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Growth of Nonoperating Room Anesthesia Care in the United States: A Contemporary Trends Analysis

Nagrebetsky, Alexander, MD, MSc*; Gabriel, Rodney A., MD; Dutton, Richard P., MD, MBA§; Urman, Richard D., MD, MBA

doi: 10.1213/ANE.0000000000001734
Healthcare Economics, Policy, and Organization: Original Clinical Research Report

BACKGROUND: Although previous publications suggest an increasing demand and volume of nonoperating room anesthesia (NORA) cases in the United States, there is little factual information on either volume or characteristics of NORA cases at a national level. Our goal was to assess the available data using the National Anesthesia Clinical Outcomes Registry (NACOR).

METHODS: We performed a retrospective analysis of NORA volume and case characteristics using NACOR data for the period 2010–2014. Operating room (OR) and NORA cases were assessed for patient, provider, procedural, and facility characteristics. NACOR may indicate general trends, since it collects data on about 25% of all anesthetics in the United States each year. We examined trends in the annual proportion of NORA cases, the annual mean age of patients, the annual proportions of American Society of Anesthesiologists physical status (ASA PS) III–V patients, and outpatient cases. Regression analyses for trends included facility type and urban/rural location as covariables. The most frequently reported procedures were identified.

RESULTS: The proportion of NORA cases overall increased from 28.3% in 2010 to 35.9% in 2014 (P < .001). The mean age of NORA patients was 3.5 years higher compared with OR patients (95% CI 3.5–3.5, P < .001). The proportion of patients with ASA PS class III–V was higher in the NORA group compared with OR group, 37.6% and 33.0%, respectively (P < .001). The median (quartile 1, 3) duration of NORA cases was 40 (25, 70) minutes compared with 86 (52, 141) minutes for OR cases (P < .001). In comparison to OR cases, more NORA cases were started after normal working hours (9.9% vs 16.7%, P < .001). Colonoscopy was the most common procedure that required NORA. There was a significant upward trend in the mean age of NORA patients in the multivariable analysis—the estimated increase in mean age was 1.06 years of age per year of study period (slope 1.06; 95% confidence interval [CI] 1.05–1.07, P < .001). Multivariable analysis demonstrated that the mean age of NORA patients increased significantly faster compared with OR patients (difference in slopes 0.39; 95% CI 0.38–0.41, P < .001). The annual increase in ordinal ASA PS of NORA patients was small in magnitude, but statistically significant (odds ratio 1.03; 95% CI 1.03–1.03, P < .001). The proportion of outpatient NORA cases increased from 69.7% in 2010 to 73.3% in 2014 (P < .001).

CONCLUSIONS: Our results demonstrate that NORA is a growing component of anesthesiology practice. The proportion of cases performed outside of the OR increased during the study period. In addition, we identified an upward trend in the age of patients receiving NORA care. NORA cases were different from OR cases in a number of aspects. Data collected by NACOR in the coming years will further characterize the trends identified in this study.

From the *John H. Stroger Hospital of Cook County, Chicago, Illinois; University of California, San Diego, San Diego, California; Brigham and Women’s Hospital/Harvard Medical School, Boston, Massachusetts; and §US Anesthesia Partners (USAP), Dallas, Texas.

Accepted for publication October 4, 2016.

Funding: None.

The authors declare no conflicts of interest.

Reprints will not be available from the authors.

Address correspondence to Richard D. Urman, MD, MBA, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women’s Hospital/Harvard Medical School, 75 Francis St, Boston, MA 02115. Address e-mail to rurman@partners.org.

Over the last decade there has been a significant growth of interventional procedures being performed outside of the traditional operating room (OR) locations. To maintain the requisite safety profile in nonoperating room anesthesia (NORA) cases, anesthesiologists must adapt to a wide variety of facilities and practice patterns.1 It is not clear precisely how frequently anesthesiologists practice outside of the OR, although many authors suggest that the volume of NORA cases in the United States is increasing.2 There is clearly a growing demand for anesthesia care in some locations remote from the OR3; however, the increase in the volume of NORA cases over time is poorly quantified.

There is little published national-level data describing the features of NORA cases, and admittedly this is a dynamic venue. Extension of anesthesiology practice beyond the OR has fueled much discussion of safety of NORA care,4 , 5 but existing literature does not provide new data on demographics or outcomes. Because NORA cases are relatively new and rapidly evolving, clinical care tends to be idiosyncratic and locally documented rather than standardized. Large-scale studies have covered limited time periods and focused primarily on complications of NORA.6 , 7 Knowledge of the potential differences between NORA and OR populations may contribute to the understanding of the relative safety of anesthesia in remote locations, particularly since the existing literature includes both reports of increased and equivalent risk of NORA compared with OR anesthesia. For example, the American Society of Anesthesiologists Closed Claims analysis has demonstrated a significantly greater proportion of mortality claims identified in NORA cases compared with OR cases,7 yet studies in a pediatric population showed that the rates of complications in anesthesia outside of the OR were low8 and comparable with those reported in the OR.9 This finding may reflect the differences between pediatric and geriatric populations and study methodologies.

Understanding the characteristics and temporal changes in the volume of NORA cases is important in determining effective and appropriate policy-making in the setting of evolving healthcare systems that increasingly focus on value.10 We aimed to characterize and compare NORA and OR cases using data from the National Anesthesia Clinical Outcomes Registry (NACOR) and to assess changes in the annual frequency and characteristics of NORA and OR cases over time.

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METHODS

Data Source

We carried out a retrospective analysis of the NACOR data provided by the Anesthesia Quality Institute (AQI). NACOR is a nationwide registry that collects and organizes electronic reports on anesthesia care provided in the United States. Such reports are submitted voluntarily by hundreds of anesthesia practices across the entire spectrum of clinical facilities, from small private practices to large university hospitals. Participating groups submit data on all of their cases, in all settings—there is no case sampling within a group or facility. On the basis of the AQI estimates, in 2015, NACOR will capture at least basic data from approximately 25% of all anesthesia cases in the United States.11 Such data comprise patient demographics, billing, procedural, diagnostic, and provider information.

NACOR contains descriptions of the location of anesthesia care for a majority of records. Cases are listed as those performed in the OR, obstetric and non-OR (NORA) settings. NORA cases are further subcategorized as unclassified, or those pertaining to cardiology, gastroenterology, and radiology. The location for a number of cases is reported as mixed.

Individual NACOR records are linked to postal (zip) code data from the US Census for the period of 2010–2013. Such a linkage allows designation of a case to a specific state within the United States and to a particular urban, rural, or urban-rural location type. Information collected by the AQI is deidentified according to national and international legal requirements, including the Health Insurance Portability and Accountability Act of 1996. This study was approved by the Brigham and Women’s Hospital institutional review board and was judged exempt from the informed consent requirement. This manuscript adheres to the STROBE guidelines.

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Study Sample

Figure 1

Figure 1

The NACOR dataset analyzed in this study included 26,541,720 records of anesthesia cases that occurred from January 1, 2010, to December 31, 2014. We analyzed cases of NORA and OR anesthesia defined as records with corresponding case type descriptions. We excluded cases of anesthesia for obstetric procedures and records with missing data on the location of anesthesia care or the location of care reported as “mixed” (Figure 1). We also excluded records with American Society of Anesthesiologists physical status (ASA PS) VI.

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Statistical Analysis

In addition to NORA cases, we analyzed OR cases to provide a reference group for comparison. We used Pearson χ2 test to compare categorical variables. The 2-sample t-test was used to compare means of normally distributed continuous variables and the Wilcoxon rank-sum test to compare non-normally distributed variables. To account for multiple comparisons, we set the threshold of statistical significance at P values <.001. Given that we carried out 42 statistical tests, at such a threshold of statistical significance the probability of at least one false-positive result is 4% [type I error = 1 − (1 − significance criterion)K, where K is the number of tests]. For normally distributed continuous variables we presented mean values with standard deviations, and for non-normally distributed variables we presented median values with quartiles 1 and 3.

We compared patient, provider, procedural, and facility characteristics between cases performed in the OR and in the non-OR setting. Patient information available in NACOR included age, sex, state of residence, urban versus rural residence, and ASA PS. Anesthesia provider data included presence of an anesthesiology resident or certified registered nurse anesthetist. Case-related data that were compared included case duration in minutes and case start time—normal working hours from 07:00 AM to 5:00 PM and after-hours from 5:01 PM to 06:59 AM; weekday and weekend cases. The facility types compared in this study included the following: university hospitals, large community hospitals (consisting of >500 beds), medium community hospitals (100–500 beds), small community hospitals (<100 beds), and “other facility types.” We compared proportions of patients within specific age groups, facility types, and urban/rural categories between NORA and OR groups using Pearson χ2 test and dichotomous variables describing whether a patient belongs to the analyzed age group, facility type, or urban/rural category.

We used regression analyses to assess for potential time trends in the annual proportion of NORA cases, the annual mean age of patients receiving anesthesia care, the annual proportions of patients with a specific ASA PS class, and the annual proportion of outpatient cases. We performed both univariable and multivariable regression analyses. In univariable analyses, year of study period was used as an independent variable. Multivariable analyses included year of study period, facility type, and urban/rural location as independent variables. NORA/OR case type and outpatient/inpatient status were included as dependent variables in logistic regression models. Patient age was used as a dependent variable in a linear regression analysis. Ordinal ASA PS scale was included as a dependent variable in an ordinal logistic regression analysis.

We compared regression coefficients for age and year of study period between NORA and OR groups by testing for interaction between year of study period and NORA/OR case type using a t-test in a multivariable linear regression model including patient age as a dependent variable and facility type, urban/rural location as independent variables. To compare odds ratios for outpatient/inpatient status and year of study period between NORA and OR groups, we tested for interaction between year of study period and NORA/OR case type using a z-test in the multivariable logistic regression model including outpatient/inpatient status as a dependent variable and facility type, urban/rural location as independent variables. To compare odds ratios for ordinal ASA PS scale and year of study period between NORA and OR groups, we tested for interaction between year of study period and NORA/OR case type using a z-test in the multivariable logistic regression model including ordinal ASA PS scale as a dependent variable and facility type, urban/rural location as independent variables.

In addition to the main analysis for trends, we carried out a number of sensitivity analyses. To address the concern that the observed trends may reflect a change in the composition of contributing practices over time, we analyzed data from practices that submitted cases for each year of the observation period. To address potential selection bias, we also carried out a time trend analysis in NACOR cases that were excluded from the main study. The most frequently reported procedures were identified by the surgical Current Procedural Terminology codes. We used Stata 11.0 (StataCorp LP, College Station, TX) to perform all statistical analyses.

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RESULTS

Among all NACOR records for 2010–2014, we identified 5,929,953 (32.4%) NORA cases and 12,387,574 (67.6%) OR cases eligible for analysis. Of the 8,224,193 cases excluded from analysis, the majority (7,196,006) did not have information on the location of anesthesia services and 765,522 cases were reported as cases of obstetric anesthesia (Figure 1). The characteristics of cases included in this analysis are presented in Table 1. The subcategories of NORA cases included 2,694,966 of NORA unspecified cases, 260,612 of NORA cardiology, 2,690,899 of NORA gastroenterology, and 283,476 of NORA radiology (Table 2). The analyzed cohort included data reported from 2439 different healthcare facilities covered by 298 anesthesia practices.

Table 1

Table 1

Table 2

Table 2

The proportions of NORA cases among all cases included in the analysis are presented in Figure 2A. The proportion of NORA cases increased from 28.3% in 2010 to 35.9% in 2014 (P < .001). There was a significant upward trend in the proportion of NORA among all cases reported to NACOR—odds ratio of 1.08 for NORA versus OR during each year of the study period (95% confidence interval [CI] 1.08–1.08, P < .001) in the multivariable analysis that included facility type and urban/rural location as covariables. The absolute number of NORA cases reported to NACOR was 632,134 in 2010 and 1,955,542 in 2014.

Figure 2

Figure 2

The mean age of NORA patients was 3.5 years higher compared with OR patients (95% CI 3.5–3.5, P < .001). Comparisons of individual age strata demonstrated that there also were differences in patient age distribution between NORA and OR (Table 1). There were no clinically significant differences in sex distribution between NORA and OR groups. The proportion of patients with ASA PS class III–V was greater in the NORA group compared with OR group, at 37.6% and 33.0%, respectively (P < .001).

The proportions of cases performed in different facility types and rural versus urban locations were statistically significantly different between NORA and OR groups, but the difference was small (Table 1). The median (quartiles 1, 3) duration of NORA cases was 40 (25, 70) minutes compared with 86 (52, 141) minutes for OR cases (P < .001); the median duration of NORA gastroenterology cases was 32 (23, 45) minutes. In comparison to OR cases, more NORA cases were started after normal working hours (9.9% vs 16.7%, P < .001).

Time trend analysis of NORA cases demonstrated considerable variation in patient and case characteristics during the 5-year study period. The mean age of NORA patients was 51.5 years in 2010 and 55.0 years in 2014, with an increase of 3.5 years (95% CI 3.4–3.5, P < .001; Figure 2B). In the univariable analysis, there was a significant upward trend in the mean age of NORA patients with an increase of 0.87 years of age (slope 0.87; 95% CI 0.86–0.89, P < .001) per each year of the study period. The multivariable analysis that included facility type and urban/rural location as covariables demonstrated that the mean age of NORA patients increased by 1.06 years (slope 1.06; 95% CI 1.05–1.07, P < .001) per year of study period. In the multivariable analysis, the mean age of OR patients increased by 0.66 years (slope 0.66; 95% CI 0.65–0.67, P < .001) per year of study period. The upward trend in mean age was significantly greater in NORA patients compared with OR patients, with a difference in slopes of 0.39 years per year of study period (95% CI 0.38–0.41, P < .001) in the multivariable analysis.

The proportion of patients with ASA PS III–V among NORA cases was 36.5% in 2010 and 38.8% in 2014 (Figure 2C). In a multivariable analysis that included facility type and urban/rural location as covariables, the annual increase in ordinal ASA PS scale in NORA group was small in magnitude, but statistically significant—odds ratio of 1.04 for increase in one unit of ASA PS scale per year of study period (95% CI 1.04–1.05, P < .001). The multivariable analysis also demonstrated that the upward trend in ordinal ASA PS scale was greater in NORA group compared with OR group (ratio of odds ratios 1.004; 95% CI 1.003–1.006, P < .001), but this difference was not clinically important.

Table 3

Table 3

Among all NORA cases, the proportion of outpatient cases increased from 69.7% in 2010 to 73.3% in 2014 (P < .001). A multivariable analysis that included facility type and urban/rural location as covariables demonstrated a small in magnitude upward trend in the proportion of outpatient cases in the NORA group—an odds ratio of 1.07 for outpatient versus inpatient during each year of the study period (95% CI 1.07–1.07, P < .001). There was no clinically significant difference between trends in proportions of outpatient cases in NORA and OR groups, although the upward trend was greater in the NORA group (ratio of odds ratios 1.04; 95% CI 1.04–1.04, P < .001). In the sensitivity analyses, we identified time trends of the same direction and comparable magnitude: (1) in NACOR cases that were excluded from the main study and (2) in NORA cases from practices that submitted cases for each year of the observation period. The annual proportions of the most frequently reported procedures that required NORA care are presented in Table 3.

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DISCUSSION

The results of this study offer a contemporary insight into nonoperating room anesthesia care in the United States based on recent data from NACOR and suggest ways in which data collection needs to be improved. Although information on the location of anesthesia care was missing in a considerable number of cases, available data suggest that approximately one third of all cases reported to NACOR are NORA cases. The proportion of cases performed outside of the OR demonstrates a steady increase during the period of 2010–2014. Compared with OR patients, NORA patients are older. We have identified upward trends in the age of both NORA and OR patients, but NORA patients were becoming older significantly faster compared with OR patients, even after adjustment for facility type and urban/rural location. The proportion of patients with ASA PS III–V was greater in NORA than in the OR. On the whole, NORA cases took half the time of OR cases and were more likely to be started after normal working hours. Among NORA cases with specified location, most were performed in the gastroenterology suite. Anesthesia for colonoscopy was the most common procedure-specific type of NORA.

The results of this study, in general, fall in line with the very limited existing literature that focuses on NORA. A strong upward trend in the proportion of NORA cases in NACOR observed in this study is consistent with an earlier report of more than doubling of the number of NORA cases from 2003 to 2012 in an individual pediatric hospital.12 An increase in the proportion of NORA cases also parallels a similar increase in the proportion of outpatient surgeries that has been measured over 2 decades.13 An increase in provision of NORA care may reflect an emphasis on endoscopic screening for colon cancer and advanced endovascular diagnostic and therapeutic approaches, as well as development of percutaneous approaches to treatments that were previously performed only in a surgical setting. If the increase we observed reflects the nationwide trend, and if such a trend continues over the coming years, it is possible that the number of NORA cases may approach or even exceed the number of OR cases. A more robust system of data collection and analysis would be required to make accurate assessments and projections. This would allow us to reframe the fundamental vision of anesthesiology to include emerging markets in non-OR areas.

The growth of NORA cases indicates the increasing role of NORA in the overall efficiency of anesthesia care. Development of consistent pre and postprocedural platforms for NORA patients may improve not only safety, but also efficiency and ergonomics.14 , 15 For example, the recently updated ASA Statement on Nonoperating Room Anesthetizing Locations generally focuses only on essential safety equipment and does not provide any recommendations on the ergonomics or efficiency of NORA care.16 The increasing role of NORA may prompt the ASA and other professional associations to advocate for procedural areas that take into account not only the essential safety, but also the ergonomics of anesthesia care. Assignment of an appropriate number of anesthesiologists should also be addressed given the concerns related to availability of anesthesiology services in at least some NORA locations17 and high demand for anesthesiologists.18

High demand for anesthesiologists outside of the OR is also reflected in the fact that the frequency of cases started after normal working hours was approximately 1.7 times greater in NORA compared with OR locations. Such a finding suggests that a considerable number of cases are performed by anesthesiologists in NORA environment with further limitations in available resources after normal working hours. Suboptimal case planning and frequent add-on cases may contribute to greater frequency of after-hours cases in NORA. The addition of emergency cases is a less likely explanation of greater frequency of after-hours NORA cases in this study, because the proportions of cases performed on weekends and official holidays, typically emergency cases, were comparable between NORA and OR locations.

We demonstrated a strong upward trend in the mean age of NACOR patients undergoing NORA: with each subsequent year of the study period, the mean age of NORA patients increased by more than a year. Such a trend was significantly greater than the upward trend in the mean age of OR patients. An upward trend in mean age of NORA patients is unlikely to be due to increasing life expectancy alone,19 since the annual increase in mean patient age in this study considerably exceeds the magnitude of life expectancy gained in the United States during the same time period.20 An upward trend in age observed in NACOR patients may be true for all NORA patients in the United States. It is also possible that the magnitude of the upward trend in mean patient age is affected by sampling bias if the true mean age of NORA patients in the United States is greater than that of the NACOR sample. An increase in sample size from 2010 to 2014 might have gradually brought the NACOR mean age estimates closer to the higher true mean value, thus creating a spurious trend. By contrast, if the true mean age of NORA patients in the United States is lower than in our sample, the annual increase in the mean age of patients in this study may be an underestimate. An upward trend in the mean age of patients receiving anesthesia care is concerning since older age is a known perioperative risk factor.21 , 22 Thus, it would be important to assess for increased complication rates that might parallel an upward trend in age.

Our study indicates that a large proportion of NORA patients are of advanced age. Approximately one third of patients in this analysis were aged 65 years and older, and a similar proportion of advanced endoscopy patients were aged 71 years and older in an earlier study.23 The difference in mean age between this analysis and the latter study of adult patients was expected since we analyzed both adult and pediatric cases. Older age may potentially explain the higher proportion of patients with ASA PS III–V in NORA compared with OR. Other factors, however, such as medical condition requiring a procedure, are likely to affect the overall health status of NORA patients.

The age distribution of NORA cases is likely to be affected by the large number of endoscopic screening cases requiring anesthesia care. The American Cancer Society Guidelines for the Early Detection of Cancer recommend screening colonoscopy at the age of 50 years with repeated colonoscopies performed each decade of life.24 Adherence to such guidelines in clinical practice may explain a larger proportion of patients aged 50 years and older in NORA group compared with OR cases. Our results suggest that NORA gastroenterology cases were the most frequent case type among NORA cases which had a specified location of anesthesia services in NACOR database. Furthermore, in our analysis, colonoscopy accounted for the majority of cases requiring NORA with more than 10 times greater absolute number of cases compared with the most common procedures in NORA cardiology and NORA radiology. Data from earlier studies also indicate that gastroenterology suites accounted for the largest number of legal claims among procedures performed outside of the OR.7

In this study and in a previously described advanced endoscopy cohort,23 patients with ASA PS I and II constituted the majority of NORA patients; however, the proportion of patients with ASA PS III–V was greater among NORA cases compared with OR cases. These results are consistent with observations from an analysis of closed legal claims in the United States, which demonstrated that most NORA claims involved older patients with greater disease severity than OR-related claims.7 The authors of the latter study also concluded that NORA poses a significant risk for patients. We found that a larger proportion of NORA cases were started after normal working hours, compared with OR cases. Such a finding may potentially explain greater periprocedural risk in NORA cases as the result of limited personnel and resources after normal working hours. We observed the lowest proportion of patients with ASA PS III–V in 2011. The lowest proportion of outpatient cases was also in 2011. The reason for such a co-occurrence is unclear.

We obtained data from NACOR, the largest and most comprehensive national anesthesia database. This study included a large number of NORA cases, and the results of this analysis are likely generalizable, because our data were obtained from NORA cases performed in a broad range of patients, in multiple settings, and with anesthesia personnel of various experience levels. Ongoing accumulation of data in NACOR will enable continued observation of the identified trends in the proportion of NORA cases and characteristics of NORA patients.

The type and volume of data contained in NACOR offer excellent opportunities for descriptive research but result in methodologic limitations. The lack of a standardized data collection procedure or a standardized set of outcome definitions, at least at present, makes NACOR data heterogeneous. We had to exclude from analysis a large number of cases as the result of missing data on the location of anesthesia care. It was not possible to impute the location of anesthesia care, because the vast majority of such cases also were missing data on the type of procedure. Selection bias, however, is unlikely to have a major effect on our main findings since time trends in characteristics of excluded cases were similar to those observed in the main analysis.

Also, we did not include cases of obstetric anesthesia, because the demographic and clinical characteristics of obstetric patients differ considerably from those of most NORA patients. We did not have a specific definition for cases with location of care reported as “mixed,” although the number of such cases was small compared with the size of the analyzed sample. Our study does not address concerns about the safety of NORA or specific patient outcomes, because we chose to focus on the relative volume of NORA cases and its change over time. The question of how representative NACOR is as a sample of all anesthesia cases nationwide remains unanswered at this time.

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CONCLUSIONS

The results of this study offer an insight into nonoperating room anesthesia care in the United States. Available data suggest that approximately one third of all cases reported to NACOR are NORA cases. The proportion of cases performed outside of the OR has been increasing steadily during the study period. We also have identified a significant upward trend in the age of patients receiving NORA care. NORA cases were different from OR cases in a number of aspects. The frequency of cases started after normal working hours was higher in NORA compared with OR locations. Our results demonstrate that NORA is a rapidly growing component of anesthesiology practice. Data collected by NACOR in the coming years will further characterize the trends identified in this study.

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DISCLOSURES

Name: Alexander Nagrebetsky, MD, MSc.

Contribution: This author helped to design the study, collect the data, analyze the data, interpret findings, and prepare the manuscript.

Name: Rodney A. Gabriel, MD.

Contribution: This author helped to design the study and prepare the manuscript.

Name: Richard P. Dutton, MD, MBA.

Contribution: This author helped to design the study, collect the data, interpret findings, and prepare the manuscript.

Name: Richard D. Urman, MD, MBA.

Contribution: This author helped to design the study, collect the data, interpret findings, and prepare the manuscript.

This manuscript was handled by: Nancy Borkowski, DBA, CPA, FACHE, FHFMA.

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