Monitoring adequacy of alpha-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: Abnormal coupling between primary sensory afferent and sympathetic efferent neurons has been documented in animal models of neuropathic and inflammatory pain. These models have been used to improve the understanding of similar pain states in humans. Therapies that modulate sympathetic nervous system function have been advocated for the treatment of chronic pain of diverse etiology. One such therapy, the phentolamine infusion test, reduces pain by pharmacologic antagonism of peripheral α-adrenergic receptors. Patients who show reduction in pain after phentolamine infusion may benefit from future therapies designed to modulate sympathetic tone or adrenergic receptor function. Copyright © 2001 by W.B. Saunders CompanyTechniques in Regional Anesthesia [amp ] Pain Management 01/2001; 5(3):123-128.
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ABSTRACT: A majority of pancreatic cancer patients present with pain at the time of diagnosis. Pain management can be challenging in light of the aggressive nature of this cancer. Apart from conventional pharmacotherapy, timely treatment with neurolytic celiac plexus block (NCPB) has been shown to be of benefit. NCPB has demonstrated efficacious pain control in high quality studies with analgesic effects lasting one to two months. NCPB has also shown to decrease the requirements of narcotics, and thus decrease opioid related side effects. Another option for the control of moderate to severe pain is intrathecal therapy (IT). Delivery of analgesic medications intrathecally allows for lower dosages of medications and thus reduced toxicity. Both of the above mentioned interventional procedures have been shown to have low complication rates, and be safe and effective. Ultimately, comprehensive pancreatic cancer pain management necessitates understanding of pain mechanisms and delivery of sequential validated therapeutic interventions within a multidisciplinary patient care model.Cancers. 01/2010; 3(1):43-60.