Publication | Open Access
Systemic Alpha-adrenergic Blockade with Phentolamine
296
Citations
0
References
1991
Year
Pain MedicineNeuropathic PainPharmacotherapySympathetic GangliaAnalgesiaNeuromuscular BlockadeAlpha-adrenergic PharmacologyAdrenal GlandSympathetic Nervous SystemPain ManagementNeurologyHealth SciencesLocal Anesthetic PharmacologyAdrenal DiseaseNervous SystemPharmacologyPain ResearchPain TreatmentPain ReliefNeurophysiologySystemic Alpha-adrenergic BlockadeAnesthesiaMedicineEmergency MedicineAnesthesiology
Sympathetically maintained pain is typically diagnosed by assessing pain relief during local anesthetic blockade of the sympathetic ganglia that supply the painful area. This study aimed to evaluate whether systemic alpha‑adrenergic blockade with phentolamine could serve as an alternative diagnostic test for sympathetically maintained pain by comparing its effects to local anesthetic sympathetic ganglion blocks in 20 chronic pain patients. Patients received randomized, blinded blocks on separate days, with pain intensity recorded every five minutes before, during, and after each block while the investigator and patients were unaware of the timing of intravenous phentolamine (25–35 mg). Pain relief from phentolamine and local anesthetic blocks correlated strongly (r = 0.84) with no significant difference in maximum relief, and nine patients achieved over 50 % reduction with both, confirming intravenous phentolamine as a sensitive diagnostic alternative for sympathetically maintained pain.
The diagnosis of sympathetically maintained pain (SMP) is typically established by assessment of pain relief during local anesthetic blockade of the sympathetic ganglia that innervate the painful body part. To determine if systemic alpha-adrenergic blockade with phentolamine can be used to diagnose SMP, we compared the effects on pain of local anesthetic sympathetic ganglion blocks (LASB) and phentolamine blocks (PhB) in 20 patients with chronic pain and hyperalgesia that were suspected to be sympathetically maintained. The blocks were done in random order on separate days. Patients rated the intensity of ongoing and stimulus-evoked pain every 5 min before, during, and after the LASB and PhB. Patients and the investigator assessing pain levels were blinded to the time of intravenous administration of phentolamine (total dose 25-35 mg). The pain relief achieved by LASB and PhB correlated closely (r = 0.84), and there was no significant difference in the maximum pain relief achieved with the two blocks (t = 0.19, P greater than 0.8). Nine patients experienced a greater than 50% relief of pain and hyperalgesia from both LASB and PhB and were considered to have a clinically significant component of SMP. We conclude that alpha-adrenergic blockade with intravenous phentolamine is a sensitive alternative test to identify patients with SMP.