Capillary blood gas analysis in complex regional pain syndrome: a pilot study

Background: The pathophysiology of complex regional pain syndrome type 1 (CRPS 1) is still a matter of debate. An inflammatory reaction may cause the syndrome. Increasing evidence points to a role for impairment of oxygen metabolism in the affected limb.

Methods: In this pilot study (16 patients) we performed capillary blood gas analysis in extremities with acute CRPS 1, in order to assess oxygen saturation and lactate concentrations. Comparison was made with the unaffected limb for capillary blood pH, pO2, SaO2, and lactate and glucose concentrations.

Results: No statistically significant differences could be found.

Conclusions: Capillary blood gas analysis is not useful to detect changes in oxygen saturation and lactate concentrations in CRPS 1.

Mechanical hyperalgesia in complex regional pain syndrome: A role for TNF- ?

Plasma concentrations of soluble tumor necrosis factor alpha (TNF-alpha) receptor type I (sTNF-RI) were assessed in two complex regional pain syndrome (CRPS) patient groups (n = 30 and n = 16) and healthy controls (n = 25). Patients with CRPS and mechanical hyperalgesia had higher levels of sTNF-RI (1,661.8 +/- 146.8 pg/mL) compared with those with CRPS with identical clinical appearance but without hyperalgesia (1,155.9 +/- 56.3 pg/mL) and controls (1,239.5 +/- 42.9 pg/mL). This study suggests involvement of TNF-alpha in mechanical hyperalgesia of CRPS.

Immune responses to Campylobacter and serum autoantibodies in patients with complex regional pain syndrome

We hypothesised that some complex regional pain syndromes (CRPS) may have a postinfectious and/or autoimmune basis. Sera from 92 patients with CRPS and 92 controls were investigated for immunoreactivity to Campylobacter strains and to rodent tissues. Both IgA-antibodies to Campylobacter and tissue-specific reactivity were often present in patients with short disease duration (< or = 1.5 years). Patients with minimal preceding trauma had stronger nervous tissue-specific reactivity than other patients, regardless of disease duration. These results provide preliminary evidence for immune activation early in CRPS and, additionally, that patients with minimal trauma may comprise an autoimmune subgroup.

Plasma endothelin-1 levels in patients with complex regional pain syndrome

The clinical characteristics of complex regional pain syndrome (CRPS)--spontaneous and stimulus-evoked pain, autonomic abnormalities, motor dysfunction, and trophic changes in the affected limb--are well known. However, its pathogenesis is unclear, and the diagnosis is often delayed, in part due to lack of objective laboratory tests. Endothelin-1 (ET-1) is a potent vasoconstrictor that has recently been shown to produce pain, allodynia, edema, and muscle weakness, as well as to exert a direct excitatory effect on nociceptive afferents. Furthermore, new evidence indicates that ET-1 is involved in various cancer- and non-cancer-related painful conditions. The aim of the present explorative study was to determine the ET-1 plasma levels in patients with CRPS in an attempt to identify a 'laboratory marker' for CRPS and to search for evidence suggesting that ET-1 may be involved in the pathogenesis of CRPS. ET-1 plasma levels were determined in 20 severely affected CRPS patients, in eight patients with non-CRPS chronic painful conditions, and in 10 healthy volunteers. The results showed that there were no significant differences in ET-1 plasma levels between the three groups. We conclude that the plasma level of ET-1 cannot be regarded as a 'marker' for CRPS. Yet, the possibility that ET-1 is involved in the pathophysiology of CRPS has not been excluded and deserves further investigation.

Increased systemic catecholamines in complex regional pain syndrome and relationship to psychological factors: a pilot study

We have demonstrated that subjects with complex regional pain syndrome (CRPS) have asymmetric venous pool plasma concentrations of norepinephrine (NE) when affected and unaffected limbs are compared, with most demonstrating decreased NE levels in the affected limb. This pilot study explored whether systemic venous plasma catecholamine levels in CRPS subjects with sympathetically maintained pain (SMP) differ from those found in healthy volunteers. We also explored whether catecholamine levels were correlated with scores on psychometric measures of depression, anxiety, and personality. Venous blood samples from 33 CRPS/SMP patients (from unaffected limbs) and 30 healthy control subjects were assayed for plasma NE and epinephrine (E) concentrations. Plasma NE levels were significantly higher in the CRPS group (P < 0.001). Statistical comparisons of E levels across groups did not achieve significance (P < 0.06), although 52% of CRPS/SMP patients had E levels exceeding the 95% confidence interval based on control data. Significant positive correlations were found between E levels and scores on the Beck Depression Inventory and Scales 1, 3, and 6 on the Minnesota Multiphasic Personality Inventory-2 (all P < 0.05). This preliminary work suggests that increased NE and E levels in CRPS/SMP patients may result from the pain of CRPS, consequent affective distress, or both. Alternatively, our findings could reflect premorbid adrenergic hyperactivity caused by affective, endocrine, or other pathology, which might predispose these individuals to develop the syndrome. Definitive studies are needed to examine these hypotheses in detail.

Facilitated neurogenic inflammation in unaffected limbs of patients with complex regional pain syndrome

Pain, edema, increased skin temperature, reddening and trophic changes characterize complex regional pain syndrome (CRPS). Recently, we have been able to show facilitated neurogenic inflammation on the affected limb. In the current study unaffected limbs were examined after resolution of the CRPS symptoms to assess possible generalized changes predisposing to CRPS. In 12 patients and in 12 healthy volunteers dermal microdialysis in combination with electrical C-fiber stimulation was employed to induce neuropeptide release. Dialysate protein concentration and axon reflex vasodilation were measured. Neither in patients nor in controls did electrical stimulation lead to protein extravasation, while axon reflex vasodilation was significantly enhanced even on the patients' unaffected limbs (P < 0.05). Our results support the hypothesis that facilitated neurogenic inflammation is a predisposing factor for CRPS. The lack of protein extravasation indicates that an initiating trauma is necessary to induce neuropeptide up-regulation in primary afferents.

Does a Viral Infection Cause Complex Regional Pain Syndrome?

In 1990 Omura, Y. reported that Herpes Simplex Virus Type 1 as the major cause of chronic intractable pain and its effective treatment using mixture of EPA & DHA with Selective Drug Uptake Enhancement Method. Subsequently among the other causes of pain, he included Chlamydia Trachomatis, Borrelia Burgdorferi, Mycobacterium Tuberculosis, human Herpes Virus type 6, and Circulatory Disturbances. In order to test possible involvement of viral infection in Complex Regional Pain Syndrome (CRPS), a disease which usually occurs in the extremities, we did a study of 17 patients with CRPS. They were examined for Herpes Simplex Virus (HSV) and Varicella Zoster Virus (VZV) by measuring IgG and IgM antibody titers, and 14 of these patients were also examined for Cytomegalo-Virus (CMV). As a control group 100 healthy Japanese employees at SRL, Inc. were also studied. In CRPS group, HSV IgG was positive in 12 of the 17 patients with an average antibody titer of 90.0 EIA value. VZV IgG was positive in all 17 patients with an average antibody titer of 26.8 EIA value. CMV IgG was positive in all 14 patients with an average antibody titer of 66.6 UA/ml. In control group, HSV IgG was positive in 54 subjects with an average antibody titer of 42.3 EIA value. VZV IgG was positive in 97 subjects with an average antibody titer of 26.2 EIA value. CMV IgG was positive in 82 subjects. There were no significant differences of positive rate of IgG antibody for the three viruses between patient and control groups. Although the difference was not significant, the average antibody titers of HSV in CRPS group were more than twice of those in healthy group. Antibody titers were almost equal in both groups for VZV. Possibly, some people in the control group who had latent virus, were also asymptomatic. In 2000, Takasaki, I. et al. in a separate animal study, inoculated with HSV Type-I the shin of the mouse causing allodynia and hyperalgesia (which are some of the characteristic findings seen in CRPS in humans). Also, VZV, which causes shingles which is sometimes followed by Post-Herpetic Neuralgia (PHN), is in the same family of HSV. As PHN resembles CRPS in symptoms, it is possible that HSV contributes to CRPS. Therefore, virus infection theory is an attractive hypothesis that accounts for many enigmas of CRPS.

Local sympathetic denervation in painful diabetic neuropathy

This study assessed whether painful diabetic neuropathy is associated with abnormal sympathetic nervous function in the affected limbs. Nine patients with diabetes (four men, five women; age 61 +/- 7 years) and painful peripheral neuropathy of the feet, but without evidence of generalized autonomic neuropathy, underwent intravenous infusion of tritiated norepinephrine (NE) and sampling of arterial and venous blood in both feet and in one arm to quantify the rate of entry of NE into the local venous plasma (NE spillover). In the same patients, positron emission tomography (PET) scanning after intravenous injection of the sympathoneural imaging agent 6-[(18)F]fluorodopamine was used to visualize sympathetic innervation and after intravenous [(13)N]ammonia to visualize local perfusion. The results were compared with those in the feet of normal volunteers and in an unaffected foot of patients with unilateral complex regional pain syndrome (CRPS). In addition, neurochemical results obtained in painful diabetic neuropathy were compared with those obtained in diabetic control patients with painless neuropathy and diabetic control patients without neuropathy. Local arteriovenous difference in plasma NE levels (DeltaNE(AV)) and NE spillover in the arms did not differ across the groups. However, DeltaNE(AV) in the feet was significantly less in the group with painful diabetic neuropathy than in the control groups. Also NE spillover in the feet tended to be lower in painful neuropathy. DeltaNE(AV) of diabetic control patients without neuropathy (n = 6) resembled values in the control groups without diabetes, whereas patients with painless diabetic neuropathy (n = 6) had evidence suggesting partial loss of sympathetic innervation. PET scanning revealed decreased flow-corrected 6-[(18)F]fluorodopamine-derived radioactivity in patients with painful diabetic neuropathy, compared with values in normal volunteers and patients with CRPS. The results provide neurochemical and neuroimaging evidence for regionally selective sympathetic denervation in the painful feet of patients with diabetic neuropathy.

The important role of neuropeptides in complex regional pain syndrome

OBJECTIVE

To test the contribution of neurogenic inflammation and neuropeptide release to the pathophysiology of complex regional pain syndrome (CRPS).

BACKGROUND

CRPS is characterized by edema and increased skin temperature, sympathetic dysfunction and pain, or hyperalgesia. This investigation was prompted by a recent study by the authors that suggested a facilitated neurogenic inflammation in CRPS.

METHODS

In addition to physical examination, calcitonin gene-related peptide (CGRP) serum concentrations were measured using a radioimmunoassay (RIA) for human CGRP in 19 patients with acute CRPS, on the affected and unaffected sides (n = 13), before and 9 months after therapy (n = 9). In addition, an age- and sex-matched group of 16 healthy controls was investigated.

RESULTS

In blood from the cubital vein, CGRP levels in patients with CRPS (122.2 +/- 14.6 pmol/L) were increased (controls 83.8 +/- 6.7 pmol/L, p < 0.03). There was no difference between the affected and unaffected sides. There was, however, a reduction of serum CGRP after therapy (acute disease: 141.2 +/- 18.5 pmol/L, after therapy 106.7 +/- 11.3 pmol/L, p < 0.005); absolute CGRP levels then no longer differed from controls. Increased serum CGRP was correlated to the incidence of nerve lesions (p < 0.02) and hyperhidrosis (p < 0.04). There was no correlation to other clinical symptoms, duration of CRPS, or pain. However, normalization of CGRP after therapy was accompanied by clinical improvement of local inflammatory signs, but not by pain reduction.

CONCLUSIONS

Increased systemic CGRP levels in patients with acute CRPS suggest neurogenic inflammation as a pathophysiologic mechanism contributing to vasodilation, edema, and increased sweating. However, pain and hyperalgesia, in particular in chronic stages, were independent of increased neuropeptide concentration.

Innate cytokine profile in patients with complex regional pain syndrome is normal

Complex regional pain syndrome (CRPS) is a disabling disease characterized by the classic symptoms and signs of inflammation. In this study we investigated the innate cytokine profile in patients with CRPS to determine a possible role of the immune system in the pathophysiology of CRPS. The cytokine profile before and after lipopolysaccharide and thrombin stimulation was determined in 26 severely affected CRPS patients and 20 healthy controls. No difference in the production of pro- and anti- inflammatory cytokines between patients and controls was found. Hence, our results do not support a role of genetic factors responsible for the cytokine profile in the pathophysiology of CRPS. These findings encourage further investigations of mechanisms responsible for neurogenic-induced inflammation.