Pain
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In this longitudinal population study, the aims were to study associations of mode of delivery with new onset of pelvic pain and changes in pelvic pain scores up to 7 to 18 months after childbirth. We included 20,248 participants enrolled in the Norwegian Mother and Child Cohort Study (1999-2008) without preexisting pelvic pain in pregnancy. Data were obtained by 4 self-administered questionnaires and linked to the Medical Birth Registry of Norway. ⋯ We conclude that new onset of pelvic pain after childbirth was not commonly reported, particularly following cesarean delivery. Overall, pelvic pain scores were rather low at all time points and women with a history of pain reported increased pelvic pain scores over time. Hence, clinicians should follow up women with pelvic pain after a difficult childbirth experience, particularly if they have a history of pain.
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Previous investigations on acute postoperative pain dynamicity have focused on daily pain assessments, and so were unable to examine intraday variations in acute pain intensity. We analyzed 476,108 postoperative acute pain intensity ratings, which were clinically documented on postoperative days 1 to 7 from 8346 surgical patients using Markov chain modeling to describe how patients are likely to transition from one pain state to another in a probabilistic fashion. The Markov chain was found to be irreducible and positive recurrent, with no absorbing states. ⋯ There were also slightly increased probability densities in transitioning to a state of asleep or 0 from the current state. An examination of the number of steps required to traverse from a particular first pain score to a target state suggested that overall, fewer steps were required to reach a state of 0 (range 6.1-8.8 steps) or asleep (range 9.1-11) than were required to reach a mild pain intensity state. Our results suggest that using Markov chains is a feasible method for describing probabilistic postoperative pain trajectories, pointing toward the possibility of using Markov decision processes to model sequential interactions between pain intensity ratings, and postoperative analgesic interventions.
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It has been recently proposed that α5-subunit containing GABAA receptors (α5-GABAA receptors) that mediate tonic inhibition might be involved in pain. The purpose of this study was to investigate the contribution of α5-GABAA receptors in the loss of GABAergic inhibition and in formalin-induced, complete Freund's adjuvant (CFA)-induced and L5 and L6 spinal nerve ligation-induced long-lasting hypersensitivity. Formalin or CFA injection and L5 and L6 spinal nerve ligation produced long-lasting allodynia and hyperalgesia. ⋯ Formalin injection enhanced α5-GABAA receptor fluorescence intensity in spinal cord and DRG at 3 and 6 days. Intrathecal administration of L-655,708 (15 nmol) prevented and reversed formalin-induced impairment of rate-dependent depression. These results suggest that α5-GABAA receptors play a role in the loss of GABAergic inhibition and contribute to long-lasting secondary allodynia and hyperalgesia.