequelae would significantly affect hospital length of stay and survival to discharge. In the study by Nathan and colleagues, the authors did establish a correlation between the development of a postoperative pulmonary complication and 5-year survival. However, they did not comment on whether patients who experienced ventilator-dependent respiratory failure, pneumonia, a pleural effusion requiring drainage, or reintubation had a worse 30-day mortality. There was also no mention of whether the development of a respiratory complication affected the hospital length of stay.

In the Mayo Clinic study, the patients who underwent open repair versus endovascular surgery were found to have a longer length of stay (median 8 days vs. 3 days) in conjunction with their increased frequency of pulmonary complications (16.1% vs. 3.2%). Although the authors did not establish a statistical correlation between the presence of respiratory morbidity and length of stay, it is reasonable to speculate that they were interrelated. On the other hand, other variables such as cardiac morbidity, which was also more common in the patients who underwent open repair, and recovery from the surgical incision, likely affected the postprocedure length of stay.

In addition to the Mayo clinic study, the outcome of open versus endovascular AAA repair has been addressed in several large multicenter trials. In one of these studies, the specific cause of postoperative death was prospectively explored. With respect to in-hospital mortality, there were 8 deaths of 174 patients in the open repair group versus 2 deaths of 171 patients in the endovascular repair group. Only one of the deaths in the endovascular group was attributed to a pulmonary cause. The patients surviving to discharge were then subsequently followed for a total of 6 years. Additional pulmonary-related deaths were reported in this postdischarge period, but there was no difference between the open repair group (5 deaths of 166 patients) and the endovascular repair group (5 deaths of 169 patients).

In summary, pulmonary complications are common following open repair of an AAA. Depending on the study population and the definition of a pulmonary complication, the overall incidence of pulmonary morbidity ranges between 10% and 15%. Thus, patients who require major vascular surgery and are at high risk for respiratory morbidity should be managed in a way, whenever possible, to minimize pulmonary complications.

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