Monitoring adequacy of α-adrenoceptor blockade following systemic phentolamine administration
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 alpha-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 alpha-adrenoceptor function than a dose of 0.5 mg/kg over 20 min. We therefore recommend that to ensure adequate alpha-adrenoceptor blockade the higher phentolamine dose be used in the phentolamine diagnostic test for SMP.
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ABSTRACT: Complex Regional Pain Syndrome (CRPS) is a limb-confined post-traumatic pain syndrome with sympathetic features. The cause is unknown, but the results of a randomized crossover trial on low-dose IVIG treatment point to a possible autoimmune mechanism. We tested purified serum immunoglobulin G (IgG) from patients with longstanding CRPS for evidence of antibodies interacting with autonomic receptors on adult primary cardiomyocytes, comparing with control IgG from healthy and disease controls, and related the results to the clinical response to treatment with low-dose intravenous immunoglobulins (IvIG). We simultaneously recorded both single cell contractions and intracellular calcium handling in an electrical field. Ten of 18 CRPS preparations and only 1/57 control preparations (p<0.0001) increased the sensitivity of the myocytes to the electric field and this effect was abrogated by pre-incubation with alpha1a receptor blockers. By contrast, effects on baseline calcium were blocked by pre-incubation with atropine. Interestingly, serum-IgG preparations from all four CRPS patients who had responded to low-dose IVIG with meaningful pain relief were effective in these assays, although 4/8 of the non-responders were also active. To see if there were antibodies to the alpha1a receptor, CRPS-IgG was applied to alpha 1a receptor transfected rat1-fibroblast cells. The CRPS serum IgG induced calcium flux, and FACS showed that there was serum IgG binding to the cells. The results suggest that patients with longstanding CRPS have serum antibodies to alpha 1a receptors, and that measurement of these antibodies may be useful in the diagnosis and management of the patients.Pain 09/2014; 155(11). DOI:10.1016/j.pain.2014.09.022 · 5.64 Impact Factor
Article: Reply to Bonicalzi and CanaveroPain 01/1999; 79(2):318-319. DOI:10.1016/S0304-3959(98)00174-2 · 5.84 Impact Factor
Pain 01/1999; 79(2):319-321. DOI:10.1016/S0304-3959(98)00189-4 · 5.84 Impact Factor