Chronic pain after surgery: pathophysiology, risk factors and prevention

Incidence and risk factors of chronic pain following hysterectomy among Southern Jiangsu Chinese Women

BACKGROUND

Chronic post-surgical pain (CPSP) after hysterectomy has been recognized as a major clinical problem in the Western World. Reports on post-hysterectomy pain are relatively scarce in China. The aim of the current study was to prospectively investigate the incidence and the potential risk factors of CPSP at 3 months following hysterectomy in Chinese population.

METHODS

We assessed and collected data on preoperative socio-demographic characteristics, preexisting pain, anxiety and depression, sexual satisfaction, intra-operative variables, and acute postoperative pain intensity in a cohort of 870 women undergoing hysterectomy. The participants were interviewed to determine their suitability to diagnostic criteria of CPSP 3 months later. Logistic regression analyses were subsequently performed to identify predictors for CPSP.

RESULTS

The incidence of CPSP at 3 months after hysterectomy was 27.7%. Most of the women with CPSP suffered from mild pain and had a slight impact on daily life with sleep and emotion functional limitation. Risk factors for CPSP after hysterectomy were preoperative anxiety, depression, pelvic pain, preexisting pain, very-moderate sexual dissatisfaction, and acute postoperative pain at movement. Intra-operative dexmedetomidine infusion with 0.5 μg/kg/h was associated with a decreased incidence rate of chronic post-hysterectomy pain.

CONCLUSION

Twenty-eight percent of patients after hysterectomy in southern Jiangsu china had CPSP with 92% of those women describing it as mild with sleep and emotion functional limitation. Patients with preoperative anxiety and depression, poor sexual satisfaction, preexisting pain, and acute postoperative pain on movement have been identified to be at risk to develop CPSP.

Can Chronic Pain Be Prevented?

All chronic pain begins at some discrete point in time. Significant strides in the understanding of mechanisms and risk factors associated with the transition from a new, or acute, pain experience to a chronic pain condition have been made over the past 20 years. These insights provide the hope of one day being able to modify or even halt this pathophysiologic progression. This article reviews some of the current knowledge of this transition as well as the evidence currently available to best prevent and treat it using persistent surgical pain as a model.

The effect of preoperative dexamethasone on pain 1 year after lumbar disc surgery: a follow-up study

Background

It has been hypothesized that dexamethasone can inhibit persistent postoperative pain, but data on humans is lacking and results from animal studies are conflicting. We explored the effect of 16 mg dexamethasone IV administered preoperatively on persistent pain 1 year after lumbar discectomy.

Methods

This is a prospective 1-year follow-up on a single-centre, randomized, and blinded trial exploring the analgesic effect of 16 mg IV dexamethasone or placebo after lumbar discectomy. One year follow-up was a written questionnaire including back and leg pain (VAS 0–100 mm), Short Form 36 survey (SF-36), EuroQol 5D (EQ-5D), OSWESTRY Low Back Pain Questionnaire, duration of sick leave, working capability, contentment with surgical result.

Results

Response rate was 71% (55 patients) in the dexamethasone group, 58% (44 patients) in the placebo group. Leg pain (VAS) was significantly lower in the placebo group compared to the dexamethasone group: 17 (95% CI 10–26) vs 26 (95% CI 19–33) mm, respectively (mean difference 9 mm (95% CI −1 to 0), (P = 0.03). No difference regarding back pain. The placebo group reported significantly more improvement of leg pain and were significantly more satisfied with the surgical result. Patients in the dexamethasone group reported significantly higher pain levels in EQ-5D- and Oswestry questionnaires. No difference in the SF-36 survey or daily analgesic consumption.

Conclusions

We found significantly higher pain levels in the dexamethasone group compared to placebo 1 year after lumbar disc surgery.

Trial registration

Clinicaltrials.gov (NCT01953978). Registered 26 Sep 2013.

An extended release local anaesthetic: potential for future use in veterinary surgical patients?

One of the most effective means of preventing the transduction and transmission of acute and perioperative pain is through the use of local anaesthetics. However, local anaesthetics currently available have a relatively short duration of action. Although there are several tools available to treat perioperative pain in companion animals, overall, there is an unmet need for products that can be administered in the clinic, and provide pain relief for the crucial first few days following surgery in the home environment. Specifically, in relation to local anaesthetics, there is a clear unmet need for a long-acting local anaesthetic that can be added to the multimodal analgesic protocol to provide pain relief to patients in the home environment or during extended hospitalization. Bupivacaine liposomal injectable suspension recently became available for use in humans, and has proven efficacious and safe. This paper will review the use of local anaesthetics, particularly bupivacaine, in dogs and cats, and introduce a new formulation of prolonged release bupivacaine that is in development for dogs and cats.

Effect of preemptive ketamine administration on postoperative visceral pain after gynecological laparoscopic surgery

The pain following gynecological laparoscopic surgery is less intense than that following open surgery; however, patients often experience visceral pain after the former surgery. The aim of this study was to determine the effects of preemptive ketamine on visceral pain in patients undergoing gynecological laparoscopic surgery. Ninety patients undergoing gynecological laparoscopic surgery were randomly assigned to one of three groups. Group 1 received placebo. Group 2 was intravenously injected with preincisional saline and local infiltration with 20 mL ropivacaine (4 mg/mL) at the end of surgery. Group 3 was intravenously injected with preincisional ketamine (0.3 mg/kg) and local infiltration with 20 mL ropivacaine (4 mg/mL) at the end of surgery. A standard anesthetic was used for all patients, and meperidine was used for postoperative analgesia. The visual analogue scale (VAS) scores for incisional and visceral pain at 2, 6, 12, and 24 h, cumulative analgesic consumption and time until first analgesic medication request, and adverse effects were recorded postoperatively. The VAS scores of visceral pain in group 3 were significantly lower than those in group 2 and group 1 at 2 h and 6 h postoperatively (P<0.05 and P<0.01, respectively). At 2 h and 6 h, the VAS scores of incisional pain did not differ significantly between groups 2 and 3, but they were significantly lower than those in group 1 (P<0.01). Groups 1 and 2 did not show any differences in visceral pain scores at 2 h and 6 h postoperatively. Moreover, the three groups showed no statistically significant differences in visceral and incisional pain scores at 12 h and 24 h postoperatively. The consumption of analgesics was significantly greater in group 1 than in groups 2 and 3, and the time to first request for analgesics was significantly longer in groups 2 and 3 than in group 1, with no statistically significant difference between groups 2 and 3. However, the three groups showed no significant difference in the incidence of shoulder pain or adverse effects. Preemptive ketamine may reduce visceral pain in patients undergoing gynecological laparoscopic surgery.

Genetic susceptibility to postherniotomy pain. The influence of polymorphisms in the Mu opioid receptor, TNF-α, GRIK3, GCH1, BDNF and CACNA2D2 genes

BACKGROUND AND AIMS

Despite improvements in surgical technique, 5%-8% of patients undergoing herniorrhaphy still suffer from clinically relevant persistent postherniotomy pain. This is a problem at both individual and society levels. The aim of this study was to determine whether or not a single nucleotide polymorphism in a specific gene contributes to the development of persistent pain after surgery.

METHODS

One hundred individuals with persistent postherniotomy pain, along with 100 without pain matched for age, gender and type of surgery were identified in a previous cohort study on patients operated for groin hernia. All patients underwent a thorough sensory examination and blood samples were collected. DNA was extracted and analysed for single nucleotide polymorphism in the Mu opioid receptor, TNF-α, GRIK3, GCH1, BDNF and CACNA2D2 genes.

RESULTS

Patients with neuropathic pain were found to have a homozygous single nucleotide polymorph in the TNF-α gene significantly more often than pain-free patients (P=0.036, one-tailed test).

CONCLUSIONS

SNP in the TNF-α gene has a significant impact on the risk for developing PPSP.

IMPLICATIONS

The result suggests the involvement of genetic variance in the development of pain and this requires further investigation.

Pain experiences of men and women after cardiac surgery

AIMS AND OBJECTIVES

To compare the prevalence and severity of pain in men and women during the first year following cardiac surgery and to examine the predictors of persistent postoperative pain 12 months post surgery.

BACKGROUND

Persistent pain has been documented after cardiac surgery, with limited evidence for differences between men and women.

DESIGN

Prospective cohort study of patients in a randomised controlled trial (N = 416, 23% women) following cardiac surgery.

METHODS

Secondary data analysis of data collected prior to surgery, across postoperative days 1-4, at two weeks, and at one, three, six and 12 months post surgery. The main outcome was worst pain intensity (Brief Pain Inventory-Short Form).

RESULTS

Twenty-nine percent (97/339) of patients reported persistent postoperative pain at rest at 12 months that was worse in intensity and interference for women than for men. For both sexes, a more severe co-morbidity profile, lower education and postoperative pain at rest at one month post surgery were associated with an increased probability for persistent postoperative pain at 12 months. Women with more concerns about communicating pain and a lower intake of analgesics in the hospital had an increased probability of pain at 12 months.

CONCLUSION

Sex differences in pain are present up to one year following cardiac surgery. Strategies for sex-targeted pain education and management pre- and post-surgery may lead to better pain outcomes.

RELEVANCE TO CLINICAL PRACTICE

These results suggest that informing patients (particularly women) about the benefits of analgesic use following cardiac surgery may result in less pain over the first year post discharge.

Recovery 3 and 12 months after hysterectomy: epidemiology and predictors of chronic pain, physical functioning, and global surgical recovery

Chronic postsurgical pain (CPSP) is 1 important aspect of surgical recovery. To improve perioperative care and postoperative recovery knowledge on predictors of impaired recovery is essential. The aim of this study is to assess predictors and epidemiological data of CPSP, physical functioning (SF-36PF, 0-100), and global surgical recovery (global surgical recovery index, 0-100%) 3 and 12 months after hysterectomy for benign indication.A prospective multicenter cohort study was performed. Sociodemographic, somatic, and psychosocial data were assessed in the week before surgery, postoperatively up to day 4, and at 3- and 12-month follow-up. Generalized linear model (CPSP) and linear-mixed model analyses (SF-36PF and global surgical recovery index) were used. Baseline data of 468 patients were collected, 412 (88%) patients provided data for 3-month evaluation and 376 (80%) patients for 12-month evaluation.After 3 and 12 months, prevalence of CPSP (numeric rating scale ≥ 4, scale 0-10) was 10.2% and 9.0%, respectively, SF-36PF means (SD) were 83.5 (20.0) and 85.9 (20.2), global surgical recovery index 88.1% (15.6) and 93.3% (13.4). Neuropathic pain was reported by 20 (5.0%) patients at 3 months and 14 (3.9%) patients at 12 months. Preoperative pain, surgery-related worries, acute postsurgical pain on day 4, and surgery-related infection were significant predictors of CPSP. Baseline level, participating center, general psychological robustness, indication, acute postsurgical pain, and surgery-related infection were significant predictors of SF-36PF. Predictors of global surgical recovery were baseline expectations, surgery-related worries, American Society of Anesthesiologists classification, type of anesthesia, acute postsurgical pain, and surgery-related infection.Several predictors were identified for CPSP, physical functioning, and global surgical recovery. Some of the identified factors are modifiable and optimization of patients' preoperative pain status and psychological condition as well as reduction of acute postsurgical pain and surgery-related infection may lead to improvement of outcome.

Physiological Indices of Stress Prior to and Following Total Knee Arthroplasty Predict the Occurrence of Severe Post-Operative Pain

OBJECTIVE

The severe pain and disability associated with osteoarthritis often motivate individuals to undergo arthroplastic surgery. However, a significant number of surgical patients continue to experience pain following surgery. Prior research has implicated both the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system (SNS) in the sensitization of pain receptors and chronic pain conditions. This study uses a prospective, observational, cohort design to examine whether physiological stress responses before and after surgery could predict post-operative pain severity.

SUBJECTS

Participants included 110 patients undergoing total knee arthroplasty.

METHODS

Physiological indices of stress included the measurement of catecholamine and cortisol levels in 15-hour urine samples collected prior to and 1 month following surgery, as well as in-hospital heart rate and blood pressure (before and after surgery), which were abstracted from medical records. Patients completed the pain subscale of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [Bellamy et al., J Orthop Rheumatol 1: , 95 (1988)] 2.5 weeks prior to surgery and at a 3-month follow-up.

RESULTS

Contrary to expectations, lower stress hormone levels at baseline were related to more severe post-operative pain. Data at later time points, however, supported our hypothesis: cardiovascular tone shortly before surgery and urinary levels of epinephrine 1 month following surgery were positively related to pain severity 3 months later.

CONCLUSION

Results suggest that the occurrence of post-operative pain can be predicted on the basis of stress physiology prior to and following arthroplastic surgery.

Chronic post-thyroidectomy pain: Incidence, typology, and risk factors

Chronic postoperative pain exists in varying degrees for every type of surgery. An evaluation of the incidence, the typology and predictive factors of chronic pain was carried out at 3 and 6months after thyroidectomy. A prospective observational study, having included each of the patients prior to their thyroidectomy, was carried out over 12months. The patients used an 11-point numerical rating scale (NRS), a neuropathic pain screening questionnaire (DN4), an evaluation scale for anxiety and for the need for information related to anaesthesia and surgery (APAIS), a questionnaire describing pain (QDSA) and a questionnaire evaluating neuropathic pain (NPSI) before surgery and at three and six months later. Three hundred and four patients were included. The questionnaires were completed by 251 patients (57 males and 194 females) at 3 and 6months (82%). At 3months, 31 out of 251 (12%) patients mentioned a DN4≥3; at 6months, this rate dropped to 23 out of 251 (9%). The average intensity of chronic postoperative pain remained low to moderate. Levels of anxiety and the need for information were higher in patients with postoperative pain at 3 and 6months. In contrast, the number of intraoperative procedures using a bilateral superficial cervical plexus block (BSCPB) was lower in patients with DN4≥3. Multivariate analysis demonstrated that the type of anaesthesia procedure interfered with the risk of delayed pain after thyroidectomy. The presence of a DN4≥3 was nearly three-fold greater in patients without BSCPB (OR 2.647, CI=1.198-5.848).

Glial dysfunction and persistent neuropathic postsurgical pain

BACKGROUND

Acute pain in response to injury is an important mechanism that serves to protect living beings from harm. However, persistent pain remaining long after the injury has healed serves no useful purpose and is a disabling condition. Persistent postsurgical pain, which is pain that lasts more than 3 months after surgery, affects 10-50% of patients undergoing elective surgery. Many of these patients are affected by neuropathic pain which is characterised as a pain caused by lesion or disease in the somatosensory nervous system. When established, this type of pain is difficult to treat and new approaches for prevention and treatment are needed. A possible contributing mechanism for the transition from acute physiological pain to persistent pain involves low-grade inflammation in the central nervous system (CNS), glial dysfunction and subsequently an imbalance in the neuron-glial interaction that causes enhanced and prolonged pain transmission.

AIM

This topical review aims to highlight the contribution that inflammatory activated glial cell dysfunction may have for the development of persistent pain.

METHOD

Relevant literature was searched for in PubMed.

RESULTS

Immediately after an injury to a nerve ending in the periphery such as in surgery, the inflammatory cascade is activated and immunocompetent cells migrate to the site of injury. Macrophages infiltrate the injured nerve and cause an inflammatory reaction in the nerve cell. This reaction leads to microglia activation in the central nervous system and the release of pro-inflammatory cytokines that activate and alter astrocyte function. Once the astrocytes and microglia have become activated, they participate in the development, spread, and potentiation of low-grade neuroinflammation. The inflammatory activated glial cells exhibit cellular changes, and their communication to each other and to neurons is altered. This renders neurons more excitable and pain transmission is enhanced and prolonged. Astrocyte dysfunction can be experimentally restored using the combined actions of a μ-opioid receptor agonist, a μ-opioid receptor antagonist, and an anti-epileptic agent. To find these agents we searched the literature for substances with possible anti-inflammatory properties that are usually used for other purposes in medicine. Inflammatory induced glial cell dysfunction is restorable in vitro by a combination of endomorphine-1, ultralow doses of naloxone and levetiracetam. Restoring inflammatory-activated glial cells, thereby restoring astrocyte-neuron interaction has the potential to affect pain transmission in neurons.

CONCLUSION

Surgery causes inflammation at the site of injury. Peripheral nerve injury can cause low-grade inflammation in the CNS known as neuroinflammation. Low-grade neuroinflammation can cause an imbalance in the glial-neuron interaction and communication. This renders neurons more excitable and pain transmission is enhanced and prolonged. Astrocytic dysfunction can be restored in vitro by a combination of endomorphin-1, ultralow doses of naloxone and levetiracetam. This restoration is essential for the interaction between astrocytes and neurons and hence also for modulation of synaptic pain transmission.

IMPLICATIONS

Larger studies in clinical settings are needed before these findings can be applied in a clinical context. Potentially, by targeting inflammatory activated glial cells and not only neurons, a new arena for development of pharmacological agents for persistent pain is opened.

Acute Pain Medicine in the United States: A Status Report

BACKGROUND

Consensus indicates that a comprehensive,multimodal, holistic approach is foundational to the practice of acute pain medicine (APM),but lack of uniform, evidence-based clinical pathways leads to undesirable variability throughout U. S. healthcare systems. Acute pain studies are inconsistently synthesized to guide educational programs. Advanced practice techniques involving regional anesthesia assume the presence of a physician-led, multidisciplinary acute pain service,which is often unavailable or inconsistently applied.This heterogeneity of educational and organizational standards may result in unnecessary patient pain and escalation of healthcare costs.

METHODS

A multidisciplinary panel was nominated through the APM Shared Interest Group of the American Academy of Pain Medicine. The panel met in Chicago, IL, in July 2014, to identify gaps and set priorities in APM research and education.

RESULTS

The panel identified three areas of critical need: 1) an open-source acute pain data registry and clinical support tool to inform clinical decision making and resource allocation and to enhance research efforts; 2) a strong professional APM identity as an accredited subspecialty; and 3) educational goals targeted toward third-party payers,hospital administrators, and other key stake holders to convey the importance of APM.

CONCLUSION

This report is the first step in a 3-year initiative aimed at creating conditions and incentives for the optimal provision of APM services to facilitate and enhance the quality of patient recovery after surgery, illness, or trauma. The ultimate goal is to reduce the conversion of acute pain to the debilitating disease of chronic pain.

Axotomy of tributaries of the pelvic and pudendal nerves induces changes in the neurochemistry of mouse dorsal root ganglion neurons and the spinal cord

Using immunohistochemical techniques, we characterized changes in the expression of several neurochemical markers in lumbar 4-sacral 2 (L4-S2) dorsal root ganglion (DRG) neuron profiles (NPs) and the spinal cord of BALB/c mice after axotomy of the L6 and S1 spinal nerves, major tributaries of the pelvic (targeting pelvic visceral organs) and pudendal (targeting perineum and genitalia) nerves. Sham animals were included. Expression of cyclic AMP-dependent transcription factor 3 (ATF3), calcitonin gene-related peptide (CGRP), transient receptor potential cation channel subfamily V, member 1 (TRPV1), tyrosine hydroxylase (TH) and vesicular glutamate transporters (VGLUT) types 1 and -2 was analysed seven days after injury. L6-S1 axotomy induced dramatic de novo expression of ATF3 in many L6-S1 DRG NPs, and parallel significant downregulations in the percentage of CGRP-, TRPV1-, TH- and VGLUT2-immunoreactive (IR) DRG NPs, as compared to their expression in uninjured DRGs (contralateral L6-S1-AXO; sham mice); VGLUT1 expression remained unaltered. Sham L6-S1 DRGs only showed a small ipsilateral increase in ATF3-IR NPs (other markers were unchanged). L6-S1-AXO induced de novo expression of ATF3 in several lumbosacral spinal cord motoneurons and parasympathetic preganglionic neurons; in sham mice the effect was limited to a few motoneurons. Finally, a moderate decrease in CGRP- and TRPV1-like-immunoreactivities was observed in the ipsilateral superficial dorsal horn neuropil. In conclusion, injury of a mixed visceral/non-visceral nerve leads to considerable neurochemical alterations in DRGs matched, to some extent, in the spinal cord. Changes in these and potentially other nociception-related molecules could contribute to pain due to injury of nerves in the abdominopelvic cavity.

Risk factors for chronic postsurgical abdominal and pelvic pain

SUMMARY 

Chronic postsurgical pain (CPSP) may develop after any surgical procedure, and is a common feature after abdominal and pelvic surgery with a prevalence varying between 10 and 40%. The pathological mechanisms leading to chronic CPSP are probably inflammation, tissue and nerve damage and alterations in central pain processing. The mechanisms in chronic postsurgical abdominal and pelvic pain are poorly studied and research has largely focused on reporting of prevalence and describing risk factors, including patient characteristics, psychological factors, surgical procedure and pre- and acute postoperative pain. In this review, the most important risk factors are discussed, and aiming for preventive, personalized health care, possible methods for prediction of susceptibility and potential strategies for diminishing chronic postsurgical abdominal and pelvic pain are provided.

Neonatal pain: What's age got to do with it?

Background:

The neurobiology of neonatal pain processing, especially in preterm infants, differs significantly from older infants, children, adolescence, and adults. Research suggests that strong painful procedures or repeated mild procedures may permanently modify individual pain processing. Acute injuries at critical developmental periods are risk factors for persistent altered neurodevelopment. The purpose of this narrative review is to present the seminal and current literature describing the unique physiological aspects of neonatal pain processing.

Methods:

Articles describing the structures and physiological processes that influence neonatal pain were identified from electronic databases Medline, PubMed, and CINAHL.

Results:

The representation of neonatal pain physiology is described in three processes: Local peripheral nervous system processes, referred to as transduction; spinal cord processing, referred to as transmission and modulation; and supraspinal processing and integration or perception of pain. The consequences of undermanaged pain in preterm infants and neonates are discussed.

Conclusion:

Although the process and pain responses in neonates bear some similarity to processes and pain responses in older infants, children, adolescence, and adults; there are some pain processes and responses that are unique to neonates rendering them at risk for inadequate pain treatment. Moreover, exposure to repeated painful stimuli contributes to adverse long-term physiologic and behavioral sequelae. With the emergence of studies showing that painful experiences are capable of rewiring the adult brain, it is imperative that we treat neonatal pain effectively.

Anesthetic premedication: new horizons of an old practice

The practice of anesthetic premedication embarked upon soon after ether and chloroform were introduced as general anesthetics in the middle of the 19(th) century. By applying opioids and anticholinergics before surgery, the surgical patients could achieve a less anxious state, and more importantly, they would acquire a smoother course during the tedious and dangerous induction stage. Premedication with opioids and anticholinergics was not a routine practice in the 20(th) century when intravenous anesthetics were primarily used as induction agents that significantly shorten the induction time. The current practice of anesthetic premedication has evolved into a generalized scheme that incorporates several aspects of patient care: decreasing preoperative anxiety, dampening intraoperative noxious stimulus and its associated neuroendocrinological changes, and minimizing postoperative adverse effects of anesthesia and surgery. Rational use of premedication in modern anesthesia practice should be justified by individual needs, the types of surgery, and the anesthetic agents and techniques used. In this article, we will provide our readers with updated information about premedication of surgical patients with a focus on the recent application of second generation serotonin type 3 antagonist, antidepressants, and anticonvulsants.