Background:
It has been reported that patients hospitalized outside regular working hours have worse outcomes. This study aims to compare outcomes following liver transplantation (LT) performed during public holidays and nonholidays.
Methods:
We analyzed the United Network for Organ Sharing registry data for 55 200 adult patients who underwent an LT between 2010 and 2019. Patients were grouped according to LT receipt during public holidays ±3 d (n = 7350) and nonholiday periods (n = 47 850). The overall post-LT mortality hazard was analyzed using multivariable Cox regression models.
Results:
LT recipient characteristics were similar between public holidays and nonholidays. Compared with nonholidays, deceased donors during public holidays had a lower donor risk index (median [interquartile range]: holidays 1.52 [1.29–1.83] versus nonholidays 1.54 [1.31–1.85]; P = 0.001) and shorter cold ischemia time (median [interquartile range]: holidays 5.82 h [4.52–7.22] versus nonholidays 5.91 h [4.62–7.38]; P < 0.001). Propensity score matching 4-to-1 was done to adjust for donor and recipient confounders (n = 33 505); LT receipt during public holidays (n = 6701) was associated with a lower risk of overall mortality (hazard ratio 0.94 [95% confidence interval, 0.86-0.99]; P = 0.046). The number of livers that were not recovered for transplant was higher during public holidays compared with nonholidays (15.4% versus 14.5%, respectively; P = 0.03).
Conclusions:
Although LT performed during public holidays was associated with improved overall patient survival, liver discard rates were higher during public holidays compared with nonholidays.
It has been suggested that hospitalized patients may receive suboptimal care during nights, weekends, or summer holidays because of reduced medical staffing, fatigue, or sleep deprivation by hospital staff.1 Many studies have shown that patients hospitalized outside regular working hours with various medical and surgical problems have worse outcomes,2-4 but there are conflicting reports.5-7 The impact of nighttime or weekend surgeries on survival had been previously examined in thoracic organs and kidney transplants with discordant results.8-11
Liver transplantation (LT) with successful outcomes depends on the coordination of a multidisciplinary team. Organ transplantation from deceased donors, in contrast to living donors, is performed as an on-demand procedure where the timing of organ procurement largely determines the timing of surgery. Recent studies have found that weekend transplant surgeries involve better-quality organs with shorter ischemia times, implying a more conservative selection of transplantable organs on weekends.12,13 A single-center study that examined LT outcomes stratified by day and night showed longer operating time and greater risk of early death rates when LTs were done at night.14 Another study that examined outcomes based on United Network for Organ Sharing (UNOS) data from 1987 to 2010 showed that both nighttime and weekend LT was associated with an increased risk of 1-y graft failure.12 A recent large study using the UNOS database showed that LT performed regardless of the time of day, week, or month did not have an effect on graft or patient survival, irrespective of center volume, patient, or donor risk factors.15 A study by Grodin et al16 examined the impact of public holidays on heart transplant rates but did not evaluate any posttransplant outcomes; the effect of public holidays on LT outcomes remains unclear.
We hypothesized that post-LT outcomes would differ depending on whether they were performed during public holidays or nonholidays. Using data from the Organ Procurement and Transplantation Network (OPTN) and UNOS database for the last 10 y, overall graft and patient survival outcomes of LT done during public holidays with those performed during nonholiday periods were compared.
MATERIALS AND METHODS
Patient Cohort
This study uses data from the OPTN/UNOS in the Standard Transplant Analysis and Research file, including de-identified waiting list and transplant data of all LT candidates registered since October 1, 1987, in the United States. For the analysis of posttransplant outcomes, adult patients (18 y or older at LT) who underwent LT between January 1, 2010, and December 31, 2019, were evaluated. Patients who received a living donor transplant, retransplant, and those who underwent LT combined with kidney, thoracic organs, intestine, or pancreas were excluded (Figure 1). This study was approved for an institutional review board waiver after review.
FIGURE 1.
Flowchart showing patient selection. LT, liver transplantation.
Patients were stratified based on the transplant timing into 2 groups: those transplanted within 3 d before or following a public holiday and those transplanted during a similar period around nonholidays. Holiday periods included Easter/Spring break, Memorial Day, July 4th, Labor Day, Thanksgiving, and a composite of Christmas and New Years (winter holidays). Baseline donor and recipient demographics, recipient transplant characteristics, and the mean number of transplants per day (transplant rate) were compared between groups using the Mann–Whitney test. Patients were stratified based on the state they were listed/transplanted into 3 groups according to the mean winter temperature in those states during the months of December, January, and February. The state temperatures were based on data collected over 30 y and accessed through the National Oceanic and Atmospheric Administration National Climatic Data Center of the United States.17
Analysis of Posttransplant Outcomes
In adult deceased LT recipients, overall posttransplant liver graft and patient survival were compared according to the timing of LT. Given that many organ offers are made days after the initial donor decline, we defined a holiday period by 3 d before or after public holidays.16 In addition, this allows us to capture the effect of the entire time period, including the holiday weekend. Possible risk factors for posttransplant graft loss and patient mortality were investigated. The hazards of mortality and graft loss were adjusted for the following variables based on previous literature.18 We defined 2 era groups with 5-y range: era 1 included patients transplanted between 2010 and 2014 and era 2 between 2015 and 2019. Recipient variables at transplant included the following based on a previous methodology: age at LT, gender, ethnicity (White, Black, Hispanic, and others), body mass index, Model for End-stage Liver Disease score (6–14, 15–25, and ≥26), diabetes, Karnofsky Performance Status score (>30% and 10%–30%), hepatocellular carcinoma, diagnosis of end-stage liver disease (hepatitis C, nonalcoholic steatohepatitis, alcohol-related liver disease, cholestatic liver disease, and other), dialysis requirement or life support requirement, presence of ascites (none/mild and moderate/severe) or encephalopathy (none/grade 1–2 and grade 3–4), transplant center volume (low-, mid-, and high-volume centers), and era of transplant (eras 1 and 2). Donor variables included age, body mass index, split liver graft, type of donation (donation after circulatory death and donation after brain death), organ share type (local, regional, and national), gender, ethnicity (White, Black, Hispanic, and others), cold ischemia time (≤8 h and >8 h), and cause of death (anoxia, cerebrovascular accident, and head trauma). According to criteria established by Zhang et al,19 grafts were categorized as “marginal” if they were from deceased donors with at least one of the following characteristics: >70 y of age, donation after circulatory death, national share organ, and macrovesicular steatosis ≥30%. To adjust risks for transplant center experience, transplant centers were classified into 3 groups based on their average annual volume: group 1: centers that performed ≥62 cases of LT per year during the study period (high-volume center group); group 2: centers that performed between 62 and 30 LT per year during the study period (mid-volume center group); and group 3: centers that performed <30 LT per year during the study period (low-volume center group). We used the 75th percentile value (62 transplants/y) and 50th percentile value (30 transplants/y) of the number of LTs in each center as the threshold. A subgroup analysis was conducted to assess posttransplant outcomes according to the transplant center experience.
Discard Liver Analysis
The deceased donor registry was obtained based on variables collected from the OPTN database in the United States. We performed a retrospective analysis of the UNOS de-identified patient-level data of all deceased donors between January 1, 2010, and December 31, 2019. The liver disposition was classified by UNOS into the following categories: organ not recovered, organ recovered for transplant but not transplanted, organ recovered but not for transplant, and transplanted organs.
Statistical Analysis
Regarding graft discard analysis, percentages of discarded liver allografts were analyzed using Pearson’s chi-square test for independence. Data regarding patient/graft survival outcomes were analyzed using the median with interquartile range for continuous variables and using percentages for discrete variables. Comparisons of continuous variables and discrete variables were performed using the Mann–Whitney test and the chi-square test. Patient survival and liver graft survival rates were estimated by a Kaplan–Meier method with log-rank tests. The exposure of interest was considered LT during a public holiday. We performed comparisons of posttransplant patient and graft survival after 4-to-1 propensity score matching to balance the effect of baseline confounders between LT recipients during public holidays and nonholiday groups. The patient characteristics after matching are included in Table S1 (SDC, http://links.lww.com/TXD/A515). Risk factors for posttransplant mortality and the hazard ratio were analyzed using Cox proportional hazards models and compared among both groups. The hazards of patient death were adjusted for recipient and donor variables as described. A P value of <0.05 was considered statistically significant. All statistical analyses were completed using SPSS version 25 (IBM, Armonk, NY) and EZR version 1.37 (Saitama, Japan), which is a graphical user interface for R (The R Foundation for Statistical Computing, Vienna, Austria).
RESULTS
Patient Characteristics at Transplant
A total of 66 719 adult patients underwent LT during the study period. The following populations were excluded: 6261 received a multiorgan transplant, 2580 for a retransplant, and 2678 received a living donor transplant. Among them, 7350 (13.3%) were transplanted 3 d before or after public holidays, and 47 850 (86.7%) were transplanted during nonholiday periods (Figure 1). Baseline recipient characteristics at the time of transplantation were similar for both groups (Table 1). There was no significant difference between groups in terms of recipients’ characteristics, including time spent on the waitlist, Model for End-stage Liver Disease score, life-support requirement at transplant, and hospital length of stay after transplant. Compared with nonholidays, deceased donors during public holidays had a lower proportion of marginal grafts (holidays 18.2% versus nonholidays 20.3%; P < 0.001), a lower donor risk index (DRI; median [interquartile range]: holidays 1.52 [1.29–1.83] versus nonholidays 1.54 [1.31–1.85]; P = 0.001), and a shorter cold ischemia time (median [interquartile range]: holidays 5.83 h [4.54–7.22] versus nonholidays 5.9 h [4.6–7.4]; P < 0.001; Table 2). The daily transplant rates during all public holidays compared with nonholidays were similar (15.0 versus 15.1 transplants/d, respectively; P = 0.35). Each holiday demonstrated similar transplant rates to nonholidays (Figure 2). Compared with nonholidays, deceased donors during Labor Day and 4th of July holiday had the lowest median DRI (Labor Day: 1.50 [1.28–1.79], July 4th: 1.51 [1.29–1.83] versus nonholidays: 1.54 [1.31–1.85]; P = 0.013; Figure 2).
TABLE 1.
Characteristics of liver transplant recipients at transplant
| Recipient characteristics | Nonholiday (n = 47 850) | Public holidays (n = 7350) | P | |
|---|---|---|---|---|
| Age (y), median (IQR) | 58.0 (51.0–63.0) | 58.0 (51.0–63.0) | 0.06 | |
| Gender, n (%) | Male | 31 845 (66.6) | 4923 (67.0) | 0.49 |
| Female | 16 005 (33.4) | 2427 (33.0) | ||
| BMI (kg/m2), median (IQR) | 28.6 (25.1–32.8) | 28.6 (25.1–32.8) | 0.56 | |
| Ethnicity, n (%) | White | 34,065 (71.2) | 5239 (71.3) | 0.42 |
| Black | 4162 (8.7) | 634 (8.6) | ||
| Hispanic | 6812 (14.2) | 1008 (13.7) | ||
| Asian | 2062 (4.3) | 348 (4.7) | ||
| Others | 749 (1.6) | 121 (1.6) | ||
| Diabetes, n (%) | 5024 (10.5) | 763 (10.4) | 0.27 | |
| MELD score, median (IQR) | 21 (13–31) | 21 (13–31) | 0.74 | |
| Encephalopathy grade 3-4, n (%) | 5507 (11.5) | 813 (11.1) | 0.25 | |
| Moderate ascites, n (%) | 14 255 (29.8) | 2260 (30.8) | 0.09 | |
| Karnofsky score, n (%) | >30% | 33 900 (71.4) | 5236 (71.9) | 0.37 |
| 10%–30% | 13 548 (28.6) | 2049 (28.1) | ||
| Recipient on mechanical support, n (%) | 3781 (7.9) | 555 (7.6) | 0.21 | |
| Recipient on dialysis, n (%) | 736 (10.3) | 5051 (10.5) | 0.56 | |
| Diagnosis, n (%) | HCV | 10 850 (23.1) | 1629 (22.6) | 0.35 |
| NASH | 6368 (13.6) | 1031 (14.3) | ||
| ALD | 9445 (20.1) | 1446 (20.1) | ||
| CLD | 6457 (13.7) | 968 (13.8) | ||
| HCC | 9906 (20.7) | 1587 (21.6) | ||
| Others | 4824 (12.8) | 689 (9.3) | ||
| Transplant center volume, n (%) | High volume ≥62 Tx/y | 17 221 (36.0) | 2630 (35.8) | 0.92 |
| Mid volume 30–62 Tx/y | 23 419 (48.9) | 3605 (49.0) | ||
| Low volume <30 Tx/y | 7 210 (15.1) | 1115 (15.2) | ||
| Recipient state at transplant, n (%) | Warm states | 18 296 (38.4) | 2757 (37.7) | 0.36 |
| Intermediate states | 12 776 (26.8) | 2013 (27.5) | ||
| Cold states | 16 529 (34.7) | 2549 (34.8) | ||
| Era, n (%) | 2015–2019 | 26 690 (55.6) | 3968 (55.4) | 0.86 |
| 2010–2014 | 21 353 (44.4) | 3189 (44.6) | ||
| Status 1A, n (%) | 1182 (2.5) | 176 (2.4) | 0.49 | |
| Days on waitlist, median (IQR) | 258 (493) | 264 (492) | 0.35 | |
| Hospital length of stay, median (IQR) | 9 (7–16) | 9 (7–16) | 0.91 |
ALD, alcoholic liver disease; BMI, body mass index; CLD, cholestatic liver disease; DCD, donation after circulatory death; HCC, hepatocellular carcinoma; HCV, hepatitis C virus; IQR, interquartile range; MELD, Model for End-stage Liver Disease; NASH, nonalcoholic steatohepatitis; Tx, transplant.
TABLE 2.
Characteristics of liver transplant deceased donors
| Donor characteristics | Nonholiday (n = 47,850) | Public holidays (n = 7350) | P | |
|---|---|---|---|---|
| Age (y), median (IQR) | 42.0 (28.0–54.0) | 42.0 (28.0–55.0) | 0.04 | |
| Gender, n (%) | Male | 28 498 (59.6) | 4478 (60.9) | 0.03 |
| Female | 19 352 (40.4) | 2872 (39.1) | ||
| BMI, median (kg/m2), median (IQR) | 26.9 (23.5–31.3) | 26.9 (23.5–31.3) | 0.97 | |
| Ethnicity, n (%) | White | 30 991 (64.8) | 4736 (64.4) | 0.42 |
| Black | 8638 (18.1) | 1325 (18.0) | ||
| Hispanic | 6111 (12.8) | 979 (13.3) | ||
| Asian | 1188 (2.5) | 160 (2.2) | ||
| Others | 922 (1.9) | 150 (2.0) | ||
| History of diabetes, n (%) | 6111 (12.8) | 907 (12.7) | 0.90 | |
| History of MI, n (%) | 1950 (4.3) | 302 (4.1) | 0.54 | |
| History of hypertension, n (%) | 17 709 (37.1) | 2636 (37.0) | 0.85 | |
| Cause of death, n (%) | Trauma | 16 521 (35.3) | 2553 (35.4) | 0.95 |
| Anoxia | 15 990 (34.1) | 2415 (33.5) | ||
| Cerebrovascular | 14 157 (30.2) | 2211 (30.7) | ||
| Others | 186 (0.4) | 29 (0.4) | ||
| DCD donor, n (%) | 3274 (6.8) | 476 (6.5) | 0.29 | |
| Marginal graft, n (%) | 9690 (20.3) | 1335 (18.2) | <0.001 | |
| Allocation type, n (%) | Local | 32 918 (68.8) | 5116 (69.6) | 0.15 |
| Regional | 12 880 (26.9) | 1912 (26.0) | ||
| National | 2052 (4.3) | 322 (4.4) | ||
| Split graft, n (%) | 630 (1.3) | 79 (1.1) | 0.16 | |
| DRI, median (IQR) | 1.54 (1.31–1.85) | 1.52 (1.29–1.83) | 0.001 | |
| CIT (h), median (IQR) | 5.90 (4.62– 7.38) | 5.83 (4.54–7.22) | 0.001 |
Bold type indicates statistically significant differences.
BMI, body mass index; CIT, cold ischemia time; DCD, donation after circulatory death; DRI, donor risk index; IQR, interquartile range; MI, myocardial infarction.
FIGURE 2.
Daily liver transplant rates from 2010 to 2019 stratified by composite and individual holidays. Composite and individual holiday rates are compared with nonholiday rates using Mann–Whitney test. P value comparing composite and individual holidays to nonholidays.
Posttransplant Outcomes Analysis of Adult LT Recipients Based on Time of Transplant Surgery
The Kaplan–Meier survival curves for overall patient survival rates were superior for patients who underwent LT during public holidays, and graft survival was similar in the 2 groups (Figure 3). After adjusting for recipient and donor factors via 4-to-1 propensity score matching with a total of 33,505 patients, LT performed during public holidays (n = 6701) was associated with a significantly lower risk of overall mortality (hazard ratio 0.94 [95% CI, 0.86-0.99], P = 0.046). No significant differences were noted overall between groups in the proportion of contributing causes of graft failure except for a lower proportion of acute rejection for patients transplanted during public holidays than nonholidays (5.9% versus 9.6%, respectively; P = 0.02; Table 3).
FIGURE 3.
Kaplan–Meier curves for overall patient and graft survival (entire cohort). LT, liver transplantation.
TABLE 3.
Causes of graft failure based on timing of transplant (public holiday versus nonholiday)
| Cause of graft failure | Nonholiday group (n = 2295) | Public holiday group (n = 360) | P |
|---|---|---|---|
| Biliary complications, n (%) | 158 (12.6) | 27 (14.8) | 0.49 |
| Recurrent disease, n (%) | 387 (14.7) | 66 (16.9) | 0.36 |
| Infection, n (%) | 389 (14.9) | 58 (14.9) | 0.17 |
| Primary nonfunction, n (%) | 280 (0.6) | 51 (0.7) | 0.22 |
| Patient noncompliance, n (%) | 58 (8.0) | 5 (4.7) | 0.96 |
| Acute rejection, n (%) | 251 (9.6) | 23 (5.9) | 0.02 |
| Chronic rejection, n (%) | 280 (16.2) | 42 (16.5) | 0.91 |
| Vascular thrombosis, n (%) | 231 (18.4) | 42 (23.0) | 0.20 |
| Hepatic artery thrombosis, n (%) | 261 (17.9) | 46 (21.4) | 0.25 |
Bold type indicates statistically significant differences.
Donor Graft Discard Data
In total, there were 92 063 donors in the allograft discard analysis with 79 954 (86.8%) during nonholidays and 12 109 (13.2%) during public holidays. During public holidays, the number of livers that were not recovered was higher compared with nonholidays (15.4% versus 14.5%; P = 0.03), whereas the number of livers recovered but not for transplant was lower (3.2% versus 3.8%; P < 0.001) during public holidays compared with nonholidays (Table 4). When comparing the discarded deceased donor characteristics, there was no difference between those who passed away on public holidays versus nonholidays (data not shown). Compared with nonholidays, July 4th (9.0% versus 7.6%) and New Year (8.3% versus 7.6%) had the highest number of livers that were recovered for transplant but not transplanted (P = 0.02).
TABLE 4.
Comparison of liver offers between public holiday and nonholiday
| Variable | Nonholiday | Public holiday | P |
|---|---|---|---|
| Organ not recovered, n (%) | 11 567 (14.5) | 1859 (15.4) | 0.03 |
| Recovered but not for transplant (ie, research), n (%) | 3035 (3.8) | 382 (3.2) | <0.001 |
| Recovered for transplant but not transplanted, n (%) | 6155 (7.7) | 948 (7.8) | 0.85 |
| Transplanted, n (%) | 58374 (73) | 8920 (73.7) | 0.81 |
| Total | 79131 | 11727 |
Bold type indicates statistically significant differences.
DISCUSSION
In this large study that included over 55 000 deceased-donor single-organ LTs performed in the United States of America over 10 y, we noted similar rates of LT during public holidays when considered in aggregate, compared with other times. When considering individual holidays, transplant rates were no different than nonholidays. The overall patient survival was higher after LTs performed during public holidays compared with those performed during nonholidays. The difference in patient survival remained significant after adjustment for clinically relevant confounders, including donor, recipient, and transplant center volume. Although recipient characteristics were similar between the groups, deceased donors during public holidays had favorable characteristics. The number of livers that were not recovered during public holidays was higher compared with nonholidays. To our knowledge, this is the first study examining the effect of public holidays on LT/discard practices and posttransplant outcomes after LT.
Transplant activity can be affected by several factors, including transplant policy, surgeon availability, and the number of donor offers. Compared with nonholidays, a significantly higher heart transplant activity was noted on July 4th (July 4th: 5.69 versus nonholidays 5.09 transplants/d), whereas the winter holiday had lower heart transplant rates (winter holiday: 4.50 versus nonholidays: 5.09 transplants/d).16 In their study, information regarding the number and quality of transplant offers was unavailable, and it was unable to determine whether this observation was because of decreased offers or decreased acceptance during winter holidays. Further evaluation is needed to explore whether deceased donor offers decreased during the winter holidays, as this could negatively impact organ donation preferences. Our study noted that the transplant activity was similar between public holidays and nonholidays (public holiday: 15.0 versus nonholidays: 15.1 transplants/d; P = 0.35). These results may suggest that transplant centers have standardized protocols to allow rapid mobilization of resources throughout the year to perform LT safely.
Our study revealed that the overall patient survival after LT was improved during public holidays compared with nonholidays. Several recent registry studies in the transplant literature revealed similar patient and graft survival in the thoracic and abdominal transplants when performed during weekends compared with weekdays.1,8,15 One potential explanation for the better LT outcomes during the holidays could be because of better donor characteristics, potentially secondary to a more conservative graft selection by transplant centers during public holidays. We noted that deceased donors during public holidays had a lower proportion of marginal grafts (holidays 18.2% versus nonholidays 20.3%) and a lower DRI than nonholidays. This is contrary to results by Thuluvath et al15 who did not find significant differences in donor quality using DRI for LT that occurred during weekends or nights compared with weekdays or days, respectively. Another factor could be the surgeon’s preference/availability, which might influence institutional practices of accepting livers during public holidays. Limited resource and surgeon availability during the holidays are expected, and this was evident by the higher number of livers not recovered during public holidays compared with nonholidays (15.4% versus 14.5%; P = 0.03). A previous study demonstrated that deceased heart donors were younger (29.7 versus 31.6 y) and more commonly died of nonnatural deaths (70% versus 61%) during the July 4th holiday.16 The relative increase in deceased donors dying secondary to nonnatural causes during this period may result from people being more likely to be outdoors during the warm weather.20 According to the American Automobile Association and the Insurance Institute for Highway Safety, when compared with the winter months, the summer months have a much higher incidence of fatal motor vehicle accidents, with July having the highest incidence.21 These observations might be contributing similarly to the findings of lower DRI for liver donors during the 4th of July holiday.
Our study has several strengths. To the best of our knowledge, this is the first study that examined the impact of public holidays on liver discard practices and long-term patient and allograft survival. This study included a large sample size spanning 10 y of clinical practice within the United States and the nationally representative cohort of deceased donors and their LT recipients. Given that many liver graft offers are made days after the initial donor decline, we arbitrarily defined a holiday period by 3 d. The primary limitation is because of the nature of the study, as potential residual confounding factors are not being captured in the UNOS database. This includes availability of surgeons and other staff availability, which varies by institution.
CONCLUSION
Based on the observations from this large retrospective study using US national registry data, we conclude that LT performed during public holidays was associated with improved overall patient survival compared with nonholidays. In addition, our study highlights the issue of increased discarded livers during public holidays. The “Holiday effect” is likely multifactorial and could be related to patient selection, timing, surgeon preference, among other reasons. Transplant centers might be encouraged to improve logistics during public holidays to maximize the use of deceased donors while maintaining good outcomes.
ACKNOWLEDGMENTS
The United Network for Organ Sharing has supplied the data reported here as the contractor for the Organ Procurement and Transplantation Network. The interpretation and reporting of these data are the responsibility of the authors and in no way should be seen as an official policy of or interpretation by the Organ Procurement and Transplantation Network or the US Government.
Supplementary Material
Footnotes
T.M.S. and S.N. participated in conception of project, literature review, data analysis, interpretation of results, and write up of the article. T.K., T.I., S.S., A.M., S.Y., M.R., K.C., A.Y., and M.A. participated in interpretation of results and write up of the article. All authors have given final approval for this article to be submitted to Transplantation Direct.
The authors declare no funding or conflicts of interest.
The data that support the findings of this study are available from the Organ Procurement and Transplantation Network. Restrictions apply to the availability of these data, which were used under license for this study. Data are available from the Organ Procurement and Transplantation Network at https://optn.transplant.hrsa.gov/data/request-data/ with the permission of the Organ Procurement and Transplantation Network and United Network of Organ Sharing.
Supplemental digital content (SDC) is available for this article. Direct URL citations appear in the printed text, and links to the digital files are provided in the HTML text of this article on the journal’s Web site (www.transplantationdirect.com).
REFERENCES
- 1.Baid-Agrawal S, Martus P, Feldman H, et al. Weekend versus weekday transplant surgery and outcomes after kidney transplantation in the USA: a retrospective national database analysis. BMJ Open. 2016;6:e010482. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Bell CM, Redelmeier DA. Mortality among patients admitted to hospitals on weekends as compared with weekdays. N Engl J Med. 2001;345:663–668. [DOI] [PubMed] [Google Scholar]
- 3.Horwich TB, Hernandez AF, Liang L, et al. ; Get With Guidelines Steering Committee and Hospitals. Weekend hospital admission and discharge for heart failure: association with quality of care and clinical outcomes. Am Heart J. 2009;158:451–458. [DOI] [PubMed] [Google Scholar]
- 4.Peberdy MA, Ornato JP, Larkin GL, et al. ; National Registry of Cardiopulmonary Resuscitation Investigators. Survival from in-hospital cardiac arrest during nights and weekends. JAMA. 2008;299:785–792. [DOI] [PubMed] [Google Scholar]
- 5.Brunot V, Landreau L, Corne P, et al. Mortality associated with night and weekend admissions to ICU with on-site intensivist coverage: results of a nine-year cohort study (2006-2014). PLoS One. 2016;11:e0168548. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Barnett MJ, Kaboli PJ, Sirio CA, et al. Day of the week of intensive care admission and patient outcomes: a multisite regional evaluation. Med Care. 2002;40:530–539. [DOI] [PubMed] [Google Scholar]
- 7.Cortes MB, Fernandes SR, Aranha P, et al. Association between weekend and holiday admission with pneumonia and mortality in a tertiary center in Portugal: a cross-sectional study. Acta Med Port. 2017;30:361–367. [DOI] [PubMed] [Google Scholar]
- 8.George TJ, Arnaoutakis GJ, Merlo CA, et al. Association of operative time of day with outcomes after thoracic organ transplant. JAMA. 2011;305:2193–2199. [DOI] [PubMed] [Google Scholar]
- 9.Anderson BM, Mytton JL, Evison F, et al. Outcomes after weekend admission for deceased donor kidney transplantation: a population cohort study. Transplantation. 2017;101:2244–2252. [DOI] [PubMed] [Google Scholar]
- 10.Fechner G, Pezold C, Hauser S, et al. Kidney’s nightshift, kidney’s nightmare? Comparison of daylight and nighttime kidney transplantation: impact on complications and graft survival. Transplant Proc. 2008;40:1341–1344. [DOI] [PubMed] [Google Scholar]
- 11.Seow YY, Alkari B, Dyer P, et al. Cold ischemia time, surgeon, time of day, and surgical complications. Transplantation. 2004;77:1386–1389. [DOI] [PubMed] [Google Scholar]
- 12.Orman ES, Hayashi PH, Dellon ES, et al. Impact of nighttime and weekend liver transplants on graft and patient outcomes. Liver Transpl. 2012;18:558–565. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Mohan S, Foley K, Chiles MC, et al. The weekend effect alters the procurement and discard rates of deceased donor kidneys in the United States. Kidney Int. 2016;90:157–163. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Lonze BE, Parsikia A, Feyssa EL, et al. Operative start times and complications after liver transplantation. Am J Transplant. 2010;10:1842–1849. [DOI] [PubMed] [Google Scholar]
- 15.Thuluvath PJ, Amjad W, Savva Y, et al. Survival outcomes are not affected when liver transplant surgery is done at night, during weekends, or summer months. Transplant Direct. 2019;5:e449. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Grodin JL, Ayers CR, Thibodeau JT, et al. Variation of heart transplant rates in the United States during holidays. Clin Transplant. 2014;28:877–882. [DOI] [PubMed] [Google Scholar]
- 17.Osborn L. Winter temperature averages for every state. Available at https://www.currentresults.com/Weather/US/average-state-temperatures-in-winter.php. Accessed August 13, 2021.
- 18.Nagai S, Collins K, Chau LC, et al. Increased risk of death in first year after liver transplantation among patients with nonalcoholic steatohepatitis vs liver disease of other etiologies. Clin Gastroenterol Hepatol. 2019;17:2759–2768.e5. [DOI] [PubMed] [Google Scholar]
- 19.Zhang T, Dunson J, Kanwal F, et al. Trends in outcomes for marginal allografts in liver transplant. JAMA Surg. 2020;155:926–932. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Reinberg O, Lutz N, Reinberg A, et al. Trauma does not happen at random. Predictable rhythm pattern of injury occurrence in a cohort of 15,110 children. J Pediatr Surg. 2005;40:819–825. [DOI] [PubMed] [Google Scholar]
- 21.National Highway Traffic Safety Administration. Fatality analysis reporting system. Available at http://www-fars.nhtsa.dot.gov. Accessed September 1, 2021.
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.