INTRAVENOUS PHENTOLAMINE TEST - AN AID IN THE EVALUATION OF PATIENTS WITH PERSISTENT PAIN AFTER LOW-BACK SURGERY

Background: Persistent pain following surgery in the treatment of chro nic low-back pain patients is still relatively frequent. Most of these patients with persistent pain have clinical signs of neuropathic pain . The neuropathic pain might be sympathetically maintained pain (SMP) or sympathetically independent pain (SIP). Systemic administration of phentolamine, a competitive alpha-adrenergic antagonist, has been used as a diagnostic tool to identify patients with SMP. Methods: Thirty-s even patients with persistent pain after low-back surgery (lumbar lami nectomy, with or without discectomi, or a posterior fusion, with or wi thout decompression) received intravenous phentolamine (0.5 mg/kg over 30 min) in a single-blind, placebo-controlled manner. Prior to this i nfusion the patients were classified clinically into different pain gr oups based on physical examination and imaging findings. An opioid epi dural test blockade was used as a control. Results: Clinical classific ation divided the patients into nociceptive pain (n=7), neuropathic pa in (n=22) and mixed pain (n= 8). In the phentolamine test there were o nly one responder, 34 non-responders and 2 patients were placebo-respo nders. In the control epidural blockade there were 11 non-responders, 23 fentanyl/local anaesthetic-responders and 3 placebo-responders. Con clusions: SMP is either an uncommon cause of persistent pain in this t ype of failed back surgery patients or the phentolamine test, as we pe rformed it, was unable to identify SMP. (C) Acta Anaesthesiologica Sca ndinavica 41 (1997).