Monitoring adequacy of α-adrenoceptor blockade following systemic phentolamine administration

Srinivasa N. Raja, Jennifer L. Turnquist, Sherif Meleka, James N. Campbell

Research output: Contribution to journalArticlepeer-review

Abstract

Systemic phentolamine administration has been suggested as a diagnostic tool for identifying patients with sympathetically maintained pain (SMP) (Raja et al. 1991). The dose of phentolamine to produce adequate blockade of peripheral α-adrenoceptor function has, however, not been previously determined. In this study, the effects of two different doses of phentolamine on peripheral sympathetic vasoconstrictor function were investigated. One-hundred and seventeen (117) patients with chronic extremity pain underwent 130 phentolamine diagnostic tests using two different doses of phentolamine (0.5 mg/kg over 20 min (n = 60) and 1 mg/kg-over 10 min (n = 59)). Eleven (11) patients did not receive phentolamine during the test. Cutaneous temperature was measured in the distal extremity before and after administration of phentolamine. In a subset of patients, baseline blood flow and sympathetically mediated vasoconstrictor response (SMR) to deep inhalation were measured on glabrous skin using laser Doppler flowmetry. SMR was elicited with a 5-sec maximal inspiratory gasp. A dose-related increase in cutaneous temperature was observed. In addition, baseline blood flow increased and SMR was attenuated after both doses of phentolamine, but to a greater degree after the 1 mg/kg dose. However, SMR was not completely attenuated, even after administration of the higher phentolamine dose. These results indicate that a phentolamine dose of 1 mg/kg over 10 min more completely blocks α-adrenoceptor function than a dose of 0.5 mg/kg over 20 min. We therefore recommend that to ensure adequate α-adrenoceptor blockade the higher phentolamine dose be used in the phentolamine diagnostic test for SMP.

Original languageEnglish (US)
Pages (from-to)197-204
Number of pages8
JournalPain
Volume64
Issue number1
DOIs
StatePublished - Jan 1996

Keywords

  • Laser Doppler
  • Phentolamine
  • Reflex sympathetic dystrophy
  • Sympathetic nervous system
  • Sympathetically maintained pain
  • α-Adrenoceptor blocker

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology
  • Anesthesiology and Pain Medicine

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