Articles: hyperalgesia.
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Both local infiltration analgesia (LIA) and nerve block are common analgesic modalities for pain relief after surgery. The aim of the current study was to investigate the effects of those two modalities on pain behavior and the expression of pro-inflammatory cytokines such as interleukin (IL)-1β and IL-6 and tumor necrosis factor-α (TNF-α) in the spinal cord and dorsal root ganglion (DRG) in a rat model of perioperative fentanyl induced hyperalgesia. Rats were injected with fentanyl (60 μg/kg) 4 times and received a plantar incision after the second injection or they received pre-incision LIA and sciatic nerve block (SNB) or post-incision LIA with levobupivacaine (0.5%, 0.2 mL). ⋯ Fentanyl and an incision induced a significantly delayed mechanical hyperalgesia in the tail and thermal hyperalgesia in both hind paws and up-regulation of pro-inflammatory cytokines in the spinal cord and dorsal root ganglia. Rats treated with pre-incision LIA and SNB or post-incision LIA had alleviated hyperalgesia and significantly reduced levels of IL-1β, IL-6, and TNF-α compared to the control group. LIA and SNB partly prevented perioperative fentanyl-induced hyperalgesia and up-regulation of pro-inflammatory cytokines in the spinal cord and dorsal root ganglia.
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The experience of pain is characterized by the presence of a noxious sensory stimulus combined with negative affect, which is often treated clinically through administration of drugs such as morphine or other opioids. This study investigated the effects of morphine one and seven days after intraplantar administration of complete freund's adjuvant (CFA) in male and female rats. Hargreaves test for thermal nociception and conditioned place preference (CPP) were performed following subcutaneous administration of saline or morphine (1.0, 4.0, 8.0, 12.0 mg/kg). ⋯ Seven days after CFA treatment, both male and female rats exhibited a CPP with morphine doses of 4.0 mg/kg and higher. These results reveal sexually dimorphic properties of morphine in the paw withdrawal latencies and conditioned place preference models, representing reflexive and non-reflexive behavioral assays employed to examine inflammatory nociception. Our findings also suggest that antinociceptive effects of morphine are dynamic across early and later periods of CFA-induced inflammatory pain.
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Placebo and nocebo mechanisms can lead to clinically significant modulation of pain. Although learning is considered to be the broad mechanism underlying placebo analgesia as well as nocebo hyperalgesia, critical differences have emerged in their specific mechanisms. One of the most interesting of these is that whereas placebo analgesia seems to be relatively short-lived, nocebo hyperalgesia appears more resistant to extinction, often persisting indefinitely. ⋯ The conditioning procedure successfully induced placebo analgesia as well as nocebo hyperalgesia in the relevant groups, with nocebo hyperalgesia outlasting placebo analgesia, confirming nocebo hyperalgesia's resistance to extinction. Most interestingly, nocebo treatment led to heightened anticipatory anxiety ratings and autonomic arousal. Further, autonomic arousal completely mediated the effect of nocebo versus placebo training on extinction, suggesting that heightened autonomic arousal may be an important mechanism in the persistence of nocebo hyperalgesia.
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Anesthesia and analgesia · May 2018
ReviewPredicting Severity of Acute Pain After Cesarean Delivery: A Narrative Review.
Cesarean delivery is one of the most common surgical procedures in the United States, with over 1.3 million performed annually. One-fifth of women who undergo cesarean delivery will experience severe pain in the acute postoperative period, increasing their risk of developing chronic pain and postpartum depression, and negatively impacting breastfeeding and newborn care. A growing body of research has investigated tools to predict which patients will experience more severe pain and have increased analgesic consumption after cesarean delivery. ⋯ Thirteen articles were included in the final review: 5 utilizing quantitative sensory testing, including patient responses to pressure, electrical, and thermal stimuli; 1 utilizing hyperalgesia testing; 1 using response to local anesthetic wound infiltration; 4 utilizing preoperative psychometric evaluations including the State-Trait Anxiety Inventory, the Pain Catastrophizing Scale, the Pittsburgh Sleep Quality Index, the Hospital Anxiety and Depression Scale, and simple questionnaires; and 2 utilizing a combination of quantitative sensory tests and psychometric evaluations. A number of modalities demonstrated statistically significant correlations with pain outcomes after cesarean delivery, but most correlations were weak to modest, and many modalities might not be clinically feasible. Response to local anesthetic infiltration and a tool using 3 simple questions enquiring about anxiety and anticipated pain and analgesic needs show potential for clinical use, but further studies are needed to evaluate the utility of these predictive tests in clinical practice.