An Italian study has found a linear correlation between the presence of acute pain within the first few hours of surgery and postoperative pain persisting for as long as six months afterward. The researchers hypothesized that anesthetic technique, including regional approaches, may influence the development and prevention of persistent postoperative pain.
“Our goal was to evaluate the incidence of persistent postoperative pain in children, since there’s nothing very clear in the literature, with an incidence varying from 5% to 20% in children,” said Valeria Mossetti, MD, a staff anesthesiologist at Regina Margherita Children’s Hospital, in Turin. “We hope in the future we will be able to understand if our work as anesthesiologists may change this incidence.”
Although there is no exact definition of the mechanisms and risk factors that determine the presence of persistent postoperative pain, the main cause of chronic pain is acute postoperative pain, she added.
To better understand this problem, Dr. Mossetti and her colleagues enrolled 331 American Society of Anesthesiologists [ASA] stage I to II patients (aged 1-16 years) into the multicenter, observational, prospective study. The patients were undergoing urologic, abdominal or orthopedic outpatient surgery. Each patient received general anesthesia and regional anesthesia comprising a central or peripheral block. Postoperative pain was evaluated using either the Face, Legs, Activity, Cry, Consolability (or FLACC) scale pain scale (for patients <6 years old) or the 11-point Numeric Pain Rating Scale (for those 6 years and older). Nurses performed pain evaluation at one and three hours after surgery, and every four hours thereafter until discharge.
Follow-up to Six Months
“Patients were followed up by telephone interviews at one, three and six months after surgery,” Dr. Mossetti said. The presence of persistent postoperative pain was determined using the Parent’s Postoperative Pain Measures scale for children less than 8 years old and the Child Activity Limitations Interview for those 8 years and older.
As Dr. Mossetti reported at the ASA 2015 annual meeting (abstract A1055), 264 children (mean age, 5.5±0.43 years) were included. Of these, 84.6% were deemed to be free of pain (pain score <4) in the first hour and 91.2% in the third hour after surgery. In addition, 15.4% had moderate pain (pain score 4-7) in the first hour after surgery and 8.8% in the third hour. Acetaminophen and/or ketorolac were administered by IV as rescue medication for children with moderate pain.
“Nobody had severe acute pain [pain score 8-10],” she noted.
Persistent postoperative pain affected 31.1% of children at one month, 7.9% at three months and 4.2% at six months. “But interestingly, we had a strong linear correlation between the presence of acute pain and the presence of persistent postoperative pain,” Dr. Mossetti said. Indeed, 72.7% of patients with persistent postoperative pain experienced acute pain in the first three hours after surgery. “In other words,” Dr. Mossetti said, “if they don’t experience acute pain, they don’t get persistent postoperative pain.”
Myron Yaster, MD, questioned how the investigators determined persistent postoperative pain. “When you did your follow-up phone calls, did you look at other kinds of pain?” Dr. Yaster is the Richard J. Traystman Distinguished Professor of Anesthesiology/Critical Care Medicine and Pediatrics at Johns Hopkins University School of Medicine, in Baltimore.
“I’m also curious whether you looked to see if the pain affected their lives in any way. I may have pain, but if I can’t go to school, well, that’s a much bigger thing than just hurting a little.”
“That’s a difficult question to answer, because we’re not able to differentiate with 100% certainty whether the feeling is coming from the pain of surgery or from something else,” Dr. Mossetti replied. “However, I can say that the patients with persistent postoperative pain are the ones that don’t go to school and don’t play sports because their lives are changed from the pain.”
Given the strong correlation between acute and persistent postoperative pain, the researchers suggested that the anesthetic technique used during surgery may influence the development of persistent postoperative pain. “Since we noticed a lower incidence of persistent postoperative pain in previous data from literature, we can assume that regional anesthesia techniques also offer an advantage in prevention,” she added.