Our findings suggest that, compared with general anesthesia, the use of regional anesthesia in patients with severe COPD is associated with a lower incidence of postoperative pulmonary complications. Our findings are novel, in that the improved outcomes are only present in patients receiving spinal or peripheral nerve block and not in epidural anesthetics. Furthermore, the improved outcomes were not present in patients with dyspnea at rest.
Although composite morbidity, as well as nonpulmonary composite morbidity, was lower in patients not receiving general anesthesia, this advantage did not extend to mortality, which was similar between groups. This differs from a meta-analysis of older studies comparing 9559 patients randomized to regional or general anesthesia that found a one-third reduction in mortality with regional anesthesia.6 However, more recent studies have found no mortality benefit for regional over general anesthesia,7–9 and 1 very recent study showed potential harm as a result of increased cardiovascular morbidity.10 These recent studies, as well as our findings, challenge previous data that avoiding general anesthesia provides a mortality benefit. However, those studies6–10 included non-COPD patients whereas, our study is limited to patients with COPD.
We also found that although patients who received spinal anesthetics had fewer composite morbidities, there was no difference between those who received epidural and general anesthesia. Our study was not designed or powered to find a difference among the different types of regional anesthetics, and therefore, this lack of difference may simply be loss of power from the smaller sample size.
We found better outcomes in the regional anesthesia group only in the subgroups with moderate dyspnea or none but not in those with dyspnea at rest. Although this lack of effect may have been attributable to lack of statistical power or hidden confounders, such as the spectrum of COPD severity in patients with dyspnea at rest, it may also have reflected physiological differences. In severely symptomatic COPD patients, the adverse effects of regional anesthesia, including loss of accessory muscles of respiration, phrenic nerve paralysis, and poor tolerance for supine positioning, tend to negate the potential benefits of avoiding operative endotracheal intubation and mechanical ventilation.15,16 Given the high rate of composite morbidities (25% vs 23%) and mortality (7.5% vs 9.6%), further study is needed to determine how best to provide anesthesia to COPD patients with dyspnea at rest. Additional subgroup analysis of ASA-3 and ASA-4 patients found that only in ASA-3 patients was receiving general anesthesia found to be associated with a higher composite morbidity than regional patients. This further suggests that the beneficial effects of regional anesthesia may be muted in the sickest patients.
COPD patients with moderate or no reported dyspnea did benefit from avoiding general anesthesia. They were less likely to require prolonged mechanical ventilation and had a lower composite morbidity if they received regional anesthesia. There are several mechanisms by which general anesthesia may result in pulmonary complications in patients with COPD. Residual effect of neuromuscular blocking drugs increases the incidence of hypoxia and unplanned intubation in the postoperative care unit.15 COPD patients may be particularly sensitive to this effect. General anesthesia and positive pressure ventilation disturb pulmonary physiology, causing atelectasis, gas exchange abnormalities, and ventilation/perfusion mismatch.16 These disturbances are less likely to be tolerated by patients with COPD.
There were several limitations to this study. COPD was clinically defined, not defined on the basis of pulmonary function tests. Although the clinical definitions were standardized, we cannot exclude the possibility that anesthesiologists had other clinical information that may have influenced their decision on the type of anesthetic to provide. We attempted to mitigate this using exact matching for level of dyspnea to control for varying clinical severities of COPD. Although propensity matching is a well-accepted method for controlling for differences in populations, it cannot control for hidden confounders, and these may have introduced unknown biases into our analysis. In addition, because this was a retrospective observational study, we cannot determine causation but only an association between type of anesthesia and outcomes. Furthermore, the results of this study only apply to surgical procedures for which avoiding general anesthesia is feasible.
Finally, postoperative patient management data, including the type, dose, and duration of postoperative analgesia used, are not reported in NSQIP nor are postoperative inflammatory biomarkers or core temperatures, which would have been interesting to correlate with our primary outcome. Postoperative epidural analgesia has been shown to reduce the incidence of pulmonary complications in patients with COPD,5 and therefore, any confounding effects of postoperative analgesia regimens cannot be determined. Although epidural and peripheral nerve block anesthesia can be converted to postoperative analgesia using the same catheter, spinal anesthesia cannot. Patients receiving spinal anesthesia showed significant reduction in postoperative pulmonary complications, supporting our hypothesis that the type of operative anesthetic is associated with outcome.
One strength of our study is that by using propensity scoring and exact matching, we were able to remove the confounding effects of other factors, such as obstructive sleep apnea, age, and obesity, which can contribute to postoperative pulmonary complications. This allowed us to isolate the association between anesthetic type and outcome. Another strength is that we used a national database with >1.3 million patients from 186 hospitals to assess for our end points of interest. Furthermore, our findings were supported by a validity assessment showing significant relationships among pulmonary end points. This suggests that our findings should be both credible and generalizable.
In conclusion, our results suggest that in patients with severe COPD, the use of regional anesthesia is associated with less composite morbidity, driven by fewer pulmonary complications, as well as less nonpulmonary composite morbidity. This beneficial association was most notable in COPD patients with moderate or no dyspnea and in patients receiving spinal anesthesia.
From the National Surgical Quality Improvement Program manual (site.acsnsqip.org), definitions for severe chronic obstructive pulmonary disease (COPD), pulmonary infection, and level of dyspnea are provided below.
Chronic obstructive pulmonary disease (such as emphysema and/or chronic bronchitis) resulting in any one or more of the following: functional disability from COPD (e.g., dyspnea, inability to perform activities of daily living), hospitalization in the past for treatment of COPD, chronic bronchodilator therapy requirement with oral or inhaled agents, or a forced expiratory volume in 1 second (FEV1) of <75% of predicted on pulmonary function testing. The following conditions are not included in definition for severe COPD: patients whose only pulmonary disease is asthma, an acute and chronic inflammatory disease of the airways resulting in bronchospasm, and patients with diffuse interstitial fibrosis or sarcoidosis.
Patients with pneumonia must meet criteria from both Radiology and Signs/Symptoms/Laboratory sections listed below.
One definitive chest radiological examination (x-ray or CT) with at least one of the following: new or progressive and persistent infiltrate, consolidation, opacity, or cavitation. Note in patients with underlying pulmonary or cardiac disease (e.g., respiratory distress syndrome, bronchopulmonary dysplasia, pulmonary edema, or chronic obstructive pulmonary disease), 2 or more serial chest radiological examinations (x-ray or CT) are required.
For any patient, at least one of the following: fever (>380°C or >100.40°F) with no other recognized cause, as well as leukopenia (<4000 WBC/mm3) or leukocytosis (>12,000 WBC/mm3). For adults >70 years old, altered mental status with no other recognized cause and at least one of the following: 5% bronchoalveolar lavage (BAL)–obtained cells contain intracellular bacteria on direct microscopic exam (e.g., Gram stain), positive growth in blood culture not related to another source of infection, positive growth in culture of pleural fluid, positive quantitative culture from minimally contaminated lower respiratory tract specimen (e.g., BAL or protected specimen brushing), or at least 2 of the following: new onset of purulent sputum, or change in character of sputum, or increased respiratory secretions, or increased suctioning requirements, new onset or worsening cough, or dyspnea, or tachypnea, rales or bronchial breath sounds, or worsening gas exchange (e.g., O2 desaturations [e.g., PaO2/FIO2 < 240], increased oxygen requirements, or increased ventilator demand).
The patient describes difficult, painful, or labored breathing. Dyspnea may be symptomatic of numerous disorders that interfere with adequate ventilation or perfusion of the blood with oxygen. The dyspneic patient is subjectively aware of difficulty with breathing. The levels and definitions for dyspnea are as follows: no dyspnea, dyspnea upon moderate exertion (e.g., is unable to climb one flight of stairs without shortness of breath), and dyspnea at rest (e.g., cannot complete a sentence without needing to take a breath). The time frame is at the time the patient is being considered as a candidate for surgery (which should be no longer than 30 days before surgery).
Name: Mark S. Hausman, Jr., MD.
Contribution: This author helped design the study, interpret the results, and prepare the manuscript.
Attestation: Mark S. Hausman, Jr., has approved the final manuscript, attests to the integrity of the original data and the analysis reported in the manuscript, and is the designated archival author.
Name: Elizabeth S. Jewell, MS.
Contribution: This author helped design the study and statistical analysis, performed the statistical analysis, and helped prepare the manuscript.
Attestation: Elizabeth S. Jewell has approved the final manuscript and attests to the integrity of the original data and the analysis reported in the manuscript.
Name: Milo Engoren, MD.
Contribution: This author helped design the study, interpret the results, and prepare the manuscript.
Attestation: Milo Engoren has approved the final manuscript and attests to the integrity of the original data and the analysis reported in the manuscript.
This manuscript was handled by: Terese T. Horlocker, MD.
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© 2015 International Anesthesia Research Society
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