***TASK***
the task is to simplify the input abstract of a biomedical literature

***INPUT***
the input is the abstract of a biomedical literature

***OUTPUT***
the output is the simplified abstract for the input abstract of a biomedical literature

***DOCUMENTATION***

***EXAMPLES***

Input: In total, we included 31 studies (with 3231 participants) in our review. Of those 31 studies, 28 (2976 participants) provided data for the meta-analyses. For the 28 studies, 24 were used for the comparison of neuraxial block versus general anaesthesia. Based on 11 studies that included 2152 participants, we did not find a difference between the two anaesthetic techniques for mortality at one month: risk ratio (RR) 0.78, 95% confidence interval (CI) 0.57 to 1.06; I2 = 24% (fixed-effect model). Based on six studies that included 761 participants, we did not find a difference in the risk of pneumonia: RR 0.77, 95% CI 0.45 to 1.31; I2 = 0%. Based on four studies that included 559 participants, we did not find a difference in the risk of myocardial infarction: RR 0.89, 95% CI 0.22 to 3.65; I2 = 0%. Based on six studies that included 729 participants, we did not find a difference in the risk of cerebrovascular accident: RR 1.48, 95% CI 0.46 to 4.83; I2 = 0%. Based on six studies that included 624 participants, we did not find a difference in the risk of acute confusional state: RR 0.85, 95% CI 0.51 to 1.40; I2 = 49%. Based on laboratory tests, the risk of deep vein thrombosis was decreased when no specific precautions or just early mobilization was used: RR 0.57, 95% CI 0.41 to 0.78; I2 = 0%; (number needed to treat for an additional beneficial outcome (NNTB) = 3, 95% CI 2 to 7, based on a basal risk of 76%) but not when low molecular weight heparin was administered: RR 0.98, 95% CI 0.52 to 1.84; I2 for heterogeneity between the two subgroups = 58%. For neuraxial blocks compared to general anaesthesia, we rated the quality of evidence as very low for mortality (at 0 to 30 days), pneumonia, myocardial infarction, cerebrovascular accident, acute confusional state, decreased rate of deep venous thrombosis in the absence of potent thromboprophylaxis, and return of patient to their own home. The number of studies comparing other anaesthetic techniques was limited. We did not find a difference between the two techniques, except for deep venous thrombosis in the absence of potent thromboprophylaxis. The studies included a wide variety of clinical practices. The number of participants included in the review is insufficient to eliminate a difference between the two techniques in the majority of outcomes studied. Therefore, large randomized trials reflecting actual clinical practice are required before drawing final conclusions.
Output:

The evidence is current to March 2014. In total, we included 31 studies (with 3231 participants) in our review. Of those 31 studies, 28 (2976 participants) provided data for the meta-analyses. The mean age of the participants varied from 75 to 86 years. Those studies were published between 1977 and 2013 and so covering a wide range of clinical practices and improvements in techniques over time. Two studies were funded by the anaesthetic drug manufacturer or by an agency with a commercial interest, one received charitable funding, and one was funded by a government agency. We reran the search in February 2017. Potential new studies of interest were added to a list of "Studies awaiting Classification" and will be incorporated into the formal review findings during the review update. The trial reports of many of the studies indicated a sub-suboptimal level of methodological rigour and the number of participants included was often insufficient to allow us to draw a definitive conclusion on many of the outcomes studied. We did not find any difference in mortality at one month (11 trials with 2152 participants) between neuraxial blocks and general anaesthesia. We also did not find a difference for pneumonia, myocardial infarction, cerebrovascular accident, acute confusional state, congestive heart failure, acute kidney injury, pulmonary embolism, number of patients transfused with red blood cells, length of surgery and length of hospital stay between these two anaesthetic techniques in two to twelve studies. Likewise, when potent prophylactic drugs (such as low molecular weight heparin) were used against postoperative clot formation, we did not find a difference in the risk of deep venous thrombosis. Without prophylaxis with potent anticoagulant drugs the risk of deep venous thrombosis was less with neuraxial block. The level of evidence was very low for mortality, pneumonia, myocardial infarction, cerebrovascular accident, acute confusional state, decrease in the incidence of deep venous thrombosis in the absence of potent prophylaxis, and return of patient to their own home. This means that any estimate of effect is very uncertain.