More than just joy: A qualitative analysis of participant experiences during nitrous oxide sedation.

BACKGROUND: Nitrous oxide use is shifting from general anesthesia to sedation and pain control. Interest in novel uses of nitrous oxide in psychiatry is also growing. Thus, understanding the consequences of using nitrous oxide remains relevant. Previous quantitative research might not have fully captured the whole spectrum of nitrous oxide, whereas qualitative analysis can provide a more comprehensive description. This qualitative study aims to describe the subjective experiences of nitrous oxide use in healthy volunteers who have no prior history of recreational substance misuse. METHODS: Twenty healthy male volunteers inhaled 50% nitrous oxide for 20 min. Females were excluded due to higher incidence of nausea with nitrous oxide. Afterwards, all participants answered an open-ended question about their experiences during sedation. The answers were then analyzed with inductive qualitative content analysis to identify emergent subcategories, categories, and overarching themes. RESULTS: We identified two themes: nitrous oxide is mind-altering and produces sensory overload. The mind-altering properties were represented by dreamlike states and heightened emotions. Dreamlike states comprised changes in consciousness and scary, bizarre, or transcendental dreams. Pleasant dreams were not reported. Heightened emotions included euphoria, anxiety, and fear of losing control. Sensory overload consists of distorted perception, bodily sensations, and a heightened sense of surroundings. CONCLUSIONS: Experiences under nitrous oxide sedation are extremely variable and not always pleasant. These findings can improve our understanding of the likes/dislikes of patients undergoing nitrous oxide sedation. Further qualitative studies should focus on the experiences of other groups, such as children or women in labor.

Awake proning in patients with COVID-19-related hypoxemic acute respiratory failure: Endorsement by the Scandinavian Society of Anaesthesiology and Intensive Care Medicine.

BACKGROUND: Awake proning in spontaneously breathing patients with hypoxemic acute respiratory failure was applied during the coronavirus disease 2019 (COVID-19) pandemic to improve oxygenation while avoiding tracheal intubation. An updated systematic review and meta-analysis on the topic was published. METHODS: The Clinical practice committee (CPC) of the Scandinavian Society of Anaesthesiology and Intensive Care Medicine (SSAI) assessed the clinical practice guideline "Awake proning in patients with COVID-19-related hypoxemic acute respiratory failure: A rapid practice guideline" for possible endorsement. The Appraisal of Guidelines for REsearch and Evaluation (AGREE) II tool was used. RESULTS: Four out of six SSAI CPC members completed the appraisal. The individual domain totals were: Scope and Purpose 90%; Stakeholder Involvement 89%; Rigour of Development 74%; Clarity of Presentation 85%; Applicability 75%; Editorial Independence 98%; Overall Assessment 79%. CONCLUSION: The SSAI CPC endorses the clinical practice guideline "Awake proning in patients with COVID-19-related hypoxemic acute respiratory failure: A rapid practice guideline". This guideline serves as a useful decision aid for clinicians caring for critically ill patients with COVID-19-related acute hypoxemic respiratory failure and can be used to provide guidance on use of prone positioning in this group of patients.

Saudi Critical Care Society clinical practice guidelines on the prevention of venous thromboembolism in adults with trauma: Endorsement by the Scandinavian Society of Anaesthesiology and Intensive Care Medicine.

The Clinical Practice Committee of the Scandinavian Society of Anaesthesiology and Intensive Care Medicine endorses the clinical practice guideline Saudi Critical Care Society clinical practice guidelines on the prevention of venous thromboembolism in adults with trauma: reviewed for evidence-based integrity and endorsed by the Scandinavian Society of Anaesthesiology and Intensive Care Medicine. This clinical practice guideline serves as a useful decision aid for Nordic anaesthesiologists managing adult trauma patients in the operating room and in the intensive care unit.

ISTH guidelines for antithrombotic treatment in COVID-19: Endorsement by the Scandinavian Society of Anaesthesiology and Intensive Care Medicine.

The Clinical Practice Committee of the Scandinavian Society of Anaesthesiology and Intensive Care Medicine endorses the ISTH guidelines for antithrombotic treatment in COVID-19. This evidence-based guideline serves as a useful decision aid for Nordic anaesthesiologists caring for patients with COVID-19.

Self-warming blanket versus forced-air warming blanket during total knee arthroplasty under spinal anaesthesia: A randomised non-inferiority trial.

BACKGROUND: Arthroplasty patients are at high risk of hypothermia. Pre-warming with forced air has been shown to reduce the incidence of intraoperative hypothermia. There is, however, a lack of evidence that pre-warming with a self-warming (SW) blanket can reduce the incidence of perioperative hypothermia. This study aims to evaluate the effectiveness of an SW blanket and a forced-air warming (FAW) blanket peri-operatively. We hypothesised that the SW blanket is inferior to the FAW blanket. METHODS: In total, 150 patients scheduled for primary unilateral total knee arthroplasty under spinal anaesthesia were randomised to this prospective study. Patients were pre-warmed with SW blanket (SW group) or upper-body FAW blanket (FAW group) set to 38°C for 30 min before spinal anaesthesia induction. Active warming was continued with the allocated blanket in the operating room. If core temperature fell below 36°C, all patients were warmed using the FAW blanket set to 43°C. Core and skin temperatures were measured continuously. The primary outcome was core temperature on admission to the recovery room. RESULTS: Both methods increased mean body temperature during pre-warming. However, intraoperative hypothermia occurred in 61% of patients in the SW group and in 49% in the FAW group. The FAW method set to 43°C could rewarm hypothermic patients. Core temperature did not differ between groups on admission to the recovery room, p = .366 (CI: -0.18-0.06). CONCLUSIONS: Statistically, the SW blanket was non-inferior to the FAW method. Yet, hypothermia was more frequent in the SW group, requiring rescue warming as we strictly held to the NICE guideline. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT03408197.

Posterior quadratus lumborum block versus epidural analgesia for postoperative pain management after open radical cystectomy: A randomized clinical trial.

BACKGROUND: In open abdominal surgery, continuous epidural analgesia is commonly used method for postoperative analgesia. However, ultrasound (US)-guided fascial plane blocks may be a reasonable alternative. METHODS: In this randomized controlled trial, we compared posterior quadratus lumborum block (QLB) with epidural analgesia for postoperative pain after open radical cystectomy (ORC). Adult patients aged 18-85 with bladder cancer (BC) scheduled for open RC were randomized in two groups. Exclusion criteria were complicated diabetes mellitus type I, lack of cooperation, and persistent pain for reasons other than BC. In one group, a bilateral US-guided single injection posterior QLB was performed with 3.75 mg/ml ropivacaine 20 ml/side. In the other group, continuous epidural analgesia with ropivacaine was used. Basic analgesia was oral paracetamol 1000 mg three times daily, and long-acting opioid twice daily in both groups. All patients had patient-controlled rescue analgesia with oxycodone. Postoperative cumulative rescue opioid consumption was recorded for the day of surgery, and the following 2 postoperative days (POD 0-2). Secondary outcomes were postoperative pain and nausea and vomiting. RESULTS: In total, 20 patients (QLB), and 19 patients (epidural analgesia) groups, were included in the analyses. Cumulative rescue opioid consumption on POD 0, being of duration 9-12 h, was 14 mg (7.6-33.3) in the QLB group versus 6.1 mg (2.0-16.1) in the epidural analgesia group, p = 0.089, and as doses, 8 doses (3.6-15.7) versus 4 doses (1.3-8.5), p = .057. On POD 1 consumption was 25.3 mg (11.0-52.9) versus 18.0 mg (14.4-43.7), p = .749, and as doses 12 (5.5-23.0) versus 10 (8-20), p > .9, respectively. On POD 2 consumption was 19.1 mg (7.9-31.0) versus 18.0 mg (5.4-27.6) p = .749, and as doses 8.5 (5.2-14.7) versus 11 (3.0-18.0) p > .9, respectively. CONCLUSION: Opioid consumption did not differ significantly between posterior QLB and an epidural infusion with ropivacaine for the first 2 postoperative days following RC. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT03328988.

Peripheral nerve blocks in advanced cancer pain: retrospective case series.

OBJECTIVES: Patients with cancer often suffer severe pain that is not relieved with systemic analgesics and requires further treatment options. This study aims to investigate whether peripheral nerve blocks are a feasible treatment option in patients with incurable cancer who suffer from severe pain. METHODS: All patients with advanced cancer who received a peripheral nerve block for the management of pain at the Tampere University Hospital between January 2015 and December 2018 were included in this retrospective study. The characteristics of the patients' features of the nerve blocks, opioid dosing (daily morphine equivalent) before and after the blocks, and patient-reported pain relief following peripheral block were assessed from the medical records. RESULTS: Sixteen of the 17 patients included in this study received pain relief through a nerve block. Daily opioid dose was decreased with the block in 12 (71%) patients with a median change in daily morphine equivalent of -20 mg (IQR: -180 to 9). One infection of the catheter and two other transient adverse events occurred, but none was serious or fatal. CONCLUSIONS: Peripheral nerve blocks seem safe and may provide considerable analgesia and decrease the need for opioids in patients with advanced cancer.

Opioid trends in Finland: a register-based nationwide follow-up study.

The opioid epidemic in the U.S has gotten payers, prescribers, and policymakers alike interested in trends in opioid use. Despite no recognized opioid crisis in Europe, several countries have reported an increase in opioid-related deaths, which has further prompted discussion on the need of monitoring of opioid prescriptions. This study was conducted to offer information on opioid use during the escalation of the U.S. opioid epidemic in Finland, a Nordic country with universal tax-based health care. This is a nationwide retrospective register-based cohort study on all individuals in Finland who were dispensed opioids in 2009-2017 (n of unique patients = 1,761,584). By using the unique personal identification code assigned to every Finnish resident, we linked data from nationwide registers on dispensed drugs, medical history, and socio-demographic parameters. We report a wide set of patient demographics, dispensing trends for all opioid Anatomical Therapeutic Chemical (ATC) classes, and reasons for opioid initiation based on diagnostic coding for the most recent health care visit. For a cohort of incident opioid users with a four-year wash-out period (n = 1 370 057), we also present opioid use patterns in a three-year follow-up: the likelihood of becoming a persistent user or escalating from weak to strong opioids. A steady 7% of the Finnish population were dispensed opioids annually in 2009-2017. The mean annual quantity of dispensed opioids per opioid patient increased between 2009 and 2017 by 33%, reaching 2 583 oral morphine equivalent mg (OMEQ)/patient/year in 2017. The median quantity of dispensed opioids was lower: 315 OMEQ/year/patient. Depending on the opioid ATC class, there were either increasing or decreasing numbers of patients who had been dispensed said opioid class, and also in the mean quantity. The most common reason for opioid initiation was post-surgical pain (20%), followed by musculoskeletal pain (15%), injury (8.3%), and non-postsurgical dental pain (6.2%). 94% of new opioid initiators started with a weak opioid, i.e. codeine or tramadol. 85% of the patients who had been dispensed a weak opioid were not dispensed an opioid subsequently 3-6 months after the first one, and 95% of them had not escalated to a strong opioid in a 3-year follow-up. The number of patients dispensed opioids in Finland did not change during the escalation of the opioid epidemic in the U.S., but there were changes in the quantity of opioids dispensed per patient. Opioid therapy was typically initiated with weak opioid, the initial dispensed prescription was relatively small, and escalation to strong opioids was rare. A considerable share of patients had been prescribed opioids for chronic non-cancer pain - a type of pain where the risk-benefit ratio of opioids is controversial.

Comparison of zero heat flux and double sensor thermometers during spinal anaesthesia: a prospective observational study.

Because of the difficulties involved in the invasive monitoring of conscious patients, core temperature monitoring is frequently neglected during neuraxial anaesthesia. Zero heat flux (ZHF) and double sensor (DS) are non-invasive methods that measure core temperature from the forehead skin. Here, we compare these methods in patients under spinal anaesthesia. Sixty patients scheduled for elective unilateral knee arthroplasty were recruited and divided into two groups. Of these, thirty patients were fitted with bilateral ZHF sensors (ZHF group), and thirty patients were fitted with both a ZHF sensor and a DS sensor (DS group). Temperatures were saved at 5-min intervals from the beginning of prewarming up to one hour postoperatively. Bland-Altman analysis for repeated measurements was performed and a proportion of differences within 0.5 °C was calculated as well as Lin`s concordance correlation coefficient (LCCC). A total of 1261 and 1129 measurement pairs were obtained. The mean difference between ZHF sensors was 0.05 °C with 95% limits of agreement - 0.36 to 0.47 °C, 99% of the readings were within 0.5 °C and LCCC was 0.88. The mean difference between ZHF and DS sensors was 0.33 °C with 95% limits of agreement - 0.55 to 1.21 °C, 66% of readings were within 0.5 °C and LCCC was 0.59. Bilaterally measured ZHF temperatures were almost identical. DS temperatures were mostly lower than ZHF temperatures. The mean difference between ZHF and DS temperatures increased when the core temperature decreased.Trial registration: The study was registered in ClinicalTrials.gov on 13th May 2019, Code NCT03408197.

Thermal suit connected to a forced-air warming unit for preventing intraoperative hypothermia: A randomised controlled trial.

BACKGROUND: Inadvertent intraoperative hypothermia is a common occurrence in surgical patients. A thermal suit is an option for passive insulation. However, active warming is known to be more effective. Therefore, we hypothesised that a forced-air warming (FAW) unit connected to the thermal suit is superior to a commercial FAW blanket and a warming mattress in breast cancer surgery. METHODS: Forty patients were randomised to this prospective, clinical trial to wear either the thermal suit or conventional hospital clothes under general anaesthesia. The Thermal suit group had a FAW unit set to 38°C and connected to the legs of the suit. The Hospital clothes group had a lower body blanket set to 38°C and a warming mattress set to 37°C. Core temperature was measured with zero-heat-flux sensor. The primary outcome was core temperature on admission to the recovery room. RESULTS: There was no difference in mean core temperatures at anaesthetic induction (P = .4) or on admission to the recovery room (P = .07). One patient in the Thermal suit group (5%) vs six patients in the Hospital clothes group (32%) suffered from intraoperative hypothermia (P = .04, 95% CI 1.9%-49%). Mean skin temperatures (MSTs) were higher in the Thermal suit group during anaesthesia. No burns or skin irritations were reported. Two patients in the Thermal suit group sweated. CONCLUSIONS: A thermal suit connected to a FAW unit was not superior to a commercial FAW blanket, although the incidence of intraoperative hypothermia was lower in patients treated with a thermal suit.

Ultrasound-guided quadratus lumborum block for postoperative analgesia: A systematic review and meta-analysis.

BACKGROUND: Ultrasound-guided quadratus lumborum block (QLB) is a truncal block with several technique variations. It has been reported as providing effective analgesia for postoperative pain. OBJECTIVES: The aim of this review was to evaluate the efficacy and safety of QLB for postoperative analgesia. The primary outcome was cumulative opioid consumption at 24 h postoperatively. The main secondary outcomes were the time to the first rescue opioid analgesic, pain scores at 24 h postoperatively and the incidence of postoperative nausea and vomiting (PONV). DESIGN: This was a systematic review and meta-analyses of observational studies and randomised controlled trials (RCTs). PRISMA-P guidelines were followed, and the review was registered in PROSPERO. GRADE was used to assess the quality of evidence. DATA SOURCES: The search was performed from several databases (Ovid MEDLINE, PubMed, Scopus, Web of Science, CINAHL and the Cochrane CENTRAL) from inception up to June 2019. ELIGIBILITY CRITERIA: RCTs and prospective observational studies that investigated the postoperative analgesic properties of US-guided single shot QLB in adult patients undergoing abdominal or hip surgery were included. QLB was compared with other analgesics. RESULTS: Twenty-seven studies constituting 1557 patients were reviewed. Twelve studies with 803 patients were included in the meta-analysis on the primary outcome. Overall opioid consumption at 24 h postoperatively was reduced [mean difference, -11.15 (95% CI, -15.33 to -6.97) mg, I2 = 99%, moderate certainty in GRADE] and the time to the first opioid analgesic was longer in patients with QLB: 7 studies with 499 patients, mean difference, 189.32 (95% CI, 114.4 to 264.23) min, I2 = 98%. There were no differences in pain grades. The incidence of PONV was lower in patients with QLB [11 studies with 744 patients, OR 0.40 (95% CI, 0.27 to 0.58), I2 = 7%]. Reported complications and adverse effects of QLB were minimal. CONCLUSION: QLB reduced postoperative opioid consumption, prolonged the time to the first rescue opioid analgesic and diminished the incidence of PONV. QLB appears to be an applicable option for postoperative analgesia after abdominal and hip surgery. REGISTRATION NUMBER: PROSPERO, https://www.crd.york.ac.uk/prospero/, CRD42016039921.

Persistent pain in intensive care survivors: a systematic review.

BACKGROUND: According to earlier studies where the main aim has been quality of life, there is growing evidence of increased levels of persistent pain in survivors of critical illness. The cause of admission and several factors during intensive care may have associated risk factors for pain persistence. This systematic review aims to determine the incidence or prevalence of persistent pain after critical illness and to identify risk factors for it. METHODS: Six databases were searched, and eventually nine studies were included in the final systematic process. The validity of observational and cross-sectional studies was analysed using the National Institute of Health 'Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies'. RESULTS: The incidence of persistent pain after intensive care varied from 28% to 77%. Risk factors for persistent pain were acute pain at discharge from ICU, higher thoracic trauma score, surgery, pre-existing pain, organ failure, longer length of ventilator or hospital stay, and sepsis. No difference in incidence between medical and surgical patients was found. CONCLUSIONS: New systematic, observational studies are warranted to identify persistent pain-related factors in intensive care to improve pain management protocols and thereby diminish the risk of persistent pain after ICU stay.

Characterization of persistent pain after hysterectomy based on gynaecological and sensory examination.

BACKGROUND AND AIMS: Previous studies have shown that pelvic pain is common after hysterectomy. It is stated that only a minor part of that pain can be defined as persistent postsurgical pain. Our primary aim was to find out if the pelvic pain after hysterectomy may be classified as postsurgical. Secondary aims were to characterize the nature of the pain and its consequences on the health related quality of life. METHODS: We contacted the 56 women, who had reported having persistent pelvic pain six months after hysterectomy in a previously sent questionnaire. Sixteen women participated. Clinical examinations included gynaecological examination and clinical sensory testing. Patients also filled in quality of life (SF-36) and pain questionnaires. RESULTS: Ten out of sixteen patients still had pain at the time of examination. In nine patients, pain was regarded as persistent postsurgical pain and assessed probable neuropathic for five patients. There were declines in all scales of the SF-36 compared with the Finnish female population cohort. CONCLUSIONS: In this study persistent pelvic pain after vaginal or laparoscopic hysterectomy could be defined as persistent postsurgical pain in most cases and it was neuropathic in five out of nine patients. Pain had consequences on the health related quality of life. IMPLICATIONS: Because persistent postsurgical pain seems to be the main cause of pelvic pain after hysterectomy, the decision of surgery has to be considered carefully. The management of posthysterectomy pain should be based on the nature of pain and the possibility of neuropathic pain should be taken into account at an early postoperative stage.

Genetic susceptibility to postherniotomy pain. The influence of polymorphisms in the Mu opioid receptor, TNF-α, GRIK3, GCH1, BDNF and CACNA2D2 genes.

BACKGROUND AND AIMS: Despite improvements in surgical technique, 5%-8% of patients undergoing herniorrhaphy still suffer from clinically relevant persistent postherniotomy pain. This is a problem at both individual and society levels. The aim of this study was to determine whether or not a single nucleotide polymorphism in a specific gene contributes to the development of persistent pain after surgery. METHODS: One hundred individuals with persistent postherniotomy pain, along with 100 without pain matched for age, gender and type of surgery were identified in a previous cohort study on patients operated for groin hernia. All patients underwent a thorough sensory examination and blood samples were collected. DNA was extracted and analysed for single nucleotide polymorphism in the Mu opioid receptor, TNF-α, GRIK3, GCH1, BDNF and CACNA2D2 genes. RESULTS: Patients with neuropathic pain were found to have a homozygous single nucleotide polymorph in the TNF-α gene significantly more often than pain-free patients (P=0.036, one-tailed test). CONCLUSIONS: SNP in the TNF-α gene has a significant impact on the risk for developing PPSP. IMPLICATIONS: The result suggests the involvement of genetic variance in the development of pain and this requires further investigation.

Persistent posthysterectomy pain: A prospective, observational study.

BACKGROUND: There is a large variation in the prevalence of persistent postsurgical pain depending on the type of surgery. It is unclear how common persistent postsurgical pain is after vaginal or laparoscopic hysterectomy. OBJECTIVES: The objective of this study was to define the prevalence of persistent postsurgical pain 6 months after laparoscopic or vaginal hysterectomy for benign causes and to ascertain the intensity of the pain and its possible predictors. DESING: A prospective, observational study. SETTING: Pirkanmaa Hospital District between October 2008 and September 2013. PATIENTS: Two hundred and forty-two women who underwent laparoscopic (150) or vaginal (92) hysterectomy for benign causes and who also participated in our earlier studies concerning acute pain. INTERVENTIONS: A pain questionnaire and a prestamped return envelope were mailed to all women 6 months after surgery. If the questionnaire had not been returned within 4 weeks, a reminder was sent. Data regarding preoperative pain and acute postoperative pain were collected from the records of our earlier studies concerning acute pain. The patient characteristics and surgical outcomes were collected from the patients' medical records. MAIN OUTCOME MEASURE: The prevalence of persistent postsurgical pain 6 months after hysterectomy. RESULTS: The response rate was 94% (227 respondents). Twenty-seven (18.9%) of 143 patients who had no pain preoperatively had persistent pain after surgery. Overall, 26.0% of patients had persistent pelvic pain 6 months after surgery. On an 11-point numeric rating scale (NRS), most of the patients rated their average pain as mild (NRS 0 to 3) and only 6.9% rated their worst pain as severe (NRS 7 to 10). Smoking, acute postoperative pain at 4 h after surgery and a laparoscopic approach were significantly associated with persistent pain in a multivariable analysis. CONCLUSION: Persistent posthysterectomy pain is common, but pain is mild and does not interfere with daily activities for most of the patients 6 months after surgery. Smoking is the strongest predictor for persistent pain. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT 01537731.

Less postoperative pain after laparoscopic hysterectomy than after vaginal hysterectomy.

PURPOSE: To find out whether the severity of acute postoperative pain differs between laparoscopic (LH) or laparoscopically assisted vaginal hysterectomy (LAVH) and vaginal hysterectomy. METHODS: In a prospective, powered, non-randomized trial, the consumption of oxycodone and pain scores were evaluated in 164 women up to 20 h after VH or LH/LAVH. All hysterectomies were performed under standardized general anesthesia and the pain medication was similar in both groups. The primary endpoint was the cumulative oxycodone consumed. Main secondary endpoints were pain scores (numeric rating scale NRS), operative time and hospital stay. RESULTS: The patients in LH/LAHV group consumed less opioid than the patients in the vaginal group during the 20 h period after surgery. The difference was significant at time point 4 and 6 h. The oxycodone consumed at time point 4 h was 19.9 (95 % CI 18.1-21.7) mg in laparoscopic group and 22.8 (20.7-25.0) mg in vaginal group (p = 0.040) and at time point 6 h was 23.5 (21.5-25.6) mg in laparoscopic group and 27.4 (24.7-30.0) mg in vaginal group (p = 0.026). Pain scores were lower after laparoscopic approach and the difference was significant at time point 60 min after surgery (p = 0.026). CONCLUSION: In this study, LH was associated with reduced need of analgesics and lower acute postoperative pain scores than VH.

Natural course of long-term postherniorrhaphy pain in a population-based cohort.

Background Persistent pain after hernia repair is widely recognised as a considerable problem, although the natural course of postoperative pain is not fully understood. The aim of the present study was to explore the natural course of persistent pain after hernia repair in a population-based cohort and identify risk factors for prolonged pain duration. Methods The study cohort was assembled from the Swedish Hernia Register (SHR), which has compiled detailed information on more than 140 000 groin hernia repairs since 1992. All patients operated on for groin hernia in the County of Uppsala, Sweden, 1998-2004 were identified in the SHR. Those who were still alive in 2005 received the Inguinal Pain Questionnaire, a validated questionnaire with 18 items developed with the aim of assessing postherniorrhaphy pain, by mail. Reminders were sent to non-responders 5 months after the first mail. The halving time was estimated from a linear regression of the logarithmic transformation of the prevalence of pain each year after surgery. A multivariate analysis with pain persisting more than 1 month with a retrospective question regarding time to pain cessation as dependent variable was performed. Results Altogether 2834 repairs in 2583 patients were recorded, 162 of who had died until 2005. Of the remaining patients, 1763 (68%) responded to the questionnaire. In 6.7 years the prevalence of persistent pain had decreased by half for the item "pain right now" and in 6.8 years for the item "worst pain last week". The corresponding figures if laparoscopic repair was excluded were 6.4 years for "pain right now" and 6.4 years for "worst pain past week". In a multivariate analysis, low age, postoperative complication and open method of repair were found to predict an increased risk for pain persistence exceeding 1 month. Conclusion Persistent postoperative pain is a common problem following hernia surgery, although it often recedes with time. It is more protracted in young patients, following open repair and after repairs with postoperative complications. Whereas efforts to treat persistent postoperative pain, in particular neuropathic pain, are often fruitless, this group can at least rely on the hope that the pain, for some of the patients, gradually decreases with time. On the other hand, 14% still reported a pain problem 7 years after hernia surgery. We do not know the course after that. Although no mathematical model can provide a full understanding of such a complex process as the natural course of postoperative pain, assuming an exponential course may help to analyse the course the first years after surgery, enable comparisons with other studies and give a base for exploring factors that influence the duration of the postoperative pain. Halving times close to those found in our study could also be extrapolated from other studies, assuming an exponential course.

Prolactin-releasing peptide affects pain, allodynia and autonomic reflexes through medullary mechanisms.

Prolactin-releasing peptide (PrRP) and neuropeptide FF (NPFF) are RF-amide peptides expressed in brain areas involved in pain modulation. NPFF displays multiple effects on acute, inflammatory and neuropathic pain. The potential role of PrRP in pain was addressed by intrathecal and intracerebral injections of PrRP on pain-related responses in both neuropathic and normal rats. Particularly in the dorsal medulla, PrRP produced significant antinociception in normal rats and an antiallodynic effect in neuropathic rats. To understand the basis of PrRP-induced pain modulation, distributions of PrRP, PrRP receptor, and NPFF were compared in the rat central nervous system. PrRP and NPFF mRNA were expressed in different parts of the nucleus of the solitary tract. In the medulla, PrRP receptor mRNA expression was abundant only in area postrema. Of the peptides studied, only NPFF mRNA was found in the dorsal horn of the spinal cord and spinal nucleus of the trigeminal nerve. PrRP-immunoreactivity corresponded to the mRNA distribution. Even if the neuronal groups producing NPFF and PrRP were distinct, the fiber networks immunoreactive for PrRP and NPFF overlapped. The results show that PrRP modulates nociception due to supraspinal rather than spinal action, and that its antinociceptive mechanism differs from that previously characterized for NPFF.