***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: Background :  Pain after coronary artery bypass surgery persists for several days . A continuous intravenous infusion of an opioid adequately accomplishes good pain control in the intensive care unit , but it is often not suitable on the ordinary ward . Patient‐controlled analgesia ( PCA ) with intermittent injections delivered by one of the new devices now available could be an alternative to conventional nurse‐controlled analgesia ( NCA ) based on intermittent injections . The aim was to compare these two techniques with respect to efficacy and the amount of opioid used The pharmacy and nursing time requirements , quality of postoperative pain control , and cost of patient-controlled analgesia ( PCA ) and intramuscular ( i.m . ) analgesic therapy were studied . All timings were conducted with a stopwatch on a single nursing unit that primarily receives gynecologic surgery patients . The various work elements involved in each type of therapy were timed individually . Both quality of analgesia and cost were evaluated in a prospect i ve , r and omized study in hysterectomy patients . I.M. patients received meperidine hydrochloride 75 - 100 mg every three to four hours as needed . PCA  patients had access to morphine sulfate 1 mg or meperidine hydrochloride 10 mg , with a six-minute lockout period . The patients scored their pain every four hours . Direct costs for PCA were calculated as drug cost plus tubing cost plus form cost plus maintenance cost plus depreciation cost . Direct costs for i.m . therapy consisted of the cost of drugs . The total mean nursing time per patient was 16.9 minutes for PCA and 10.7 minutes for i.m . therapy . Pharmacy time per patient was 5.1 minutes longer for PCA than for i.m . therapy . Thirty-six hysterectomy patients ( 17 i.m . and 19 PCA ) were enrolled in the study of pain control and cost . Among i.m . patients , 64 % of the pain scores were mild or worse , compared with 40 % for PCA patients . The median pain scores were moderate for i.m . patients and mild for PCA patients . Scores tended to be lower for PCA patients at 16 and 20 hours . Although equal numbers of patients in the two groups experienced nausea , i.m . patients needed more doses of antiemetics than PCA patients . ( ABSTRACT TRUNCATED AT 250 WORDS The purpose of this comparative study was to examine differences in pain intensity , sleep disturbance , sleep effectiveness , fatigue , and vigor between patients undergoing cholecystectomy who received either patient-controlled analgesia ( PCA ) or intramuscular ( IM ) injections of narcotics for postoperative pain . The PCA group consisted of 16 women , aged 22 - 58 ; the IM group consisted of 10 women , aged 22 - 60 . Data were collected on patients ' postoperative days 1 and 2 . Findings indicated that patients receiving PCA reported less pain on postoperative day 1 and less fatigue on postoperative day 2 than patients receiving IM injections of narcotics BACKGROUND In previous studies comparing patient-controlled-analgesia and intramuscular pain management have been unable to provide conclusive evidence of the benefits of either method of postoperative pain control . AIM The purpose of the study was to compare the efficacy and cost-effectiveness of intravenous patient-controlled-analgesia with intermittent intramuscular morphine for Chinese women in the first 24 hours following elective gynaecological surgery . METHODS A r and omized control design was used . The main outcomes were level of pain and cost for the two types of pain management . Participants indicated their level of pain at rest and when deep breathing or coughing on a 100 mm Visual Analogue Scale , on seven occasions within 24 postoperative hours . Costs for the two types of pain management were based on the costs of equipment , drugs and nursing time . RESULTS A total of 125 women participated in the study .  Mean pain level over the 24 hours in the patient-controlled-analgesia group was significantly lower than in the intramuscular group ( P < 0.001 ) . Mean pain level over the seven occasions for the patient-controlled-analgesia group was 11.83 points ( 95 % CI 7.14 - 16.52 ) lower when at rest and 11.73 points ( 95 % CI 5.96 - 17.50 ) lower during motion than the intramuscular group . Cost per patient was $ 81.10 ( Hong Kong ) higher for patient-controlled-analgesia than for intramuscular pain management . Women in the patient-controlled-analgesia group had significantly greater satisfaction with pain management than those in the intramuscular group ( P < 0.001 ) , but reported significantly more episodes of nausea ( P < 0.05 ) . CONCLUSIONS While patient-controlled-analgesia was more costly , it was also more effective than conventional on-dem and intramuscular opioid injections after laparotomy for gynaecological surgery Purpose This prospect i ve study was undertaken to compare the effectiveness and safety of a multimodal pain control protocol with those of intravenous patient-controlled analgesia in rotator cuff repair . Methods Seventy patients scheduled for rotator cuff repair were r and omized to either a multimodal pain control group ( group 1 , 40 patients ) or an intravenous patient-controlled analgesia group ( group 2 , 30 patients ) . We compared these two groups with respect to level of pain before surgery to the fifth postoperative day , duration of postoperative rehabilitation , consumption of additional analgesics , and adverse effects . Results Mean visual analogue scale scores immediately after surgery ( day 0 ) and on postoperative days 1–5 were 6.9 , 5.5 , 4.3 , 3.3 , 3.0 , and 2.6 in group 1 and 7.8 , 5.9 , 4.4 , 4.7 , 4.3 , and 3.7 in group 2 . Pain relief was significantly better in group 1 on days 0 , 3 , 4 , and 5 ( P = 0.026 , 0.006 , 0.010 , and 0.009 , respectively ) . Furthermore , functional recovery occurred earlier in group 1 . No significant differences were observed between the two groups with respect to nausea , vomiting , urinary retention , and headache ( n.s . ) , but group 1 was found to be significantly less likely to experience dizziness or urticaria ( P = 0.007 , 0.017 , respectively ) . One other significant difference was observed : 1 patient ( 2.5 % ) in group 1 and 6 patients ( 20 % ) in group 2 discontinued regimen because of medication-related adverse effects ( P = 0.016 ) . Conclusion The multimodal pain control protocol was found to offer more effective postoperative pain control with fewer adverse effects than intravenous patient-controlled analgesia . However , achieving adequate pain control within the first 48 h of surgery remains challenging , and thus , the developments of more effective and safer multimodal pain control protocol s are required Background and Objectives : To compare the use of patient-controlled analgesia to intermittent intramuscular injections of morphine following major gynecological laparoscopic procedures in order to assess differences in level of pain , sedation , episodes of nausea and /or vomiting , hospitalization time and patient satisfaction with their postoperative analgesia . Methods : Seventy-two patients undergoing major gynecological laparoscopic surgery were r and omized to receive either postoperative analgesia via intermittent intramuscular injection of morphine ( Group 1 ) or patient controlled analgesia ( PCA - Group 2 ) . All patients received anesthesia via a st and ardized protocol . Postoperative pain levels were recorded via a 10 cm visual analogue scale , and sedation scores were recorded on a st and ard PCA form . Episodes of nausea and vomiting were also recorded on the same form . Results : There were no statistically significant differences between intramuscular analgesia and PCA for any of the factors studied . Most significantly it was found that most patients ceased to require either form of parenteral analgesia within 24 hours of their procedure , regardless of the operating time . Conclusion : It is important for the surgeon to be aware of the effects of postoperative analgesia on his or her patients ' level of satisfaction . We do not recommend the use of PCA analgesia following major laparoscopic gynecological surgery 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 After open prostatectomy , 52 patients were r and omly allocated to two treatment groups . Group A ( 26 patients ) received buprenorphine sublingually , and in group B ( 26 patients ) the analgesia was induced using a patient-controlled analgesia system with morphine . The total dose of morphine given during the first 24 h was 72 + /- 8 mg compared to 1.6 + /- 0.45 mg of buprenorphine . The total dose of buprenorphine  on days 2 and 3 was significantly lower than the total dose of morphine ( p < 0.01 ) . There were no significant differences in visual pain scores , side effects , mean arterial blood pressure , pulse rate and respiration rate between the two groups . Sublingual application of buprenorphine offers an effective and easy alternative to the parenteral route of morphine for the management of postoperative pain A r and omized , controlled clinical trial was conducted on 66 patients undergoing elective cardiac surgery to compare patient-controlled analgesia ( PCA ) to nurse-controlled analgesia ( NCA ) with continuous morphine infusion . Hourly assessment of pain ( at rest and on movement ) using a visual analogue scale ( VAS ) , of respiratory rate , and level of sedation took place for the 24 h following extubation . The incidence of nausea was also recorded . Mean pain scores were calculated , and peak pain and sedation scores , together with lowest respiratory rates , were identified .  Morphine consumption was measured at 24 h. No significant differences were found between the groups ' scores for pain or sedation . The PCA group had significantly lower respiratory rates ( P = 0.02 ) and a lower incidence of nausea ( P = 0.008 ) . The PCA group also consumed significantly more  morphine  ( P = 0.0001 ) . The study suggests a beneficial effect from PCA after cardiac surgery in reducing nausea , compared to NCA . It confirms nurse-controlled infusion analgesia as an effective form of pain relief in an intensive care and high-dependency setting We have evaluated the level of state and trait anxiety , neuroticism , extroversion and coping style as predictors of the effectiveness of patient-controlled analgesia ( PCA ) in 110 patients undergoing total abdominal hysterectomy . After operation patients were allocated to receive pain control with either PCA or i.m . injections ( IMI ) .  Pain was assessed using the short form McGill pain question naire at 6 , 18 and 24 h after operation , and by recording the amount of analgesic consumed in the first 24 h after surgery . Both state anxiety and coping style were significant predictors of postoperative pain , irrespective of the method of analgesia used . Patients using PCA experienced significantly better pain control than those receiving IMI . However , it was those with high levels of state anxiety who experienced the greatest reduction in pain with PCA . In addition to achieving better pain control , patients who received PCA used significantly less analgesia and were discharged earlier than patients who received IMI We have compared patients ' and nurses ' assessment s of postoperative pain and anxiety after different analgesic treatments . Sixty orthopaedic patients were allocated r and omly to receive i.v . piritramide ( either nurse-controlled or patient-controlled ) or subarachnoid bupivacaine ( nurse-controlled or patient-controlled ) 
    Output:
    
Although Ballantyne 's meta- analysis found that PCA did have a small but statistically significant benefit upon pain intensity , a 2001 review by Walder et al did not find statistically significant differences in pain intensity or pain relief between PCA and groups treated with non-patient controlled analgesia .
There was no difference in the length of hospital stay .
This review provides moderate to low quality evidence that PCA is an efficacious alternative to non-patient controlled systemic analgesia for postoperative pain control