Pain
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In a previous report we presented a novel behavioral model of neuropathic pain disorders, produced in rat by a unilateral ligation of about half of the sciatic nerve. The model is characterized by rapid onset of behaviors suggesting spontaneous pain and disordered responses to non-noxious and noxious stimuli. These include reduced withdrawal thresholds to repetitive touch in the partially deafferented skin ('touched-evoked hyperesthesia'), touch-evoked allodynia, reduced withdrawal thresholds to noxious thermal stimuli and exaggerated responses to noxious heat and mechanical stimuli ('thermal hyperalgesia'). ⋯ Reversible sympathectomy was carried out using guanethidine injected intraperitoneally in 3 experiments, each at a different time in relation to the partial nerve injury. We found that: (1) sympathectomy performed several months postoperatively alleviated the sensory disorders bilaterally; (2) sympathectomy prior to nerve injury partially prevented the appearance of thermal hyperalgesia but did not affect hyperesthesia to repetitive touch; and (3) sympathectomy at the time of nerve injury aggravated the sensory disorders during the first few days. As maintenance and production of the sensory disorders in this animal model depended on sympathetic nervous outflow, we conclude that the rats were suffering from a syndrome analogous to sympathetically maintained causalgia in man.
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Clinical Trial
Prevalence, onset, and risk of psychiatric disorders in men with chronic low back pain: a controlled study.
This study used structured diagnostic interviews and DSM-III criteria to assess lifetime prevalence and pre-morbid risk of psychiatric disorder in a sample of men with long-standing chronic back pain (CLPB) attending a primary care clinic. A control group of age and demographically matched men without history of back pain was also studied. Compared to controls, men with CLBP had significantly higher lifetime rates of major depression (32% vs. 16%), alcohol use disorder (64.9% vs. 38.8%), and a major anxiety disorder (30.9% vs. 14.3%). ⋯ After age of pain onset, CLBP subjects had over 9 times the risk of developing major depression, but had similar rates of developing alcoholism. We conclude that (1) alcohol use disorders rather than depression may increase risk of developing CLBP, and (2) risk of new onset and recurrent major depression remains high for men throughout their pain career. This suggests that psychological adaptation to long-standing pain may be less successful than previously thought, especially with regard to recurrent mood disorder.
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Three patients with terminal malignancy reporting ineffective analgesia using systemic and subsequently spinal opiates were treated with subcutaneous infusion of 10% lidocaine hydrochloride. During the infusion, reasonably stable blood concentrations were achieved and maintained using a subcutaneous infusion at varying dose rates over days to months with improvement of the pain complaints which continued to be refractory to conventional analgesics. Blood lidocaine levels obtained at regular intervals revealed effective concentrations between 2 and 5 micrograms/ml for each patient.
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Randomized Controlled Trial Clinical Trial
CSF and blood pharmacokinetics of hydromorphone and morphine following lumbar epidural administration.
Sixteen consenting patients scheduled for elective thoracotomy were enrolled into a randomized trial of epidural morphine and hydromorphone. Each patient had a lumbar epidural catheter placed preoperatively for the purpose of post-thoracotomy analgesia. Shortly before the end of the operative procedure each patient received 5 mg of morphine and 0.75 mg of hydromorphone via the epidural catheter. ⋯ The mean peak CSF opioid concentrations of 1581 ng/ml for morphine and 309 ng/ml for hydromorphone occurred 60 min after epidural administration. The blood and CSF pharmacokinetic profiles for morphine and hydromorphone are presented. These profiles are similar for the two drugs after lumbar epidural administration.