Limited data exist regarding the in-hospital outcomes in patients with cardiac arrest (CA) in teaching versus nonteaching hospital settings. Using the Nationwide (National) Inpatient Sample (2008 to 2012), 731,107 cases of CA were identified using International Classification of Diseases, Ninth Edition codes. Among these patients, 348,368 (47.6%) were managed in teaching hospitals and 376,035 (51.4%) in nonteaching hospitals. Patients in teaching hospitals with CA were younger (62.42 vs 68.08 years old), had less co-morbidities (p <0.001), were less likely to be white (54.6% vs 65.5%) and more likely to be uninsured (9.1% vs 7.6%). Mortality in patients with CA was significantly lower in teaching hospitals than in nonteaching hospitals (55.3% vs 58.8%; all p <0.001). The mortality remained significantly lower after adjusting for baseline patient and hospital characteristics (odds ratio 0.917, CI 0.899 to 0.937, p <0.001). However, the survival benefit was no longer present after adjusting for in-hospital procedures (OR 0.997, CI 0.974 to 1.02, p = 0.779). In conclusion, teaching status of the hospital was associated with decreased in-hospital mortality in patients with CA. The differences in mortality disappeared after adjusting for in-hospital procedures, indicating that routine application of novel therapeutic methods in patients with CA in teaching hospitals could translate into improved survival outcomes.
Cardiac arrest (CA) has been defined as a sudden and unexpected pulseless condition attributable to cessation of cardiac mechanical activity. It is estimated that more than 200,000 patients experience CA in US hospitals each year with survival to discharge of 25.5%. Inherent differences between teaching and nonteaching hospitals have been previously considered as a potential systems-level variable affecting patient outcomes. Integrating medical education as part of patient care is among the differences observed between teaching and nonteaching hospitals. Although multiple reports have compared the outcomes of teaching and nonteaching hospitals in different clinical settings, data regarding the outcomes of CA are lacking. In addition, morbidity and mortality has remained the main focus of previous studies, and the impact of hospital teaching status on other outcome measures including length of hospital stay and hospital costs have not been fully investigated. Therefore, in the present study, we used the National (Nationwide) Inpatient Database (NIS) to assess the effect of hospital teaching status on outcomes, length of stay, and hospital costs in patients with CA.
Methods
The NIS is the largest all-payer inpatient database consisting of approximately 20% of inpatient admissions to nonfederal, nonrehabilitation hospitals in the United States. We collected data from NIS database from 2008 to 2012. National estimates could also be predicted using sampling weights provided in the database.
The International Classification of Diseases , Ninth Edition, Clinical Modification was used to identify all patients with CA from 2008 to 2012. Primary diagnostic code 427.5 was used to identify this population. In addition, primary procedure codes were used to identify patients who underwent post-CA procedures ( Supplementary Table 1 ). Teaching status of a hospital was used as provided in the NIS database.
Agency for Healthcare Research and Quality co-morbidity measures using International Classification of Diseases , Ninth Edition, Clinical Modification diagnoses were used to identify the co-morbidities in patients with CA. The Charlson Comorbidity Index (CCI) was used to evaluate the severity of co-morbidities. In this index, 17 co-morbid conditions are included; they are assigned differential weights with a total score ranging from 0 to 33. Higher CCI scores correspond to greater burden of co-morbid diseases.
Inpatient cost of hospitalization was calculated by merging data from the NIS database with cost-to-charge ratios available from the Healthcare Cost and Utilization Project of the Agency for Healthcare Research and Quality. Given total charges for each inpatient stay available in the database, costs were then calculated by multiplying the total hospital charge with cost-to-charge ratios which were used to account for the inherent variability among hospitals and regions for any given procedure. All costs were adjusted for inflation according to the latest consumer price index data released by the US government on January 16, 2016.
Hospital-level discharge weights provided by NIS were used to generate national estimates. Categorical variables were compared using the chi-square, whereas Wilcoxon signed-rank test was used for continuous variables. Two-level hierarchical models (with patient level factors nested within hospital-level factors) were created using the unique hospital identification number incorporated as random effects within the model. A p value of <0.05 was considered significant. All analyses were performed using Stata IC 13 (Stata Corp, College Station, Texas).
Results
A total of 731,107 cases of CA were estimated between the years of 2008 and 2012 (348,368 in teaching hospitals and 376,035 in nonteaching hospitals). Demographics and clinical characteristics are presented in Table 1 . The mean (SD) age of patients with CA was 65.3 (18.5) with male predominance. Among all patients, more than a half were of white race, 8.4% had no governmental or private insurance, and 40% had CCI of more than 2. The median length of stay was 4 days (interquartile range 1 to 11), whereas cost of stay varied with a mean cost of $31,221.
| Variable | All (731,107) | Teaching (348,368) | Non-Teaching (376,035) | P -Value |
|---|---|---|---|---|
| Patient Age (year) | ||||
| Mean, (SD) | 65.32, (18.5) | 62.42 (20.32) | 68.08 (16.38) | <0.001 |
| < 65 | 42.8% | 48.4% | 37.5% | |
| 65-74 | 21.6% | 20.8% | 22.4% | |
| >75 | 35.6% | 30.9% | 40.1% | |
| Gender | <0.001 | |||
| Male | 55.1% | 56.3% | 54.1% | |
| Female | 44.9% | 43.7% | 45.9% | |
| Race | <0.001 | |||
| White | 60.2% | 54.6% | 65.5% | |
| Black | 14.5% | 18.2% | 11.0% | |
| Hispanic | 7.4% | 7.6% | 7.2% | |
| Asian or Pacific Islander | 2.3% | 2.5% | 2.2% | |
| Native American | 0.6% | 0.5% | 0.6% | |
| Other | 3.0% | 3.3% | 2.7% | |
| Missing | 11.9% | 13.2% | 10.8% | |
| Charlson Comorbidity Index | <0.001 | |||
| 0 | 16.4% | 18.5% | 14.5% | |
| 1 | 22.2% | 22.1% | 22.4% | |
| 2 | 21.4% | 20.7% | 21.9% | |
| >2 | 40.0% | 38.6% | 41.2% | |
| Primary Payment type | <0.001 | |||
| Government | 70.9% | 68.3% | 73.3% | |
| Private | 20.5% | 22.4% | 18.9% | |
| Other/None | 8.4% | 9.1% | 7.6% | |
| Region of Hospital | <0.001 | |||
| Northeast | 16.7% | 22.5% | 11.6% | |
| Midwest | 22.2% | 25.3% | 18.8% | |
| South | 41.0% | 36.8% | 45.1% | |
| West | 20.0% | 15.4% | 24.5% | |
| Hospital Bed Size | <0.001 | |||
| Small | 10.3% | 10.9% | 10.0% | |
| Medium | 22.9% | 24.3% | 22.0% | |
| Large | 65.8% | 64.8% | 67.9% | |
| Length of Stay median (IGR) | 4 (1-11) | 5 (2-13) | 4 (1-9) | <0.001 |
| Cost, mean (SD), | $31,221, (46,220) | $38,851 (58,058) | $24,232 (30,192) | <0.001 |
| Mortality | 57.1% | 55.3% | 58.8% | <0.001 |
The most common associated condition was aspiration pneumonia followed by coma and hyperglycemia. Among all patients, the most commonly associated intervention was percutaneous coronary intervention (PCI) followed by tracheostomy and intraaortic balloon pump.
Similar percentage of patients was managed in nonteaching hospitals and teaching hospitals (51.4% vs 47.6%, respectively). Comparisons between baseline characteristics, crude associated conditions, and outcomes between the patients in teaching and nonteaching hospitals are presented in Tables 1 and 2 . Patients with CA in teaching hospital were younger, had less co-morbidities, were less likely to be white, and were more likely to be uninsured. Patients with CA were more likely to be treated in a teaching hospital in Northeast and Midwest and less likely to be treated in a teaching hospital in South and on the West coast. Further analysis did not reveal any significant correlation between mortality rates after CA and hospital density in 9 main Census Divisions of the US ( Supplementary Table 2 ). Nonteaching hospitals managing patients with CA more often belonged to the top tertile by number of beds.
| Variable | All (731,107) | Teaching (348,368) | Non-Teaching (376,035) | P -Value |
|---|---|---|---|---|
| Complications | ||||
| Coma | 5.5% | 5.4% | 5.6% | 0.005 |
| Myoclonus | 0.8% | 1.0% | 0.7% | <0.001 |
| Pulmonary Embolism | 0.30% | 0.33% | 0.27% | <0.001 |
| Aspiration Pneumonia | 13.8% | 13.5% | 14.0% | <0.001 |
| Hyperglycemia | 2.0% | 2.1% | 2.0% | 0.001 |
| In-Hospital Interventions | ||||
| Percutaneous Coronary Intervention | 8.1% | 8.5% | 7.8% | <0.001 |
| Coronary Artery Bypass Grafting | 2.4% | 2.9% | 1.9% | <0.001 |
| Extracorporeal Membrane Oxygenation | 0.4% | 0.8% | 0.03% | <0.001 |
| Intra-Aortic Balloon Pump | 4.7% | 5.4% | 4% | <0.001 |
| Left Ventricular Assist Device | 0.2% | 0.3% | 0.1% | <0.001 |
| Hypothermia | 2.5% | 2.8% | 2.2% | <0.001 |
| Implantable Cardioverter Defibrillator | 3.5% | 4.3% | 2.8% | <0.001 |
| Tracheostomy | 4.8% | 6.2% | 3.5% | <0.001 |
| Percutaneous endoscopic gastrostomy/jejunostomy | 3.7% | 4.1% | 3.3% | <0.001 |
Patients in teaching hospitals were much more likely to undergo certain life-sustaining interventions including PCI, extracorporeal membrane oxygenation, left ventricular assist devices, tracheostomies, and implantable cardioverter-defibrillator placement ( Table 2 ). Most importantly, mortality in patients with CA was significantly lower in teaching hospitals than in nonteaching hospitals.
All the teaching hospitals in NIS are attributed to urban areas. Mortality was significantly higher in rural hospitals than in hospitals in urban areas (65.6% vs 56.4%, respectively, p <0.001). Subgroup analysis of the urban hospitals revealed significantly lower mortality in urban teaching hospitals than in urban nonteaching hospitals (55.3% vs 57.2%, respectively, p <0.001).
As listed in Table 3 , 2 multivariate-adjusted models were used to compare the outcomes between patients treated in teaching versus nonteaching hospitals. In model 1, after adjusting for patient demographics, co-morbidities, hospital characteristics, volume, and complications, teaching hospitals were shown to be independently associated with lower mortality rates. However, after addition of in-hospital procedures into the regression model (model 2), there was no longer any significant difference between the 2 groups with respect to mortality rate. This finding indicates that the higher volume of life-sustaining procedures in teaching hospitals could be responsible for improved survival in this group.
| Variable | Model 1 ∗ | Model 2 † | ||||
|---|---|---|---|---|---|---|
| OR/coefficient ‡ | 95% CI | P value | OR/coefficient ‡ | 95% CI | P-value | |
| Mortality | 0.92 | 0.89- 0.93 | <0.001 | 0.997 | 0.97- 1.02 | 0.779 |
| LOS | 2.67 | 1.35-3.99 | <0.001 | 2.66 | 1.33-3.98 | <0.001 |
| Cost | 12695 | 12187-13203 | <0.001 | 9435 | 8976 -9894 | <0.001 |
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