Systematic review, meta-analysis and meta-regression of the effect of tranexamic acid on surgical blood loss

Background

Tranexamic acid (TXA) reduces blood transfusion in surgery but the extent of the reduction in blood loss and how it relates to the dose of TXA is unclear.

Methods

A systematic review of randomized trials was performed. Data were extracted on blood loss from trials comparing intravenous TXA with no TXA or placebo in surgical patients. A Bayesian linear regression was used to describe the relationship between the reduction in blood loss with TXA and the extent of bleeding as measured by the mean blood loss in the control group. A meta-analysis of the log-transformed data was conducted to quantify the effect of TXA on blood loss, stratified by type of surgery, timing of TXA administration and trial quality. Meta-regression was used to explore the effect of TXA dosage.

Results

Data from 104 trials were examined. Although the absolute reduction in blood loss with TXA increased as surgical bleeding increased, the percentage reduction was similar. TXA reduced blood loss by 34 per cent (pooled ratio 0·66, 95 per cent confidence interval 0·65 to 0·67; P < 0·001). The percentage reduction in blood loss with TXA differed by type of surgery, timing of TXA administration and trial quality, but the differences were small. The effect of TXA on blood loss did not vary over the range of doses assessed (5·5–300 mg/kg).

Conclusion

TXA reduces blood loss in surgical patients by about one-third. A total dose of 1 g appears to be sufficient for most adults. There is no evidence to support the use of high doses.

Beta-2 receptor antagonists for traumatic brain injury: a systematic review of controlled trials in animal models

A systematic review and meta-analysis of controlled trials was undertaken to assess the effects of beta-2 receptor antagonists in animal models of traumatic brain injury (TBI). Database and reference list searches were performed to identify eligible studies. Outcome data were extracted on functional status, as measured by the grip test or neurological severity score (NSS), and cerebral edema, as measured by brain water content (BWC). Data were pooled using the random-effects model. Seventeen controlled trials involving 817 animals were identified. Overall methodological quality was poor. Results from the grip test suggest that the treatment group maintained grip for a longer period than the control group; pooled weighted mean difference (WMD) = 8.28 (95% CI 5.78-10.78). The treatment group was found to have a lower NSS (i.e., better neurological function); pooled WMD =-3.28 (95% CI -4.72 to -1.85). Analysis of the cerebral edema data showed that the treatment group had a lower BWC than the control; pooled WMD =-0.42 (95% CI -0.59 to -0.26). There was evidence of statistical heterogeneity between comparisons for all outcomes. Evidence for small study effects was found for the grip test and BWC outcomes. The evidence from animal models of TBI suggests that beta-2 receptor antagonists can improve functional outcome and lessen cerebral edema. However, the poor methodological quality of the included studies and presence of small study effects may have influenced these findings.

Detection thresholds for 2-isopropyl-3-methoxypyrazine in Concord and Niagara grape juice

2-isopropyl-3-methoxypyrazine (IPMP) is the compound responsible for the off-flavor known as ladybug taint, which occurs when Harmnonia axyridis beetles become incorporated with the grapes during juice processing. It is also an important grape-derived component of juice flavor in some varieties. The main objective of this study was to determine the orthonasal (ON) and retronasal (RN) detection thresholds for IPMP in juice. The ASTM E679 ascending forced choice method of limits was used to determine detection thresholds for 26 individuals in Concord and Niagara juices. Group best estimate thresholds (BETs) averaged 0.93 ng/L and were 50% and 21% higher in Concord than in Niagara juices for ON and RN evaluation, respectively. Group BETs for IPMP (ng/L) for Concord were ON: 1.11; RN: 1.02 and for Niagara were ON: 0.74; RN: 0.84. Variation in individual detection thresholds was observed, although familiarity with ladybug taint was not associated with individual threshold values. We conclude that humans are very sensitive to IPMP in juice, and that detection thresholds are more strongly influenced by grape variety than evaluation mode. These results may assist juice producers in establishing tolerance levels for IPMP in juice affected by ladybug taint or derived from grapes of suboptimal ripeness.

Determination of ortho- and retronasal detection thresholds for 2-isopropyl-3-methoxypyrazine in wine

2-Isopropyl-3-methoxypyrazine (IPMP) is a grape-derived component of wine flavor in some wine varieties as well as the causal compound of the off-flavor known as ladybug taint (LBT), which occurs when Harmonia axyridis beetles are incorporated with the grapes during juice and wine processing. The main objective of this study was to obtain robust estimates of the orthonasal (ON) and retronasal (RN) detection thresholds (DTs) for IPMP in wines of differing styles. The ASTM E679 ascending forced choice method of limits was used to determine DTs for 47 individuals in 3 different wines--Chardonnay, Gewürztraminer, and a red wine blend of Baco Noir and Marechel Foch. The group best estimate thresholds (BETs) obtained for IPMP (ng/L) were Chardonnay, ON: 0.32; Gewürztraminer, ON: 1.56, RN: 1.15, and red wine blend, ON: 1.03, RN: 2.29. A large variation in individual DTs was observed. Familiarity with LBT was inversely correlated with DTs for Gewürztraminer, and no difference in thresholds was observed between winemakers and nonwinemakers. We conclude that the human DT for IPMP is extremely low and influenced significantly by wine style and evaluation mode. We recommend against the reporting of single-threshold values for wine flavor compounds, and encourage the determination of consumer rejection thresholds for IPMP in wine.

Beta-2 receptor antagonists for acute traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Cerebral oedema, the accumulation of fluid within the brain, is believed to be an important contributor to the secondary brain damage that occurs following injury. The release of kinins is thought to be an important factor in the development of cerebral vasogenic oedema and the use of beta-2 receptor antagonists, which prevent the release of these kinins, have been proposed as a potential therapeutic intervention.

OBJECTIVES

The objective was to assess the safety and effectiveness of beta-2 receptor antagonists for TBI.

SEARCH STRATEGY

We searched the Cochrane Injuries Group's specialised register, CENTRAL, MEDLINE, EMBASE, National Research Register, LILACs, Zetoc, Web of Knowledge and Current Controlled Trials. We also searched the internet and checked the reference lists of relevant papers to identify any further studies. The searches were conducted in March 2007.

SELECTION CRITERIA

Randomised controlled trials of beta-2 receptor antagonists versus placebo for TBI.

DATA COLLECTION AND ANALYSIS

Two authors independently screened search results and assessed the full texts of potentially relevant studies for inclusion. Data were extracted and methodological quality was examined. Relative risks (RR) and 95% confidence intervals (CIs) were calculated and data were pooled using a fixed effect model.

MAIN RESULTS

Three studies were included, involving 178 participants. All three studies reported the effects of beta-2 receptor antagonists on mortality. The pooled RR for mortality was 0.63 (95% CI 0.36 to 1.10). Two studies measured disability, the RR of death or severe disability with beta-2 receptor antagonists was 0.81 (95% CI 0.59 to 1.09). Two studies measured the effect on intracranial pressure (ICP), although in only one did this finding reach statistical significance. There was no evidence for the presence of heterogeneity.

AUTHORS' CONCLUSIONS

There is no reliable evidence that beta-2 receptor antagonists are effective in reducing mortality or disability after TBI. Further well conducted randomised controlled trials are required.

Interventions in the alcohol server setting for preventing injuries

BACKGROUND

Injuries are a significant public health burden and alcohol intoxication is recognised as a risk factor for injuries. There is increasing attention on supply-side interventions, which aim to modify the environment and context within which alcohol is supplied and consumed.

OBJECTIVES

To quantify the effectiveness of interventions implemented in the server setting for reducing injuries.

SEARCH STRATEGY

We searched the Cochrane Injuries Group Specialised Register (September 2004), Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2004), MEDLINE (January 1966 to September 2004), EMBASE (1980 to 2004, wk 36), other specialised databases and reference lists of articles. We also contacted experts in the field.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and non-randomised controlled studies (NRS) of the effectiveness of interventions administered in the server setting which attempted to modify the conditions under which alcohol is served and consumed, to facilitate sensible alcohol consumption and reduce the occurrence of alcohol-related harm.

DATA COLLECTION AND ANALYSIS

Two authors independently screened search results and assessed the full texts of potentially relevant studies for inclusion. Data were extracted and methodological quality was examined. Due to variability in the intervention types investigated, a pooled analysis was not appropriate.

MAIN RESULTS

Twenty studies met the inclusion criteria. Overall methodological quality was poor. Five studies used an injury outcome measure; only one of these studies was randomised. The studies were grouped into broad categories according to intervention type. One NRS investigated server training and estimated a reduction of 23% in single vehicle night-time crashes in the experimental area (controlled for crashes in the control area). Another NRS examined the impact of a drink driving service, and reported a reduction in injury road crashes of 15% in the experimental area, with no change in the control; no difference was found for fatal crashes. One NRS investigating the impact of a policy intervention, reported that pre-intervention the serious assault rate in the experimental area was 52% higher than the rate in the control area. After intervention, the serious assault rate in the experimental area was 37% lower than in the control. The only RCT targeting the server setting environment with an injury outcome compared toughened glassware (experimental) to annealed glassware (control) on number of bar staff injuries; a greater number of injuries were detected in the experimental group (relative risk 1.72, 95% CI 1.15 to 2.59). A NRS investigating the impact of a intervention aiming to reduce crime experienced by drinking premises; found a lower rate of all crime in the experimental premises (rate ratio 4.6, 95% CI 1.7 to 12, P = 0.01), no difference was found for injury (rate ratio 1.1. 95% CI 0.1 to 10, P = 0.093). The effectiveness of the interventions on patron alcohol consumption is inconclusive. One randomised trial found a statistically significant reduction in observed severe aggression exhibited by patrons. There is some indication of improved server behaviour but it is difficult to predict what effect this might have on injury risk.

AUTHORS' CONCLUSIONS

There is no reliable evidence that interventions in the alcohol server setting are effective in reducing injury. Compliance with interventions appears to be a problem; hence mandated interventions may be more likely to show an effect. Randomised controlled trials, with adequate allocation concealment and blinding are required to improve the evidence base. Further well conducted non-randomised trials are also needed, when random allocation is not feasible.

Colloids versus crystalloids for fluid resuscitation in critically ill patients

BACKGROUND

Colloid solutions are widely used in fluid resuscitation of critically ill patients. There are several choices of colloid and there is ongoing debate about the relative effectiveness of colloids compared to crystalloid fluids.

OBJECTIVES

To assess the effects on mortality of colloids compared to crystalloids for fluid resuscitation in critically ill patients.

SEARCH STRATEGY

We searched the Injuries Group specialised register, Cochrane Controlled Trials Register, MEDLINE, EMBASE and BIDS Index to Scientific and Technical Proceedings, and checked reference lists of trials and review articles.

SELECTION CRITERIA

All randomised and quasi-randomised trials of colloids compared to crystalloids, in patients requiring volume replacement. Cross-over trials and trials in pregnant women and neonates were excluded.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and rated quality of allocation concealment. Trials with a 'double-intervention', such as those comparing colloid in hypertonic crystalloid to isotonic crystalloid, were analysed separately. The analysis was stratified according to colloid type and quality of allocation concealment.

MAIN RESULTS

Colloids compared to crystalloidsAlbumin or plasma protein fraction. Nineteen trials reported data on mortality, including a total of 7576 patients. The pooled relative risk (RR) from these trials was 1.02 (95% confidence interval [95% CI] 0.93 to 1.11). When the trial with poor quality allocation concealment was excluded, pooled RR was 1.01 (95% CI 0.92 to 1.10). Hydroxyethyl starch. Ten trials compared hydroxyethyl starch with crystalloids, including a total of 374 randomised participants. The pooled RR was 1.16 (95% CI 0.68 to 1.96). Modified gelatin. Seven trials compared modified gelatin with crystalloid, including a total of 346 randomised participants. The pooled RR was 0.54 (95% CI 0.16 to 1.85). Dextran. Nine trials compared dextran with a crystalloid, including a total of 834 randomised participants. The pooled relative risk was RR 1.24 (95% CI 0.94 to 1.65). Colloids in hypertonic crystalloid compared to isotonic crystalloidEight trials compared dextran in hypertonic crystalloid with isotonic crystalloid, including 1283 randomised participants. Pooled RR was 0.88 (95% CI 0.74 to 1.05).

REVIEWERS' CONCLUSIONS

There is no evidence from randomised controlled trials that resuscitation with colloids reduces the risk of death, compared to resuscitation with crystalloids, in patients with trauma, burns or following surgery. As colloids are not associated with an improvement in survival, and as they are more expensive than crystalloids, it is hard to see how their continued use in these patients can be justified outside the context of randomised controlled trials.

Traffic calming for the prevention of road traffic injuries: systematic review and meta-analysis

OBJECTIVE

To assess whether area-wide traffic calming schemes can reduce road crash related deaths and injuries.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Cochrane Injuries Group Specialised Register, Cochrane Central Register of Controlled Trials, Medline, EMBASE, Sociological Abstracts Science (and social science) citation index, National Technical Information service, Psychlit, Transport Research Information Service, International Road Research Documentation, and Transdoc, and web sites of road safety organisation were searched; experts were contacted, conference proceedings were handsearched, and relevant reference lists were checked.

INCLUSION CRITERIA

Randomised controlled trials, and controlled before/after studies of area-wide traffic calming schemes designed to discourage and slow down through traffic on residential roads.

METHODS

Data were collected on road user deaths, injuries, and traffic crashes. For each study rate ratios were calculated, the ratio of event rates before and after intervention in the traffic calmed area divided by the corresponding ratio of event rates in the control area, which were pooled to give an overall estimate using a random effects model.

FINDINGS

Sixteen controlled before/after studies met our inclusion criteria. Eight studies reported the number of road user deaths: pooled rate ratio 0.63 (95% confidence interval (CI) 0.14 to 2.59). Sixteen studies reported the number of injuries (fatal and non-fatal): pooled rate ratio 0.89 (95% CI 0.80 to 1.00). All studies were in high income countries.

CONCLUSION

Area-wide traffic calming in towns and cities has the potential to reduce road traffic injuries. However, further rigorous evaluations of this intervention are needed, especially in low and middle income countries.

Post-licence driver education for the prevention of road traffic crashes

BACKGROUND

Worldwide, each year over a million people are killed and some ten million people are permanently disabled in road traffic crashes. Post-licence driver education is used by many as a strategy to reduce traffic crashes. However, the effectiveness of post-licence driver education has yet to be ascertained.

OBJECTIVES

To quantify the effectiveness of post-licence driver education in reducing road traffic crashes.

SEARCH STRATEGY

We searched the following electronic databases: the Cochrane Injuries Group's Specialised Register, Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, TRANSPORT (NTIS, TRIS, TRANSDOC, IRRD), Road Res (ARRB), ATRI, National Research Register, PsycInfo, ERIC, SPECTR, Zetoc, SIGLE, Science (and Social Science) Citation Index. We searched the Internet, checked reference lists of relevant papers and contacted appropriate organisations. The search was not restricted by language or publication status.

SELECTION CRITERIA

Randomised controlled trials comparing post-licence driver education versus no education, or one form of post-licence driver education versus another.

DATA COLLECTION AND ANALYSIS

Two reviewers independently screened search results, extracted data and assessed methodological trial quality.

MAIN RESULTS

We found 24 trials of driver education, 23 conducted in the USA and one in Sweden. Twenty trials studied remedial driver education. The methodological quality of the trials was poor and three reported data unsuitable for meta-analysis. Nineteen trials reported traffic offences: pooled relative risk (RR) = 0.96, 95% confidence interval (95% CI) = 0.94, 0.98); trial heterogeneity was significant (p=<0.00001). Fifteen trials reported traffic crashes: pooled RR = 0.98 (95% CI 0.96, 1.01), trial heterogeneity was not significant (p=0.75). Four trials reported injury crashes: pooled RR = 1.12 (95% CI 0.88, 1.41), trial heterogeneity was significant (p=<0.00001). No one form of education (correspondence, group or individual) was found to be substantially more effective than another, nor was a significant difference found between advanced driver education and remedial driver education. Funnel plots indicated the presence of publication bias affecting the traffic offence and crash outcomes.

REVIEWER'S CONCLUSIONS

This systematic review provides no evidence that post-licence driver education is effective in preventing road traffic injuries or crashes. Although the results are compatible with a small reduction in the occurrence of traffic offences, this may be due to selection biases or bias in the included trials. Because of the large number of participants included in the meta-analysis (close to 300,000 for some outcomes) we can exclude, with reasonable precision, the possibility of even modest benefits.

Area-wide traffic calming for preventing traffic related injuries

BACKGROUND

It is estimated that by 2020 road traffic crashes will have moved from ninth to third in the world disease burden ranking, as measured in disability adjusted life years, and second in developing countries. The identification of effective strategies for the prevention of traffic related injuries is of global health importance. Area-wide traffic calming schemes that discourage through traffic on residential roads is one such strategy.

OBJECTIVES

To evaluate the effectiveness of area-wide traffic calming in preventing traffic related crashes, injuries, and deaths.

SEARCH STRATEGY

We searched the following electronic databases: Cochrane Injuries Group's Specialised Register, Cochrane Controlled Trials Register, MEDLINE, EMBASE and TRANSPORT (NTIS, TRIS, TRANSDOC). We searched the web sites of road safety organisations, handsearched conference proceedings, checked reference lists of relevant papers and contacted experts in the area. The search was not restricted by language or publication status.

SELECTION CRITERIA

Randomised controlled trials, and controlled before-after studies of area-wide traffic calming schemes.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data on type of study, characteristics of intervention and control areas, and length of data collection periods. Before and after data were collected on the total number of road traffic crashes, all road user deaths and injuries, pedestrian-motor vehicle collisions and road user deaths. The statistical package STATA was used to calculate rate ratios for each study, which were then pooled to give an overall estimate using a random effects model.

MAIN RESULTS

We found no randomised controlled trials, but 16 controlled before-after trials met our inclusion criteria. Seven studies were done in Germany, six in the UK, two in Australia and one in the Netherlands. There were no studies in low or middle income countries. Eight trials reported the number of road traffic crashes resulting in deaths. The pooled rate ratio was 0.63 (0.14, 2.59 95% CI). Sixteen studies reported the number of road traffic crashes resulting in injuries (fatal and non fatal). The pooled rate ratio was 0.89 (0.80, 1.00 95% CI). Nine studies reported the total number of road traffic crashes. The pooled rate ratio was 0.95 (0.81, 1.11 95% CI). Thirteen trials reported the number of pedestrian-motor vehicle collisions. The pooled rate ratio was 1.00 (0.84, 1.18). There was significant heterogeneity for the total number of crashes and deaths and injuries.

REVIEWER'S CONCLUSIONS

The results from this review suggest that area-wide traffic calming in towns and cities may be a promising intervention for reducing the number of road traffic injuries, and deaths. However, further rigorous evaluations of this intervention are needed.