Recently, it has been estimated that the annual cost of medical errors is over 17 billion dollars19
and there have been a slew of newer initiatives over the last decade to incentivise better quality care. In 2008, Medicare announced that it would restrain the ability of hospitals to get reimbursed for ‘reasonably preventable events’: avoidable medical errors ranging from pressure ulcers, falls and transfusion of incompatible blood to anaesthetic complications, deep vein thrombosis and foreign bodies left in the body of patients during surgery. These and other initiatives are designed to place the burden of responsibility for such hospital-acquired adverse events squarely on hospitals and physicians.20
While these initiatives have been met with stiff objection from hospital administrations, the Centers for Medicaid and Medicare Services (CMS) has been consistent in its position that accountability for such events should rest with hospitals and not with the taxpayer.20
The Affordable Care Act of 2010 has added newer dimensions to these quality-improvement initiatives, with reimbursement likely to be dependent on both adherence to standards of care and the perceptions of patients with regard to hospital performance as measured by surveys.21
A rational approach to improving accountability for substandard care should begin with identifying the true burden of hospital-acquired adverse events. This would be particularly useful in identifying specific adverse events that warrant special attention by payers like CMS and in preferential allocation of resources by hospitals due to the growing temporal burden of such events.
In the current study, we report contemporary trends in the frequency of hospital-acquired adverse events after major surgical oncology care in the USA. Our study has a number of novel findings. First, we report a gradual increase in the national frequency of hospital-acquired adverse events after major cancer surgery over the last decade. This is important as it represents a decline, albeit small and gradual, in the quality of surgical oncology care at the national level, as measured by the primary prevention of PSI events. The increase may be attributed to changes in case-mix, including an ageing population. Conversely, the emergence of multiresistant bacteria may contribute to the recorded trends.22
Second, a simultaneous decrease in failure-to-rescue rates was observed, which may indicate that while primary prevention of hospital-acquired adverse events has deteriorated, the early recognition and timely management of these complications may have improved in the last decade. These findings may explain the significant annual reduction in mortality for patients undergoing major cancer surgery. Nonetheless, alternate explanations include refinements in coding practices, which may have led to better recognition and recording of non-lethal adverse events, thereby resulting in an apparent decrease in mortality rates. Third, significant heterogeneity in the temporal dynamics of specific hospital-acquired adverse events was noted. While marked and worrisome increases were recorded in the frequency of postoperative sepsis, pressure ulcers and respiratory failure, advances were made in the prevention of anaesthetic complications, transfusion-related complications and hip fractures. Thus, we identify numerous setting-level and process-level measures where resources need to be refocused for further improvement in the quality of surgical oncology care.
We also examined the volume-complication-mortality dynamic in patients undergoing major cancer surgery, as it applies to potentially preventable hospital-acquired adverse events (PSI). There is a well-established body of evidence describing the volume-mortality relationship in patients undergoing major cancer procedures and other surgeries. Dudley et al24
examined patients undergoing 1 of 11 diverse procedures (ranging from coronary angioplasty to oesophageal cancer surgery) in California and concluded that 602 deaths could have been prevented annually by transferring patients from low-volume to high-volume hospitals. Birkmeyer et al25
reported that Medicare patients treated at very high-volume hospitals experienced up to a 12% difference in absolute mortality for certain procedures relative to patients treated at very low-volume hospitals. However, the underlying mechanisms explaining the volume-mortality relationship have not been elucidated clearly. Silber et al26
first introduced the concept of ‘failure-to-rescue’ in a seminal report that evaluated patients undergoing cholecystectomy or transurethral prostatectomy. They concluded that overall mortality was related to both hospital-level and patient-level factors, while adverse events were related to patient-level factors at admission (severity of illness). However, failure-to-rescue was preferentially associated with hospital-level factors, and thus the underlying dynamics for failure-to-rescue were different than that for overall mortality and adverse events. The current hypothesis8
regarding the volume-complication-mortality relationship is that lower volume hospitals experience higher mortality rates not because of higher complication rates, but due to lower failure-to-rescue rates. Ghaferi et al10
demonstrated that high-volume and low-volume hospitals enrolled in the National Surgical Quality Improvement Program had similar complication rates but different failure-to-rescue rates for multiple procedures. In a subsequent analysis9
of patients undergoing gastrectomy, pancreatectomy or oesophagectomy, similar results were demonstrated. However, in the current study, very high-volume hospitals (4th quartile vs 1st quartile) had both lower PSI event rates and
lower failure-to-rescue rates. Importantly, the volume-complication-mortality relationship, as it applies to PSI events, appears to be procedure-specific and heterogeneous, with the current hypothesis not accounting for multiple individual major cancer surgeries, namely colectomy, oesophagectomy, lung resection, pancreatectomy and prostatectomy. This is an important point: CMS currently focuses its quality-improvement initiatives on complication rates, and explicit demonstration that lower failure-to-rescue rates and not higher complication rates underlying the substandard care at low-volume hospitals may require a reconsideration of these initiatives. Our findings indicate that the prevailing hypothesis may need to be re-evaluated, at least for patients undergoing major cancer surgery. In fact, for patients undergoing hysterectomy, this relationship is reversed, with patients at very high-volume hospitals experiencing higher
PSI event rates and lower failure-to-rescue rates. The underlying reason for this finding is not clear. Previous studies27
have questioned the impact of hospital volume on hysterectomy outcomes and reported that surgeon volume trumps hospital volume as the predominant factor underlying the volume–outcomes relationship for hysterectomy. While the inclusion of surgeon volume may alter these findings, the higher rates of adverse events in patients undergoing hysterectomy at very high-volume hospitals may need to be re-examined in future reports.
Our study is not without limitations. The drawbacks of using administrative data are well known,28
including limitations regarding risk-adjustment and miscoding. While PSIs have been shown to perform well as screening tools from an epidemiological perspective (overidentification and few false-negatives), problems related to high false-positive rates exist, with most validation studies reporting positive predictive values of between 43% and >90%.29
While it is clear that these drawbacks limit the use of PSIs to make reimbursement decisions or to compare hospitals, it is unclear how it affects the implications of our study, where it was used as a screening tool to identify
Second, morbidity and mortality events in NIS are characterised based on the index admission, and subsequent readmissions, while relevant, are not recorded. This may have resulted in under-recognition of the true burden of adverse events, mortality and charges after the initial cancer surgery. Third, while the heterogeneity identified in the volume–complication–mortality relationship is a key finding in the present report, our study design does not allow for the identification of the underlying mechanisms explaining these results. It is also important to emphasise that, in contrast to the previously cited studies where the overall complication rates were examined, we evaluated potentially preventable hospital-acquired events only. Previous investigators have shown that this restricted definition has limitations since not all deaths are accounted for in a given population sample31
; alternatively, these drawbacks may not apply to studies focusing on patient safety using PSI as a quality-of-care measure. Hence, while it may not be illogical to expect lower volume hospitals to provide substandard care secondary to both higher rates of preventable adverse events and
higher failure-to-rescue rates, it is certainly possible that a majority of hospital-acquired complications are an inevitable result of procedure complexity and patient comorbidities (and not just a failure of setting-level prevention measures). Consequently, while more rigorous patient care pathways might explain the lower incidence of preventable adverse events and subsequent mortality in higher volume hospitals, for the majority of (non-preventable) adverse events, the incidence rates would be the same regardless of hospital volume with lower failure-to-rescue rates preferentially explaining the low mortality rates of higher volume hospitals. Further investigation of these findings is required to test these possibilities and to fully understand the underlying dynamics of the volume–mortality relationship.