***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Abstract We studied the prevalence of chronic pain and long term sensory changes after cosmetic augmentation mammoplasty and the effects of a single i.v . preoperative dose of methylprednisolone 125 mg ( n = 74 ) , parecoxib 40 mg ( n = 71 ) , or placebo  ( n = 74 ) . A question naire was mailed 6 weeks and 1 year after surgery . Response rate after 1 year was 80 % . At 1 year non‐evoked pain was present in 13 % , and evoked pain was present in 20 % with no statistically significant differences between the groups . Methylprednisolone was associated with reduced odds for hyperesthesia at 1 year ( OR 0.3 , 95 % CI 0.1–0.6 ) , and significantly reduced the prevalence of hyperesthesia ( 30 % ) compared with placebo ( 56 % , P < 0.01 ) and parecoxib ( 51 % , P < 0.04 ) . Factors associated with increased odds for pain at 1 year were intensity of pain during the first 6 days after surgery ( OR 1.3 , 95 % CI 1.1–1.6 ) , pain at 6 weeks ( OR 18.4 , 95 % CI 6.9–49.3 ) , hyperesthesia at 6 weeks ( OR 2.3 , 95 % CI 1.1–5.1 ) and present hyperesthesia ( OR 3.1 , 95 % CI 1.4–6.7 ) . We conclude that persistent pain and sensory changes are common after augmentation mammoplasty , and that patients having pain at 6 weeks most likely will have pain also at 1 year . Acute postoperative pain , hyperesthesia at 6 weeks , and the presence of hyperesthesia increased the odds for pain at 1 year . Preoperative methylprednisolone result ed in significantly less hyperesthesia compared with both parecoxib and placebo , but did not significantly reduce the prevalence of persistent spontaneous or evoked pain Background and objective : Gabapentin has been suggested to decrease acute postoperative pain . We evaluated the effect of gabapentin on pain after abdominal hysterectomy . Methods : Sixty patients scheduled for abdominal hysterectomy were r and omized to receive orally gabapentin 400 mg 6 hourly or placebo . Treatment started 18 h preoperatively and continued for 5 postoperative days . Pain ( visual analogue score ) and consumption of morphine for 48 h and of  oral paracetamol/codeine  were recorded after 2 , 4 , 8 , 24 and 48 h and on days 3‐5 postoperatively . After 1 month , patients were interviewed by phone for pain , and analgesic intake after hospital discharge . Results : Morphine consumption ( mean ± SD ) was 35 ± 15.7 mg in the control and 28 ± 12.1 mg in the gabapentin group ( P = 0.21 ) . Median number ( range ) of paracetamol 500 mg/codeine 30 mg tablets taken during days 3‐5 was 1.0 ( 0‐6 ) in the control and 2.0 ( 0‐9 ) in the gabapentin group ( P = 0.35 ) . The visual analogue scores at rest and after cough did not differ between the two groups ( F = 0.92 , df = 1 , P = 0.34 and F = 0.56 , df = 1 , P = 0.46 , respectively ) . One month after surgery , 22/27 ( 81 % ) of the control group and 9/25 ( 36 % ) of the gabapentin group reported pain in the surgical area ( χ2 = 11.15 , P = 0.002 ) , while 11/27 ( 41 % ) of controls and 7/25 ( 28 % ) of gabapentin patients consumed analgesics for pain ( χ2 = 0.93 , P = 0.39 ) . The intensity of pain was decreased in the gabapentin group ( χ2 = 12.6 , P = 0.003 ) . Conclusions : Gabapentin has no effect on immediate pain after abdominal hysterectomy but decreases pain 1 month postoperatively Abstract  Variability  in patients ' response to interventions in pain and other clinical setting s is large . Many explanations such as trial methods , environment or culture have been proposed , but this paper sets out to show that the main cause of the variability may be r and om chance , and that if trials are small their estimate of magnitude of effect may be incorrect , simply because of the r and om play of chance . This is highly relevant to the questions of ‘ How large do trials have to be for statistical accuracy ? ’ and ‘ How large do trials have to be for their results to be clinical ly valid ? ’ The true underlying control event rate ( CER ) and experimental event rate ( EER ) were determined from single‐dose acute pain analgesic trials in over 5000 patients . Trial group size required to obtain statistically significant and clinical ly relevant ( 0.95 probability of number‐needed‐to‐treat within ±0.5 of its true value ) results were computed using these values . Ten thous and trials using these CER and EER values were simulated using varying group sizes to investigate the variation due to r and om chance alone . Most common analgesics have EERs in the range 0.4–0.6 and CER of about 0.19 . With such efficacy , to have a 90 % chance of obtaining a statistically significant result in the correct direction requires group sizes in the range 30–60 . For clinical relevance nearly 500 patients are required in each group . Only with an extremely effective drug ( EER>0.8 ) will we be reasonably sure of obtaining a clinical ly relevant NNT with commonly used group sizes of around 40 patients per treatment arm . The simulated trials showed substantial variation in CER and EER , with the probability of obtaining the correct values improving as group size increased . We contend that much of the variability in control and experimental event rates is due to r and om chance alone . Single small trials are unlikely to be correct . If we want to be sure of getting correct ( clinical ly relevant ) results in clinical trials we must study more patients . Credible estimates of clinical efficacy are only likely to come from large trials or from pooling multiple trials of conventional ( small ) size BACKGROUND Unrelieved postoperative pain may impair rehabilitation , delay recovery , and result in poor outcomes . Preventive multimodal analgesic techniques may improve long-term outcome after surgery . METHODS We r and omized 200 consecutive patients to receive acetaminophen 1000 mg and either celecoxib 400 mg or placebo 1 - 2 h before anterior cruciate ligament surgery . All patients received intraarticular analgesics and had an external cooling system applied to the operative knee . After discharge patients were instructed to take acetaminophen 1000 mg every 6 h and either celecoxib 200 mg every 12 h or matching placebo for the first 14 days postoperatively . All patients were enrolled in an accelerated rehabilitation program . Six months postoperatively , the level of activity was assessed , as was the presence of patellofemoral complications including : anterior knee pain , flexion contracture , quadriceps weakness , and complex regional pain syndrome . RESULTS More patients in the control group developed patellofemoral complications compared to the celecoxib group ( P = 0.001 ) including anterior knee pain ( 14/96 ; 15 % ) vs ( 4/95 ; 1 % ) , complex regional pain syndrome ( 7/96 ; 7 % ) vs ( 1/95 ; 1 % ) , flexion contractures ( 9/96 ; 9 % ) vs ( 2/95 ; 2 % ) , and scar tissue requiring re-arthroscopy ( 8/96 ; 8 % ) vs ( 2/95 ; 2 % ) respectively . More patients in the celecoxib group returned to a higher activity level ( 84 % vs 65 % ) ( P < 0.01 ) , were able to participate at a more intense level ( P < 0.02 ) , and return to full sports activity ( P < 0.05 ) . CONCLUSIONS The administration of celecoxib as a component of a preventive multimodal analgesic technique for anterior cruciate ligament reconstruction reduces long-term patellofemoral complications and increases the likelihood of returning to a preinjury level of activity BACKGROUND : Ketamine has been shown to have a morphine-sparing effect soon after surgery . Nevertheless , whether this effect still exists after being combined with nonsteroidal antiinflammatory drugs and acetaminophen , and whether ketamine can decrease chronic pain after nononcologic surgery remain unclear . Thus , we design ed a study to assess ketamine ’s effect on acute and chronic postoperative pain when combined with multimodal analgesia after total hip arthroplasty ( THA ) . METHODS : Patients scheduled for primary nononcologic THA using st and ardized general anesthesia were r and omized . They received IV ketamine before incision ( 0.5 mg/kg ) , and a 24-h infusion ( 2 & mgr;g · kg−1 · min−1 ) or a similar blinded saline bolus and infusion . Postoperative analgesia included IV acetaminophen , ketoprofen , plus morphine/droperidol patient-controlled analgesia for 48 h. Data pertaining to pain scores , morphine consumption , and need for crutches were collected for 6 mo after THA . Our primary outcome was 24-h morphine consumption . RESULTS : One hundred fifty-four patients were included ( placebo , 75 ; ketamine , 79 ) . Patients and operative data were similar in both groups . Ketamine  decreased morphine consumption at 24 h from 19 ± 12 mg to 14 ± 13 mg ( P = 0.004 ) . At Day 30 , ketamine decreased the proportion of patients needing 2 crutches or a walking frame from 56 % to 31 % ( P = 0.0035 ) . From Day 30 to Day 180 , ketamine decreased the proportion of patients with persistent pain at rest in the operated hip ( P = 0.008 ) . At Day 180 , 21 % of placebo group patients ( 15 of 70 ) experienced pain at rest in the operated hip versus 8 % ( 6 of 72 ) in the ketamine group ( P = 0.036 , odds ratio 0.33 , 95 % confidence interval 0.12–0.91 , risk reduction 67 % ) . CONCLUSIONS : Ketamine had a morphine-sparing effect after THA , even when morphine was combined with multimodal systemic analgesia . It also facilitated rehabilitation at 1 mo and decreased postoperative chronic pain up to 6 mo after surgery Background Perioperative administration of pregabalin , which is effective for neuropathic pain , might reduce early postoperative and chronic pain . This r and omized , double-blinded , placebo-controlled trial ( Clinical Trials.gov ID NCT00905580 ) was design ed to investigate the efficacy and safety of pregabalin for reducing both acute postoperative pain and the development of chronic pain in patients after robot-assisted endoscopic thyroidectomy . Methods Ninety-nine patients were r and omly assigned to groups that received pregabalin 150 mg or placebo 1 h before surgery , with the dose repeated after 12 h. Assessment s of pain and side effects were performed 48 h postoperatively . The incidences of chronic pain and hypoesthesia in the anterior chest were recorded 3 months after surgery . Results Ninety-four patients completed the study .  Verbal numerical rating scale scores for pain and the need for additional analgesics were lower in the pregabalin group ( n = 47 ) than the placebo group ( n = 47 ) during 48 h postoperatively ( P < 0.05 ) . However , incidences of sedation and dizziness were higher in the pregabalin group ( P < 0.05 ) . There were no differences between the groups in the incidences of chronic pain and chest hypoesthesia at 3 months after surgery . Conclusions Perioperative administration of pregabalin ( 150 mg twice per day ) was effective in reducing early postoperative pain but not chronic pain in patients undergoing robot-assisted endoscopic thyroidectomy . Caution should be taken regarding dizziness and sedation Background and objective To find out whether preoperative gabapentin use had a favourable effect on long-term postoperative pain in patients undergoing inguinal herniorrhaphy . Methods Sixty male patients – aged 20–40 years – who were scheduled for unilateral inguinal herniorrhaphy under spinal anaesthesia  were included in this prospect i ve , r and omized , double-blind study . The patients were r and omly allocated to two groups : the gabapentin group ( n = 30 ) received single-dose 1.2 g oral gabapentin 1 h before surgery , and the placebo group received a placebo capsule instead . Spinal anaesthesia was performed with heavy bupivacaine , and all operations were performed by the same surgeon with the same technique . Postoperative analgesia was evaluated during sitting and lying with a visual analogue scale . Assessment of postoperative pain at 1 , 3 and 6 months was carried out with an 11-point numerical rating scale ; 0 indicating ‘ no pain ’ and 10 indicating ‘ worst pain imaginable ’ . Patients who had numerical rating scale scores of more 
    Output:
    
Meta- analysis suggested a modest but statistically significant reduction in the incidence of chronic pain after surgery following treatment with ketamine but not gabapentin or pregabalin .
Furthermore , available evidence does not support the efficacy of gabapentin , pregabalin , non-steroidal anti-inflammatories , intravenous steroids , oral NMDA blockers , oral mexiletine , intravenous fentanyl , intravenous lidocaine , oral venlafaxine or inhaled nitrous oxide for the prevention of chronic postoperative pain