***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: Therapeutic trials often attempt to “ blind ” patient and investigator to the true nature of treatments received , reducing the influences of conscious or subconscious prejudices . In drug trials , this is accomplished with placebo tablets , but blinding in trials of physical treatments is more problematic . This issue arose in a clinical trial of transcutaneous electrical nerve stimulation ( TENS ) for patients with chronic low back pain . Several study design features were incorporated to promote blinding : use of sham TENS units visually identical with real units , exclusion of potential subjects with previous TENS experience , avoidance of a crossover design and use of identical visit frequency , instructions and modifications in electrode placement . Subjects were asked not to discuss treatments with the clinicians who performed outcome assessment s. Both patients and clinicians were asked to guess actual treatment assignments at the trial 's end . Every patient in the true TENS group believed the unit was functioning properly , but the degree of certainty varied . In the sham TENS group , 84 % also believed they had functioning units , but their certainty was significantly less than in the active treatment group . Differences in patient perceptions did not affect compliance , as the two groups had similar dropout rates , appointment compliance , days of TENS use and daily duration of TENS use . Clinicians guessed treatments correctly 61 % of the time ( as opposed to 50 % expected by chance ) , again suggesting partial success in blinding . These efforts at blinding may partly explain the negative trial results for TENS efficacy . We conclude that complete blinding is difficult to achieve because of sensory difference in treatment and unintended communication between patient and examiner . Nonetheless , trials of physical treatments can achieve partial blinding with the techniques described here , and the success of blinding can be assessed with simple questions at study completion Twenty patients undergoing decompressive lumbar laminectomy were r and omly allocated , in a double-blind manner , to receive active or inactive transcutaneous electrical nerve stimulation ( TENS ) as part of the management of their postoperative pain . All patients received the same non-narcotic general anaesthetic . The efficacy of the TENS was assessed by using a  patient-controlled analgesia system ( PRODAC )  which delivered morphine i.v . This system recorded the number of dem and s for analgesia and the total dose administered in the first 24 h. In addition , plasma morphine concentrations were measured hourly for the first 6 h and again at 24 h. There was no statistical difference between the two groups in the number of patient dem and s for analgesia , morphine dose or plasma morphine concentration .  TENS offered no advantage over a placebo in the management of acute postoperative pain in these patients & NA ; The objective was to investigate the relationship between pain relief scores produced by placebo and by active interventions in r and omised controlled trials ( RCTs ) . Individual patient categorical pain relief scores from 5 placebo‐controlled single‐dose parallel‐group RCTs in acute postoperative pain were used to calculate the percentage of the maximum possible pain relief score ( % maxTOTPAR ) for the different treatments . One hundred and thirty of the 525 patients in the 5 trials had a placebo .  Individual patients ' scores with placebo varied from 0 to 100 % of the maximum possible pain relief . The proportion who obtained more than 50 % of the maximum possible pain relief with placebo varied from 7 % to 37 % across the trials ; with the active drugs the variation was from 5 to 63 % . Mean placebo scores were related to the mean score for the active treatments in each study ; the higher the mean active score , the higher the mean placebo score . This relationship disappeared when median values were used . Medical folklore has it that the amount of relief obtained with placebo is one‐third of the maximum possible ( and does not vary ) , and that one‐third of patients respond to placebo . The results show that the amount of relief obtained with placebo varies considerably between patients , that 38 % of patients obtained more than 10 % of the maximum possible relief , and 16 % obtained greater than 50 % . In double‐blind , r and omised parallel‐group studies of high quality placebo scores should not vary . Despite these conditions being met the placebo scores did vary . The previous explanation , of a relationship between the mean placebo scores and the mean scores for the active treatments was not supported A prospect i ve r and omised trial was conducted to assess transcutaneous electrical stimulation in the management of  postoperative pain and its effect on postoperative pulmonary function and respiratory complications .  Consecutive patients undergoing abdominal surgery were allocated to receive transcutaneous electrical stimulation or ' sham ' therapy . There was no significant difference in the amount of postoperative pain as measured by linear analogue pain scales or morphine requirements . Arterial oxygen and carbon dioxide tensions were similar in both groups . There was no difference in the incidence of postoperative chest infection . These results do not support the use of transcutaneous electrical stimulation following abdominal surgery Abstract The influence of transcutaneous electrical stimulation ( TES ) and psychological factors in determining the intensity of  acute postoperative pain was examined in a prospect i ve , double‐blind controlled trial completed by 30 patients having elective surgery . Psychometric tests were administered prior to surgery . Postoperative pain was assessed by cumulative morphine requirement ( M48 ) administered intramuscularly , and the mean score of a visual analogue scale of pain ( VAS ) , in the first 48 h following surgery . M48 was significantly correlated with the VAS score ( r = 0.62 , P < 0.001 ) , and with the psychometric test scores for trait‐anxiety ( r = 0.70 , P < 0.001 ) and neuroticism ( r = 0.67 , P < 0.001 ) . Though patients treated with TES required 25 % less morphine than those treated with placebo , the difference was not significant using monovariate analysis and applying unpaired two‐tailed Student 's t‐test ( P > 0.2 ) . When the contribution of neuroticism to the variance of M48 was adjusted using multiple regression analysis , the effect of TES became significant at the 0.05 level . Covariance analysis showed that TES contributed some 19 % to the explained variance of M48 while neuroticism contributed about 80 % , and there was no interaction between these two factors . These findings allow a degree of prediction of the individual patient 's postoperative pain and narcotic requirement , and point to a strong correlation between postoperative pain perception and personality OBJECTIVE To compare the sensitivity , precision , and the costs in time of search ing by h and and by MEDLINE to identify r and omized controlled trials ( RCTs ) for systematic review s. DESIGN Nine anesthetic and pain journals were search ed by both MEDLINE and by h and for the years 1970 , 1980 , and 1990 , recording number of publications and time taken to identify r and omized double-blind controlled trials in pain research . RESULTS Thirty-four volumes , containing 5583 full publications ( 24,417 pages ) and 2889 abstract s and letters ( 1755 pages ) were h and search ed ; 142 eligible ( definite RCTs ) full papers and 171 eligible abstract s and letters were identified . The MEDLINE search strategy yielded 274 reports of which 138 were eligible ; 125 of these were full papers , 1 was a letter and 12 were abstract s. Two full papers which were identified by the MEDLINE search strategy were missed by h and search . The overall sensitivity of the MEDLINE search strategy for full papers was 87 % ( [ 125/144 ] x 100 ) with a precision of 52 % ( [ 125/242 ] x 100 ) . This is the best combination of sensitivity and precision reported to date . Abstract s were mostly in supplement issues which were not indexed . Combining the MEDLINE search strategy with selective h and search of abstract s and letters gave a sensitivity of 94 % . CONCLUSIONS H and search of entire journals remains the most accurate method for identification of the eligible reports , but it is the most time-consuming . The MEDLINE search was faster , but it failed to identify at least 13 % of the indexed eligible reports . Ideally , both h and search and MEDLINE should be used . The combination of MEDLINE with h and search restricted to letters and abstract s might be an acceptable alternative for review ers with insufficient funds to support a full h and search process Forty patients scheduled to undergo thoracotomy were r and omly allocated to receive either transcutaneous electrical nerve stimulation with intramuscular papaveretum ( 20 patients ) or intramuscular papaveretum alone ( 20 patients ) for postoperative pain relief . Total intramuscular analgesic requirements in the first 24 hours , time to satisfactory transfer to oral analgesia , antiemetic requirements and length of stay in hospital postoperatively were noted . Peak expiratory flow rate was compared pre‐ and postoperatively in the two groups . Use of nerve stimulation did not significantly alter the requirements for analgesia although there was a reduction in postoperative nausea and vomiting in the nerve stimulation group . There was no difference between the two groups with respect to changes in peak expiratory flow rate Perception and relief of pain were studied in a varied group of fifty patients who had undergone laparotomy with upper abdominal midline incisions . Twenty-six patients were supplied with functioning transcutaneous electrical stimulators . Twenty-four received nonfunctioning machines . The controls were r and omized by a nurse not otherwise involved in this study . Only seventeen of the total study group were judged failures and six of the patients had been receiving preoperative narcotics .  Patient response was very favorable and pain relief was good to excellent , especially in one group with working stimulators ( p is less than 0.008 ) . Patients with known malignant disease did not respond as well as those with benign disease although anxiety may have been an important factor here . Use of the transcutaneous electrical stimulator would seem particularly worthwhile for patients undergoing elective abdominal operations for benign disease with no history of narcotic usage . Briefing the patient preoperatively on the potential value of transcutaneous electrical stimulation as a method of pain relief may improve end- results Three rehabilitation modalities relating to in-hospital postoperative care following unilateral total knee arthroplasty ( UTKA ) were studied regarding their effect on pain management and UTKA outcome : ( 1 ) continuous passive motion ( CPM ) ; ( 2 ) CPM with transcutaneous electrical nerve stimulation ( TENS ) ; and ( 3 ) CPM with continuous cooling pad ( CCP ) . Phase I : CPM .  Twenty-two UTKA patients were r and omized into two postoperative care groups : ( 1 ) 12 with CPM ; and ( 2 ) 10 with no CPM .  Total hospitalization pain medication consumption was significantly less for the CPM group ( P less than .05 ) . Phase II : CPM With TENS .  Forty-eight UTKA patients were r and omized into three postoperative care groups : ( 1 ) 18 with an ipsilateral thigh TENS unit delivering sensory threshold stimulation ; ( 2 ) 18 with a subthreshold TENS unit ; and ( 3 ) 12 with no TENS unit . All groups used CPM . No significant difference was found regarding pain medication consumption . Phase III : CPM With CCP .  Thirty consecutive UTKA patients were divided into two postoperative care groups : ( 1 ) 15 with a CCP unit ; and ( 2 ) 15 with no CCP unit . Both groups used CPM . No significant difference was found regarding total or intramuscular hospitalization pain medication consumption . However , oral hospitalization pain medication consumption was significantly less for the CCP group ( P less than .01 ) . This postoperative UTKA study demonstrates significantly decreased total in-hospital pain medication consumption when comparing CPM vs no CPM , significantly decreased oral in-hospital pain medication consumption when comparing CPM with CCP vs CPM without CCP , but no difference when comparing CPM with TENS vs CPM without TENS . ( ABSTRACT TRUNCATED AT 250 WORDS Since the last comprehensive review of anticoagulation in acute myocardial infa rct ion four additional r and omized control trials have been reported . The overwhelming majority of all trials favored anticoagulation .  Rates of thromboembolism were higher in the control , and hemorrhagic complications in the anticoagulated group . Pooling of all r and omized control trials gives mean case fatality rates of 19.6 % for the control and 15.4 % for the anticoagulated group , a relative reduction of 21 % ( P less than 0.05 or less than 0.001 , depending on the analytic method ) . Five of six r and omized control trials reported " no effect " because the difference favoring anticoagulation was not statistically significant . However , sample sizes in these " negative " papers were too small to protect against missing a 21 % reduction in true case fatality rate due to anticoagulation ( beta greater than 0.10 ) . All patients who present no specific contraindication should receive  anticoagulants  during hospitalization for infa rct ion The effect of postoperative transcutaneous electrical nerve stimulation ( TENS ) was evaluated in 24 patients in two r and omly selected groups who underwent thoracotomy .  The patients in one group received TENS through periincisional electrodes , and the remaining patients were treated with sham stimulator setups . The stimulators remained in place for 48 hours after operation . Subjective pain scores , duration of stay in the recovery room , tolerance to chest physical therapy , complaints of nausea , time to end of mechanical ventilation , and narcotic requirements were evaluated . Patients in the TENS group had significantly lower pain scores during the first 24 hours postoperatively ( p = 0.014 ) , shorter recovery room stays ( p = 0.013 ) , and better tolerance 
    Output:
    
Non-r and omized studies overestimated treatment effects