Evaluation of Postsurgical Hyperalgesia and Sensitization After Open Inguinal Hernia Repair: A Useful Model for Neuropathic Pain?

Cutaneous mechanical hyperalgesia can be induced in healthy volunteers in early phase analgesic studies to model central sensitization, a key mechanism of persistent pain. However, such hyperalgesia is short-lived (a matter of hours), and is used only for assessing only single drug doses. In contrast, postsurgical peri-incisional hyperalgesia may be more persistent and hence be a more useful model for the assessment of the efficacy of new analgesics. We undertook quantitative sensory testing in 18 patients at peri-incisional and nonoperated sites before open inguinal hernia repair and up to the 24th postsurgical week. The spatial extent of punctate hyperalgesia and brush allodynia at the peri-incisional site were greatest at weeks 2 and 4, but had resolved by week 24. Heat allodynia, suggestive of local inflammation or peripheral sensitization, was not observed; instead, there were deficits in cold and heat sensory detection that persisted until week 24. The findings suggest that central sensitization contributes significantly to mechanical hyperalgesia at the peri-incisional site. The prolonged duration of hyperalgesia would be advantageous as a pain model, but there was considerable variability of mechanical hyperalgesia in the cohort; the challenges of recruitment may limit its use to small, early phase analgesic studies. PERSPECTIVE: Peri-incisional mechanical hyperalgesia persists for ≥4 weeks after open inguinal hernia repair and reflects central sensitization; this may have usefulness as a model of chronic pain to assess the potential of antineuropathic analgesics.

Hospitalization due to acute exacerbation of chronic pain: An intervention study in a university hospital.

BACKGROUND AND AIMS: Hospitalization as a result of acute exacerbation of complex chronic pain is a largely hidden problem, as patients are often admitted to hospital under a variety of specialities, and there is frequently no overarching inpatient chronic pain service dedicated to their management. Our institution had established an inpatient acute pain service overseen by pain physicians and staffed by specialist nurses that was intended to focus on the management of perioperative pain. We soon observed an increasing number of nurse-to-nurse referrals of non-surgical inpatients admitted with chronic pain. Some of these patients had seemingly intractable and highly complex pain problems, and consequently we initiated twice-weekly attending physician-led inpatient pain rounds to coordinate their management. From these referrals, we identified a cohort of 20 patients who were frequently hospitalized for long periods with exacerbations of chronic pain. We sought to establish whether the introduction of the physician-led inpatient pain ward round reduced the number and duration of hospitalizations, and costs of treatment. METHODS: We undertook a retrospective, observational, intervention cohort study. We recorded acute Emergency Department (ED) attendances, hospital admissions, and duration and costs of hospitalization of the cohort of 20 patients in the year before and year after introduction of the inpatient pain service. RESULTS: The patients' mean age was 38.2 years (±standard deviation 13.8 years, range 18-68 years); 13 were women (65.0%). The mode number of ED attendances was 4 (range 2-15) pre-intervention, and 3 (range 0-9) afterwards (p=0.116). The mode bed occupancy was 32 days (range 9-170 days) pre-intervention and 19 days (range 0-115 days) afterwards (p=0.215). The total cost of treating the cohort over the 2-year study period was £733,010 (US$1.12m), comprising £429,479 (US$656,291) of bed costs and £303,531 (US$463,828) of investigation costs. The intervention did not achieve significant improvements in the total costs, bed costs or investigation costs. CONCLUSIONS: Despite our attending physician-led intervention, the frequency, duration and very substantial costs of hospitalization of the cohort were not significantly reduced, suggesting that other strategies need to be identified to help these complex and vulnerable patients. IMPLICATIONS: Frequent hospitalization with acute exacerbation of chronic pain is a largely hidden problem that has very substantial implications for patients, their carers and healthcare providers. Chronic pain services tend to focus on outpatient management. Breaking the cycle of frequent and recurrent hospitalization using multidisciplinary chronic pain management techniques has the potential to improve patients' quality of life and reduce hospital costs. Nonetheless, the complexity of these patients' chronic pain problems should not be underestimated and in some cases are very challenging to treat.

Pictorial prescribing reduces fentanyl drug administration errors: a simulated controlled study.

OBJECTIVES: Transmucosal fentanyl is used to treat transient exacerbations of cancer pain. Several immediate release products are available, presented as intranasal sprays, sublingual and buccal tablets, or lozenges. These are not interchangeable, creating potential for medication errors. We compared the incidence of medication errors in a simulated scenario using handwritten drug charts and charts labelled with preprinted self-adhesive stickers with full pictorial fentanyl prescriptions. METHODS: 54 nurses were shown 5 handwritten drug charts and 5 with self-adhesive pictorial labels. Nurses indicated which preparation and dose they would administer from boxes of Instanyl, Abstral, Effentora and Actiq (Nycomed, ProStrakan, Cephalon and Teva, respectively). We measured the frequency of drug administration errors and asked them to rate the prescriptions for clarity on four-point Likert items. RESULTS: The use of pictorial self-adhesive prescriptions significantly reduced errors in choice of preparation, from 20 with traditional handwritten charts to 6 with self-adhesive labels (OR 3.52, 95% CI 1.39 to 8.90, p=0.006), but the incidence of dose error was not significantly different (OR 1.47, 95% CI 0.80 to 2.70, p=0.281). Analysis of Likert items showed using pictorial printed labels significantly improved nurses' understanding of choice of preparation, dose and maximum four hourly dose (p<0.0001, p=0.006 and p=0.028, respectively). CONCLUSIONS: The use of pictorial prescribing appears to be a promising strategy that could reduce medication errors in choice of fentanyl preparations. There may be a wider use for pictorial prescribing where non-interchangeable preparations of the same drug exist.