"Independent of surgical complications, such as infections and bleeding, there are three major types of medical risks that accompany major surgery," explains the study's lead author Gerald W. Smetana, MD, an internist in the division of general medicine and primary care at Beth Israel Deaconess Medical Center (BIDMC) and Associate Professor of Medicine at Harvard Medical School. "These include cardiac risks such as a heart attack, the risk of blood clot formation, and pulmonary risks."
Nearly 30 years ago risk indices and guidelines were developed to assess post-surgical cardiac risks, he adds, but until now, the issue of pulmonary risk factors had not been formally addressed.
"Many physicians will be surprised to learn that we found pulmonary complications to be as prevalent as cardiac complications," says Smetana. The reason, he says, is that patients' lung volumes are lower following both surgery and the administration of general anesthesia. As a result, small areas of lung become vulnerable to collapse, thereby increasing patients' chances of developing pneumonia, suffering respiratory failure or experiencing a worsening of existing lung disease, such as emphysema.
Smetana, together with coauthors Valerie Lawrence, MD, and John Cornell, PhD, of the South Texas Veterans Health Care System, performed a systematic review of nearly 1,000 medical studies published between 1980 and 2005 in order to develop the guidelines for the American College of Physicians. After calculating summary estimates of risk, the authors divided their findings into patient-related risk factors and surgery-related risk factors, according to Smetana.
"Among the patient-related risk factors we made several clear observations," he adds. "Most notably, even among otherwise healthy patients, advanced age [over 70] increased a person's risk of developing pulmonary complications four-fold to six-fold. Given that age is not a risk factor for post-surgical cardiac complications, we were quite surprised by this finding." Other patient-related factors that increased the risk of complications included preexisting emphysema, functional dependence (patients' inability to care for themselves), congestive heart failure and smoking cigarettes.
Among pulmonary risk factors related to the surgical procedure, he adds, location of the surgical site was of greatest impact.
"The closer the surgery was to the diaphragm - any thoracic, upper abdominal, gallbladder or aortic surgery for example - the greater the risk of complications," notes Smetana. In addition, emergency surgery or surgery lasting more than three hours also increased the likelihood that patients would develop postoperative pulmonary problems.
In an accompanying paper, the authors also evaluated the value of various interventions to reduce the risk of pulmonary complications, and found that two simple treatments that increase lung volume, deep breathing exercises and incentive spirometry, proved to be the most effective strategies.
"We hope that our findings will help doctors provide their patients with a good estimate of pulmonary risk prior to surgery," says Smetana. "In fact, this review points out the importance of the doctor-patient relationship. Medical consultations are extremely important for patients as they prepare for surgery and this provides both doctors and patients with another tool to use in their decision-making processes."
This study was funded, in part, by grants from the Veterans Evidence-based Research, Dissemination, and Implementation Center (VERDICT).
Beth Israel Deaconess Medical Center is a patient care, research and teaching institution of Harvard Medical School and ranks fourth in National Institutes of Health funding among independent hospitals nationwide. BIDMC is clinically affiliated with the Joslin Diabetes Center and is a research partner of the Dana-Farber/Harvard Cancer Center. BIDMC is the official hospital of the Boston Red Sox. For more information, visit www.bidmc.harvard.edu.