Pain
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Both children and adults with cognitive impairment (CI) have historically been excluded from research examining pain. This is unfortunate since patients with CI may be at higher risk for experiencing pain or having their pain undertreated due to the difficulty of pain assessment and communication. There are now several published reports about the general pain experience of both adult and pediatric patients with cognitive impairment. ⋯ Analgesic administration data include type and amount of opioid, type of non-opioid medication, and prescribed discharge medications. Results of this study show that children with CI undergoing surgery received less opioid in the perioperative period than children without CI. However, children with CI received comparable amounts and types of analgesics in the postoperative period as children without CI.
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Comparative Study
Reduced heat sensitivity and epidermal nerve fiber immunostaining following single applications of a high-concentration capsaicin patch.
Capsaicin-containing plant extracts have been used as topical treatments for a variety of pain syndromes for many centuries. Current products containing capsaicin in low concentrations (usually 0.025-0.075% w/w) have shown efficacy against a variety of pain conditions in clinical studies. However, in order to produce significant analgesic effects, these formulations require frequent re-dosing, often as much as three to five times daily for several weeks. ⋯ The results show a significant reduction of heat, but not cold, sensitivity and reduction of ENF immunostaining with high-capsaicin concentration patch applications for 60 or 120 min, compared to placebo patch applications. Application sites exposed to low-capsaicin concentration (0.04%w/w) patches for 120 min or high-concentration patches for 30 min were not significantly different from placebo with respect to either thermal threshold detection or ENF immunostaining. The ability of a single 60 min high-concentration patch application to mimic effects produced by prolonged exposure to low-concentration capsaicin creams suggests a new approach to the management of chronic pain syndromes.
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We have examined the effect of an intradermal injection of phenylephrine (1mg/0.1 ml), an alpha-1-adrenoceptor agonist in normal subjects, and patients with sympathetically-independent (SIP) and sympathetically-maintained pain (SMP). Normal subjects and SIP patients experienced only brief stinging pain, while subsets of both sympathectomized and non-sympathectomized SMP patients (6/9 and 4/8, respectively) experienced an additional abnormal pain response accompanied by mechano-allodynia around the injection site. ⋯ Abnormal pain response evoked by norepinephrine or phenylephrine injection in the ipsilateral symptomatic limb of SMP patients may be due to injury-evoked nociceptor responsiveness to catecholamines. However, such a response in contralateral asymptomatic limbs suggests an additional factor that more likely than not is of central origin and may or may not be related to sympathectomy and its success or failure to treat pain.
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Clonidine, an alpha-2 adrenergic agonist, is an extremely potent antinociceptive agent. However, the therapeutic utility of systemic clonidine for the treatment of pain is limited by centrally mediated side effects including sedation, hypotension and rebound hypertension. Given that alpha-2 adrenoceptors are expressed on the peripheral and central terminals of nociceptive fibers, we administered clonidine topically in order to avoid central effects. ⋯ Tolerance to the antinociceptive actions of clonidine was not blocked by topical administration of the NMDA antagonist, ketamine. In conclusion, topical administration of clonidine elicits antinociception by blocking the emerging pain signals at peripheral terminals via alpha-2 adrenoceptors without producing the undesirable central side effects observed following the systemic administration. The ineffectiveness of topical ketamine to block topical clonidine antinociceptive tolerance suggests that peripheral NMDA receptors do not mediate local clonidine antinociceptive tolerance.
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Comparative Study
The functional expression of mu opioid receptors on sensory neurons is developmentally regulated; morphine analgesia is less selective in the neonate.
Opioid requirements in neonatal patients are reported to be lower than older infants and this may be a reflection of the developmental regulation of opioid receptors. In this study we have investigated the postnatal regulation of Mu opioid receptor (MOR) function in both rat lumbar dorsal root ganglion (DRG) cultures and behavioural mechanical and thermal reflex tests in rat pups. Immunostaining with MOR and selective neurofilament (NF200) antibodies was combined with calcium imaging of MOR function in cultured neonatal and adult rat dorsal root ganglion cells. ⋯ These experiments show that the MOR expressed on large DRG neurons in neonates are functional and are subject to postnatal developmental regulation. This changing functional receptor profile is consistent with greater morphine potency in mechanical, but not thermal, sensory tests in young animals. These results have important clinical implications for the use of morphine in neonates and provide a possible explanation for the differences in morphine requirements observed in the youngest patients.