Postoperative pulmonary complications may be a leading cause of poor surgical outcomes, but combined regional and general anesthesia is not necessarily to blame. After adjusting for confounders, subanalysis of a recent prospective observational study showed that combined regional and general anesthesia was not associated with having at least one postoperative pulmonary complication.
According to Kristina Coger, MD, anesthesiology resident at the University of Colorado School of Medicine, in Aurora, these results indicate that greater incidence of postoperative pulmonary complications (PPCs) in patients receiving combined regional and general anesthesia is likely to be related to surgical or patient complexity.
“We will continue to advocate for regional anesthesia for patients who are suitable candidates,” Dr. Coger said. “Although definitive evidence of this technique’s superiority may be lacking, I think it’s important to limit any misinformation about the perceived risks of combining regional and general anesthesia.”
As Dr. Coger reported, although the vast majority of anesthesiologists may assume that patient outcomes are improved by combining regional anesthesia techniques with general anesthesia, this opinion is not as widely held outside the field. Investigators from the Perioperative Research Network recently published the results of a multicenter, prospective observational study that examined the incidence and clinical effect of predefined PPCs in patients undergoing noncardiothoracic surgery that required at least two hours of general anesthesia and mechanical ventilation (JAMA Surg. 2017;152:157-166).
“Initial analysis of this study suggested a possible association between PPCs and having received combined regional and general anesthesia,” Dr. Coger said. “We hypothesized that combined techniques [are] not associated with PPCs but [are] instead a marker of greater patient or surgery complexity.”
Dr. Coger and her colleagues performed a secondary analysis of the PPCs study including all 1,202 ASA physical status III patients from the original study. The researchers prospectively identified predefined PPCs occurring within the first seven postoperative days. These included:
- acute respiratory distress syndrome;
- pleural effusion;
- prolonged supplemental oxygen by nasal cannula and/or face mask;
- postoperative noninvasive ventilation; and
- reintubation with postoperative mechanical ventilation.
For this subanalysis, patients were classified as receiving regional anesthesia and general anesthesia, or general anesthesia alone. Investigators then used bivariable and multivariable hierarchical logistic regression analyses to investigate the association of combined anesthesia techniques with one or more PPCs.
As Dr. Coger reported at the 2017 annual meeting of the International Anesthesia Research Society (abstract 1124), 22.1% of patients (n=266)received combined regional and general anesthesia, while 77.9% (n=936) received general anesthesia alone.
On first analysis, patients receiving combined techniques were more likely to have cancer, abdominal/pelvic nonemergent surgery, greater estimated blood loss and intravenous fluid administration than patients receiving general anesthesia alone. Combined-anesthesia patients also had a higher incidence of one or more PPCs than general anesthesia patients (42.1% vs. 30.9%; P=0.007). After adjusting for other significant covariates from the bivariable analysis, however, combined regional and general anesthesia was not independently associated with PPCs (adjusted odds ratio, 1.37; 95% CI, 0.83-2.25; P=0.165).
According to the study authors, these results suggest that the more frequent presence of PPCs in patients receiving regional and general anesthesia in the original study is likely related to surgical or patient complexity. Nevertheless, they noted, interpretation of associated variables from observational studies should be done with caution and requires adjusting for a large number of possible confounders.
“Since this is a retrospective subanalysis of the original prospective observational study, it was a bit of a struggle to tease out differences in the data when that wasn’t the original purpose of the study, but the intent was to not continue to propagate misinformation,” Dr. Coger noted.
Despite this caveat, these findings should bolster support for regional anesthesia while mitigating concern about developing PPCs with combined anesthesia techniques, the authors concluded.
The moderator of the session, Beverley Orser, MD, PhD, FRCPC, professor of physiology and anesthesia at the University of Toronto, asked whether these findings indicate superiority or simply noninferiority.
“Noninferiority,” said Dr. Coger, who emphasized the difficulty of proving the superiority of one technique. “When you look at PPCs, there are many definitions. Our specific definition was very inclusive and even included nasal cannula use beyond postoperative day 1. Although other studies have been able to demonstrate that having epidurals can redu ce the incidence of pneumonias, for example, I think we’re still waiting for definitive evidence that shows that regional anesthesia is the absolute best thing we can do.”
When pressed about her study’s more inclusive definition, Dr. Coger said, “It’s difficult to pinpoint which definitions of PPCs are going to affect these outcomes. Having at least one PPC in the original JAMA paper showed an increase in hospital length of stay from three to five days, which is dramatic. Nevertheless, it’s hard to tease out whether that’s because the patient required reintubation, for example, or something less serious.”