Preoperative Predictors of Complex Regional Pain Syndrome Outcomes in the 6 Months Following Total Knee Arthroplasty

This prospective observational study evaluated preoperative predictors of complex regional pain syndrome (CRPS) outcomes in the 6 months following total knee arthroplasty (TKA). Participants were n = 110 osteoarthritis patients (64.5% female) undergoing unilateral TKA with no prior CRPS history. Domains of negative affect (depression, anxiety, catastrophizing), pain (intensity, widespread pain, temporal summation of pain [TSP]), pain interference, sleep disturbance, and pro-inflammatory status (tumor necrosis factor-alpha [TNF-a]) were assessed preoperatively. CRPS outcomes at 6-week and 6-month follow-up included the continuous CRPS Severity Score (CSS) and dichotomous CRPS diagnoses (2012 IASP criteria). At 6 months, 12.7% of participants met CRPS criteria, exhibiting a "warm CRPS" phenotype. Six-week CSS scores were predicted by greater preoperative depression, anxiety, catastrophizing, TSP, pain intensity, sleep disturbance, and TNF-a (P's < .05). Provisional CRPS diagnosis at 6 weeks was predicted by higher preoperative TSP, sleep disturbance, and TNF-a (P's < .05). CSS scores at 6 months were predicted by more widespread and intense preoperative pain, and higher preoperative TSP, pain interference, and TNF-a (P's < .01). CRPS diagnosis at 6 months was predicted only by more widespread and intense pain preoperatively (P's < .05). Risk for CRPS following TKA appears to involve preoperative central sensitization and inflammatory mechanisms. Preoperative negative affect is unlikely to directly influence long-term CRPS risk. PERSPECTIVE: This article identifies preoperative predictors of CRPS features at 6 months following total knee arthroplasty, including more widespread pain and higher pain intensity, temporal summation of pain, pain interference, and tumor necrosis factor-alpha levels. Findings suggest the importance of central sensitization and inflammatory mechanisms in CRPS risk following tissue trauma.

N-methyl-d-aspartate receptor subunit 2B on keratinocyte mediates peripheral and central sensitization in chronic post-ischemic pain in male rats

The spinal N-methyl-d-aspartate (NMDA) receptor, and particularly its NR2B subunit, plays a pivotal role in neuropathic pain. However, the role of peripheral NMDA receptor in neuropathic pain is less well understood. We first treated cultured human keratinocytes, HaCaT cells with NMDA or NR2B-specific antagonist, ifenprodil and evaluated the level of total and phosphorylated NR2B at 24 h using Western blot. Next, using the chronic post-ischemia pain (CPIP) model, we administered NMDA or ifenprodil subcutaneously into the hind paws of male rats. Nociceptive behaviors were assessed by measuring mechanical and thermal withdrawal thresholds. Expression and phosphorylation of NR2B on keratinocyte were analyzed at 6, 12, 18, and 24 h on day 1 (initiation of pain) as well as day 2, 6, 10 and 14 (development and maintenance of pain) after the ischemia. The level of peripheral sensitization-related proteins (nuclear factor-κB (NF-κB), extracellular regulated protein kinases (ERK), and interleukin-1β (IL-1β)) in epidermis and dorsal root ganglion (DRG) were evaluated by immunofluorescence and western blot. Central sensitization-related C-fos induction, as well as astrocytes and microglia activation in the spinal cord dorsal horn (SDH) were studied using immunofluorescence. Administration of NMDA upregulated NR2B phosphorylation on HaCaT cells. CPIP-induced mechanical allodynia and thermal hyperalgesia were intensified by NMDA and alleviated by ifenprodil. CPIP resulted in an early upregulation of NR2B (peaked at 24 h) and late phosphorylation of NR2B (peaked at 14d) in hindpaw keratinocytes. CPIP led to an upregulation and phosphorylation of NF-κB and ERK, as well as an increased IL-1β production in the ipsilateral skin and DRG. CPIP-associated c-fos induction in SDH persisted from acute to chronic stages after ischemia, while microglia and astrocyte activation were only observed in chronic phase. These CPIP-induced changes were also suppressed by ifenprodil administered subcutaneously in the hind paw. Our findings reveal a previously unrecognized role of keratinocyte NMDA receptor subunit 2B in peripheral and central nociceptive sensitization induced by CPIP.

Heat shock protein 70 protects the quail cecum against oxidant stress, inflammatory injury, and microbiota imbalance induced by cold stress

The intent of this study was to investigate the effects of cold stress on oxidative indexes, inflammatory factors, and microbiota in the quail cecum. A total of 192 male quails (15-day-old) were randomly divided into 12 groups (16 in each group) and were exposed to acute (up to 12 h) and chronic (up to 20 D) cold stress at 12 ± 1°C. After cold stress treatment, we examined morphological damage, oxidative stress indexes, inflammatory factors, and intestinal microbiota. Results of morphological examination showed that both acute and chronic cold stress can lead to cecal tissue injury. In addition, both acute and chronic cold stress, especially chronic cold stress can influence the activity of oxidative stress mediators. Glutathione (GSH) and glutathione peroxidase (GSH-Px) activities decreased significantly (p < 0.05), while the nitric oxide (NO) content and inducible nitric oxide synthase (iNOS) activity increased significantly (p < 0.05). Moreover, mRNA levels of inflammatory factors cyclooxygenase-2 (COX-2), prostaglandin E synthase (PTGES), and heat shock protein 70 (Hsp70) were higher in both acute and chronic cold stress groups when compared with the control group (p < 0.05). Furthermore, the intestinal microbiota was changed in both the acute and chronic cold stress groups. These results suggested that cold stress caused oxidative stress and inflammatory injury in cecal tissues, influenced cecal microbiota, and increased expression of Hsp70, which may contribute in protecting the cecum against cold stress in quails.

A disturbance in sensory processing on the affected side of the body increases limb pain in complex regional pain syndrome

OBJECTIVES

The aim of this study was to determine whether a central disturbance in somatosensory processing contributes to limb pain in complex regional pain syndrome (CRPS).

METHODS

In 37 patients with CRPS, the effect of cooling the ipsilateral forehead on pain in the affected limb was compared with the effect of cooling the contralateral forehead. In addition, symptoms associated with cold-evoked limb pain were explored.

RESULTS

Limb pain generally increased when the ipsilateral side of the forehead was cooled but did not change when the contralateral side of the forehead was cooled. Increases were greatest in patients with heightened sensitivity to cold, brushing, and pressure-pain in the ipsilateral forehead, in patients with heightened sensitivity to pressure-pain in the limbs, and in patients with chronic symptoms. In contrast, sensitivity to light touch was diminished in the CRPS-affected limb of patients whose limb pain remained unchanged or decreased during ipsilateral forehead cooling.

CONCLUSIONS

These preliminary findings suggest that a central disturbance in sensory processing and pain modulation, which extends beyond the affected limb to the ipsilateral forehead, contributes to symptoms in a subgroup of patients with CRPS.

Up-regulation of cutaneous α1 -adrenoceptors in complex regional pain syndrome type I

BACKGROUND

In a small radioligand-binding study of cutaneous α1 -adrenoceptors in complex regional pain syndrome (CRPS), signal intensity was greater in the CRPS-affected limb than in controls. However, it was not possible to localize heightened expression of α1 -adrenoceptors to nerves, sweat glands, blood vessels, or keratinocytes using this technique.

METHODS

To explore this in the present study, skin biopsies were obtained from 31 patients with CRPS type I and 23 healthy controls of similar age and sex distribution. Expression of α1 -adrenoceptors on keratinocytes and on dermal blood vessels, sweat glands, and nerves was assessed using immunohistochemistry.

RESULTS

α1 -Adrenoceptors were expressed more strongly in dermal nerve bundles and the epidermis both on the affected and contralateral unaffected side in patients than in controls (P<0.05). However, expression of α1 -adrenoceptors in sweat glands and blood vessels was similar in patients and controls. α1 -Adrenoceptor staining intensity in the CRPS-affected epidermis was associated with pain intensity (P < 0.05), but a similar trend for nerve bundles did not achieve statistical significance.

DISCUSSION

Epidermal cells influence nociception by releasing ligands that act on sensory nerve fibers. Moreover, an increased expression of α1 -adrenoceptors on nociceptive afferents has been shown to aggravate neuropathic pain. Thus, the heightened expression of α1 -adrenoceptors in dermal nerves and epidermal cells might augment pain and neuroinflammatory disturbances after tissue injury in patients with CRPS type I.

Perioperative management for patients with complex regional pain syndrome

SUMMARY Our knowledge of complex regional pain syndrome extends from the time of the American Civil War until today. Traumatic or surgical insults can be the precipitating factors in normal patients and can therefore be significant in the exacerbation of the condition. Complex regional pain syndrome patients complain of continuing pain that is disproportionate in severity to the inciting event. The pain is usually accompanied by sensory symptoms, such as allodynia or hyperalgesia, and vasomotor changes, such as changes in color or temperature. There has been increasing research on predicting the development of postoperative complex regional pain syndrome and its prevention. Management includes sympathetic blockades, spinal cord stimulation and medications (such as anticonvulsants, antidepressants, local anesthetics, NMDA antagonists and α-2-adrenergic agonists). In the last few years, several newer medications and supplements to prevent and treat the condition have been studied.