TRANSITION OF ACUTE HERPETIC PAIN FROM SYMPATHETICALLY DEPENDENT PAIN INTO SYMPATHETICALLY INDEPENDENT PAIN

*K. Higa, K. Hirata, H. Yotsui, M. Ishibashi, M. Matsunaga, F. Hayashi Department of Anesthesiology, Fukuoka University School of Medicine, Fukuoka, Japan

Antiviral drugs effective against varicella-zoster virus shorten
duration of zoster-associated pain. However, they cannot promptly relieve severe acute herpetic pain. Nerve blocks with local anesthetics can relieve even such severe acute herpetic pain; however, repeated nerve blocks are needed to relieve it. We have adopted continuous epidural block with a small infusion rate of local anesthetics to treat patients with severe acute herpetic pain. However, some patients showed recurrence of pain despite continuous epidural block. Since recurrence of pain during continuous epidural block may indicate transition of acute herpetic pain from sympathetically dependent pain into sympathetically independent one, we studied what factors influenced recurrence of acute herpetic pain and when acute herpetic pain recurred during continuous epidural block.
Patients admitted to our department because of severe acute herpetic pain from January 1992 to December 1999 were analyzed retrospectively. All patients were referred to us because conventional treatments including antiviral and non-steroidal anti-inflammatory drugs could not relieve their severe acute herpetic pain. Patients with trigeminal and cervical involvement received upper thoracic epidural block that was intended to block Th1-Th4 segments. Patients affected with other dermatomes received
epidural block that was aimed to block the affected segment. All patients received continuous infusion of 0.25% or 0.5% bupivacaine 0.3-1.5 ml/hr.
Recurrence of the pain was noted in 28 of 228 patients (12.3%). It occurred 17.8 + 7.4 days after the onset of skin eruptions. There was no significant difference in age between patients who had and did not have recurrence of pain (64.6 + 15.4 vs. 58.2 + 17.2 years [SD]; p=0.34). Recurrence of pain was noted in 1 of 33 patients (0.3%) with mild skin lesions, 5 of 94 patients (5.3%) with moderate skin lesions, and 22 of 97 patients (22.7%) with severe skin lesions (severe vs mild, p=0.009; severe vs moderate, p=0.0006).
Our findings suggest that acute herpetic pain becomes sympathetically independent around three weeks after the onset of skin lesions of herpes zoster in some patients with severe skin lesions.

Corresponding Author: K. Higa, M.D., Professor of Anesthesiology,
Department of Anesthesiology, Fukuoka University School of Medicine, 7-45-1, Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan