Perioperative and anesthesia-related cardiac arrest and mortality rates in Brazil: A systematic review and proportion meta-analysis.

INTRODUCTION: Studies have shown that both perioperative and anesthesia-related cardiac arrest (CA) and mortality rates are much higher in developing countries than in developed countries. This review aimed to compare the rates of perioperative and anesthesia-related CA and mortality during 2 time periods in Brazil.
METHODS: A systematic review with meta-analysis of full-text Brazilian observational studies was conducted by searching the Medline, EMBASE, LILACS and SciELO databases up to January 29, 2020. The primary outcomes were perioperative CA and mortality rates and the secondary outcomes included anesthesia-related CA and mortality events rates up to 48 postoperative hours.
RESULTS: Eleven studies including 719,273 anesthetic procedures, 962 perioperative CAs, 134 anesthesia-related CAs, 1,239 perioperative deaths and 29 anesthesia-related deaths were included. The event rates were evaluated in 2 time periods: pre-1990 and 1990-2020. Perioperative CA rates (per 10,000 anesthetics) decreased from 39.87 (95% confidence interval [CI]: 34.60-45.50) before 1990 to 17.61 (95% CI: 9.21-28.68) in 1990-2020 (P < 0.0001), while the perioperative mortality rate did not alter (from 19.25 [95% CI: 15.64-23.24] pre-1990 to 25.40 [95% CI: 13.01-41.86] in 1990-2020; P = 0.1984). Simultaneously, the anesthesia-related CA rate decreased from 14.39 (95% CI: 11.29-17.86) to 3.90 (95% CI: 2.93-5.01; P < 0.0001), while there was no significant difference in the anesthesia-related mortality rate (from 1.75 [95% CI: 0.76-3.11] to 0.67 [95% CI: 0.09-1.66; P = 0.5404).
CONCLUSIONS: This review demonstrates an important reduction in the perioperative CA rate over time in Brazil, with a large and consistent decrease in the anesthesia-related CA rate; however, there were no significant differences in perioperative and anesthesia-related mortality rates between the assessed time periods.

Introduction

The global surgical volume is increasing worldwide; however, the safety and quality of surgical care and anesthesia management remain poor in many regions, and outcome assessments are not often prioritized in developing countries [1]. Among the complications of surgery, cardiac arrest (CA) is one of the worst events, as it can result in sequelae, loss of function and death. The rates of perioperative CA and mortality can be used to explore the differences among facilities that perform surgical and anesthesia procedures in different centers and can serve as quality indicators to promote improvements in patient safety and reductions in unfavorable outcomes [2-4]. Brazil is a developing country that, over the years, has experienced great difficulty in offering adequate healthcare to its population [5].

Two systematic reviews with a proportion meta-analysis of worldwide studies have shown that the rates of both perioperative and anesthesia-related CA and mortality are much higher in developing countries than in developed countries [6, 7]. A review of the studies conducted in Brazil showed that there was a reduction in the rate of perioperative CA during the last 25 years, similar to the global trend [8].

This systematic review aimed to compare the rates of perioperative and anesthesia-related CA and mortality during 2 time periods in Brazil. We hypothesized that the rates of intraoperative and anesthesia-related CA and mortality have decreased over time.

Methods

The Cochrane Handbook for Intervention Reviews [9] guided our choice of methods. Our report adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement (S1 File) [10]. The protocol for this proportional meta-analysis was registered in a public registry (PROSPERO, #CRD42019141158).

Search strategy

We searched the medical literature to identify all Brazilian observational studies that reported perioperative and/or anesthesia-related CA or mortality rates. We searched the Medline (PubMed), EMBASE, Latin American and Caribbean Health Sciences Literature (LILACS), and Scientific Electronics Library Online (SciELO) databases from their inception to January 29, 2020. Search strategies were developed in consultation with a research librarian with systematic review expertise. The search was conducted using Index Terms (e.g., MeSH and Emtree) and text words and word variants for “an(a)esthesia”, “cardiac arrest” and “mortality”, as well as an exhaustive list of synonyms. The search strategy was adapted to each database to find relevant studies (S2 File). Five independent reviewers (L.G.B., M.P.M., R.S., M.P., and J.B.C.) performed the initial screening of the titles and abstracts of the studies to identify whether they contained relevant content. The relevant studies were downloaded and reviewed in full by 2 independent reviewers (L.G.B. and I.B.S.). These reviewers also reviewed the references of the included studies and added additional relevant studies. There were no restrictions on either year of publication or language.

Outcome definitions

The primary outcomes were perioperative CA and mortality events (regardless of triggering factors: patient’s disease/condition, surgery and anesthesia). The secondary outcomes were anesthesia-related CA and mortality events (entirely and partially anesthesia-related), and entirely anesthesia-related CA and mortality events, defined as CA or mortality deemed to be attributable only to anesthesia (e.g., depression of ventilation leading to hypoxemic CA after anesthesia induction in a stable patient without comorbidities). All perioperative, anesthesia-related, and entirely anesthesia-related CAs or mortality were defined by the authors of the studies included in this review.

Selection criteria

To ensure that the studies represented a mixed population, full-text studies were included if they fulfilled the following criteria: (1) observational studies; and (2) the study’s outcome measurements were perioperative and/or anesthesia-related CA or perioperative and/or anesthesia-related mortality up to 48 postoperative hours.

Studies were excluded if they met any of the following criteria: (1) the study focused on specific age groups (e.g., only geriatric patients); (2) the study included only a specific anesthetic technique (e.g., only neuraxial blockade); (3) the study included only a specific surgery type (e.g., only cardiac surgery); (4) the study included only a specific American Society of Anesthesiologists (ASA) physical status (e.g., only ASA I patients); and (5) the study included less than 3,000 patients because this number is the minimum required to enable estimation of the incidence of rare adverse events (≤ 1 per 1,000 anesthetics), according to the rule of three sample size approximations [11].

Assessment of methodological quality

Two independent reviewers (L.G.B. and J.R.C.B.) assessed the studies selected for retrieval for methodological validity prior to inclusion in the review using the Joanna Briggs Institute (JBI) Critical Appraisal Tool for Prevalence Studies [12]. The nine domains in this tool were target population, sampling, sample size, description of participants and setting, coverage of identified sample, methods of identifying the outcome, reliability of the outcome measurement, appropriate statistical analysis and response rate. The cutoff for inclusion/exclusion was determined through consensus between the reviewers. The cutoff point for the inclusion of a study in the review was a “yes” answer to at least five of the nine questions (more than 50%) on the standardized critical appraisal instrument. Discrepancies were resolved after discussion between the two authors; if this was not possible, the discrepancies were resolved with a third author (M.G.B.).

Data extraction

We used a standard form to extract the data from the included studies (S1 Table). Two of the authors (L.G.B. and I.B.S.) independently identified the studies that were included in the review. Any discrepancies were resolved after discussion with a third reviewer (J.R.C.B.). When more than one study was published with the same population, data were extracted from the most recent and/or complete study. If eligible articles were missing data, their authors were contacted for clarification.

Statistical analysis

Proportion meta-analysis

Using StatsDirect software (StatsDirect Ltd., Altrincham, Cheshire, UK), a random-effects model with inverse Freeman-Tukey double arcsine transformation was applied to calculate the weighted event rates across all of the studies included in the proportion meta-analysis [13, 14]. For the purpose of this study, the data were dichotomized into 2 time periods. A similar method was used in three prior systematic reviews: two on perioperative CA [6, 15] and one on perioperative CA and mortality [7]. This stratification was based on many safety-improvement measures, such as monitoring for oxygenation and ventilation parameters, anesthesia workstations with modern ventilators, new anesthesia medications, supraglottic devices, anesthesia and surgery safety protocols, advances in postoperative pain management, and an increase in the number of postanesthesia and intensive care beds, which emerged towards the end of the 1980s in developed countries and later in some developing countries [16, 17].

We performed a sensitivity analysis to define the cutoff year between the 2 time periods (from 1988 to 1992). The studies were allocated to one of the two periods based on their median patient recruitment interval [6, 7, 15]. The event rate was defined as the number of CAs or deaths per 10,000 anesthetics. The data are reported with their 95% confidence intervals (CIs). To compare differences in the proportions of events, a model with a binomial distribution adjusted for overdispersion was generated using SAS for Windows® software, v.9.4 (SAS Institute, Cary, NC). The I2 statistic was also used as an alternative approach to quantify the degree of heterogeneity among studies [18]; values higher than 40% suggested significant heterogeneity among the studies [19]. A P value < 0.05 was considered significant.

Results

Selection of studies

The literature search identified 15,265 potentially eligible articles. After reviewing the titles and abstracts, we excluded 5,670 duplicate studies using the software EndNote® (X9.2/2019 version, Clarivate Analytics, PA) and 9,580 studies because of a lack of relevance. We retrieved 15 potentially relevant full-text papers for detailed evaluations. Of these articles, 11 studies met the inclusion criteria, including 6 studies reporting perioperative CA, 4 studies reporting anesthesia-related CA, 9 studies reporting perioperative mortality, and 7 studies reporting anesthesia-related mortality (Fig 1).

Fig 1

PRISMA flow diagram showing the study selection process.

Abbreviations. CA: cardiac arrest; *some studies have been included in more than one category.

Study characteristics

The earliest study included was published in 1986 [20], and the most recent was published in 2019 [21]. The studies included 719,273 anesthetic procedures with 962 perioperative CA events, 134 anesthesia-related CA events, 1,239 perioperative deaths and 29 anesthesia-related deaths. The characteristics and designs of the studies are presented in Tables 1 and 2. The forest plots summarizing the data are presented in S3 File. As expected, there was significant heterogeneity among the studies, with a minimum I of 6.5% and a maximum of 98.3% for CA and a minimum I of 49.1% and a maximum of 99.0% for mortality (Tables 3 and 4).

Table 1

Description of included cardiac arrest studies.

Investigators and year of publication	Data source, study period, and median year	Time period of CA occurrence	Excluded	Patients (n)	Perioperative CA (n)	Anesthesia-related CA (n)	Entirely anesthesia-related CA (n)
Ruiz Neto & Amaral, 1986 [20]	Tertiary university hospital Medical records 1982–1984	OR	Cardiac surgery	51,422	205	74	36
	1983
Braz et al., 1999 [22]	Tertiary university hospital—Database	OR and PACU	-	58,553	184	21	-
	1988–1996
	1992
Braz et al., 2006 [23]	Tertiary university hospital—Database	OR and PACU	-	53,718	-	18	10
	1996–2005
	2001
Sebbag et al., 2013 [24]	Tertiary university hospital—Database2007	OR	Cardiac surgery	40,379	52	21	0
	2007
Toledo et al., 2013 [25]	Tertiary university hospital—Database2007–2009	OR	Cardiac surgery	81,587	81	-	-
			< 18 years
	2008
Carlucci et al., 2014 [26]	Tertiary university hospital—Database	OR and PACU	-	90,909	280	-	-
	1996–2009
	2003
Vane et al., 2019 [21]	Tertiary university hospital—Database2007–2014	OR	Cardiac surgery	167,574	160	-	-
	2011		< 18 years

Abbreviations. CA: cardiac arrest; OR: operating room; PACU: postanesthesia care unit

Table 2

Description of included mortality studies.

Investigators	Data source, study period, and median year	Time period in which death occurred	Excluded	Patients (n)	Perioperative mortality (n)	Anesthesia-related mortality (n)	Entirely anesthesia-related mortality (n)
Ruiz Neto & Amaral, 1986 [20]	Tertiary university hospital	OR	Cardiac surgery	51,422	99	9	-
	Medical records
	1982–1984
	1983
Cicarelli et al., 1998 [27]	Tertiary university hospital—Database	Up to	Cardiac surgery	25,926	129	2	2
		24 hours postoperative
	1995
	1995
Braz et al., 1999 [22]	Tertiary university hospital—Database	OR and PACU	-	58,553	124	5	-
	1988–1996
	1992
Chan & Auler Jr, 2002 [28]	Tertiary university hospital—Database	Up to	-	82,641	424	1	1
		24 hours postoperative
	1998–1999
	1999
Braz et al., 2006 [23]	Tertiary university hospital—Database	OR and PACU	-	53,718	-	6	3
	1996–2005
	2001
Sebbag et al., 2013 [24]	Tertiary university hospital—Database	Up to	Cardiac surgery	40,379	32	-	-
		24 hours postoperative
	2007
	2007
Carlucci et al., 2014 [26]	Tertiary university hospital—Database	OR and PACU	-	90,909	181	-	-
	1996–2009
	2003
Pignaton et al., 2016 [29]	Tertiary university hospital—Database	OR and PACU	-	55,002	88	0	0
	2005–2012
	2009
Stefani et al., 2018 [30]	Quaternary university hospital -Database	Up to	-	11,562	76	6	1
		48 hours postoperative
	2012–2013
	2013
Vane et al., 2019 [21]	Tertiary university hospital—Database2007–2014	Up to	Cardiac surgery	167,574	86	-	-
		24 hours postoperative
			< 18 years
	2011

Abbreviations. OR: operating room; PACU: postanesthesia care unit

Table 3

Proportion meta-analysis of cardiac arrest rates in Brazilian studies by time period.

Time period	Studiesn	I2%	Events n	Patients n	Proportion meta-analysis per 10,000 anesthetics (95% CI)	P value for subgroup
						Pre-1990 versus 1990–2020
Perioperative cardiac arrest
Pre-1990	1	NA	205	51,422	39.87 (34.60–45.50)	< 0.0001
1990–2020	5	98.3	757	439,002	17.61 (9.21–28.68)
Anesthesia-related cardiac arrest
Pre-1990	1	NA	74	51,422	14.39 (11.29–17.86)	< 0.0001
1990–2020	3	6.5	60	152,650	3.90 (2.93–5.01)
Entirely anesthesia-related cardiac arrest
Pre-1990	1	NA	36	51,422	7.00 (4.89–9.49)	< 0.0001
1990–2020	2	91.8	10	94,097	0.58 (0.00–3.72)

Abbreviations. I2: indicates heterogeneity among studies; CI = confidence interval; NA = not available

Table 4

Proportion meta-analysis of mortality rates in Brazilian studies by time period.

Time period	Studiesn	I2%	Events n	Patients n	Proportion meta-analysis per 10,000 anesthetics (95% CI)	P value for subgroup
						Pre-1990 versus 1990–2020
Perioperative mortality
Pre-1990	1	NA	99	51,422	19.25 (15.64–23.24)	0.1984
1990–2020	8	99.0	1,054	532,546	25.40 (13.01–41.86)
Anesthesia-related mortality
Pre-1990	1	NA	9	51,422	1.75 (0.76–3.11)	0.5404
1990–2020	6	81.0	20	287,402	0.67 (0.09–1.66)
Entirely anesthesia-related mortality
Pre-1990	-	-	-	-	-	NA
1990–2020	5	49.1	7	228,849	0.22 (0.05–0.68)

Abbreviations. I2: indicates heterogeneity among studies; CI = confidence interval; NA = not available

Methodological quality

Eleven studies meeting the inclusion criteria were assessed for methodological quality. All of them obtained more than five “yes” answers, indicating that they were of good quality (S2 Table).

Proportion meta-analysis of CA rate

The sensitivity analysis revealed no substantial change in the event rates during the time period from 1988 to 1992, justifying the establishment of 1990 as the temporal cutoff point. Thus, the event rates during 2 time periods (pre-1990 versus 1990–2020) were analyzed.

The rate of perioperative CA decreased (2.26-fold) from 39.87 (95% CI: 34.60 to 45.50) before 1990 to 17.61 (95% CI: 9.21 to 28.68) per 10,000 anesthetics in 1990–2020 (P < 0.0001) (Table 3). At the same time, the rates of both anesthesia-related and entirely anesthesia-related CA decreased consistently (by 3.7- and 12-fold, respectively) from 14.39 (95% CI: 11.29 to 17.86) and 7.00 (95% CI: 4.89 to 9.49) before 1990 to 3.90 (95% CI: 2.93 to 5.01) and 0.58 (95% CI: 0.00 to 3.72) per 10,000 anesthetics in 1990–2020, respectively (P < 0.0001 and P < 0.0001, respectively) (Table 3).

Proportion meta-analysis of mortality rate

There was no significant alteration in the rate of either perioperative mortality (from 19.25 [95% CI: 15.64 to 23.24] before 1990 to 25.40 [95% CI: 13.01 to 41.86] per 10,000 anesthetics in 1990–2020; P = 0.1984) or anesthesia-related mortality (from 1.75 [95% CI: 0.76 to 3.11] before 1990 to 0.67 [95% CI: 0.09 to 1.66] per 10,000 anesthetics in 1990–2020; P = 0.5404; Table 4). None of the Brazilian studies evaluated entirely anesthesia-related mortality rates before the 1990s, making a subanalysis of data between periods impossible; this rate in 1990–2020 was 0.22 (95% CI: 0.05 to 0.68) per 10,000 anesthetics (Table 4).

Discussion

To the best of our knowledge, this study is the first comprehensive synthesis showing the temporal trends in perioperative CA and mortality rates in a developing country. When comparing the pre-1990 and 1990–2020 periods in Brazilian studies, a reduction in the perioperative CA rates was found, with a relatively large decrease in the rate of anesthesia-related CA; however, there were no significant differences in the rates of perioperative and anesthesia-related mortality.

A systematic review with a proportion meta-analysis of the worldwide studies from developed and developing countries during 2 time periods (pre-1990 versus 1990–2014) showed a significant increase in the rate of perioperative CA and no differences in the rates of anesthesia-related and entirely anesthesia-related CA in developing countries, while in developed countries, there was a significant decrease in all CA rates [6], similar to the findings of the present study. Comparing the CA rates after 1990, we verified that the rates of both perioperative and anesthesia-related CA in Brazilian studies were similar to the rates in developing countries (19.9 and 4.5 per 10,000 anesthetics, respectively) but were 2.8- and 5.6-fold higher, respectively, than the rates in developed countries (6.2 and 0.7 per 10,000 anesthetics, respectively); the rate of entirely anesthesia-related CA in Brazilian studies was 2.7-fold lower than the rate in developing countries (1.6 per 10,000 anesthetics) and similar to the rate in developed countries (0.5 per 10,000 anesthetics) in the aforementioned review.

Contrary to the findings of Brazilian studies, a systematic review with a meta-analysis of studies from developed and developing countries showed a significant reduction in the rate of perioperative mortality over 3 time periods (pre-1970s, 1970s-1980s and 1990–2009), despite the increasing baseline ASA risk status of the patients [7]. The authors of this review suggested that their results indicated improved perioperative and anesthesia safety, particularly in developed countries. Comparing the mortality rates between the aforementioned review and Brazilian studies published after 1990, we verified that the rate of perioperative mortality in Brazil was similar to the rate in developing countries (24.45 per 10,000 anesthetics) and 2.3-fold higher than the rate in developed countries (10.95 per 10,000 anesthetics), while the rate of entirely anesthesia-related mortality in Brazil was 6.4-fold lower than the rate in developing countries (1.41 per 10,000 anesthetics) and similar to the rate in developed countries (0.25 per 10,000 anesthetics). The rate of anesthesia-related mortality was 2.4-fold higher than the rate (0.28 per 10,000 anesthetics) reported in a recent study in the USA [31].

There is no consensus about the time frame for perioperative CA or mortality events [32]. Thus, perioperative CA and mortality rates depend on how the perioperative period is defined: only intraoperative, intraoperative and recovery from anesthesia, up to 24 h postoperative or up to 48 h postoperative. It must be highlighted that all CA events reported in the studies occurred in only the intraoperative period (operating room or operating room plus postanesthesia care unit), while in the mortality studies, the events occurred in the intraoperative (55.6%) or 24–48 h postoperative (44.4%) periods. A Brazilian study reported a postoperative 24 h mortality rate (7.9 per 10,000 anesthetics) that was 2-fold higher than the intraoperative mortality rate (3.9 per 10,000 anesthetics) [24], while a Korean study reported a postoperative 24 h mortality rate (1.25 per 10,000 anesthetics) that was 8-fold higher than the intraoperative mortality rate (0.15 per 10,000 anesthetics) [33]. Thus, the time frame for the events may have interfered with the results of the current review.

Poor ASA physical status (III-V) has been reported to be the most important predictor of perioperative CA and mortality events in Brazilian studies [23, 24, 28, 29] and in studies from developed countries [31, 34, 35]. Two Brazilian studies demonstrated that many patients present for surgery with poor health at baseline and without the optimization of disease management [29, 36]. Thus, patient disease/condition remained the major triggering factor for perioperative CA and mortality, followed by surgery and anesthesia in low proportions [23, 28, 29].

The most influential cause of perioperative CA and mortality events in Brazilian studies was sepsis, followed by trauma [23, 29, 30, 37]. Therefore, comorbid conditions seem to be major contributors to the high perioperative CA and mortality rates in Brazil [5]. Thus, preanesthetic management of comorbidities plays a major role in minimizing perioperative complications and adverse effects. These findings demonstrate that there is a need to improve the quality and quantity of resources that can be used as well as access to healthcare, both of which are inadequate, in developing countries [15].

In Brazil and other developing countries, the combination of poverty and precarious healthcare with increasing and aging populations has increased both the number of patients in poor physical condition and the demand for surgical procedures in recent decades. However, the surgical volume in Brazil is approximately 2.5-fold lower [38, 39] than the international target set to achieve universal access to surgical care, which is 5 surgeries per 100 inhabitants per year [4]. In addition, in 2014, the density of the health professionals (surgeons, anesthesiologists and obstetricians) was 34.7 per 100,000 inhabitants in Brazil [38], while developed countries have an average of 56.9 of these professionals per 100,000 inhabitants [40]. These factors, combined with limited resources and numbers of surgical beds and operating rooms and increasing costs of surgery and anesthesia, seem to result in an important consequence: high perioperative CA and mortality rates in developing countries [41].

Governmental and nongovernmental organizations should prioritize and increase healthcare investments in Brazil and other developing countries [42]. Policy makers and healthcare professionals must address practices that have demonstrable effectiveness in improving perioperative outcomes. Human resources are pivotal; the number and the education and training of both anesthesiologists and surgeons must be increased [41, 42]. Preoperative management must be optimized; multidisciplinary discussions of adverse effects must be prompted; the provision of new monitoring techniques (e.g., pulse oximetry, capnography, echocardiography), modern anesthetic drugs, anesthesia equipment and workstations must be addressed universally; and practice guidelines and checklists in surgery and anesthesia as well as a structured approach to reducing errors must be adopted [41-45]. The mandatory period in the postanesthesia care unit should also be expanded, and the number of intensive care beds for critical patients should be increased to minimize the occurrence of adverse events. Global efforts should be directed towards ensuring that the increase in the surgical volume is accompanied by the implementation of basic safety measures in developing countries. Feedback regarding the implementation of such measures should be required from both developed and developing countries to ensure that the existing gap between health care systems is effectively reduced [1].

The limitations of this review must be acknowledged. This review is limited by a paucity of studies, particularly before 1990, which could have influenced the findings. Thus, we were not able to analyze publication bias because there were fewer than ten eligible studies addressing each outcome in a proportion meta-analysis; otherwise, the findings from the assessment of risk of bias would not be reliable. Despite the heterogeneity and small number of studies, the meta-analyses showed consistent results that strongly reinforce the relevance of our systematic review. The studies differed greatly in their design; differences in the time frames of the events (e.g., intraoperative or up to 24–48 h postoperative) and in the types of surgery (e.g., whether cardiac surgeries were included) accounted for most of the heterogeneity. A random-effects model with inverse Freeman-Tukey double arcsine transformation was applied to minimize this heterogeneity when assessing the trends between the two time periods. All the studies were conducted at only governmental tertiary or quaternary university hospitals. Some studies included a small sample size, and all included studies presented data from a single center; there were no multicenter studies. We included only studies with > 3,000 patients and calculated weighted event rates across all studies to minimize possible bias. The case mix, the type of anesthesia and surgery, and ASA physical status classification were not included in this review. Considering that the current review covered a 32-year period with recruitment of patients from 1982 to 2014, it must be highlighted that significant advances in resuscitation, such as, Advanced Trauma Life Support (ATLS) and Advanced Cardiovascular Life Support (ACLS), and operative protocols have occurred, which may have influenced the results of the current review.

This review demonstrates that the rates of perioperative CA have decreased over time in Brazil, and the proportional decrease has been large and consistent in the rates of anesthesia-related and entirely anesthesia-related CA. However, the rates of both perioperative and anesthesia-related mortality did not show significant differences between the time periods. Further reviews of perioperative and anesthesia-related CA and mortality must be periodically performed to continue to monitor the rates in surgical patients in Brazil.

PRISMA checklist.

(DOC)

Click here for additional data file.

Search strategy.

(DOCX)

Click here for additional data file.

Forest plots.

(DOCX)

Click here for additional data file.

Standard form used to extract information from the studies.

(DOCX)

Click here for additional data file.

Critical appraisal results for included studies.

(DOCX)

Click here for additional data file.

19 Jun 2020

PONE-D-20-08860

Perioperative and anesthesia-related cardiac arrest and mortality rates in Brazil: a systematic review and proportion meta-analysis

PLOS ONE

Dear Dr. Braz,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Aug 03 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Omid Beiki, M.D., Ph.D.

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. In the Methods, please specify any assessment of risk of bias that may affect the cumulative evidence (e.g., publication bias, selective reporting within studies). Please ensure that the specific method of assessment (funnel plot, Egger's test, Begg's test, etc) is mentioned.

3. In the Methods, please specify how study quality was assessed.

4. Thank you for stating the following in the Acknowledgments Section of your manuscript:

R.S., M.P. and J.B.C. received a scholarship from The National Council for

Scientific and Technological Development (CNPq) and L.G.B. received a fellowship

from CNPq (304466/2015-8). M.P.M. received a scholarship from Coordination of

Improvement for Higher Academic Staff (CAPES). CNPq and CAPES are Brazilian

governmental agency dedicated for promoting scientific research.

We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form.

Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows:

The authors received no specific funding for this work.

5. Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Partly

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: I Don't Know

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: No

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Thank you for the opportunity to review this manuscript.

I have a few comments and questions for the authors.

Under methods; you've indicated you adhered to the MOOSE guidelines, but this is not a methodology, this is a guideline that serves as a checklist for reporting observational studies in systematic reviews and meta-analyses. What methodological framework, or handbook did you use to conduct this systematic review and meta-analysis? The Cochrane Handbook? JBI? CRD York? You must always state the methods you followed to conduct this study, in addition to the relevant reporting guideline, which you must use to report your study, in this case it would be PRISMA.

My recommendation would be that authors indicate the methods they used to conduct the study, and include the PRISMA checklist indicating where each of the items in the guideline was reported.

Some of the diagrams are confusing, primarily due to labelling, e.g. the references workflow diagram is your PRISMA Diagram, but it's not labelled adequately.

The manuscript could also benefit from copyediting, there are instances where the syntax is unclear.

Reviewer #2: Review of 'Perioperative and anesthesia-related cardiac arrest and mortality rates...'

------------------------------------------------------------------------------------

This paper is a review and meta-analysis whose goal is to summarize the evidence surrounding changes in perioperative and anesthesia-related cardiac arrest and mortality rates in Brazil.

I am not an expert on cardiac arrest and/or surgery in Brazil, so I can only comment on the statistical part of this paper.

The writing is clear and I think it is possible from this text to evaluate what the statistical analysis that the authors have performed.

My main concern is that the meta-analysis reveals quite large amounts of heterogeneity for several important quantities; Tables 3 and 4 suggest that I2 can be as high as 99 percent, and is higher than 80 percent for 4 out of 6 of the quantities. This is somewhat subjective, but I am not confident that a meta-analysis can be meaningfully performed if there is this much heterogeneity in the effects being aggregated. The authors might at least consider reporting additional statistics intended to help the reader understand how much heterogeneity there is in the estimated true effect sizes.

Minor comments:

* pg 5 - I believe this should read 'sample size' instead of 'simple size'

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

24 Jul 2020

Answers to the Editor

Answer: First, we would like to thank the Editor for taking the time to review our manuscript and make important comments and suggestions. We tried our best to answer the questions and make the required changes in the manuscript after considering the suggestions, which certainly improved the revised manuscript.

1. “Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf”

Answer: We apologize. Our revised manuscript meets PLOS ONE´s style requirements.

2. “In the Methods, please specify any assessment of risk of bias that may affect the cumulative evidence (e.g., publication bias, selective reporting within studies). Please ensure that the specific method of assessment (funnel plot, Egger's test, Begg's test, etc) is mentioned.”

Answer: We agree with the suggestion, but we would like to clarify that our review is limited by a paucity of studies. Thus, unfortunately, we were not able to analyze publication bias because there were fewer than ten eligible studies addressing each outcome in the meta-analysis; otherwise, the findings from the assessment of risk of bias would not be reliable. Despite the heterogeneity and small number of studies, the meta-analyses showed consistent results that strongly reinforce the relevance of our systematic review. Thus, we included the information as one of the limitations of our review in the discussion section.

3. “In the Methods, please specify how study quality was assessed.”

Answer: We agree with the comment. We have added the topic “Assessment of methodological quality” to the methods, specifying the assessment of study quality using the Joanna Briggs Institute (JBI) - Critical Appraisal Tool for Prevalence Studies.

4. “Thank you for stating the following in the Acknowledgments Section of your manuscript:

R.S., M.P. and J.B.C. received a scholarship from The National Council for Scientific and Technological Development (CNPq) and L.G.B. received a fellowship from CNPq (304466/2015-8). M.P.M. received a scholarship from Coordination of Improvement for Higher Academic Staff (CAPES). CNPq and CAPES are Brazilian governmental agency dedicated for promoting scientific research.

We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form. Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows: The authors received no specific funding for this work.”

Answer: We apologize, and we have corrected the funding statement.

5. “Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information.”

Answer: The captions for the supporting information files are at the end of our revised manuscript.

Answers to the Reviewers

Reviewer #1

“Thank you for the opportunity to review this manuscript.”

Answer: We would like to thank you for taking the time to review our manuscript and to make important suggestions. We tried our best to answer the questions and make the required changes in the manuscript after considering the suggestions, which certainly improved the revised manuscript.

1. “I have a few comments and questions for the authors. Under methods; you've indicated you adhered to the MOOSE guidelines, but this is not a methodology, this is a guideline that serves as a checklist for reporting observational studies in systematic reviews and meta-analyses. What methodological framework, or handbook did you use to conduct this systematic review and meta-analysis? The Cochrane Handbook? JBI? CRD York? You must always state the methods you followed to conduct this study, in addition to the relevant reporting guideline, which you must use to report your study, in this case it would be PRISMA. My recommendation would be that authors indicate the methods they used to conduct the study, and include the PRISMA checklist indicating where each of the items in the guideline was reported. Some of the diagrams are confusing, primarily due to labelling, e.g. the references workflow diagram is your PRISMA Diagram, but it's not labelled adequatey.”

Answer: As suggested by the reviewer, we described in the first paragraph of the methods section that The Cochrane Handbook for Intervention Reviews guided our choice of methods. Our reporting adheres to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. We followed the PRISMA diagram, as requested.

2. “The manuscript could also benefit from copyediting, there are instances where the syntax is unclear.”

Answer: We apologize. The original version of the manuscript was copyedited by a native English speaker. The revised manuscript was copyedited again and improved.

Reviewer #2

1. “This paper is a review and meta-analysis whose goal is to summarize the evidence surrounding changes in perioperative and anesthesia-related cardiac arrest and mortality rates in Brazil.”

Answer: We would like to thank you for taking the time to review our manuscript and to make important comments. We tried our best to answer the comments and to clarify the revised manuscript.

2) “I am not an expert on cardiac arrest and/or surgery in Brazil, so I can only comment on the statistical part of this paper. The writing is clear and I think it is possible from this text to evaluate what the statistical analysis that the authors have performed.

My main concern is that the meta-analysis reveals quite large amounts of heterogeneity for several important quantities; Tables 3 and 4 suggest that I2 can be as high as 99 percent, and is higher than 80 percent for 4 out of 6 of the quantities. This is somewhat subjective, but I am not confident that a meta-analysis can be meaningfully performed if there is this much heterogeneity in the effects being aggregated. The authors might at least consider reporting additional statistics intended to help the reader understand how much heterogeneity there is in the estimated true effect sizes.”

Answer: We agree with the comment that most of the proportion meta-analyses are heterogeneous. As previously described in the original manuscript (limitation paragraph of the discussion section), a random-effects model with inverse Freeman-Tukey double arcsine transformation (Freeman-Tukey transformation) was applied to minimize this heterogeneity when assessing the trends between the two time periods. If we had used a fixed-effects model (please see the table below), the results of the event rates and the statistical analyses (P values) would be different and incorrect. Thus, we were aware of the high degree of heterogeneity, and we applied the best options to minimize it following Higgins JP al.’s (2003) instructions - “Measuring inconsistency in meta-analyses”.

Table. Proportion meta-analysis of mortality rates in Brazilian studies by time period

Time period Studies

n I2

% Events

n Patients

n Proportion meta-analysis

per 10,000 anesthetics

(95% CI) P value for subgroup

Pre-1990 versus 1990-2020

Anesthesia-related mortality - Random-effects model (included in the manuscript)

Pre-1990 1 NA 9 51,422 1.75 (0.76-3.11) 0.5404

1990-2020 6 81.0 20 287,402 0.67 (0.09-1.66)

Anesthesia-related mortality - Fixed-effects model (incorrect presentation)

Pre-1990 1 NA 9 51,422 1.75 (0.76-3.11) < 0.05

1990-2020 6 81.0 20 287,402 0.41 (0.18-0.71)

3) “Minor comments: * pg 5 - I believe this should read 'sample size' instead of 'simple size'”

Answer: We apologize for our mistake. We corrected the word to “sample”.

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

16 Oct 2020

PONE-D-20-08860R1

Perioperative and anesthesia-related cardiac arrest and mortality rates in Brazil: a systematic review and proportion meta-analysis

PLOS ONE

Dear Dr. Braz,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Nov 30 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Omid Beiki, M.D., Ph.D.

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #3: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #3: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #3: Interesting paper with only some issues, mainly related to abstract.

Abstract.

methods>proportion meta-analysis is not clear

methods>4 outcomes as primary outcome are too many. Authors should decide one primary outcome and other as co end points.

methods>time periods are not defined anywhere.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #3: Yes: Fabrizio D'Ascenzo

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

16 Oct 2020

Answers to the Reviewer #3

“Interesting paper with only some issues, mainly related to abstract.

Abstract:

methods>proportion meta-analysis is not clear

methods>4 outcomes as primary outcome are too many. Authors should decide one primary outcome and other as co end points.

methods>time periods are not defined anywhere.”

Answer: We would like to thank you for taking the time to review our manuscript and the compliments on our study. We appreciated the suggestions and we incorporated them into the abstract, which we believe is now improved.

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

21 Oct 2020

Perioperative and anesthesia-related cardiac arrest and mortality rates in Brazil: a systematic review and proportion meta-analysis

PONE-D-Leandro G. Braz 20-08860R2

Dear Dr.

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Ehab Farag, MD FRCA FASA

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #3: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #3: (No Response)

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: (No Response)

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #3: (No Response)

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #3: (No Response)

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #3: (No Response)

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #3: Yes: Fabrizio D'Ascenzo

23 Oct 2020

PONE-D-20-08860R2

Perioperative and anesthesia-related cardiac arrest and mortality rates in Brazil: a systematic review and proportion meta-analysis

Dear Dr. Braz:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Ehab Farag

Academic Editor

PLOS ONE