**8. Diagnosis of chronic postsurgical pain**

It has currently been considered that it is mandatory to identify the risk factors and the possibilities to prevent CPOP, because it has been studied by different authors as a preventable sequel and some others classify it as iatrogenic, since the triggering mechanisms are already known. The diagnosis of this syndrome is already described in the International Statistical Classification of Diseases (ICD-11) of 2019 [18]. One of the most common and devastating forms of presentation is postsurgical chronic neuropathic pain, both for intensity levels as well as functional alterations for the patient.

The medical history is an essential part of the patient evaluation. The characteristics of the pain, intensity, triggering and mitigating agents, as well as the history of pain prior and after the surgical procedure, in addition to the functionality report, will be important indicators that will guide us in the diagnosis. The use of scales to assess the pain, visual analog scale, or numerical analog scale can be a useful guide in the follow-up of the cases. Patients with limited pain communication, such as patients with cognitive impairment or who have a condition that makes it impossible for them to speak, should not be overlooked. For this, behavioral tools such as Pain in Advanced Dementia (PAINAD), Behavioral Pain Scale, have been created for evaluation of these type of patients [18]. Another aspect that should not be forgotten is obtaining a description of persistent postoperative pain with the degree of functional impairment and the extent of disability in the patient [19]. In the study of Stamer in 2019, the associated variables with persistent postoperative pain 6 months after surgery were found: young patients, with intense pain before the surgical procedure or severe pain in the 24 hours following postoperative recovery. In the gender relationship, men showed a risk 3.6 times greater than women; the most commonly associated surgeries were orthopedic, abdominal, and thoracic related to breast cancer [16, 18, 19].

Diagnostic criteria for this entity have not yet been described; however, the recent definition of the IASP can guide evaluation and timely treatment [10]. The type of surgery also helps to establish diagnostic suspicion, for example, in breast cancer CPOP presents 65% of the time as neuropathic pain, mainly as intercostal neuralgia and post-mastectomy pain syndrome, followed by musculoskeletal pain. Another aspect that should not be forgotten when obtaining a description of persistent postoperative pain is the degree of functional impairment and the extent of disability in the patient [19].

#### **9. Chronic postoperative pain management**

As we mentioned in previous lines, CPOP may be ominous as patient experience more emotional distress and tends to have higher pain intensity compared to those with an insidious onset, making it even more difficult to manage; biopsychosocial approach is recommended to understand and treat the source properly; rehabilitation programs must be included [10].

Exhaustive clinical examination focusing on identifying sensory dysfunction areas due to nerve damage, previous medical history detailing prior pain medications, impact on quality of life and limitation for daily-basis activity should be considered as first step to chronic pain treatment to identify the mechanisms by which chronic pain is being produced or was produced in the first place; during assessment before any intervention, possible postsurgical complication must be ruled out, complications due to surgical technic or preoperative patient's conditions such as malignancy recurrence or intestinal anastomosis leak are extremely frequent [20]. Once knowing the mechanisms and its etiology, a treatment line can be established based on its causes. Prevention is the cornerstone to avoid the perpetuation of pain; however, in case of CPOP, multimodal treatment would be the ideal choice [21].

One of the main techniques in the management is regional anesthesia, whether applied neuraxially or as peripheral nerve blocks. It has an effect through the modulation of pain to avoid central and peripheral sensitization; this technique has the ability to transform moderate or severe pain to mild, and the purpose is to avoid central sensitization or reduce the probability of it on the long run. Regional anesthesia techniques vary according to each surgical procedure, or the site of pain that the patients specify [22, 23].

Other pharmacological alternatives are gabapentinoids, through the inhibition of the alpha(2) delta unit regulate neuronal excitation, preventing the over excitation and sensitization. However, the adverse effects are significant (dizziness, nausea, vision changes), and relatively high doses are usually required for control or therapeutic efficacy [24]. Alpha2 agonists belong to another group of drugs used to relieve, reduce, and prevent pain, and these effects are produced through an agonist effect on alpha receptors in the spinal cord, causing analgesia and an opioid-sparing consumption produced by synergistic effect, the representative drugs are dexmedetomidine and clonidine, but both have important adverse effects such as sedation. Thus, there are no presentations for alpha2 agonists in the outpatient setup, and they can only be used in the hospital environment under strict surveillance. More scientific evidence is required to investigate the efficacy/safety of this therapy, since there are few important clinical studies that support these effects [25]. COX 2 inhibitors and paracetamol are adjuvants that could be used to reduce and control pain, both are involved in the regulation of the inflammatory response mediated by pro-inflammatory cytokines, by inhibiting the synthesis of prostaglandins, acute-phase reactants whose inhibition could prevent or avoid the risk of perpetuating central and peripheral pain sensitization. Currently, there are no randomized clinical studies which use COX 2 inhibitors and acetaminophen for the treatment of CPOP, though both drugs belong to treatment strategies in a multimodal analgesia scheme [26].

#### **10. Conclusions**

Above all, opioids and the use of regional anesthesia are probably the first-line treatment strategies for CPOP as they can provide an almost immediate and significant

#### *Chronic Postoperative Pain DOI: http://dx.doi.org/10.5772/intechopen.111878*

benefit in the setting of acute severe pain. Within opioids, mild-acting ones such as tramadol as well powerful opioids (oxycodone, buprenorphine, fentanyl) which have numerous presentations and routes of administration for pain control are part of the tool setting of the anesthesiologist in the acute pain scenario. However adverse effects such as sedation, nausea, constipation, and opiophobia limit its uses; it is indispensable for the anesthesiologists in the acute pain scenario to have a robust knowledge of the opioid pharmacokinetics and pharmacodynamics for adequate outcomes, as well a proper training in regional anesthesia and ultrasound management to provide an effective execution of this techniques [27].

Systematic review has been performed trying to identify the Holy Grail, all the interventions included were unimodal, none showed sufficient evidence to guide CPOP treatment, multimodal approaches must be tried in large randomized controlled trials (RCTs) to provide robust evidence as evidence-based management for CPOP still lacking.
