The Transition of Acute Postoperative Pain to Chronic Pain: An Integrative Overview of Research on Mechanisms

Postoperative pain at Landspitali: A prospective study

BACKGROUND

Moderate or severe postoperative pain is common despite advances in surgical technique and perioperative analgesia. This study aimed to assess the prevalence and severity of postoperative pain following procedures requiring anaesthesia and identify factors associated with increased risk of postoperative pain.

METHODS

Surgical patients ≥18 years of age were prospectively questioned on level of current pain on a numerical rating scale (NRS) from 0 to 10 in the post-anaesthesia care unit (PACU) and on resting, active and worst pain experienced in the first 24 h postoperatively. Clinical data was obtained from medical records. Descriptive statistics were applied, and predictors of worst pain assessed as moderate/severe (NRS ≥ 5) on postoperative day one were assessed using multivariable logistic regression.

RESULTS

Of 438 included participants, moderate/severe pain occurred in 29% on the day of surgery and 70% described their worst pain as moderate/severe on postoperative day one. Procedures with the highest incidence of moderate/severe pain on the day of surgery were gynaecology-, plastic-, abdominal-, breast-, and orthopaedic procedures. On postoperative day one, patients undergoing vascular-, orthopaedic-, and abdominal operations most commonly rated their worst pain as moderate/severe. Female sex (OR = 2.15, 95% Cl 1.21-3.88, p = .010), chronic preoperative pain (OR = 4.20, 95% Cl 2.41-7.51, p < .001), undergoing a major procedure (OR = 2.07, 95% Cl 1.15-3.80, p = .017), and any intraoperative remifentanil administration (OR = 2.16, 95% Cl 1.20-3.94, p = .01) had increased odds of rating the worst pain as moderate/severe. Increased age (OR = 0.66 per 10 years (95% Cl 0.55-0.78, p < .001)) and undergoing breast-, gynaecology-, otolaryngology-, and neurosurgery (OR = 0.15-0.34, p < .038) was associated with lower odds of moderate/severe pain on postoperative day one.

DISCUSSION

In our cohort, patients rated their current pain in the PACU similarly to other studies. However, the ratio of patients rating the worst pain experienced as moderate/severe on postoperative day one was relatively high. The identified patient- and procedural-related factors associated with higher odds of postoperative pain highlight a subgroup of patients who may benefit from enhanced perioperative monitoring and pain management strategies.

PENG for chronic pain: the clinical effectiveness of pericapsular nerve group block in chronic hip pain

OBJECTIVES

To evaluate the efficiency and tolerability of pericapsular nerve group block (PENG) for the treatment of chronic hip pain.

METHODS

This is a retrospective, single-centre, 4-group study conducted over a 3-month period to find out the most typical cause of chronic hip pain. A total of 112 patients with symptomatic hip osteoarthritis (OA), Stage 2-3, greater trochanteric pain (GTPS) and chronic pain after total hip arthroplasty (cTHA), who had an ultrasound-guided PENG block, were selected. To assess the effectiveness of the treatment, the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and visual analogue scale (VAS) scores of the patients prior to treatment were compared with their scores after the 1st week, 1st month, and 3rd month of treatment. The study also aimed to analyse the patients' initial feelings of alleviation following the block (1st VAS/2) and problems experienced both during and after the block.

RESULTS

The parameters studied included pain, stiffness, and results of physical activity in the 1st week, 1st month, and 3rd month following PENG block application. At the beginning of the 1st week, of the 112 patients who were administered a PENG block for hip pain, we reported a 62% improvement in pain, a 52% reduction in stiffness, and a 53% increase in physical activity. Even though these results slightly declined in the 1st and 3rd months, the rates were still higher than 45%.

CONCLUSIONS

Overall, the PENG block was well-tolerated by the patients in our study. No treatment-related infections or any other serious complications were observed.

Cannabinoid Analgesia in Postoperative Pain Management: From Molecular Mechanisms to Clinical Reality

Postoperative pain (POP) is a challenging clinical phenomenon that affects the majority of surgical patients and demands effective management to mitigate adverse outcomes such as persistent pain. The primary goal of POP management is to alleviate suffering and facilitate a seamless return to normal function for the patient. Despite compelling evidence of its drawbacks, opioid analgesia remains the basis of POP treatment. Novel therapeutic approaches rely on multimodal analgesia, integrating different pharmacological strategies to optimize efficacy while minimizing adverse effects. The recognition of the imperative role of the endocannabinoid system in pain regulation has prompted the investigation of cannabinoid compounds as a new therapeutic avenue. Cannabinoids may serve as adjuvants, enhancing the analgesic effects of other drugs and potentially replacing or at least reducing the dependence on other long-term analgesics in pain management. This narrative review succinctly summarizes pertinent information on the molecular mechanisms, clinical therapeutic benefits, and considerations associated with the plausible use of various cannabinoid compounds in treating POP. According to the available evidence, cannabinoid compounds modulate specific molecular mechanisms intimately involved in POP. However, only two of the eleven clinical trials that evaluated the efficacy of different cannabinoid interventions showed positive results.

Increased risk of persistent neuropathic pain after traumatic nerve injury and surgery for carriers of a human leukocyte antigen haplotype

ABSTRACT

It is not known why some patients develop persistent pain after nerve trauma while others do not. Among multiple risk factors for the development of persistent posttrauma and postsurgical pain, a neuropathic mechanism due to iatrogenic nerve lesion has been proposed as the major cause of these conditions. Because there is some evidence that the human leukocyte antigen (HLA) system plays a role in persistent postsurgical pain, this study aimed to identify the genetic risk factors, specifically among HLA loci, associated with chronic neuropathic pain after traumatic nerve injuries and surgery in the upper extremities. Blood samples were taken to investigate the contribution of HLA alleles (ie, HLA-A, HLA-B, HLA-DRB1, HLA-DQB1, and HLA-DPB1) in a group of patients with persistent neuropathic pain (n = 70) and a group of patients with neuropathy without pain (n = 61). All subjects had intraoperatively verified nerve damage in the upper extremity. They underwent bedside clinical neurological examination to identify the neuropathic pain component according to the present grading system of neuropathic pain. Statistical analyses on the allele and haplotype were conducted using the BIGDAWG package. We found that the HLA haplotype A*02:01-B*15:01-C*03:04-DRB1*04:01-DQB1*03:02 was associated with an increased risk of developing persistent neuropathic pain in the upper extremity (OR = 9.31 [95% CI 1.28-406.45], P < 0.05). No significant associations were found on an allele level when correcting for multiple testing. Further studies are needed to investigate whether this association is on a haplotypic level or if certain alleles may be causing the association.

Long-term pain outcomes after serial lidocaine infusion in participants with recent onset of peripheral neuropathic pain: A pilot double-blind, randomized, placebo-controlled trial

BACKGROUND

This study investigated the outcomes up to 12 weeks after serial lidocaine infusion for early-onset peripheral neuropathic pain.

METHODS

This pilot double-blind, randomized, 2-arm placebo-controlled trial recruited 50 participants with onset of peripheral neuropathic pain within the past 6 months and randomized them to either receive lidocaine (3 mg/kg) in normal saline (50 mL) intravenous infusion over 1 hour (lidocaine group) once a week for 4 weeks or 50 mL of normal saline infusion (placebo group) once a week for 4 weeks. Twenty-nine participants completed the protocol; 15 participants were assigned to the lidocaine group and 14 to the placebo group. The outcomes were pain intensity assessed using a numerical rating scale (NRS), quality of life assessed using EuroQol-Five Dimensions-Five Levels questionnaire (EQ-5D-5L), psychological function using the Thai version of the 21-item Depression Anxiety Stress Scales (DASS-21), pain medication use, and adverse effects, all assessed at baseline (BL) and again at 4, 8, and 12 weeks following randomization.

RESULTS

The reported tramadol use at 8 and 12 weeks following the first infusion was significantly lower in the lidocaine group (P = .023). No other significant between-group differences were observed at any time point or for any other outcome, and no serious adverse events were observed.

CONCLUSION

Multiple lidocaine infusions of 3 mg/kg once a week for 4 weeks in participants with recent onset of peripheral neuropathic pain demonstrated no significant benefits in pain intensity, quality of life, or psychological outcomes. At most, this treatment may result in less tramadol use.

Elevated circulating soluble interleukin-2 receptor (sCD25) level is associated with prefrontal excitatory-inhibitory imbalance in individuals with chronic pain: A proton MRS study

Aberrant neuronal excitability in the anterior cingulate cortex (ACC) is implicated in cognitive and affective pain processing. Such excitability may be amplified by activated circulating immune cells, including T lymphocytes, that interact with the central nervous system. Here, we conducted a study of individuals with chronic pain using magnetic resonance spectroscopy (MRS) to investigate the clinical evidence for the interaction between peripheral immune activation and prefrontal excitatory-inhibitory imbalance. In thirty individuals with chronic musculoskeletal pain, we assessed markers of peripheral immune activation, including soluble interleukin-2 receptor alpha chain (sCD25) levels, as well as brain metabolites, including Glx (glutamate + glutamine) to GABA+ (γ-aminobutyric acid + macromolecules/homocarnosine) ratio in the ACC. We found that the circulating level of sCD25 was associated with prefrontal Glx/GABA+. Greater prefrontal Glx/GABA+ was associated with higher pain catastrophizing, evaluative pain ratings, and anxiodepressive symptoms. Further, the interaction effect of sCD25 and prefrontal Glx/GABA+ on pain catastrophizing was significant, indicating the joint association of these two markers with pain catastrophizing. Our results provide the first evidence suggesting that peripheral T cellular activation, as reflected by elevated circulating sCD25 levels, may be linked to prefrontal excitatory-inhibitory imbalance in individuals with chronic pain. The interaction between these two systems may play a role as a potential mechanism underlying pain catastrophizing. Further prospective and treatment studies are needed to elucidate the specific role of the immune and brain interaction in pain catastrophizing.

Duration of the preemptive analgesic effects of low- and high-frequency transcutaneous electrical nerve stimulation in rats with acute inflammatory pain

Transcutaneous electrical nerve stimulation (TENS) activates various pathways to induce antinociceptive effects, based on the frequencies used. This study evaluates the preemptive analgesic effects and their duration of low- (LT: 4 Hz) and high-frequency TENS (HT: 100 Hz) using a rat model of acute inflammatory pain. Acute inflammation was induced by injecting 1% formalin into the hind paws of rats. LT or HT was applied for 30 min before formalin injection. Pain-related behaviors, such as licking, flinching, and lifting, were recorded for 60 min postinjection. Immunohistochemistry was used to assess the number of phosphorylated extracellular signal-regulated kinase (pERK)- and c-fos-positive cells in the spinal cord. Naloxone, a μ-opioid receptors (MORs) antagonist, and naltrindole, a δ-opioid receptors (DORs) antagonist, were administered before TENS application. Pain behavior duration and pERK- and c-fos-positive cell expression were then measured. LT and HT pretreatment significantly reduced both pain behaviors and the number of pERK- and c-fos-positive cells postformalin injection. Naloxone and naltrindole partially reversed the effects of LT and HT, respectively. Notably, HT's analgesic effect lasted up to 120 min whereas that of LT persisted for 90 min. LT and HT effectively exerted their preemptive analgesic effects on acute inflammatory pain by inhibiting pERK and c-fos expression in the spinal cord. HT presented a longer-lasting effect compared to LT. MOR and DOR activation may contribute to LT and HT's analgesic mechanisms, respectively.

Risk Factors for Chronic Abdominal Pain After RYGB: Are Patients Adequately Selected Beforehand?

PURPOSE

Chronic abdominal pain after RYGB is a known issue. Identifying the potential patient-related and modifiable risk factors might contribute to diminish the risk for this undesirable outcome.

METHODS

A single-center retrospective cohort study with prospective data collection was conducted with inclusion of all patients who underwent RYGB surgery between 2015 and 2021. Data from the NBSR and medical records were used. Patients with chronic abdominal pain were defined when pain lasting or recurring for more than 3 to 6 months.

RESULTS

Six hundred sixty-four patients who underwent RYGB surgery were included with a median follow-up of 60.5 months. Forty-nine patients (7.3%) presented with chronic abdominal pain. Postoperative complications (OR 13.376, p = 0.020) and diagnosis of depression (OR 1.971, p = 0.037) were associated with developing abdominal pain. On the other hand, ex-smokers (OR 0.222, p = 0.040) and older age (0.959, p = 0.004) presented as protective factors.

CONCLUSION

Postoperative complications and diagnosis of depression are risk factors for chronic pain after RYGB. The role of the bariatric MDT remains crucial to select these patients adequately beforehand.

Acute Effects of In-Hospital Resistance Training on Clinical Outcomes in Patients Undergoing Total Knee Arthroplasty: A Randomized Controlled Trial

OBJECTIVE

The aim of the study is to evaluate the acute responses, in the in-hospital setting, of intensive elastic resistance training on physical function, pain, psychosocial variables, and inflammatory markers in patients undergoing total knee arthroplasty.

DESIGN

In a randomized controlled trial, 40 patients with total knee arthroplasty (≥55 yrs) were assigned to either (1) the intervention group (elastic resistance strengthening) or (2) a control group (conventional protocol). Patients performed three sessions in the hospital at 24, 48, and 72 hrs after total knee arthroplasty. Outcome measures included: self-administered physical function, pain intensity, kinesiophobia, catastrophizing, self-efficacy, range of motion, perceived change, test timed up and go, knee joint effusion, isometric strength, pressure pain thresholds, and inflammatory markers (levels of procalcitonin and C-reactive protein).

RESULTS

The mixed analysis of variance model showed a significant group*time interaction in favor of the intervention group with a large effect size for kinesiophobia (ηp 2 = 0.308, P < 0.001), catastrophizing (ηp 2 = 0.242, P < 0.001), and passive range of motion flexion (ηp 2 = 0.167, P < 0.001) and a moderate effect size for physical function (ηp 2 = 0.103, P = 0.004), pain intensity (ηp 2 = 0.139, P < 0.001), timed up and go (ηp 2 = 0.132, P = 0.001), self-efficacy (ηp 2 = 0.074, P = 0.016), active range of motion flexion (ηp 2 = 0.121, P = 0.002), levels of procalcitonin (ηp 2 = 0.099, P = 0.005), and C-reactive protein (ηp 2 = 0.106, P = 0.004).

CONCLUSIONS

Three sessions of intensive elastic resistance training improve physical function, perceived pain, psychosocial variables, and inflammatory markers during the hospitalization period after total knee arthroplasty.

Update on Musculoskeletal Pain Management

Pain is the most common complaint reported to orthopedists in the outpatient clinic, emergency room, or booth. Numerous publications report the inadequate management of both acute and chronic pain by health professionals. This updated article aims to provide information about musculoskeletal pain, its classification, evaluation, diagnosis, and the multimodal therapeutic approach for each case. For acute pain, adequate control allows for earlier rehabilitation to work and reduces the rates of pain chronification. For chronic pain, the goal is to reduce its intensity and improve the quality of life. Currently, some procedures are increasingly used and aided by imaging tests for diagnostic and therapeutic purposes.

Induction of antiviral interferon-stimulated genes by neuronal STING promotes the resolution of pain in mice

Inflammation and pain are intertwined responses to injury, infection, or chronic diseases. While acute inflammation is essential in determining pain resolution and opioid analgesia, maladaptive processes occurring during resolution can lead to the transition to chronic pain. Here we found that inflammation activates the cytosolic DNA-sensing protein stimulator of IFN genes (STING) in dorsal root ganglion nociceptors. Neuronal activation of STING promotes signaling through TANK-binding kinase 1 (TBK1) and triggers an IFN-β response that mediates pain resolution. Notably, we found that mice expressing a nociceptor-specific gain-of-function mutation in STING exhibited an IFN gene signature that reduced nociceptor excitability and inflammatory hyperalgesia through a KChIP1-Kv4.3 regulation. Our findings reveal a role of IFN-regulated genes and KChIP1 downstream of STING in the resolution of inflammatory pain.

Are There Any Advantages of the Low Opioid Anaesthesia and Non-Opioid Postoperative Analgesia Protocol: A Clinical Observational Study

Purpose

The methods of perioperative analgesia and pain control have changed. The principle of opioid-based analgesia has been modified to multimodal analgesia, followed by LOA (low opioid anaesthesia) and OFA (opioid-free anaesthesia). The aim was to describe the effects of LOA on nausea, vomiting, and pain control during general anaesthesia and postoperative period after laparoscopic cholecystectomy.

Patients and Methods

The protocol included the study group-40 patients received low-opioid anaesthesia (LOA), and the control group-40 patients received general anaesthesia with opioid analgesia (OA). The scheme of LOA was based on ketamine, lidocaine, magnesium sulfate, paracetamol, and metamizole. The OA was based on standard opioid (fentanyl) administration in induction and maintenance phase due to clinical observation. Postoperative analgesia included 1g of paracetamol and 1g of metamizol intravenously, with a 6-hour interval between doses.

Results

Significant differences in the pain score in the periods of 2-6, 6-12, and 12-24 hours after anaesthesia between the groups were noticed (p < 0.001). Moreover, a significant difference in the frequency of nausea (p = 0.005) and vomiting (p = 0.04) between groups were presented. Nausea occurred in 54.05% of OA group, while in the LOA group, it occurred in a 23.08%. Vomiting occurred in 32.43% of control group, while in the study group, it occurred in 12.82% of patients.

Conclusion

The LOA protocol was more beneficial in reducing nausea and vomiting than the opioid-based method of anaesthesia. The LOA protocol of general anaesthesia during laparoscopic cholecystectomy and non-opioid postoperative analgesia have better outcomes in pain control, as well as nausea and vomiting, and improve postoperative patient comfort. The LOA protocol during anaesthesia and non-opioid postoperative analgesia should be considered in routine practice.

Pain Predictors in Patients in the Postanesthesia Care Unit

PURPOSE

To analyze the effects of pain-predicting factors on patients in the postanesthesia care unit (PACU).

DESIGN

This is an observational and prospective study.

METHODS

This study was conducted at a University Hospital in the state of Minas Gerais (Brazil). To collect data on demographic, clinical, and surgical factors, a collection instrument was devised. The verbal numerical scale was employed to measure pain levels before and after surgery in the PACU. A path analysis was used to assess a predictive model.

FINDINGS

A total of 226 patients were included in this study. The incidence of pain in the PACU was 31.9%. A model with demographic, clinical, and surgical variables was tested. The final model, after including modification indices, obtained results that indicated an acceptable data fit (comparative fit index = 0.996; root mean square error of approximation = 0.08). Age (being young), sex (being a woman), oncological diagnosis as an indication for the surgical procedure, type of surgery (surgery of the digestive system), duration of surgery (longer surgeries), and high intraoperative doses of opioids were predictive variables for pain in the PACU.

CONCLUSIONS

This study's findings provide support for pain management in the PACU. Furthermore, the results of this research can be used to anticipate the occurrence of acute postoperative pain and personalized perioperative analgesia needs.

Characterization of Common Genetic Variants in P2RX7 and Their Contribution to Chronic Pain Conditions

The adenosine triphosphate (ATP)-gated channel P2X7 is encoded by a gene enriched for common nonsynonymous variants. Many of these variants have functional cellular effects, and some have been implicated in chronic pain. In this study, we first systematically characterized all 17 common nonsynonymous variants using whole-cell patch clamp electrophysiology. Then, we analyzed these variants for statistical association with chronic pain phenotypes using both individual P2RX7 variants as predictors and cumulative allele counts of same-direction cellular effect in univariate models. Association and validation analyses were conducted in the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) cohort (N = 3260) and in the Complex Persistent Pain Conditions (CPPC) cohort (N = 900), respectively. Our results showed an association between allele A of rs7958311 and an increased risk of chronic pelvic pain, with convergent evidence for contribution to fibromyalgia and irritable bowel syndrome, confirmed in a meta-analysis. This allelic variant produced a unique cellular phenotype: a gain-of-function in channel opening, and a loss-of-function in pore opening. A computational study using a 12-state Markov model of ATP binding to the P2X7 receptor suggested that this cellular phenotype arises from an increased ATP binding affinity and an increased open channel conductance combined with a loss of sensitization. Cumulative allele count analysis did not provide additional insights. In conclusion, our results go beyond reproducing association for rs7958311 with chronic pain and suggest that its unique combination of gain-of-function in channel and loss-of-function in pore activity may explain why it is likely the only common P2RX7 variant with contribution to chronic pain. PERSPECTIVE: This study characterizes all common P2RX7 variants using cellular assays and statistical association analyses with chronic pain, with Markov state modeling of the most robustly associated variant.

Quantitative somatosensory assessments in patients with persistent pain following groin hernia repair: A systematic review with a meta-analytical approach

OBJECTIVES

Quantitative sensory testing (QST) provides an assessment of cutaneous and deep tissue sensitivity and pain perception under normal and pathological settings. Approximately 2-4% of individuals undergoing groin hernia repair (GHR) develop severe persistent postsurgical pain (PPSP). The aims of this systematic review of PPSP-patients were (1) to retrieve and methodologically characterize the available QST literature and (2) to explore the role of QST in understanding mechanisms underlying PPSP following GHR.

METHODS

A systematic literature search was conducted from JAN-1992 to SEP-2022 in PubMed, EMBASE, and Google Scholar. For inclusion, studies had to report at least one QST-modality in patients with PPSP. Risk of bias assessment of the studies was conducted utilizing the Newcastle Ottawa Scale and Cochrane's Risk of Bias assessment tool 2.0. The review provided both a qualitative and quantitative analysis of the results. A random effects model was used for meta-analysis.

RESULTS

Twenty-five studies were included (5 randomized controlled trials, 20 non-randomized controlled trials). Overall, risk of bias was low. Compared with the contralateral side or controls, there were significant alterations in somatosensory function of the surgical site in PPSP-patients. Following thresholds were significantly increased: mechanical detection thresholds for punctate stimuli (mean difference (95% CI) 3.3 (1.6, 6.9) mN (P = 0.002)), warmth detection thresholds (3.2 (1.6, 4.7) °C (P = 0.0001)), cool detection thresholds (-3.2 (-4.9, -1.6) °C (P = 0.0001)), and heat pain thresholds (1.9 (1.1, 2.7) °C (P = 0.00001)). However, the pressure pain thresholds were significantly decreased (-76 (-123, -30) kPa (P = 0.001)).

CONCLUSION

Our review demonstrates a plethora of methods used regarding outcome assessments, data processing, and data interpretation. From a pathophysiological perspective, the most consistent findings were postsurgical cutaneous deafferentation and development of a pain generator in deeper connective tissues.

TRIAL REGISTRATION

CRD42022331750.

The oral administration of Lotus corniculatus L. attenuates acute and chronic pain models in male rats

ETHNOPHARMACOLOGICAL RELEVANCE

Lotus corniculatus L. (Fabaceae) traditionally used in Persian folk medicine to heal peritoneal inflammation and back pain.

AIM OF THE STUDY

To explore the antinociceptive (acute pain) and anti-neuropathic (chronic pain) activities of Lotus corniculatus leaves essential oil (LCEO) in addition to uncovering the possible mechanisms of antinociception.

MATERIALS AND METHODS

LCEO as well as the pure oleanolic acid (OA) compound, were assayed for their effects on acute (formalin induced paw licking test or FIPT) and chronic (cervical contusion injury models on the fifth cervical vertebra or CCS; 14-day intervals) pain. The possible involvements of NO-cGMP-K+ channel, TRPV, dopamine, cannabinoid, PPAR, adrenergic, and opioid mechanisms in the antinociceptive activity of LCEO have studied by formalin test. The levels of p53 and inflammatory markers were measured using a streptavidin biotin immune peroxidase complex and ELISA methods, respectively.

RESULTS

The LCEO and OA exerted antinociceptive activity in the first-phase of FIPT. Pretreatment with antagonists of TRPV1, dopamine D2, cannabinoid type1 and 2, and NO-cGMP-K+ channel blockers (glibenclamide, L-NAME and methylene blue) attenuated the antinociceptive effect of LCEO in FIPT. In addition, LCEO and OA meaningfully reduced hyperalgesia (days 6-14) and mechanical allodynia (days 2-14) in the CCS model. LCEO suppressed the apoptotic marker (p53) in CCS model and also ameliorated IL-2, TNF-α, and IL-1 in the spinal cord.

CONCLUSION

Finally, LCEO inhibited acute (possibly via the modulation of opioid, TRPV, dopamine, cannabinoid mechanisms as well as NO-cGMP-K+ channel) and chronic pain (via suppressing apoptotic and inflammatory markers) in male rats. The results also suggest that OA has analgesic activity against acute and chronic pain conditions.

Overlap of pain-related and general measures of disability among adults with chronic pain

PURPOSE

Chronic pain is known to be correlated with disability. We aimed to determine the overlap between a general self-reported measure of disability and a measure of disability due to pain problems among adults with chronic pain.

MATERIALS AND METHODS

We used data from the National Health Interview Survey (NHIS) and analyzed respondents with chronic pain in the past 3 months. General disability was defined as being limited in the kind or amount of work one can do due to any physical, mental, or emotional problem. Pain-related disability was defined as pain limiting one's activity on "most days" or "every day."

RESULTS

Based on a sample of 6874 respondents with chronic pain, 58% had either kind of disability, including 9% who reported only pain-related, but not general disability; and 27% who reported both types of disability. Respondents reporting only pain-related, but not general disability tended to be younger and had lower rates of obesity, smoking, diabetes, and hypertension than respondents reporting both pain-related and general disability.

DISCUSSION

Among people with chronic pain, most people with disability are experiencing limitations related to pain problems. Assessment of disability without addressing pain interference has likely underestimated the disability burden in this population.

[Chronic eye pain]

Numerous conditions in the field of ophthalmology are associated with pain in or around the eye. Chronic pain associated with the eye is a common finding in the daily routine of ophthalmologists and can be associated with primary ocular or extraocular diseases as well as with other conditions. Appropriate diagnostic assessment and management of people with chronic pain requires an understanding of the condition based on the biopsychosocial model in which the interactions of biological/somatic, psychological and social factors are determining pain and suffering. Beyond the ophthalmological findings,  close interdisciplinary cooperation and assessment are required. Therefore, if eye pain is insufficiently responsive to treatment or if symptoms of chronic pain are evident, pain medicine expertise should be involved. The management of chronic ocular pain is based on interdisciplinary multimodal approaches, in addition to the ophthalmologist-specific approaches. These focus on self-efficacy, patient competence and acceptance of pain as central goals of treatment rather than pain relief. Patient information, education and the development of a suitable concept by the interdisciplinary team are essential therapeutic aspects in this context.

Effect of nociception level index-guided intra-operative analgesia on early postoperative pain and opioid consumption: a systematic review and meta-analysis

Acute postoperative pain remains a critical treatment priority and has prompted a search for technologies and techniques to assist with intra-operative analgesic monitoring and management. Anaesthetists traditionally rely on clinical judgement to guide intra-operative analgesia, but several emerging technologies such as the nociception level index herald the possibility of routine intra-operative analgesia monitoring. However, the impact of devices like nociception level index on postoperative outcomes has not been proven. We undertook a systematic review and meta-analysis of articles which compared nociception level index-guided analgesia to standard care. The primary outcomes were pain intensity and opioid consumption during the first 60-120 min after surgery. Secondary outcomes were the incidence of postoperative nausea and vomiting and duration of stay in the post-anaesthesia care unit. Ten studies, collectively including 662 patients and published between 2019 and 2023, met inclusion criteria for both the qualitative systematic review and quantitative meta-analysis. Risk of methodological bias was generally low or unclear, and six studies reported a significant conflict of interest relevant to their findings. Our meta-analysis was performed using a random-effects model. It found statistically significant benefits of nociception level index-guided analgesia for early postoperative pain (mean (95%CI) difference -0.46 (-0.88 to -0.03) on an 11-point scale, p = 0.03), and opioid requirement (mean (95%CI) difference -1.04 (-1.94 to -0.15) mg intravenous morphine equivalent, p = 0.02). Our meta-analysis of the current literature finds that nociception level index-guided analgesia statistically significantly reduces reported postoperative pain intensity and opioid consumption but fails to show clinically relevant outcomes. We found no evidence that nociception level index-guided analgesia affected postoperative nausea and vomiting nor duration of stay in the post-anaesthesia care unit.

Does Immediate Long-Span Nerve Allograft Reconstruction Affect the Incidence of Chronic Postsurgical and Neuropathic Pain in the Reconstructed Mandible Following Resection for Benign and Malignant Disease

BACKGROUND

Peripheral nerve injury can lead to chronic postsurgical pain (CPSP) and neuropathic pain following major surgery.

PURPOSE

Determine in patients undergoing ablative mandibular operations with transection of the trigeminal nerve: do those who undergo immediate repair, when compared to those whose nerves are not repaired, have a decreased or increased risk for CPSP or post-traumatic trigeminal neuropathic pain (PTTNp)?

STUDY DESIGN, SETTING, SAMPLE

A multisite, retrospective cohort of patients who underwent resection of the mandible for benign or malignant disease with either no repair or immediate repair of the intentionally transected trigeminal nerve with a long-span nerve allograft were analyzed for the presence or absence of CPSP and PTTNp at 6 months.

PREDICTOR VARIABLE

The primary predictor was the immediate repair or no repair of the trigeminal nerve.

MAIN OUTCOME VARIABLE

The primary outcome was the presence or absence of CPSP and PTTNp at 6 months postsurgery.

COVARIATES

There were 13 covariate variables, including age, sex, ethnicity, nerve injury, type of PTTNp, malignant or benign pathology and subtypes of each, use of radiation or chemotherapy, treatment of transected nerve end, longest follow-up time, pain scale, and onset of pain.

ANALYSES

Two-tailed Student's t test and Welch's t test were performed on mean scores and post hoc logistics and linear regression modeling were performed when indicated. The confidence level for statistical significance was P value <.05.

RESULTS

There were 103 and 94 subjects in the immediate and no-repair groups, respectively. The incidence of CPSP in the no-repair group was 22.3% and PTTNp was 2.12%, while there was 3.8% CPSP and 0% PTTNp in the repair group, which was statistically significant (P = <.001). Logistic regression modeling showed a statistically significant inverse relationship between the immediate repair and the incidence of CPSP/PTTNp with an odds ratio of 0.43, 95% confidence interval 0.18 to 1.01, P = .05. Greater age, malignant pathology, and chemo/radiation treatments were covariates found more frequently in the no repair group.

CONCLUSION AND RELEVANCE

Immediate repair of an intentionally transected trigeminal nerve with a long-span nerve allograft during resection of the mandible for both benign and malignant disease appears to reduce CPSP and possibly eliminate the development of PTTNp.

Chronic Pain and Functional Outcome 3 years After Total Knee Arthroplasty and Perioperative Dexamethasone: A Follow-Up of the Randomized, Clinical DEX-2-TKA Trial

BACKGROUND

Perioperative dexamethasone as an adjunct to multimodal analgesia, has an opioid-sparing and pain alleviating effect after total knee arthroplasty (TKA), however, the 3-year effects are unknown. We aimed to investigate the 3-year effect of 1 (DX1) or 2 (DX2) intravenous doses of 24 mg dexamethasone or placebo on pain, physical function, and health-related quality of life after TKA.

METHODS

Patients who participated in the Dexamethasone Twice for Pain Treatment after TKA (DEX-2-TKA) were invited to physical tests and questionnaires (self-reported characteristics, Oxford Knee Score, EuroQol-5Dimensions-5Levels (EQ5D5L), and PainDetect). The tests were 40-meter Fast Paced Walk (40FPW) test, Timed Up and Go (TUG), 30 Second Chair Stand test (30CST), Stair Climb Test (SCT), bilateral knee Range of Motion, and knee extension torque. For each test the peak pain intensity was registered on a 0 to 100 mm Visual Analogue Scale. Primary outcome was average peak pain intensity during the 40FPW, TUG, 30CST and SCT. Secondary outcomes were the tests and questionnaires. Out of 252 eligible patients, 133 (52.8%) underwent the tests and 160 (63.5%) answered the questionnaires. Mean follow-up time was 33 months (range, 23 to 40).

RESULTS

Median (interquartile range) peak pain intensity was 0 (0 to 65) for the DX2 group, 0 (0 to 51) for DX1 group and 0 (0 to 70) for the placebo group (P = .72). No differences in secondary outcomes were identified.

CONCLUSION

One or 2 intravenous doses of 24 mg dexamethasone did not impact chronic pain development or physical function 3 years after TKA.

Can Ultrasound-Guided Continuous Paravertebral Block Reduce the Incidence of Chronic Postsurgical Pain in Patients with Thoracoscopic Lung Cancer Surgery? A Randomized Controlled Trial

Background

Thoracoscopic lung cancer surgery is accompanied by severe pain. Both continuous paravertebral block (CPVB) and continuous wound infiltration (CWI) are widely used for perioperative analgesia in thoracoscopic surgery. However, the effects of these different methods on chronic postsurgical pain (CPSP) are still unknown. Patients and Methods. This prospective randomized controlled trial assessed the eligibility of 113 patients. Ninety-seven patients who met the inclusion criteria were randomly divided into a CPVB group and a CWI group, and 80 patients were analyzed in the final study. The primary outcome measures were the incidence and intensity of chronic postsurgical pain (CPSP) at 3, 6, and 9 months after surgery. The secondary outcome measures were the numerical rating scale (NRS) score of rest and activity at 12, 18, and 24 hours and on the 2nd, 3rd, and 7th days postoperatively; the Barthel Activities of Daily Living (ADL) score of activity levels on the 1st, 2nd, 3rd, and 7th days postoperatively; and the long-term quality of the life score at 3, 6, and 9 months postoperatively.

Results

The incidence of chronic postsurgical pain in the CWI group was significantly higher than that in the CPVB group at 3, 6, and 9 months after surgery (all P < 0.05). The intensity of chronic postsurgical pain was significantly decreased in the CPVB group at 3, 6, and 9 months after surgery (P < 0.05). NRS-R and NRS-A scores were significantly decreased in the CPVB group within the first week after thoracoscopic surgery (P < 0.001). ADL scores were increased in the CPVB group within 3 days postoperatively. However, there were no differences in the ADL score on the 7th postoperative day or the long-term quality of the life score at 3, 6, and 9 months postoperatively.

Conclusion

Continuous ultrasound-guided paravertebral block reduced the intensity of acute pain within 7 days postoperatively and reduced the incidence of chronic pain at 3, 6, and 9 months after surgery, but there was no significant advantage in long-term quality of life. This trial is registered with ChiCTR2000038505.

Electroacupuncture for Pain Relief After Endoscopic Sinus Surgery: A Randomized Controlled Trial

Postoperative pain is a common problem after endoscopic sinus surgery (ESS). Electroacupuncture (EA) is proven to be effective in relieving postoperative pain. However, EA has not been studied in patients undergoing ESS. This study was designed to evaluate the efficacy and safety of EA compared to a sham control in relieving pain after ESS. A total of 62 patients were randomly allocated to receive either EA (n = 31) or sham EA (n = 31) for 5 sessions, 30 minutes per session for 4 days (2 hours before and 2 hours after surgery, and 3 sessions daily for the following 3 days). There were no significant differences between the 2 groups with regard to demographic characteristics. Compared to the sham EA group, the EA group showed a significantly greater reduction in the pain intensity of single daily scoring with a numerical rating scale at the day following surgery (postoperative day 1, POD1) (-1.35; 95% confidence interval [CI], -1.74 to -0.97; P < .001) and POD2 (-1.16; 95% CI, -1.55 to -0.77; P < .001), whereas no significant between-group difference was detected at the day of surgery (POD0), POD3 or POD6. Intraoperative heart rate and mean blood pressure in the EA group showed a more stable trend. A significant improvement was found for an actigraphy-measured average time of night wakings, recovery time from anesthesia, and quality of recovery-15 in the EA group. No severe adverse events occurred during the trial. Our results demonstrate that EA can serve as an effective adjuvant therapeutic tool for pain relief after ESS. PERSPECTIVE: This randomized sham-controlled, patient-and-assessor blinded trial provided evidence for the first time that EA can relieve postoperative pain and other symptom management in patients after ESS. TRIAL REGISTRATION NUMBER: Chinese Clinical Trial Registry, ChiCTR1900024183, http://www.chictr.org.cn/showproj.aspx?proj=40573.

Descending Control of Nociception Poorly Predicts the Development of Persistent Postsurgical Pain-like Behavior in Consomic Dahl S Rat Strains

BACKGROUND

Chronic postsurgical pain is a poorly recognized outcome of surgery where patients experience pain long after healing from the surgical insult. Descending control of nociception, a phenomenon whereby application of a strong nociceptive stimulus to one part of the body of animals inhibits pain in remote body regions, offers one strategy to identify a propensity to develop chronic postsurgical pain-like behavior. Here, consomic rat panel was used to test the hypothesis that pain persistence is mechanistically linked to ineffective descending control of nociception.

METHODS

Male and female Brown Norway, Dahl S, and eight consomic strains (SS-xBN) were used to determine the presence of chronic postsurgical pain-like behaviors by using paw-withdrawal threshold evaluation (von Frey method) in the area adjacent to a hind paw plantar incision. Descending control of nociception was assessed by measuring hind paw-withdrawal thresholds (Randall-Selitto method) after capsaicin (125 µg) injection into a forepaw. Consomic rats were developed by introgressing individual Brown Norway chromosomes on the Dahl S rat genetic background, as Dahl S rats lack preoperative descending control of nociception.

RESULTS

Substitution of several chromosomes from the "pain-resistant" Brown Norway to the "pain-prone" Dahl S/Medical College of Wisconsin reduced mechanical nociceptive sensitivity and increased endogenous pain modulation capacity by differing degrees. Statistical modeling of these data revealed that descending control of nociception is a poor general predictor of the propensity to develop chronic postsurgical pain-like behavior (poor fit for model 1). However, a significant strain-by-descending control of nociception interaction was revealed (model 3, -2*log likelihood; 550.668, -2ll change; 18.093, P = 0.034) with SS-13BN and SS-15BN strains showing a negative descending control of nociception relationship with chronic postsurgical pain-like behavior.

CONCLUSIONS

Descending control of nociception poorly predicted which rat strains developed chronic postsurgical pain-like behavior despite controlling for genetic, environmental, and sex differences. Two consomic strains that mimic clinical chronic postsurgical pain criteria and display a strong negative correlation with descending control of nociception were identified, offering novel candidates for future experiments exploring mechanisms that lead to chronic postsurgical pain.

EDITOR’S PERSPECTIVE

Fasting-mimicking diet alleviates inflammatory pain by inhibiting neutrophil extracellular traps formation and neuroinflammation in the spinal cord

BACKGROUND

Neutrophil extracellular traps (NETs) promote neuroinflammation and, thus, central nervous system (CNS) disease progression. However, it remains unclear whether CNS-associated NETs affect pain outcomes. A fasting-mimicking diet (FMD) alleviates neurological disorders by attenuating neuroinflammation and promoting nerve regeneration. Hence, in this study, we explore the role of NETs in the CNS during acute pain and investigate the role of FMD in inhibiting NETs and relieving pain.

METHODS

The inflammatory pain model was established by injecting complete Freund's adjuvant (CFA) into the hind paw of mice. The FMD diet regimen was performed during the perioperative period. PAD4 siRNA or CI-amidine (PAD4 inhibitor) was used to inhibit the formation of NETs. Monoamine oxidase-B (MAO-B) knockdown occurred by AAV-GFAP-shRNA or AAV-hSyn-shRNA or was inhibited by selegiline (an MAO-B inhibitor). The changes in NETs, neuroinflammation, and related signaling pathways were examined by western blot, immunofluorescence, ELISA, and flow cytometry.

RESULTS

In the acute phase of inflammatory pain, NETs accumulate in the spinal cords of mice. This is associated with exacerbated neuroinflammation. Meanwhile, inhibition of NETs formation alleviates allodynia and neuroinflammation in CFA mice. FMD inhibits NETs production and alleviates inflammatory pain, which is enhanced by treatment with the NETs inhibitor CI-amidine, and reversed by treatment with the NETs inducer phorbol 12-myristate 13-acetate (PMA). Mechanistically, the neutrophil-recruiting pathway MAO-B/5-hydroxyindoleacetic acid (5-HIAA) / G-protein-coupled receptor 35 (GPR35) and NETs-inducing pathway MAO-B/ Reactive oxygen species (ROS) are significantly upregulated during the development of inflammatory pain. MAO-B is largely expressed in astrocytes and neurons in the spinal cords of CFA mice. However, knockdown or inhibition of MAO-B effectively attenuates CFA-induced inflammatory pain, NETs formation, and neuroinflammation in the spinal cord. Moreover, within rescue experiments, MAO-B inhibitors synergistically enhance FMD-induced pain relief, NETs inhibition, and neuroinflammation attenuation, whereas supplementation with MAO-B downstream molecules (i.e., 5-HIAA and PMA) abolished this effect.

CONCLUSIONS

Neutrophil-released NETs in the spinal cord contribute to pain development. FMD inhibits NETs formation and NETs-induced neuroinflammation by inhibiting the MAO-B/5-HIAA/GPR35 and MAO-B/ROS pathways in astrocytes and neurons, thereby relieving pain progression. Video Abstract.

Content and Quality of Mobile Apps for the Monitoring of Musculoskeletal or Neuropathic Pain in Australia: Systematic Evaluation

Background

Mobile apps offer a potential mechanism for people with persistent pain to monitor pain levels conveniently within their own environment and for clinicians to remotely monitor their patients' pain. However, the quality of currently available apps and the usefulness of included features from a clinical perspective are not known.

Objective

The aim of this study was to examine the content and quality of currently available smartphone apps designed for monitoring the intensity or presence of musculoskeletal or neuropathic pain.

Methods

A systematic search was performed in the Australian Apple and Google Play stores. Apps were included if they were designed to monitor the intensity or presence of musculoskeletal or neuropathic pain and were available in the English language within the Australian app stores. Data pertaining to the intended use of the app and clinical population were extracted by using a custom-designed data extraction form, and app quality was assessed by using the 23-item Mobile App Rating Scale.

Results

Of the 2190 apps screened, 49 met the inclusion criteria. Apps were primarily designed for adult users (36/49, 73%) with nonspecific musculoskeletal or neuropathic pain conditions, arthritis, and joint pain. All apps monitored pain intensity, with almost half (23/49, 47%) also specifying pain location. Overall, the mean quality scores from the Mobile App Rating Scale ranged from 1.5 to 4.4 (out of 5.0). Between 20% (10/49) and 22% (11/49) of apps involved clinicians, consumers, or both in their development, and 20% (10/49) had published literature related to the development or use of the app in clinical scenarios. Although 71% (35/49) had data sharing features, only 5 apps enabled client-clinician communication through the app.

Conclusions

The overall quality of mobile apps that are currently available for monitoring pain intensity is acceptable. Presently, mobile apps for remote pain monitoring lack functionality for clinicians to view data between consults. Both users and clinicians should be aware of the limitations of these apps and make informed choices in using or recommending apps that best suit the clinical need.

Current Evidence for Biological Biomarkers and Mechanisms Underlying Acute to Chronic Pain Transition across the Pediatric Age Spectrum

Chronic pain is highly prevalent in the pediatric population. Many factors are involved in the transition from acute to chronic pain. Currently, there are conceptual models proposed, but they lack a mechanistically sound integrated theory considering the stages of child development. Objective biomarkers are critically needed for the diagnosis, risk stratification, and prognosis of the pathological stages of pain chronification. In this article, we summarize the current evidence on mechanisms and biomarkers of acute to chronic pain transitions in infants and children through the developmental lens. The goal is to identify gaps and outline future directions for basic and clinical research toward a developmentally informed theory of pain chronification in the pediatric population. At the outset, the importance of objective biomarkers for chronification of pain in children is outlined, followed by a summary of the current evidence on the mechanisms of acute to chronic pain transition in adults, in order to contrast with the developmental mechanisms of pain chronification in the pediatric population. Evidence is presented to show that chronic pain may have its origin from insults early in life, which prime the child for the development of chronic pain in later life. Furthermore, available genetic, epigenetic, psychophysical, electrophysiological, neuroimaging, neuroimmune, and sex mechanisms are described in infants and older children. In conclusion, future directions are discussed with a focus on research gaps, translational and clinical implications. Utilization of developmental mechanisms framework to inform clinical decision-making and strategies for prevention and management of acute to chronic pain transitions in children, is highlighted.

Assessment of pain management adequacy among hospitalized pediatric patients: institutional-based cross-sectional study

Background

As the evidence showed, despite the magnitude of the effects that pain can have on a child, it is often inadequately assessed and treated. However, whether pain is adequately treated or not, evidence is lacking in the study setting.

Objectives

This study assessed pain management adequacy among hospitalized pediatric patients at the University of Gondar Comprehensive Specialized Hospital, Ethiopia.

Methods

An institution-based cross-sectional study was conducted among pediatric patients admitted to the University of Gondar Comprehensive and Specialized Hospital between June and August 2021. Eligible patients were enrolled in the study using consecutive sampling techniques. Data were collected using a structured interview-based questionnaire and a review of the patient's medical records that were prepared after reviewing earlier studies. Pain management adequacy was determined using the pain management index (PMI) score. Statistical Software for Social Sciences (SPSS) version 22 was used for data entry and analysis. Descriptive statistics such as frequencies, percentages, and means with standard deviation were used to describe the respective variables. Logistic regression was used to assess predictor variables of pain management adequacy. A p-value <0.05 at a 95% CI was considered statistically significant.

Results

Of the 422 participants enrolled in the study, most (58.1%) were males, with a mean age of 3.9 ± 0.8 years. Pain medication was prescribed to 62.8% (95% CI: 57.3-68.2) of the participants. About 63.3% (95% CI: 58.8%-68%) received inadequate analgesics. The type of painkillers administered also did not match the severity of the pain. Pediatric patients less than 1 month and between 1 month and 1 year (AOR = 2.891, 95% CI: 1.274-12.899 and AOR = 2.657, 95% CI: 1.350-5.175), respectively, and patients with severe and moderate levels of pain (AOR = 3.448, 95% CI: 1.902-6.251 and AOR = 5.345, 95% CI: 1.956-9.828), respectively, were found to have inadequate pain medication compared with their counterparts.

Conclusion

This study revealed that pain was hardly managed based on its severity. Overall, two-thirds of pediatric patients received inadequate pain medication. This indicates majority of patients experienced pain did not manage appropriately.

Association of Intraoperative Opioid Administration With Postoperative Pain and Opioid Use

IMPORTANCE

Opioids administered to treat postsurgical pain are a major contributor to the opioid crisis, leading to chronic use in a considerable proportion of patients. Initiatives promoting opioid-free or opioid-sparing modalities of perioperative pain management have led to reduced opioid administration in the operating room, but this reduction could have unforeseen detrimental effects in terms of postoperative pain outcomes, as the relationship between intraoperative opioid usage and later opioid requirements is not well understood.

OBJECTIVE

To characterize the association between intraoperative opioid usage and postoperative pain and opioid requirements.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study evaluated electronic health record data from a quaternary care academic medical center (Massachusetts General Hospital) for adult patients who underwent noncardiac surgery with general anesthesia from April 2016 to March 2020. Patients who underwent cesarean surgery, received regional anesthesia, received opioids other than fentanyl or hydromorphone, were admitted to the intensive care unit, or who died intraoperatively were excluded. Statistical models were fitted on the propensity weighted data set to characterize the effect of intraoperative opioid exposures on primary and secondary outcomes. Data were analyzed from December 2021 to October 2022.

EXPOSURES

Intraoperative fentanyl and intraoperative hydromorphone average effect site concentration estimated using pharmacokinetic/pharmacodynamic models.

MAIN OUTCOMES AND MEASURES

The primary study outcomes were the maximal pain score during the postanesthesia care unit (PACU) stay and the cumulative opioid dose, quantified in morphine milligram equivalents (MME), administered during the PACU stay. Medium- and long-term outcomes associated with pain and opioid dependence were also evaluated.

RESULTS

The study cohort included a total of 61 249 individuals undergoing surgery (mean [SD] age, 55.44 [17.08] years; 32 778 [53.5%] female). Increased intraoperative fentanyl and intraoperative hydromorphone were both associated with reduced maximum pain scores in the PACU. Both exposures were also associated with a reduced probability and reduced total dosage of opioid administration in the PACU. In particular, increased fentanyl administration was associated with lower frequency of uncontrolled pain; a decrease in new chronic pain diagnoses reported at 3 months; fewer opioid prescriptions at 30, 90, and 180 days; and decreased new persistent opioid use, without significant increases in adverse effects.

CONCLUSIONS AND RELEVANCE

Contrary to prevailing trends, reduced opioid administration during surgery may have the unintended outcome of increasing postoperative pain and opioid consumption. Conversely, improvements in long-term outcomes might be achieved by optimizing opioid administration during surgery.

Desktop Virtual Reality Offers a Novel Approach to Minimize Pain and Anxiety during Burn Wound Cleaning/Debridement in Infants and Young Children: A Randomized Crossover Pilot Study

Although most scald burn injuries involve children under six, because of the challenges of using head mounted displays with young children there is very little research exploring the use of VR in children under six. The current clinical pilot study measured the analgesic effectiveness of our new desktop VR system (with no VR helmet) in children under six during burn wound care (a within-subjects design with randomized treatment order). Between December 2021-April 2022, nine children with burn injuries (10 months to 5 years age, mean = 18 months) participated. The mean burn size was 10% Total Body Surface Area, range 2-22%. Using nurse's ratings, VR significantly reduced children's pain during burn wound care by 40% on the observational Faces, Legs, Activity, Crying, and Consolability (FLACC) pain scale. Specifically, non-parametric within-subject sign tests compared nurse's ratings of the young patients' pain during burn wound care using usual pain medications with no VR = 6.67, (SD = 2.45) vs. adjunctive Animal Rescue World VR (VR = 4.00, SD = 2.24, p < 0.01). The observational Procedure-Behavior Checklist (PBCL) nurse's scale measured a 34% reduction in anxiety with VR as compared to pharmacologic treatment alone (p < 0.005). Similarly, when using single graphic rating scales the patients' parents reported a significant 36% decrease in their child's pain during VR (p < 0.05), a 38% (p < 0.005) decrease in their child's anxiety during VR, and a significant increase in patients' joy during VR. It can be concluded that during burn wound care with no distraction (traditional pain medications), children under 6 years old experienced severe pain during a 10 min burn wound cleaning session. During burn wound care combining desktop virtual reality and traditional pain medications, the same pediatric patients experienced only mild pain during burn wound cleaning/debridement. VR significantly reduced the children's pain and anxiety during burn wound care.

Pre-Trauma Pain Is the Strongest Predictor of Persistent Enhanced Pain Patterns after Severe Trauma: Results of a Single-Centre Retrospective Study

Background and Objectives: Traumatic injuries are a significant public health issue worldwide, with persistent enhanced pain being a common complication following severe trauma. Persistent and chronic pain can have a profound impact on patients' quality of life, affecting physical, emotional, and social functioning. This study aimed to investigate the pain patterns of trauma patients before and after severe trauma, and identify the predictors of persisting pain after injury. Materials and Methods: A total of 596 patients of a level-one trauma centre with severe trauma were included in this study. The Trauma Outcome Profile Scale was used to assess pain severity before and after trauma, and a logistic regression analysis was performed to determine the most significant predictors of relevant pain after severe trauma. Results: The mean age of the included patients was 48.2 years, and 72% were males. The most frequent cause of injury was traffic accidents, and the mean Injury Severity Score was 17.6. Nearly half of the patients experienced reduced pain-related quality of life after trauma, with persisting pain predominantly occurring in the neck, spine, shoulder, pelvis, hip, knee, and feet. Even minor injuries led to increased pain scores. Preexisting pain before injury (OR: 5.43; CI: 2.60-11.34), older age (OR: 2.09, CI: 1.22-3.27), female gender (OR: 1.08, CI: 0.73-1.59), and high injury severity (OR: 1.80, CI: 1.20-2.69) were identified as significant predictors of enhanced pain. Conclusions: These findings highlight the importance of considering pre-existing pain, body area, and injury severity in assessing the risk of persistent pain in trauma patients.

Identifying risk factors for chronic postsurgical pain and preventive measures: a comprehensive update

INTRODUCTION

Chronic postsurgical pain (CPSP) is a prevalent condition that can diminish health-related quality of life, cause functional deficits, and lead to patient distress. Rates of CPSP are higher for certain types of surgeries than others (thoracic, breast, or lower extremity amputations) but can occur after even uncomplicated minimally invasive procedures. CPSP has multiple mechanisms, but always starts as acute postsurgical pain, which involves inflammatory processes and may encompass direct or indirect neural injury. Risk factors for CPSP are largely known but many, such as female sex, younger age, or type of surgery, are not modifiable. The best strategy against CPSP is to quickly and effectively treat acute postoperative pain using a multimodal analgesic regimen that is safe, effective, and spares opioids.

AREAS COVERED

This is a narrative review of the literature.

EXPERT OPINION

Every surgical patient is at some risk for CPSP. Control of acute postoperative pain appears to be the most effective approach, but principles of good opioid stewardship should apply. The role of regional anesthetics as analgesics is gaining interest and may be appropriate for certain patients. Finally, patients should be better informed about their relative risk for CPSP.

Fear Learning in Genital Pain: Toward a Biopsychosocial, Ecologically Valid Research and Treatment Model

Although fear learning mechanisms are implicated in the development, maintenance, exacerbation, and reduction of genital pain, systematic research on how fear of genital pain emerges, spreads, persists, and reemerges after treatment is lacking. This paper provides an overview of the literature on pain-related fear, integrates the ideas on learning and sexual arousal responding, and specifies the pathways through which compromised learning may contribute to the development and persistence of genital pain. In order to refine theories of genital pain and optimize treatments, we need to adopt a biopsychosocial framework to pain-related fear learning and uncover potential moderators that shape individual trajectories. This involves examining the role of physiological processes, subjective experiences, as well as partner and relational cues in fear acquisition, excessive generalization and impaired safety learning, extinction of fear, counterconditioning, and return of fear. Recent methodological advances in fear conditioning and sex research are promising to enable more symptom-specific and ecologically valid experimental paradigms.

The role of catastrophizing and basic psychological needs satisfaction on health-related quality of life and pain in patients with lumbar disc herniation

Introduction

Lumbar disc herniation (LDH) is one of the most common conditions associated with functional disability, affecting patients' quality of life (QOL). Disability can be affected by cognitive factors, such as pain catastrophizing. Similarly, unfulfilled basic psychological needs (i.e., autonomy, competence, relatedness) are associated with biases in pain perception and QOL. Using the fear-avoidance model and the self-determination theory, this study investigates: (1) the separate contribution of pain-related variables and basic psychological needs satisfaction in predicting QOL in patients proposed for LDH surgery; (2) pre- and post-surgical differences in pain catastrophizing and basic psychological needs satisfaction.

Methods

First, we used hierarchical regression on 193 patients (M_age = 46.10, SD_age = 11.40) to identify predictors of QOL. Second, we performed paired t-tests on 55 patients to investigate pre- and post-surgical differences in pain catastrophizing and basic psychological needs satisfaction.

Results

Hierarchical regression showed that the model predicts 27% of the variance in QOL; medium pain level, age, pain catastrophizing, and basic psychological needs satisfaction were significant predictors. Also, pain catastrophizing significantly decreased after surgery [t (54) = 6.07, p < 0.001, Cohen's d = 0.81], but basic psychological needs satisfaction did not modify significantly.

Discussion

This research confirms the importance of pain perception and pain catastrophizing for LDH patients' QOL and broadens the applicability of the self-determination theory for spinal patients.

In search of a composite biomarker for chronic pain by way of EEG and machine learning: where do we currently stand?

Machine learning is becoming an increasingly common component of routine data analyses in clinical research. The past decade in pain research has witnessed great advances in human neuroimaging and machine learning. With each finding, the pain research community takes one step closer to uncovering fundamental mechanisms underlying chronic pain and at the same time proposing neurophysiological biomarkers. However, it remains challenging to fully understand chronic pain due to its multidimensional representations within the brain. By utilizing cost-effective and non-invasive imaging techniques such as electroencephalography (EEG) and analyzing the resulting data with advanced analytic methods, we have the opportunity to better understand and identify specific neural mechanisms associated with the processing and perception of chronic pain. This narrative literature review summarizes studies from the last decade describing the utility of EEG as a potential biomarker for chronic pain by synergizing clinical and computational perspectives.

Kinins' Contribution to Postoperative Pain in an Experimental Animal Model and Its Implications

Postoperative pain causes discomfort and disability, besides high medical costs. The search for better treatments for this pain is essential to improve recovery and reduce morbidity and risk of chronic postoperative pain. Kinins and their receptors contribute to different painful conditions and are among the main painful inflammatory mediators. We investigated the kinin's role in a postoperative pain model in mice and reviewed data associating kinins with this painful condition. The postoperative pain model was induced by an incision in the mice's paw's skin and fascia with the underlying muscle's elevation. Kinin levels were evaluated by enzyme immunoassays in sham or operated animals. Kinin's role in surgical procedure-associated mechanical allodynia was investigated using systemic or local administration of antagonists of the kinin B₁ receptor (DALBk or SSR240612) or B₂ receptor (Icatibant or FR173657) and a kallikrein inhibitor (aprotinin). Kinin levels increased in mice's serum and plantar tissue after the surgical procedure. All kinin B₁ or B₂ receptor antagonists and aprotinin reduced incision-induced mechanical allodynia. Although controversial, kinins contribute mainly to the initial phase of postoperative pain. The kallikrein-kinin system can be targeted to relieve this pain, but more investigations are necessary, especially associations with other pharmacologic targets.

Post-injury pain and behaviour: a control theory perspective

Injuries of various types occur commonly in the lives of humans and other animals and lead to a pattern of persistent pain and recuperative behaviour that allows safe and effective recovery. In this Perspective, we propose a control-theoretic framework to explain the adaptive processes in the brain that drive physiological post-injury behaviour. We set out an evolutionary and ethological view on how animals respond to injury, illustrating how the behavioural state associated with persistent pain and recuperation may be just as important as phasic pain in ensuring survival. Adopting a normative approach, we suggest that the brain implements a continuous optimal inference of the current state of injury from diverse sensory and physiological signals. This drives the various effector control mechanisms of behavioural homeostasis, which span the modulation of ongoing motivation and perception to drive rest and hyper-protective behaviours. However, an inherent problem with this is that these protective behaviours may partially obscure information about whether injury has resolved. Such information restriction may seed a tendency to aberrantly or persistently infer injury, and may thus promote the transition to pathological chronic pain states.

Shared Decision-Making in Acute Pain Services

PURPOSE OF REVIEW

The implementation of shared decision-making (SDM) in acute pain services (APS) is still in its infancies especially when compared to other medical fields.

RECENT FINDINGS

Emerging evidence fosters the value of SDM in various acute care settings. We provide an overview of general SDM practices and possible advantages of incorporating such concepts in APS, point out barriers to SDM in this setting, present common patient decisions aids developed for APS and discuss opportunities for further development. Especially in the APS setting, patient-centred care is a key component for optimal patient outcome. SDM could be included into everyday clinical practice by using structured approaches such as the "seek, help, assess, reach, evaluate" (SHARE) approach, the 3 "MAking Good decisions In Collaboration"(MAGIC) questions, the "Benefits, Risks, Alternatives and doing Nothing"(BRAN) tool or the "the multifocal approach to sharing in shared decision-making"(MAPPIN'SDM) as guidance for participatory decision-making. Such tools aid in the development of a patient-clinician relationship beyond discharge after immediate relief of acute pain has been accomplished. Research addressing patient decision aids and their impact on patient-reported outcomes regarding shared decision-making, organizational barriers and new developments such as remote shared decision-making is needed to advance participatory decision-making in acute pain services.

Can perioperative psychological interventions reduce chronic pain after surgery?

Chronic post-surgical pain is a relatively common adverse effect following surgery. Several prognostic factors for chronic post-surgical pain have been identified, including psychological states and traits. Psychological factors are modifiable, and perioperative psychological interventions may reduce the incidence of chronic post-surgical pain. A meta-analysis showed preliminary evidence for the benefits of such interventions for the prevention of chronic post-surgical pain. Further research must be conducted to better understand the specific type, intensity, duration and timing of interventions that are most effective. The number of studies in this area has recently increased, with additional randomised controlled trials currently being carried out, which may allow for the development of more robust conclusions in the coming years. In order to implement perioperative psychological care alongside routine surgical interventions, efficient and accessible interventions should be available. In addition, demonstration of cost-effectiveness may be a prerequisite for wider adoption of perioperative psychological interventions in regular healthcare. Offering psychological interventions selectively to patients at risk of chronic post-surgical pain could be a means to increase cost-effectiveness. Stepped-care approaches should also be considered, where the intensity of psychological support is adapted to the needs of the patient.

Evaluation and Comparison of Physics Forceps and Conventional Forceps in Bilateral Dental Extraction: A Randomized, Split-Mouth, Clinical Study

Background Interest in atraumatic tooth extraction has increased because it aims to preserve the dental alveolus. Several tools have been designed for atraumatic extraction, including the recently invented physics forceps. This study aims to assess the physics forceps and compare the clinical outcomes to the conventional forceps. Methodology A prospective, randomized, split-mouth, single-blind study was conducted among 20 healthy patients needing bilateral extraction. Participants were randomly assigned to perform physics forceps extraction on one quadrant and conventional forceps extraction on the opposite quadrant. Clinical outcomes were recorded and compared, including time taken for extraction, root fracture, buccal cortical plate fracture, postoperative pain, patient satisfaction, and post-extraction socket healing. Results The mean extraction time of physics forceps was shorter than conventional forceps but without statistical significance. Root and buccal cortical plate fractures were lower in the physics forceps group. Statistical difference in postoperative pain was found on the third postoperative day as pain scored higher in the physics group (p = 0.038). Higher patient satisfaction was found in the physics forceps group (85%). Post-extraction socket healing was equal in 75% of the cases. Conclusions Physics forceps is a novel and efficient atraumatic dental extractor. It reduces intraoperative time, is associated with higher patient satisfaction, and has comparable clinical outcomes to conventional forceps.

Genome-wide association study suggests a critical contribution of the adaptive immune system to chronic post-surgical pain

Chronic post-surgical pain affects a large proportion of people undergoing surgery, delaying recovery time and worsening quality of life. Although many environmental variables have been established as risk factors, less is known about genetic risk. To uncover genetic risk factors we performed genome-wide association studies in post-surgical cohorts of five surgery types- hysterectomy, mastectomy, abdominal, hernia, and knee- totaling 1350 individuals. Genetic associations between post-surgical chronic pain levels on a numeric rating scale (NRS) and additive genetic effects at common SNPs were evaluated. We observed genome-wide significant hits in almost all cohorts that displayed significance at the SNP, gene, and pathway levels. The cohorts were then combined via a GWAS meta-analysis framework for further analyses. Using partitioned heritability, we found that loci at genes specifically expressed in the immune system carried enriched heritability, especially genes related to B and T cells. The relevance of B cells in particular was then demonstrated in mouse postoperative pain assays. Taken altogether, our results suggest a role for the adaptive immune system in chronic post-surgical pain.

Age and sex drive differential behavioral and neuroimmune phenotypes during postoperative pain

Surgical procedures in the geriatric population are steadily increasing, driven by improved healthcare technologies and longer lifespans. However, effective postoperative pain treatments are lacking, and this diminishes quality of life and recovery. Here we present one of the first preclinical studies to pursue sex- and age-specific differences in postoperative neuroimmune phenotypes and pain. We found that aged males, but not females, had a delayed onset of mechanical hypersensitivity post-surgery and faster resolution than young counterparts. This sex-specific age effect was accompanied by decreased paw innervation and increased local inflammation. Additionally, we find evidence of an age-dependent decrease in hyperalgesic priming and perioperative changes in nociceptor populations and spinal microglia in the aged. These findings suggest that impaired neuronal function and maladaptive inflammatory mechanisms influence postoperative pain development in advanced age. Elucidation of these neuroimmune phenotypes across age and sex enables the development of novel therapies that can be tailored for improved pain relief.

Post-amputation pain: Comparing pain presentations between adults with and without increased amputated-region sensitivity

OBJECTIVE

Among adults with persistent post-amputation pain, increased amputated-region pain sensitivity may reflect peripheral sensitization or indicate underlying central sensitization. To determine whether underlying central sensitization may contribute to increased pain sensitivity in this population, this study compared clinical signs and symptoms associated with central sensitization between adults with post-amputation pain who demonstrate or lack increased amputated-region sensitivity (as compared to reference data).

DESIGN

Cross-sectional.

SUBJECTS

Ninety-nine adults (60 with a unilateral, transtibial amputation and post-amputation pain, 39 pain-free controls with intact limbs).

METHODS

Participants underwent pain-pressure threshold testing of amputated-region and secondary (non-amputated region) sites and completed outcome measures assessing central sensitization symptoms (Patient-Reported Outcomes Measurement Information System® pain intensity and interference domains, Central Sensitization Inventory). Among the full sample, the presence and frequency of specific central sensitization symptoms were evaluated. Participants with post-amputation pain were then grouped based on whether normalized, amputated-region pain-pressure thresholds fell below (i.e., sensitive) or above (i.e., non-sensitive) the 25th percentile of sex-specific reference data. Between-group differences in normalized secondary-site sensitivity were evaluated using a multivariate analysis of variance; central sensitization symptom scores were compared using a Kruskal-Wallis test.

RESULTS

Noteworthy symptoms associated with central sensitization (e.g., fatigue, sleep disturbance, cognitive difficulty) were reported by 33%-62% of participants. Secondary-site pain sensitivity was greater among individuals with increased amputated-region sensitivity (n = 24) compared to peers without increased amputated-region sensitivity ([n = 36], mean difference > 1.33 standard deviation [SD], p < 0.001). Central sensitization symptom scores, however, were similar between groups (p > 0.187).

CONCLUSIONS

Participants with increased amputated-region sensitivity demonstrate generalized, secondary-site pain hypersensitivity, potentially indicating underlying central sensitization. Central sensitization symptom scores, however, were similar between groups, suggesting differences in physiological pain sensitivity may not manifest in subjective post-amputation pain descriptions.

Integrating mechanistic-based and classification-based concepts into perioperative pain management: an educational guide for acute pain physicians

Chronic pain begins with acute pain. Physicians tend to classify pain by duration (acute vs chronic) and mechanism (nociceptive, neuropathic and nociplastic). Although this taxonomy may facilitate diagnosis and documentation, such categories are to some degree arbitrary constructs, with significant overlap in terms of mechanisms and treatments. In clinical practice, there are myriad different definitions for chronic pain and a substantial portion of chronic pain involves mixed phenotypes. Classification of pain based on acuity and mechanisms informs management at all levels and constitutes a critical part of guidelines and treatment for chronic pain care. Yet specialty care is often siloed, with advances in understanding lagging years behind in some areas in which these developments should be at the forefront of clinical practice. For example, in perioperative pain management, enhanced recovery protocols are not standardized and tend to drive treatment without consideration of mechanisms, which in many cases may be incongruent with personalized medicine and mechanism-based treatment. In this educational document, we discuss mechanisms and classification of pain as it pertains to commonly performed surgical procedures. Our goal is to provide a clinical reference for the acute pain physician to facilitate pain management decision-making (both diagnosis and therapy) in the perioperative period.

Applications of Gene Therapy in Dentistry: A Review Article

Gene therapy promises to possess a good prospect in bridging the gap between dental applications and medicine. The dynamic therapeutic modalities of gene therapy have been advancing rapidly. Conventional approaches are being revamped to be more comprehensive and pre-emptive, which could do away with the need for surgery and medicine altogether. The complementary base sequences known as genes convey the instructions required to manufacture proteins. The oral cavity is one of the most accessible locations for the therapeutic intervention of gene therapy for several oral tissues. In 1990, the first significant trial of gene therapy was overseen to alleviate adenosine deaminase deficiency. The notion of genetic engineering has become increasingly appealing as a reflection of its benefits over conventional treatment modalities. An example of how this technology may alter dentistry is the implementation of gene therapy for dental and oral ailments. The objective of this article is to examine the effects of gene therapy on the field of dentistry, periodontology and implantology. Furthermore, the therapeutic factors of disease therapy, minimal invasion, and appropriate outcome have indeed been taken into consideration.

Stress-induced changes in nociceptive responding post-surgery in preclinical rodent models

Chronic post-surgical pain affects up to 85% of individuals depending on the type of surgery, the extent of inflammation, tissue and/or nerve damage. Pre-surgical stress is associated with greater pain intensity, prolonged recovery and is one of the main risk factors for the development of chronic post-surgical pain. Clinically valid animal models provide an important means of examining the mechanisms underlying the effects of stress on post-surgical pain and identifying potential novel therapeutic targets. This review discusses the current data from preclinical animal studies examining the effect of stress on post-surgical pain, the potential underlying mechanisms and gaps in the knowledge that require further investigation.

Chronic pain and local pain in usually painless conditions including neuroma may be due to compressive proximal neural lesion

It has been unexplained why chronic pain does not invariably accompany chronic pain-prone disorders. This question-driven, hypothesis-based article suggests that the reason may be varying occurrence of concomitant peripheral compressive proximal neural lesion (cPNL), e.g., radiculopathy and entrapment plexopathies. Transition of acute to chronic pain may involve development or aggravation of cPNL. Nociceptive hypersensitivity induced and/or maintained by cPNL may be responsible for all types of general chronic pain as well as for pain in isolated tissue conditions that are usually painless, e.g., neuroma, scar, and Dupuytren's fibromatosis. Compressive PNL induces focal neuroinflammation, which can maintain dorsal root ganglion neuron (DRGn) hyperexcitability (i.e., peripheral sensitization) and thus fuel central sensitization (i.e., hyperexcitability of central nociceptive pathways) and a vicious cycle of chronic pain. DRGn hyperexcitability and cPNL may reciprocally maintain each other, because cPNL can result from reflexive myospasm-induced myofascial tension, muscle weakness, and consequent muscle imbalance- and/or pain-provoked compensatory overuse. Because of pain and motor fiber damage, cPNL can worsen the causative musculoskeletal dysfunction, which further accounts for the reciprocity between the latter two factors. Sensitization increases nerve vulnerability and thus catalyzes this cycle. Because of these mechanisms and relatively greater number of neurons involved, cPNL is more likely to maintain DRGn hyperexcitability in comparison to distal neural and non-neural lesions. Compressive PNL is associated with restricted neural mobility. Intermittent (dynamic) nature of cPNL may be essential in chronic pain, because healed (i.e., fibrotic) lesions are physiologically silent and, consequently, cannot provide nociceptive input. Not all patients may be equally susceptible to develop cPNL, because occurrence of cPNL may vary as vary patients' predisposition to musculoskeletal impairment. Sensitization is accompanied by pressure pain threshold decrease and consequent mechanical allodynia and hyperalgesia, which can cause unusual local pain via natural pressure exerted by space occupying lesions or by their examination. Worsening of local pain is similarly explainable. Neuroma pain may be due to cPNL-induced axonal mechanical sensitivity and hypersensitivity of the nociceptive nervi nervorum of the nerve trunk and its stump. Intermittence and symptomatic complexity of cPNL may be the cause of frequent misdiagnosis of chronic pain.

Pretreatment of the ROS Inhibitor Phenyl-N-tert-butylnitrone Alleviates Sleep Deprivation-Induced Hyperalgesia by Suppressing Microglia Activation and NLRP3 Inflammasome Activity in the Spinal Dorsal Cord

Sleep deprivation, a common perioperative period health problem, causes ocular discomfort and affects postsurgical pain. However, the mechanism of sleep deprivation-induced increased pain sensitivity is elusive. This study aims to explore the role of ROS in sleep deprivation (SD)-induced hyperalgesia and the underlying mechanism. A 48-h continuous SD was performed prior to the hind paw incision pain modeling in mice. We measured ROS levels, microglial activation, DNA damage and protein levels of iNOS, NLRP3, p-P65 and P65 in mouse spinal dorsal cord. The involvement of ROS in SD-induced prolongation of postsurgical pain was further confirmed by intrathecal injection of ROS inhibitor, phenyl-N-tert-butylnitrone (PBN). Pretreatment of 48-h SD in mice significantly prolonged postsurgical pain recovery, manifesting as lowered paw withdrawal mechanical threshold and paw withdrawal thermal latency. It caused ROS increase and upregulation of iNOS on both Day 1 and 7 in mouse spinal dorsal cord. In addition, upregulation of NLRP3 and p-P65, microglial activation and DNA damage were observed in mice pretreated with 48-h SD prior to the incision. Notably, intrathecal injection of PBN significantly reversed the harmful effects of SD on postsurgical pain recovery, hyperalgesia, microglial activation and DNA damage via the NF-κB signaling pathway. Collectively, ROS increase is responsible for SD-induced hyperalgesia through activating microglial, triggering DNA damage and enhancing NLRP3 inflammasome activity in the spinal dorsal cord.