About 10% of patients who have had cardiac surgery suffer from persistent postoperative pain 2 years after surgery, according to a large, multicentre study designed to assess risk factors for this pain published in CMAJ (Canadian Medical Association Journal).

Cardiac surgeries, including coronary artery bypass grafting (CABG) and valve replacement, are performed frequently around the world but can result in residual after the operation that may affect quality of life.

A study of 1247 patients aged 18 years or older in centres in 4 Canadian cities (Montréal, Quebec City, Toronto and Halifax) looked at the prevalence of ongoing up to 2 years after surgery and associated with this pain. About 40% of patients felt postoperative pain after 3 months, with a significant decrease over time, to 22% at 6 months, 17% at 12 months and 10% at 24 months.

"These prevalence rates are not negligible given that more than 400 000 patients undergo CABGs annually in the US," writes Dr. Manon Choinière, researcher with the Centre hospitalier de l'Université de Montréal Research Centre and professor, Department of Anesthesiology, Faculty of Medicine, l'Université de Montréal. Dr Choinière and her coauthors also note that the presence of persistent postoperative pain after cardiac surgery is not insignificant, and patients should be informed about this possibility before surgery.

Several risk factors emerged for in the 2 years following cardiac surgery:

  • Age: Younger patients were more likely to report persistent postoperative pain than older people.
  • Pre-existing chronic pain: Patients with chronic nonanginal pain before surgery had a greater risk of persistent postoperative pain.
  • Pre-surgery anxiety: Greater anxiety before surgery was linked to a higher likelihood of persistent pain.
  • Pain severity during the first week after surgery : The more intense the pain during the first few days after surgery and the more it interfered with functioning, the more likely patients were to report persistent pain in the following months or years.

The following factors predicted the severity of pain in the 2 years following cardiac surgery:

  • Sex: Female patients were more likely to report more intense persistent pain.
  • Acute pain: The amount of pain felt in the first week after surgery predicted not only the presence of long-term pain but also its severity.
  • Time in hospital: Earlier discharge from hospital was associated with persistent pain of greater intensity.

"It is noteworthy that acute pain levels (observed in the first few days after surgery) were quite high in this study," state the authors. "It is troublesome that similar observations have been made over and over again in the past 3 decades and that postoperative pain continues to be undertreated despite numerous awareness campaigns, pain care guidelines and educational efforts."

The authors note that two risk factors of persistent pain after cardiac surgery are modifiable—pre-surgical anxiety and acute pain severity in the first few days after surgery.

The authors urge more research into how to prevent or minimize pain to help eliminate unnecessary suffering and reduced quality of life in the months or years after .