Most patients believe following their surgery, they will experience relief from the pain and complications faced before entering the operating room. However, for five to ten percent of patients, recovery does not bring relief, but persistent postoperative pain that can affect daily activities more than six months after surgery.
Several predisposing factors have been suggested to increase the risk for postoperative pain including age, pre-operative pain, anxiety, depression, sensory function and nerve injury. As the relative role of these factors has remained unclear, a new study presented today at the Annual Meeting of the American Society of Anesthesiologists seeks to identify specific risk groups for persistent postoperative pain, leading to prevention or treatment suggestions of the condition.
In a prospective cohort study, Henrik Kehlet, M.D., Ph.D., and colleagues from Copenhagen University in Copenhagen, Denmark and Bethesda Krankenhaus Stuttgart in Stuttgart, Germany investigated 19 potential predisposing factors for the development of persistent pain following surgery in 463 adult male patients scheduled to undergo primary groin hernia repair.
Before surgery, patients were examined using a standardized questionnaire collecting data on pain from the hernia and the affect of that pain on daily activities, pain from other body regions, pain occurrence after previous surgery, age, Body Mass Index (BMI), activity level, anxiety, depression and coping strategies. Additionally, the ability to sense heat and the pain response to 47 degree Celsius stimulus applied to the groin and arm was assessed preoperatively and six months postoperatively. To compare the effect of open Lichetenstein mesh repair (open sutured mesh repair) and laparoscopic procedures using glue fixation of mesh, surgeries were performed at two high-volume specialist centers.
Pain for each participant was assessed in telephone interviews one week after surgery and again 30 days after surgery. Using the validated activities assessment scale (AAS) and patients were examined six months after surgery, assessing sensory function in the groin, pain levels and pain impairment of daily activities. After six months, 16 percent of patients with open surgery and 8 percent of patients with laparoscopic surgery complained of pain affecting daily activities.
Researchers successfully identified four factors that were independently predictive for the development of persistent postoperative pain in participants. "Through our analysis, we found that persistent pain could be predicted by pain impairment of daily activities before surgery, high pain response to heat stimulation, high pain intensity reports 30 days after surgery and signs of nerve injury." said Dr. Kehlet.
It was concluded that age, anxiety, depression, other pain syndromes and BMI were not predictors for the development of persistent pain following hernia surgery.
Dr. Kehlet added, "These findings prove that persistent pain following surgery is related to both surgical and patient specific factors, suggesting that patients with high pain response before surgery should be operated laparoscopically- a procedure that is less likely to inflict nerve damage and resulting further pain development."