Newborns with hypoplastic left heart syndrome and other single right ventricular variants require substantial health care resources. Weekend acute care has been associated with worse outcomes and increased resource use in other populations but has not been studied in patients with single ventricle. Subjects of the Single Ventricle Reconstruction trial were classified by whether they had a weekend admission and by day of the week of Norwood procedure. The primary outcome was hospital length of stay (LOS); secondary outcomes included transplant-free survival, intensive care unit (ICU) LOS, and days of mechanical ventilation. The Student’s t test with log transformation and the Wilcoxon rank-sum test were used to analyze associations. Admission day was categorized for 533 of 549 subjects (13% weekend). The day of the Norwood was Thursday/Friday in 39%. There was no difference in median hospital LOS, transplant-free survival, ICU LOS, or days ventilated for weekend versus non-weekend admissions. Day of the Norwood procedure was not associated with a difference in hospital LOS, transplant-free survival, ICU LOS, or days ventilated. Prenatally diagnosed infants born on the weekend had lower mean birth weight, younger gestational age, and were more likely to be intubated but did not have a difference in measured outcomes. In conclusion, in this cohort of patients with single right ventricle, neither weekend admission nor end-of-the-week Norwood procedure was associated with increased use of hospital resources or poorer outcomes. We speculate that the complex postoperative course following the Norwood procedure outweighs any impact that day of admission or operation may have on these outcomes.
Infants with hypoplastic left heart syndrome (HLHS) and other single right ventricle (RV) anomalies typically undergo the Norwood procedure within the first several days of life. Although highly resource intensive, the factors that affect resource utilization after the Norwood procedure the most remain unknown. The day of the week when the highest acuity of care is provided may have a significant impact on resource utilization. The “weekend effect” has been associated with increased resource utilization in children <18 years who underwent cardiac surgery and poorer clinical outcomes in adults admitted on the weekend for several clinical indications. The weekend effect may be modifiable and previously has been improved with high-intensity staffing. Determining whether weekend admission or day of surgery affects clinical outcomes or resource utilization may be valuable for planning perinatal management, surgical timing, and modifying health care delivery systems. Using the cohort enrolled in the Single Ventricle Reconstruction (SVR) trial, we sought to determine if weekend admission and/or day of surgery in neonates who underwent the Norwood procedure was associated with measures of increased postoperative resource utilization or worse clinical outcomes.
Methods
We performed a secondary analysis of SVR trial data, the details of which have previously been published. Briefly, patients with a diagnosis of HLHS or other single RV anomalies and a planned Norwood procedure were randomized to receive a modified Blalock-Taussig Shunt or right ventricular-to-pulmonary artery shunt to compare the incidence of death or transplant. Age at admission to the surgical center and the presence of a prenatal diagnosis were recorded. The main outcomes from the SVR trial that were used for this analysis were inhospital mortality, heart transplant status, hospital length of stay (LOS), intensive care unit (ICU) LOS, days to surgery, and days of mechanical ventilation.
A primary exposure status of “weekend admission” (Saturday or Sunday) or “weekday admission” (Monday to Friday) to the surgical center was assigned for each subject. Date of admission was unavailable in the SVR trial database. Therefore, for the prenatally diagnosed subjects, date of birth was used for classification of date of admission. For subjects who were postnatally diagnosed, the date of diagnosis at the surgical center was considered the date of admission. This was determined from age at diagnosis, which was rounded to the nearest full day to determine group assignment. For those <12 hours of age at diagnosis, we assumed that the day of diagnosis was the day of birth. Subjects whose weekend versus weekday designation was unclear based on the earlier mentioned algorithm were excluded from the analysis.
The day of week of the Norwood procedure was also analyzed as an exposure. Subjects were divided into those who underwent the Norwood procedure on Thursday or Friday (end of the week) versus those who underwent the Norwood procedure on Monday through Wednesday. This classification was chosen because the highest acuity care, primarily the first few days postoperatively, would have occurred largely on the weekend in the “end of the week” Norwood group. Only 1 Norwood procedure occurred on the weekend and that subject was excluded from this portion of the analysis.
Surrogates for resource utilization previously described in the literature were selected as outcomes. The primary outcome for this analysis was hospital LOS for the Norwood hospitalization. Secondary outcomes included ICU LOS, number of hospital days before surgery after diagnosis, number of days mechanically ventilated during hospitalization, and a composite outcome of death or heart transplant before discharge from the Norwood hospitalization. Because of the variable effect of death or transplant on LOS, those who died or were transplanted before discharge were excluded from the LOS analyses.
Based on the previously reported predictive models for these outcomes from the SVR trial, we compared subjects with respect to the variables identified as associated with the outcomes of interest to assess comparability of the groups. Baseline characteristics and risk factors are listed in Tables 1 and 2 . To deal with any potential interaction between prenatal versus postnatal diagnosis and day of admission, a subgroup analysis restricted to the prenatally diagnosed group was performed.
| Variable | Weekend admission (N=71) | Weekday admission (N=462) | p value | Mon-Wed Norwood (N=336) | Thu-Fri Norwood (N=212) | p value |
|---|---|---|---|---|---|---|
| Male | 46 (65%) | 285 (62%) | 0.7 | 211 (63%) | 128 (60%) | 0.6 |
| Prenatally diagnosed | 46 (65%) | 374 (81%) | 0.003 | 254 (76%) | 165 (78%) | 0.6 |
| Gestational age, weeks, mean ±SD | 37.9±2.0 | 38.2±1.5 | 0.2 | 38.2±1.6 | 38.1±1.6 | 0.3 |
| Birth weight, kg, mean±SD | 3.00±0.59 | 3.12±0.53 | 0.07 | 3.1±0.54 | 3.12±0.55 | 0.7 |
| Birth weight <2.5 kg | 15 (21%) | 59 (13%) | 0.07 | 46 (14%) | 30 (14%) | 0.9 |
| APGAR at 1 minute, median (IQR) | 8 (8–9) | 8 (8–9) | 0.9 | 8 (7–9) | 8 (8–9) | 0.5 |
| APGAR at 5 minutes, median (IQR) | 9 (8–9) | 9 (8–9) | 0.8 | 9 (8–9) | 9 (8–9) | 0.2 |
| Hypoplastic Left Heart Syndrome | 59 (83%) | 400 (87%) | 0.5 | 288 (86%) | 185 (87%) | 0.7 |
| Genetic syndrome | 4 (6%) | 19 (4%) | 0.04 | 15 (5%) | 11 (5%) | 0.9 |
| Unknown/no genetic evaluation | 31 (44%) | 140 (30%) | 107 (32%) | 69 (33%) | ||
| Non-syndromic abnormality | 9 (13%) | 92 (20%) | 65 (19%) | 40 (19%) | ||
| Unknown/no evaluation | 31 (44%) | 139 (30%) | 0.06 | 106 (32%) | 69 (33%) | >0.9 |
| Age at Norwood, days, median (IQR) | 5 (4–6) | 5 (3–7) | 5 (4–6) | 5 (3–7) | ||
| Center volume, per yr, median (IQR) | 21.5 (17.1–32.2) | 27.5 (17.1–32.2) | 27.5 (17.1–32.2) | 21.5 (17.1–32.2) | ||
| Center volume | 0.7 | 0.009 | ||||
| ≤15/yr | 11 (16%) | 82 (18%) | 0.4 | 61 (18%) | 32 (15%) | 0.9 |
| 16-20/yr | 19 (27%) | 86 (19%) | 0.4 | 61 (18%) | 48 (23%) | 0.6 |
| 21-30/yr | 23 (32%) | 144 (31%) | 108 (32%) | 38 (32%) | ||
| >30/yr | 18 (25%) | 150 (33%) | 106 (32%) | 34 (30%) | ||
| Surgeon Norwood volume, per yr median (IQR) | 12 (7.9–14.8) | 12.3 (6.9–13.6) | 12.0 (6.9– 13.3) | 12.6 (7.3–14.8) | ||
| Surgeon Norwood volume | ||||||
| ≤5/yr | 14 (20%) | 93 (20%) | 0.5 | 69 (21%) | 39 (18%) | 0.2 |
| 6-10/yr | 14 (20%) | 96 (21%) | >0.9 | 68 (20%) | 45 (21%) | 0.2 |
| 11-15/yr | 31 (44%) | 201 (44%) | 154 (46%) | 85 (40%) | ||
| >15/yr | 12 (17%) | 72 (16%) | 45 (13%) | 43 (20%) | ||
| Variable | Weekend admission (N=71) | Weekday admission (N=462) | p value | Mon-Wed Norwood (N=336) | Thu-Fri Norwood (N=212) | p value |
|---|---|---|---|---|---|---|
| Preoperative highest lactate (mmol/L), median (IQR) | 3.2 (2.4–5.1) | 3.1 (2.5–4.2) | 0.1 | 3.1 (2.5–4.6) | 3.1 (2.4–4.3) | 0.2 |
| Preoperative intubation | 44 (62%) | 209 (45%) | 0.01 | 163 (49%) | 100 (47%) | 0.7 |
| Intubation due to apnea or transport | 13 (18%) | 84 (18%) | >0.9 | 63 (19%) | 38 (18%) | 0.8 |
| Intubation due to shock, respiratory failure, or metabolic acidosis | 26 (37%) | 86 (19%) | 0.001 | 72 (22%) | 45 (21%) | >0.9 |
| Preoperative intervention for atrial septum | 2 (3%) | 19 (4%) | >0.9 | 10 (3%) | 11 (5%) | 0.3 |
| Composite indicator for preoperative shock/arrest | 9 (13%) | 27 (6%) | 0.04 | 22 (7%) | 16 (8%) | 0.7 |
| Preoperative TR ≥2.5 mm | 10 (15%) | 52 (12%) | 0.5 | 40 (12%) | 21 (10%) | 0.6 |
| ECMO used in OR | 3 (4%) | 32 (7%) | 0.6 | 18 (5%) | 17 (8%) | 0.2 |
| ECMO during Norwood hospitalization | 12 (17%) | 73 (16%) | 0.9 | 46 (14%) | 42 (20%) | 0.07 |
| Delayed sternal closure | 58 (84%) | 357 (78%) | 0.3 | 259 (78%) | 166 (79%) | 0.7 |
| Delayed sternal closure | 0.4 | 0.9 | ||||
| Yes, non-elective | 31 (45%) | 207 (45%) | 149 (45%) | 95 (46%) | ||
| Yes, elective | 27 (39%) | 150 (33%) | 110 (33%) | 71 (34%) | ||
| No, primary closure | 11 (16%) | 102 (22%) | 75 (23%) | 43 (21%) | ||
| Norwood perfusion type | 0.5 | 0.8 | ||||
| DHCA only | 34 (49%) | 255 (56%) | 184 (55%) | 111 (53%) | ||
| RCP and DHCA ≤10 min | 20 (29%) | 106 (23%) | 78 (24%) | 52 (25%) | ||
| RCP and DHCA ≥10 min | 15 (22%) | 98 (21%) | 70 (21%) | 48 (23%) | ||
| Total support time (min), mean±SD | 144±50 | 144±55 | >0.9 | 144±50 | 145±60 | 0.8 |
| Total DHCA time (min), mean±SD | 28±22 | 32±23 | 0.1 | 31±21 | 32±27 | 0.5 |
| DHCA time ≤45 min | 54 (76%) | 345 (75%) | 0.9 | 248 (74%) | 163 (77%) | 0.5 |
| Total RCP time (min), mean±SD | 27±29 | 23±29 | 0.3 | 23±30 | 24±28 | 0.8 |
| Infection prior to discharge | 30 (43%) | 193 (42%) | 0.9 | 147 (44%) | 89 (42%) | 0.7 |
| Number of other surgical procedures during Norwood hospitalization, median (IQR) | 1 (1,2) | 1 (1,2) | 0.6 | 1 (1,2) | 1 (1,3) | 0.3 |
The distributions of patient characteristics by day of week and day of Norwood groups were compared using the Fisher’s exact test for categorical variables, the Wilcoxon rank-sum test for continuous skewed variables, and Student’s t test for other continuous variables. The association between the day of week and day of Norwood group and death or transplant before Norwood discharge was examined with the Fisher’s exact test. The associations between the day of week and day of Norwood group and LOS, number of days before surgery, and total number of days ventilated were analyzed using the Student’s t test of the log-transformed measure or a Wilcoxon rank-sum test. Multivariable linear and logistic regression was also used to evaluate the weekend versus weekday effect controlling for other known risk factors for post-Norwood outcomes, such as birth weight, presence of a genetic syndrome, number of pre-Norwood surgeries, pre-Norwood intubation for shock, pre-Norwood tricuspid regurgitation, and center single ventricle patient volume. A 2-sided p value of 0.05 was considered significant. Analyses were conducted using SAS, version 9.3 (Statistical Analysis System Corp., Cary, North Carolina).
Results
Of the 549 subjects in the SVR trial who underwent Norwood, admission day could be categorized in 533 (97%). Weekend admission occurred in 71 (13%) and weekday admission in 462 (87%). There was a higher proportion of prenatally diagnosed patients admitted on weekdays ( Table 1 ). Subjects admitted on the weekend were more likely to be intubated preoperatively and more likely to be intubated for shock, respiratory failure, or metabolic acidosis as opposed to electively before transport and to have had preoperative shock or cardiac arrest ( Table 2 ). In the prenatally diagnosed group, those admitted on the weekend were more likely to have a birth weight <2.5 kg and be of an earlier gestational age ( Table 3 ). Similar to the overall cohort, they were more likely to be intubated because of shock, respiratory failure, or metabolic acidosis ( Table 3 ).
| Weekend admission (N=46) | Weekday admission (N=374) | p value | |
|---|---|---|---|
| Male | 33 (72%) | 226 (60%) | 0.2 |
| Gestational age, (weeks), mean ±SD | 37.5±2.1 | 38.1±1.5 | 0.04 |
| Birth weight, (kg), mean±SD | 2.91±0.65 | 3.11±0.53 | <0.05 |
| Birth weight <2.5 kg | 13 (28%) | 52 (14%) | 0.02 |
| APGAR at 1 minute, median (IQR) | 8 (7,8) | 8(8,9) | 0.4 |
| APGAR at 5 minutes, median (IQR) | 9 (8,9) | 9(8,9) | 0.3 |
| Hypoplastic Left Heart Syndrome | 41 (89%) | 326 (87%) | 0.8 |
| Genetic syndrome present | 2 (4%) | 15 (4%) | 0.2 |
| Unknown/no genetic evaluation | 20 (44%) | 115 (31%) | |
| Non-syndromic abnormality present | 5 (11%) | 79 (21%) | 0.1 |
| Unknown/no evaluation | 20 (44%) | 114 (31%) | |
| Age at Norwood, (days), median (IQR) | 4 (3,5) | 5 (3,6) | 0.7 |
| Center volume, per year, median (IQR) | 27.5 (18.9–49.6) | 27.5 (17.1–32.2) | 0.6 |
| Center volume | 0.2 | ||
| ≤15/yr | 4 (9%) | 60 (16%) | |
| 16-20/yr | 13 (28%) | 66 (18%) | |
| 21-30/yr | 12 (26%) | 122 (32.6%) | |
| >30/yr | 17 (37%) | 126 (34%) | |
| Surgeon volume, per year, median, IQR | 12.3 (8.2–13.6) | 12.6 (7.1–13.6) | 0.6 |
| Surgeon Norwood volume | 0.5 | ||
| ≤5/yr | 5 (11%) | 68 (18%) | |
| 6-10/yr | 13 (28%) | 78 (21%) | |
| 11-15/yr | 22 (48%) | 167 (45%) | |
| >15/yr | 6 (13%) | 61 (16%) | |
| Risk factors | |||
| Preoperative highest lactate, (mmol/L), median (IQR) | 3.1 (2.3–4.4) | 3.1 (2.4–4.0) | 0.7 |
| Preoperative intubation | 25 (54%) | 147 (39%) | 0.06 |
| Intubation due to apnea or transport | 8 (17%) | 64 (17%) | >0.9 |
| Intubation due to shock, respiratory failure, or metabolic acidosis | 13 (28%) | 55 (15%) | 0.03 |
| Preoperative intervention for atrial septum | 1 (2%) | 15 (4%) | >0.9 |
| Composite indicator for preoperative shock/arrest | 1 (2%) | 15 (4%) | 0.5 |
| Preoperative TR ≥2.5 mm | 4 (9%) | 35 (10%) | >0.9 |
| ECMO used in OR | 1 (2%) | 26 (7%) | 0.3 |
| ECMO during Norwood hospitalization | 7 (15%) | 62 (17%) | >0.9 |
| Delayed sternal closure | 34 (76%) | 290 (78%) | 0.7 |
| Delayed sternal closure | 0.6 | ||
| Yes, non-elective | 16 (36%) | 161 (43%) | |
| No, primary closure | 11 (24%) | 82 (22%) | |
| Norwood perfusion type | 0.9 | ||
| DHCA only | 24 (53%) | 207 (56%) | |
| RCP and DHCA≤10 min | 11 (24%) | 83 (23%) | |
| RCP and DHCA≥10 min | 10 (22%) | 80 (21%) | |
| Total support time, (min), mean±SD | 135±40 | 143±53 | 0.2 |
| Total DHCA time, (min), mean±SD | 28±19 | 32±23 | 0.2 |
| DHCA time ≤ 45 min | 35 (76%) | 277 (74%) | 0.9 |
| Total RCP time, (min), mean±SD | 25±29 | 23±29 | 0.7 |
| Infection prior to discharge | 16 (35%) | 150 (40%) | 0.5 |
| Number of other surgical procedures during Norwood hospitalization, median (IQR) | 1 (1–2) | 1 (1–2) | 0.9 |
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