Hypothermic Circulatory Arrest Alone vs With Perfusion
Hypothermic Circulatory Arrest Alone vs With Perfusion
Electronic searches were performed using Ovid Medline, PubMed, Cochrane Central Register of Controlled Trials (CCTR), Cochrane Database of Systematic Reviews (CDSR), ACP Journal Club, and Database of Abstracts of Review of Effectiveness (DARE) from their date of inception to January 2013. To achieve the maximum sensitivity of the search strategy and identify all studies, we combined the terms "cerebral perfusion" or "antegrade" and "circulatory arrest" and "aortic arch" as either key words or MeSH terms. The reference lists of all retrieved articles were reviewed for further identification of potentially relevant studies. All identified articles were systematically assessed using the inclusion and exclusion criteria. Expert academic cardiothoracic surgeons from the International Aortic Arch Surgery Study Group (IAASSG) formed the expert advisory panel and were asked whether they knew of any unpublished data.
Eligible comparative studies for the present meta-analysis included those in which patient cohorts underwent DHCA alone, or DHCA with SACP, for aortic arch surgery. Circulatory arrest temperatures of comparative arms must be between 14.1 and 20 °C, determined either by protocol, or reported as minimal mean temperature. This temperature category was established by a recent Consensus of IAASSG, which classified profound (≤14 °C), deep (14.1–20 °C), moderate (20.1–28 °C) and mild (>28 °C) hypothermia utilized in arch surgery.
Studies that did not include stroke as a primary endpoint, or those whose primary patient set had a mean or median age less than 18 years old, were excluded. All publications were limited to those involving human subjects and in the English language. Abstracts, case reports, conference presentations, editorials, and expert opinions were excluded. Review articles were omitted because of potential publication bias and duplication of results. Studies that included fewer than 10 patients were also excluded.
Primary endpoints assessed included permanent neurological deficit (PND) and temporary neurological deficit (TND). Secondary endpoints included perioperative death, renal failure and reoperation for bleeding. PND was defined as stroke and/or coma and somnolence, while TND was defined as postoperative confusion, obtundation, agitation, delirium, focal deficits resolving within 24–72 hours, seizures or psychosis, or transient ischemic attacks. Perioperative death was defined as death occurring within 30 days or within the same hospital stay.
All data were extracted from article texts, tables and figures. Two investigators (D.H.T. and B.W.) independently reviewed each retrieved article. Discrepancies between the two reviewers were resolved by discussion and consensus. The final results were confirmed by the senior investigator (T.D.Y.).
The odds ratio (OR) was used as a summary statistic. In the present study, both fixed- and random-effect models were tested. In a fixed-effects model, it was assumed that treatment effect in each study was the same, whereas in a random-effects model, it was assumed that there were variations between studies. χ tests were used to study heterogeneity between trials. I statistic was used to estimate the percentage of total variation across studies, owing to heterogeneity rather than chance, with values greater than 50% considered as substantial heterogeneity. Possible clinical and methodological reasons for any substantial heterogeneity were explored qualitatively where appropriate. In the present meta-analysis, the results using the random-effects model were presented to take into account the possible clinical diversity and methodological variation between studies. Specific analyses considering confounding factors were not possible due to absence of raw data.
Evidence of publication bias was sought using the methods of Egger et al. and Begg et al.. Contour-enhanced funnel plot was performed to aid in interpretation of the funnel plot. If studies appear to be missing in areas of low statistical significance, then it is possible that the asymmetry is due to publication bias. If studies appear to be missing in areas of high statistical significance, then publication bias is a less likely cause of the funnel asymmetry. Intercept significance was determined by the t-test suggested by Egger et al. P<0.05 was considered representative of statistically significant publication bias.
All P values were 2-sided. All statistical analysis was conducted with Review Manager version 5.2.1 (Cochrane Collaboration, Software Update, Oxford, United Kingdom), or STATA version 11.0 (Stata Corporation, College Station, TX).
Methods
Literature Search Strategy
Electronic searches were performed using Ovid Medline, PubMed, Cochrane Central Register of Controlled Trials (CCTR), Cochrane Database of Systematic Reviews (CDSR), ACP Journal Club, and Database of Abstracts of Review of Effectiveness (DARE) from their date of inception to January 2013. To achieve the maximum sensitivity of the search strategy and identify all studies, we combined the terms "cerebral perfusion" or "antegrade" and "circulatory arrest" and "aortic arch" as either key words or MeSH terms. The reference lists of all retrieved articles were reviewed for further identification of potentially relevant studies. All identified articles were systematically assessed using the inclusion and exclusion criteria. Expert academic cardiothoracic surgeons from the International Aortic Arch Surgery Study Group (IAASSG) formed the expert advisory panel and were asked whether they knew of any unpublished data.
Selection Criteria
Eligible comparative studies for the present meta-analysis included those in which patient cohorts underwent DHCA alone, or DHCA with SACP, for aortic arch surgery. Circulatory arrest temperatures of comparative arms must be between 14.1 and 20 °C, determined either by protocol, or reported as minimal mean temperature. This temperature category was established by a recent Consensus of IAASSG, which classified profound (≤14 °C), deep (14.1–20 °C), moderate (20.1–28 °C) and mild (>28 °C) hypothermia utilized in arch surgery.
Studies that did not include stroke as a primary endpoint, or those whose primary patient set had a mean or median age less than 18 years old, were excluded. All publications were limited to those involving human subjects and in the English language. Abstracts, case reports, conference presentations, editorials, and expert opinions were excluded. Review articles were omitted because of potential publication bias and duplication of results. Studies that included fewer than 10 patients were also excluded.
Primary endpoints assessed included permanent neurological deficit (PND) and temporary neurological deficit (TND). Secondary endpoints included perioperative death, renal failure and reoperation for bleeding. PND was defined as stroke and/or coma and somnolence, while TND was defined as postoperative confusion, obtundation, agitation, delirium, focal deficits resolving within 24–72 hours, seizures or psychosis, or transient ischemic attacks. Perioperative death was defined as death occurring within 30 days or within the same hospital stay.
Data Extraction and Critical Appraisal
All data were extracted from article texts, tables and figures. Two investigators (D.H.T. and B.W.) independently reviewed each retrieved article. Discrepancies between the two reviewers were resolved by discussion and consensus. The final results were confirmed by the senior investigator (T.D.Y.).
Statistical Analysis
The odds ratio (OR) was used as a summary statistic. In the present study, both fixed- and random-effect models were tested. In a fixed-effects model, it was assumed that treatment effect in each study was the same, whereas in a random-effects model, it was assumed that there were variations between studies. χ tests were used to study heterogeneity between trials. I statistic was used to estimate the percentage of total variation across studies, owing to heterogeneity rather than chance, with values greater than 50% considered as substantial heterogeneity. Possible clinical and methodological reasons for any substantial heterogeneity were explored qualitatively where appropriate. In the present meta-analysis, the results using the random-effects model were presented to take into account the possible clinical diversity and methodological variation between studies. Specific analyses considering confounding factors were not possible due to absence of raw data.
Evidence of publication bias was sought using the methods of Egger et al. and Begg et al.. Contour-enhanced funnel plot was performed to aid in interpretation of the funnel plot. If studies appear to be missing in areas of low statistical significance, then it is possible that the asymmetry is due to publication bias. If studies appear to be missing in areas of high statistical significance, then publication bias is a less likely cause of the funnel asymmetry. Intercept significance was determined by the t-test suggested by Egger et al. P<0.05 was considered representative of statistically significant publication bias.
All P values were 2-sided. All statistical analysis was conducted with Review Manager version 5.2.1 (Cochrane Collaboration, Software Update, Oxford, United Kingdom), or STATA version 11.0 (Stata Corporation, College Station, TX).
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