Application of changes in serum NOx (nitrite/nitrate) levels measured by a highly sensitive

HPLC-UV method using dolorimetry, based on nerve block for herpes zoster

Abstract

To explore the potential role of nitric oxide (NO) production in patients with pain, the relation between pain and serum NO production was evaluated by changes in pain reactions and serum levels of NOx before and after the nerve block in patients with herpes zoster. Twenty patients aged 68.6±4.0 (seven males and thirteen females) and diagnosed as having herpes zoster infection between C6 and L2 were enrolled in this study. The visual analogue scale (VAS) score of each patient was more than 3. The nerve block was performed by the epidural administration of 6ml of 0.375% ropivacaine. In order to acknowledge pain relief, the VAS value in each patient was recorded before, 30 and 90min after nerve blocking. A each time point, blood samples were obtained from by all patients venipuncture needling. Serum NOx levels were then assessed by a highly sensitive HPLC-UV method. Results were statistically analyzed by two-way ANOVA. (1) In all patients, the VAS value was significantly lowered 30 and 90min after nerve blocking when compared to the value obtained before nerve blocking; (2) The serum NOx level measured 90min after nerve blocking was also significantly less than that measured before nerve blocking. However, these levels in the healthy volunteers did not show any significant change. (3) By studying the three different stages of herpes zoster, such correlation between pain relief and the reduction of serum NOx levels was observed in the middle and later stages of herpes zoster, but not in the early stage. These findings indicate that the progress of the neuropathic pain relates the serum NO productions and that the measurement of serum NOx levels can be an indicator of dolorimetry.