We have shown that while manifestations of poor glycemic control as described by the Centers for Medicare and Medicaid Services are relatively rare, these events are associated with disproportionately high costs and mortality. Having more chronic conditions and being admitted through the emergency room are associated with higher odds of poor glycemic control events. We have also shown a significant relationship between poor glycemic control and nurse staffing, particularly at non-teaching hospitals. This suggests one potential organizational intervention, which may reduce these events, is improved nurse staffing.
Nurses are at the frontlines of managing glycemia among hospitalized patients. Nurses conduct the core functions responsible for maintaining euglycemia—blood glucose monitoring and administration of insulin and other glucose-lowering medications. Nurses are responsible for the delivery of other care essential to successful outcomes for patients with diabetes including bedside symptom management and surveillance, coordination of nutrition and transportation services in order to avoid blood glucose derangements, implementation of physician order sets and protocols and educational programs focusing on enhanced glycemic control and diabetes self-management. The work that nurses do to manage diabetes and maintain glycemic control is time intensive, complex and requires good organization, training, communication and organizational support [9
A nursing staff with an excessive workload is a systemic failure that can compromise patient safety [16
]. A broad literature base has linked poor nurse staffing to a number of adverse patient outcomes [23
]. Medical errors, while occurring at the point of care where nurses interact with patients, are often the result of predictable systematic failures that undermine how nurses can effectively do their work [24
]. Nurses are fundamental to error prevention and the rescue of patients from potential adverse events such as poor glycemic control. In a study of two hospitals for example, Leape et al
] demonstrated that nurses were responsible for intercepting 86% of all errors that would result in adverse drug events. Organizational system failures and impediments undermine nurses’ ability to carry out the complex surveillance and management required to control blood glucose in the hospitalized patient and can lead to errors and poor outcomes.
Although our research does not identify the mechanism by which insufficient nurse staffing leads to poor glycemic control events, poor staffing is associated with a number of conditions that might reasonably lead to breakdowns in a hospital's ‘culture of safety.’ First, an overburdened staff is less able to provide back-ups and checks on each other. When there are holes in the resources and defenses against mistakes, errors are more likely to occur [24
]. Under-resourced nurses may also be more likely to use workarounds to get their work done, leading to errors and inconsistent, inefficient care [26
]. Finally, an overburdened nursing staff may be less able to communicate effectively with physicians and other members of the healthcare team. Nurse–physician communication is critical for the management of complex patients [27
]. Optimally managed patients with diabetes often have complex insulin delivery orders, intensive blood glucose monitoring protocols, nutrition orders and scheduling and other factors that need to be communicated across many members of the healthcare team. Effective and timely communication is essential to promoting the highest quality of care. An excessive workload among nurses may result in information falling through the cracks particularly during critical moments such as hand-offs and shift-changes.
Despite controlling for patient factors, we found that the effect of nurse staffing depended on hospital teaching status. It is possible that the high-paced environment of the teaching hospital, with increased technological demands, rotating personnel and increased hand-offs, may undermine the potential benefits of additional nurse staffing. Evidence varies about the effect of hospital teaching status on patient outcomes with most papers showing that teaching status is associated with better patient outcomes but some research finding the opposite or no relationship [28
]. The findings specific to the relationship between teaching status and adverse events is equally mixed. Brennan et al.
] for example, found that adverse events occurred more frequently in teaching hospitals but were less likely to be due to substandard care. Other investigators have found that teaching status was associated higher rates of patient safety incidents [30
One hypothesis for poorer outcomes in teaching institutions is that, in some cases, inexperienced resident physicians may be providing care for complex critically ill patients [31
]. Another potential issue is that teaching hospitals may care for more complex patients and perform more complicated procedures—both of which may introduce factors that we could not control for. We matched our cases and controls on severity of illness and there was no statistically significant difference between the severity of illness or the number of chronic conditions of our sample in teaching hospitals compared with those in non-teaching hospitals. Additionally, the bulk of services provided by teaching hospitals are routine services provided to the general population. Nonetheless, the administrative data we used lacks the clinical specificity that we might like to use to examine more detailed patient risk factors. Although balance between cases and controls was good, as in many observational studies, we were only able to control for observable factors. More specific clinical data might have allowed us to control for additional severity of illness, the immediate availability of consulting endocrinologists, certain laboratory values and certain medication use that might be relevant to poor glycemic control.
Additional limitations are worthy of note. First, the cross-sectional nature of our study limits our ability to draw conclusions about causation. It is also possible that there was systematic undercoding of manifestations of poor glycemic control. This is, however, the type of data that the Centers for Medicare and Medicaid Services will use in applying their ‘no-pay’ rule. While there are limitations to the use of administrative data to identify safety indicators, many have been validated and are commonly used in health services and patient safety research and have been shown to have higher validity when used, as we have, with present on admission flags and lookback procedures [19
]. Administrative data are also particularly useful with matched case–control studies of extremely rare events [33
]. Nonetheless, future research should consider chart review and clinical validation of data on these events. Additionally, because 2009 Medicare data—the first complete year of Medicare data with present on admission flags—were not available when we began our analysis, we utilized state discharge abstract data from the Office of Statewide Health Planning and Development. While these data have been shown to have reliable and valid present on admission indicators [34
], we were unable to examine new secondary diabetes complications (ICD-9 codes 249.1x
) that are part of the cluster of poor glycemic control events defined by the Centers for Medicare and Medicaid Services. We do not know if the factors we found related to poor glycemic control in our sample would be similarly related to secondary diabetes. Our sample also excluded hypoglycemic coma events among patients that we could not establish as having pre-existing diabetes. These critically ill patients are at risk for poor outcomes but were not within the scope of our study on patients with pre-existing diabetes. Likewise, we note that our findings represent only a small subset of the most extreme manifestations of poor glycemic control across a potentially wide range of blood glucose variation. Our findings may not be generalizable to the more common variations in blood glucose that occur in response to patient care or lack thereof. Finally, we acknowledge the view that the conditions we examined may not always be preventable. Even though the Centers for Medicare and Medicaid Services rule notes that the events should be ‘reasonably preventable,’ there may be instances when a negative outcome occurs despite very good care. On average, however, this is not the most likely scenario. While the most costly and time-intensive glucose monitoring is not indicated for all patients, systematic processes and safeguards, including adequate nursing staff and resources should be in place to prevent hypoglycemic and hyperglycemic crisis in all patients, and particularly those receiving glucose-lowering medications.
In conclusion, low nurse staffing undermines the ‘culture of safety’ necessary to provide safe and effective care to patients with diabetes. A projected US nursing workforce shortage has the potential to magnify the burdens on nursing systems to care for patients with complex conditions that require focused surveillance and intensive management such as diabetes mellitus. While policy interventions may be necessary to support robust nursing workforce nationally and internationally, hospital administrators must be proactive in investing in nursing as part of the culture of safety. Our results point to the need for prospective work to clarify the clinical significance of our findings and add to a mounting body of evidence supporting an investment in nursing resources, particularly in non-teaching hospitals.