Pain versus Nociception
A frequently seen phenomenon is that the pain scores a patient reports seem to have little to do with the severity of the trauma or the extent of the surgery the patient experienced. Reported and experienced pain frequently does not reflect the extent of the tissue damage or potential tissue injury caused by trauma, surgery or an inflammatory process. It is important to understand that the perception of pain and nociceptive input, the ‘pain signaling’ that is caused when painful stimuli activate nociceptors, are linked but are very different processes.
Pain is a subjective and multidimensional experience that is modulated by various factors. It is in fact a highly processed signal.
Predictors of Acute Pain after Surgery
A systematic review of 48 studies with 23,037 patients investigating the independent risk factors for pain after surgery identified the following predictors of acute pain after surgery 1:
- Type of surgery: The type of surgery is non-surprisingly found to be a strong predictor for both postoperative pain and analgesic consumption. The most painful operations are orthopedic surgery with major joints surgery, thoracic, and open abdominal surgery.
- Preexisting pain: Often underappreciated, preexisting pain, chronic pain, and low preoperative pain thresholds have a strong predictive value for postoperative pain.
- Anxiety: Psychosocial and behavioral factors such as anxiety and catastrophizing have been identified as very strong predictors of postoperative pain.
- Age: Younger age has been associated with more postoperative pain and increased needs for pain medication.
Other factors frequently associated with more challenging pain control after surgery (but with less data supporting their role), are female gender, history of substance use disorder, and preoperative opioid use.
In addition, there is evidence that our genetic make up may be responsible for the extent of our pain: genetic polymorphisms have been correlated with altered pain perception and processing. 2
Predictors for Persistent Postsurgical Pain
The predictors for the development of chronic pain after surgery (also called persistent postsurgical pain) are related to the risk factors for acute pain after surgery. As a matter of fact, suboptimal pain control after surgery is the most important risk factor for the development of persistent postsurgical pain.
A narrative review on the risk factors for persistent postsurgical pain lists genetics, psychosocial factors and pain cognition, preoperative pain, operative factors and anesthetic technique are predictors for pain.3
Anesthesia and pain management strategies to reduce acute pain as well as the development of persistent postsurgical pain are:
- Preventive analgesia: Interventions that aim at reducing nociceptive input and thus reduce central sensitization. Examples are the use of regional anesthesia or using ketamine during anesthesia and surgery
- Multimodal analgesia: Using several analgesic drugs from different classes to improve pain control and to reduce opioid use. This approach appears to reduce both nociception- and opioid- evoked hyperalgesia.
Lastly, a recent review on the epidemiology of chronic pain (not limited to postsurgical pain) featured the following table listing factors associated with the development of chronic pain:⁴
Ip HY, Abrishami A, Peng PW, Wong J, Chung F. Predictors of postoperative pain and analgesic consumption: a qualitative systematic review. Anesthesiology. 2009 Sep;111(3):657-77. doi: 10.1097/ALN.0b013e3181aae87a. PMID: 19672167.
Lariviere WR, Wilson SG, Laughlin TM, Kokayeff A, West EE, Adhikari SM, Wan Y, Mogil JS: Heritability of nociception. III. Genetic relationships among commonly used assays of nociception and hypersensitivity. Pain 2002; 97:75–86
Fregoso G, Wang A, Tseng K, Wang J. Transition from Acute to Chronic Pain: Evaluating Risk for Chronic Postsurgical Pain. Pain Physician. 2019 Sep;22(5):479-488. PMID: 31561647
Mills SEE, Nicolson KP, Smith BH. Chronic pain: a review of its epidemiology and associated factors in population-based studies. Br J Anaesth. 2019 Aug;123(2):e273-e283. doi: 10.1016/j.bja.2019.03.023. Epub 2019 May 10. PMID: 31079836; PMCID: PMC6676152.