San Diego—Add severe acute postoperative pain to the ever-growing list of negative effects related to smoking.
A multicenter study of more than 2,000 patients who underwent ambulatory surgery has found that two days after discharge, more than half of smokers report severe postoperative pain compared with fewer than one-third of nonsmokers.
More than 15 million Americans suffer from severe postoperative pain every year, said Christian C. Apfel, PhD, MD, associate professor of anesthesiology at the University of California, San Francisco, who led the study. Recognizing the risk factors for postoperative pain ultimately will allow physicians to identify and treat patients who are particularly prone to discomfort.
Although previous research suggested that smokers experience more postoperative pain and complications (Figure) than do nonsmokers, those studies were limited by small sample sizes, Dr. Apfel said. So he and colleagues from 12 hospitals prospectively collected preoperative, intraoperative and postoperative data on 2,157 adults having elective ambulatory surgery under general anesthesia. Severe acute postoperative pain was defined as a score of 7 or higher on a 10-point verbal rating scale. Pain was assessed at numerous time points after cessation of anesthesia, until 48 hours after hospital discharge.
As Dr. Apfel reported at the 2010 annual meeting of the American Society of Anesthesiologists (abstract A788), 24.5% of all patients experienced severe postoperative pain while in the postanesthesia care unit (PACU). By 48 hours after discharge, this number had risen to 33.6%.
At all time points, smokers were more likely than nonsmokers to report severe pain. In the PACU, severe pain was present in 38.5% of smokers and 22% of nonsmokers. By 48 hours after discharge, 54.1% of smokers and 29.9% of nonsmokers called their pain severe.
Pain intensity in the PACU also was greater in smokers than in nonsmokers (score, 4.94 vs. 3.74, respectively; P<0.001), and again at 48 hours after discharge (6.35 vs. 4.60, respectively; P<0.001).
“It was also important for us to determine the relevant risk factors for severe post-discharge pain,” Dr. Apfel said. Logistic regression analysis identified current smoking status as a significant independent predictor of pain (P=0.001). Smoking was associated with a higher risk for severe postoperative pain in the PACU (odds ratio [OR], 1.74) and at 48 hours after discharge (OR, 2.25; P>0.001).
Other significant independent predictors for severe pain in the PACU included age 50 years or older (OR, 1.53), a body mass index greater than 30 (OR, 1.36) and surgery times longer than one hour (OR, 1.36). Patients who before surgery anticipated experiencing a postoperative pain score of 4 or higher also were at increased risk for severe pain in the PACU (OR, 1.45).
Given these results, the investigators recommended that physicians include patient’s smoking status during preoperative evaluations. “We want to develop a predictive model to see if we can get a better idea of who will be at risk for severe postoperative pain, and whether this predicts the development of chronic postoperative pain,” Dr. Apfel said.
Pamela D. Flood, MD, associate professor of clinical anesthesiology at Columbia University Medical Center, in New York City, said the study has important clinical implications. “If smoking is a strong predictor of severe postoperative pain, is this a mediator for the heightened risk of smokers to develop chronic pain syndromes?” Dr. Flood asked. “If smokers are specifically targeted for enhanced pain management and/or smoking cessation, this intervention may ameliorate acute postoperative pain or the conversion to chronic pain.”
Most doctors consider smoking history as an important part of medical history, particularly with regard to cardiac and respiratory risks. Pain should be added to that list. “I use the preoperative period as a teaching moment, and explain that volatile anesthetic drugs are potent inhibitors of nicotine receptors [Toxicol Lett 1998;100-101:149-153],” Dr. Flood said.
“There is evidence that a patient is essentially detoxified from smoking after general anesthesia and has reduced cravings for nicotine after surgery and anesthesia [Anesthesiology 2006;104:356-367; Anesthesiology 2010;113:977-992],” she added. “If they want to stop—and most people do—this would be a good time.”
The poster was selected as one of the best presented at the meeting.